Serratia

Appl Environ Microbiol, 2001 Nov, 67(11), 5100 - 6
Identification and characterization of the three chitin-binding domains within the multidomain chitinase Chi92 from Aeromonas hydrophila JP101; Wu ML et al.; The gene (chi92) encoding the extracellular chitinase of Aeromonas hydrophila JP101 has been cloned and expressed in Escherichia coli . The mature form of Chi92 is an 842-amino-acid (89.830-kDa) modular enzyme comprised of a family 18 catalytic domain, an unknown-function region (the A region), and three chitin-binding domains (ChBDs; Chi92-N, ChBD(CI), and ChBD(CII)) . The C-terminally repeated ChBDs, ChBD(CI) and ChBD(CII), were grouped into family V of cellulose-binding domains on the basis of sequence homology . Chitin binding and enzyme activity studies with C-terminally truncated Chi92 derivatives lacking ChBDs demonstrated that the ChBDs are responsible for its adhesion to unprocessed and colloidal chitins . Further adsorption experiments with glutathione S-transferase (GST) fusion proteins (GST-CI and GST-CICII) demonstrated that a single ChBD (ChBD(CI)) could promote efficient chitin and cellulose binding . In contrast to the two C-terminal ChBDs, the Chi92-N domain is similar to ChiN of Serratia marcescens ChiA, which has been proposed to participate in chitin binding . A truncated derivative of Chi92 that contained only a catalytic domain and Chi92-N still exhibited insoluble-chitin-binding and hydrolytic activities . Thus, it appears that Chi92 contains Chi92-N as the third ChBD in addition to two ChBDs (ChBD(CI) and ChBD(CII)).

Infect Immun, 2001 Nov, 69(11), 6707 - 17
Identification and characterization of the hemophore-dependent heme acquisition system of Yersinia pestis; Rossi MS et al.; Yersinia pestis possesses a heme-protein acquisition system (Hmu) that allows it to utilize heme and heme-protein complexes as the sole sources of iron . Analysis of the Y . pestis CO92 genomic sequence revealed a second heme-protein acquisition gene cluster that shares homology with the hemophore-dependent heme acquisition system (Has system) of Serratia marcescens . This locus consisted of the hasR(yp) receptor gene, the hasA(yp) hemophore gene, and genes encoding components of the HasA(yp) dedicated ABC transporter factor (hasDE(yp)), as well as a tonB homologue (hasB(yp)) . By using a reconstituted secretion system in Escherichia coli, we showed that HasA(yp) is a secreted heme-binding protein and that expression of HasA(yp) is iron regulated in E . coli . The use of a transcriptional reporter fusion showed that the hasRADEB promoter is Fur regulated and has increased activity at 37 degrees C . Hemoglobin utilization via the Has(yp) system was studied with both E . coli and Y . pestis, for which has and has hmu mutant strains were used . No contribution of the Has system to heme utilization was observed in either E . coli or Y . pestis under the conditions we tested . Previously it was shown that a deletion of the Hmu system had no effect on the virulence of Y . pestis in a mouse model of bubonic plague . An Hmu(-) Has(-) double mutant also retained full virulence in this model of infection . This report constitutes the first attempt to investigate the contribution of the hemophore-dependent heme acquisition system in bacterial pathogenicity.

Am J Infect Control, 2001 Oct, 29(5), 312 - 5
An outbreak of Serratia marcescens associated with the anesthetic agent propofol; Henry B et al.; BACKGROUND: In October 1999, 7 patients with postoperative infections caused by Serratia marcescens were identified at a community hospital in Ontario, Canada . We describe the investigation of this outbreak . METHODS: We undertook a case-control study to determine risk factors associated with infection . Case subjects consisted of patients who had undergone surgery and acquired bacteremia or wound infections that, when cultured, grew S marcescens . Control subjects were selected from the cohort of patients who underwent surgery at the same hospital during the outbreak period . Chart reviews were conducted for case and control subjects . Environmental samples were taken from medications and liquids in the operating rooms and from one health care professional who was involved in all the cases . S marcescens isolates were forwarded to a reference laboratory for pulsed field gel electrophoresis . RESULTS: We identified 7 case subjects and 29 control subjects . Five patients had bacteremia and 2 patients had wound infections . Two patients with bacteremia died . All patients with bacteremia or wound infections were exposed to a single anesthetist (anesthetist A) and were administered the anesthetic medication propofol . These patients were more than 40 times more likely to have had anesthetist A administer their anesthetic (OR 41.6, 95% CI 3.6-1120) and 22 times more likely to have received propofol (OR 22, 95% CI 2.1-550) than were control subjects . None of the environmental samples or cultures from anesthetist A were positive for S marcescens . Six of the 7 human isolates had an identical pulsed field gel electrophoresis pattern, and the seventh was untypable . CONCLUSIONS: This outbreak of postoperative infections was very strongly linked to the use of propofol by one anesthetist . Health care professionals must follow strict aseptic techniques when using propofol and should review these techniques regularly.

Microbiol Res, 2001, 156(2), 185 - 9
Pythium perplexum isolated from soil in France: morphology, molecular characterisation and biological control; Galland D et al.; Pythium perplexum (F-926) was isolated from a soil sample taken in the Burgundy region in France . In 1907, it was mistakenly described by Bulter as P . vexans . Despite morphological resemblance, the comparison between the internal transcribed spacer 1 regions of the ribosomal DNA of the two fungi leaves no doubt of their different identities . P . perplexum was found to be highly pathogenic to cucumber seedlings . Damping-off disease of cucumber caused by P . perplexum can effectively be controlled by using the soil bacterium Serratia plymuthica (B-781) . The details of the morphology and the molecular characterisation of P . perplexum and its biological control with S . plymuthica are described here.

Biochemistry, 2001 Sep 25, 40(38), 11338 - 43
High resolution structural analyses of mutant chitinase A complexes with substrates provide new insight into the mechanism of catalysis; Papanikolau Y et al.; Chitinase A (ChiA) from the bacterium Serratia marcescens is a hydrolytic enzyme, which cleaves beta-1,4-glycosidic bonds of the natural biopolymer chitin to generate di-N-acetyl-chitobiose . The refined structure of ChiA at 1.55 A shows that residue Asp313, which is located near the catalytic proton donor residue Glu315, is found in two alternative conformations of equal occupancy . In addition, the structures of the cocrystallized mutant proteins D313A, E315Q, Y390F, and D391A with octa- or hexa-N-acetyl-glucosamine have been refined at high resolution and the interactions with the substrate have been characterized . The obtained results clearly show that the active site is a semiclosed tunnel . Upon binding, the enzyme bends and rotates the substrate in the vicinity of the scissile bond . Furthermore, the enzyme imposes a critical "chair" to "boat" conformational change on the sugar residue bound to the -1 subsite . According to our results, we suggest that residues Asp313 and Tyr390 along with Glu315 play a central role in the catalysis . We propose that after the protonation of the substrate glycosidic bond, Asp313 that interacts with Asp311 flips to its alternative position where it interacts with Glu315 thus forcing the substrate acetamido group of -1 sugar to rotate around the C2-N2 bond . As a result of these structural changes, the water molecule that is hydrogen-bonded to Tyr390 and the NH of the acetamido group is displaced to a position that allows the completion of hydrolysis . The presented results suggest a mechanism for ChiA that modifies the earlier proposed "substrate assisted" catalysis.

Biol Pharm Bull, 2001 Sep, 24(9), 1093 - 6
A comparative study of characteristics of current-type and conventional-type cationic bactericides; Ohta S et al.; We have synthesized new polycationic bactericides, polyloxyethylene(dimethyliminio)trimethylene(dimethyliminio)ethylene dichloridel (OXD) and poly(hexamethyleneguanidine phosphate) (HEP), in order to develop more active but less skin-irritative bactericides . The effects of these bactericides on Pseudomonas aeruginosa, Escherichia coli, Serratia marcescens, Klebsiella pneumoniae, methicillin resistant Staphylococcus aureus (MRSA) and the degree of their irritations on skin were compared with those of a widely used low molecular-weight cationic bactericide, benzalkonium chloride (BAC), and a polycationic bactericide, poly{2-hydroxyethylene(dimethyliminio)methylene chloride} (2HYC) . The minimum bactericidal concentration (MBC) of OXD for 10 min contact incubation was 16 microg/ml against P . aeruginosa, E . coli, S . marcescens and K . pneumoniae, and >1000 microg/ml against MRSA . The MBC of HEP for 10 min contact incubation was 16 microg/ml against P . aeruginosa, 32 microg/ml against E . coli and K . pneumoniae, and 64 microg/ml against S . marcescens and MRSA . Itch, edema, erythema, heat, injury, desquamation and keratinization caused by skin irritation were examined in 21 subjects by patch tests . Only one subject treated with OXD experienced edema, and one subject with HEP experienced keratinization . However, BAC caused itch in 3 subjects, edema in 1, erythema in 10 and desquamation in 2, indicating that the incidence of skin irritation of BAC was higher than that of OXD or HEP . OXD and HEP had sterilization ability similar to BAC, however, they were less skin-irritative than BAC . This indicates that OXD and HEP can be used as safe bactericides.

Oral Microbiol Immunol, 2001 Oct, 16(5), 306 - 10
Subgingival occurrence and antimicrobial susceptibility of enteric rods and pseudomonads from Brazilian periodontitis patients; Barbosa FC et al.; The occurrence and in vitro antimicrobial sensitivity of isolates of enteric rods and pseudomonads were examined in 80 periodontitis patients, 17 to 58 years of age, in Sao Paulo, Brazil . Speciation and in vitro antimicrobial susceptibility testing were performed using the BBL Crystal enteric/nonfermenter system and the Etest for amoxicillin/clavulanic acid, ciprofloxacin and doxycycline . A total of 30 strains were isolated from 25 (31.2%) of the study subjects . Pseudomonas aeruginosa occurred in nine patients, Serratia marcescens in seven, and five other species were recovered in lower prevalence . All study organisms demonstrated high susceptibility to ciprofloxacin but exhibited variable susceptibility patterns to the other antimicrobial agents tested . In conclusion, the high occurrence of enteric rods and pseudomonads in these subjects may be important in the pathogenesis of periodontitis, and ciprofloxacin might be the antibiotic of choice to eradicate these pathogens from periodontal pockets.

Bioorg Med Chem, 2001 Sep, 9(9), 2403 - 9
Stereochemistry of cleavage of internucleotide bonds by Serratia marcescens endonuclease; Koziolkiewicz M et al.; Endonuclease from Serratia marcescens hydrolyzes internucleotide phosphorothioate linkages of R(P) configuration with inversion of configuration at P-atom . This observation supports a reported architecture of the active site, with 3'-bridging and pro-S(P) non-bridging oxygen atoms of the scissile phosphate group involved in direct contact with hydrated magnesium cation, while His-89 activates a water molecule which attacks the phosphorus atom according to a one-step in-line mechanism . The presence of a phosphorothioate bond of S(P) configuration downstream to that one being cleaved reduces the rate of hydrolysis . This suggests participation of the pro-S(P) oxygen atom of that phosphate bond in the mechanism of action of the enzyme, which was not detected in published crystallographic analyses.

EMBO J, 2001 Sep 3, 20(17), 4657 - 63
Folded HasA inhibits its own secretion through its ABC exporter; Debarbieux L et al.; Gram-negative bacterial proteins secreted by ABC exporters carry a secretion signal in their carboxylic extremities . This characteristic suggests that the polypeptide needs to be fully synthesized before it can be secreted and, therefore, presumably may fold at least in part before its secretion . We investigated the relationship between folding and secretion using HasA, a hemoprotein of Serratia marcescens secreted into the extracellular medium by a dedicated Has ABC exporter . We first demonstrated that when HasA is sequestered in the cytoplasm it can acquire its tertiary structure, as assessed from its capacity to bind heme . The cytoplasmic pool of HasA cannot be secreted and inhibits the secretion of newly synthesized molecules . HasA folding in the cytoplasm was independent of either its capacity to bind heme or the presence of SecB, although SecB is essential for HasA secretion . Our findings indicate a strong coupling between synthesis and secretion in the type I secretion pathway.

Clin Neurol Neurosurg, 2001 Oct, 103(3), 171 - 4
Protean infectious types and frequent association with neurosurgical procedures in adult Serratia marcescens CNS infections: report of two cases and review of the literature; Huang CR et al.; Serratia marcescens is a rare pathogen of adult central nervous system (CNS) infection . We report on the clinical features and therapeutic outcomes of two adult patients with such infections . The clinical characteristics of 13 other reported adult cases are also included for analysis . The 15 cases were nine males and six females, aged 19-83 years, in whom, underlying post-neurosurgical states and ear operation were noted in 93% (14/15) . Fever and conscious disturbance were the most common clinical manifestations of these 15 cases, followed by hydrocephalus, seizures, and wound infections . The manifestation types were protean, including meningitis and focal suppurations such as brain abscess, cranial and spinal epidural abscess, cranial subdural abscess, and infected lumbar pseudomeningocele . One case of S . marcescens CNS infection was diagnosed postmortem; the other 14 were diagnosed by the positive culture from CSF or pus . Antibiotic therapy with or without neurosurgical intervention was the management strategy in 14/15 cases . The therapeutic results showed a high mortality rate.

Prikl Biokhim Mikrobiol, 2001 Jul-Aug, 37(4), 439 - 43
{Immobilization of chloroperoxidase from Serratia marcescens}; Preobrazhenskaia IuV et al.; A bacterial non-heme chloroperoxidase from Serratia marcescens W 250 was immobilized in calcium-alginate gel . Methods for stabilization of the immobilized enzyme were developed, and some kinetic parameters of the immobilized preparations were determined . The enzyme encapsulated into the gel granules in the presence of potassium ferricyanide followed by treatment with glutaraldehyde demonstrated the highest stability under the reaction conditions.

Appl Environ Microbiol, 2001 Sep, 67(9), 4225 - 32
Photoreactivation in airborne Mycobacterium parafortuitum; Peccia J et al.; Photoreactivation was observed in airborne Mycobacterium parafortuitum exposed concurrently to UV radiation (254 nm) and visible light . Photoreactivation rates of airborne cells increased with increasing relative humidity (RH) and decreased with increasing UV dose . Under a constant UV dose with visible light absent, the UV inactivation rate of airborne M . parafortuitum cells decreased by a factor of 4 as RH increased from 40 to 95%; however, under identical conditions with visible light present, the UV inactivation rate of airborne cells decreased only by a factor of 2 . When irradiated in the absence of visible light, cellular cyclobutane thymine dimer content of UV-irradiated airborne M . parafortuitum and Serratia marcescens increased in response to RH increases . Results suggest that, unlike in waterborne bacteria, cyclobutane thymine dimers are not the most significant form of UV-induced DNA damage incurred by airborne bacteria and that the distribution of DNA photoproducts incorporated into UV-irradiated airborne cells is a function of RH.

J Biol Chem, 2001 Nov 2, 276(44), 41343 - 9 Epub 2001 Aug 24.
Roles of the exposed aromatic residues in crystalline chitin hydrolysis by chitinase A from Serratia marcescens 2170; Uchiyama T et al.; Four exposed aromatic residues, two in the N-terminal domain (Trp-69 and Trp-33) and two in the catalytic domain (Trp-245 and Phe-232) of Serratia marcescens chitinase A, are linearly aligned with the deep catalytic cleft . To investigate the importance of these residues in the binding activity and hydrolyzing activity against insoluble chitin, site-directed mutagenesis to alanine was carried out . The substitution of Trp-69, Trp-33, or Trp-245 significantly reduced the binding activity to both highly crystalline beta-chitin and colloidal chitin . The substitution of Phe-232, which is located closest to the catalytic cleft, did not affect the binding activity . On the other hand, the hydrolyzing activity against beta-chitin microfibrils was significantly reduced by the substitution of any one of the four aromatic residues including Phe-232 . None of the mutations reduced the hydrolyzing activity against soluble substrates . These results clearly demonstrate that the four exposed aromatic residues are essential determinants for crystalline chitin hydrolysis . Three of them, two in the N-terminal domain and one in the catalytic domain, play vital roles in the chitin binding . Phe-232 appeared to be important for guiding the chitin chain into the catalytic cleft . Based on these observations, a model for processive hydrolysis of crystalline chitin by chitinase A is proposed.

Syst Appl Microbiol, 2001 Jul, 24(2), 245 - 51
Novel endophytes of rice form a taxonomically distinct subgroup of Serratia marcescens; Tan Z et al.; Six endophytic strains isolated from surface-sterilized rice roots and stems of different rice varieties grown in the Philippines were characterized . They were analyzed by physiological and biochemical tests, SDS-PAGE of whole-cell protein patterns, DNA-DNA hybridization and 16S rDNA sequencing . SDS-PAGE of whole-cell patterns showed that the six isolates fell into two subgroups which were similar but not identical in protein patterns to S . marcescens . The phylogenetic analysis of 16S rDNA sequences of two representative strains IRBG 500 and IRBG 501 indicated that they were closely related to S . marcescens (more than 99% identity) . Physiological and biochemical tests corroborated that the isolates were highly related to each other and to S . marcescens . In cluster analysis, all six isolates were clustered together at 93% similarity level and grouped closely with Serratia marcescens at 86% similarity level . DNA-DNA hybridization studies revealed that the isolates shared high similarity levels with S . marcescens (> or =86% DNA-DNA binding), indicating they belong to the same species . However, the isolates differed in several biochemical characteristics from the type strain . They produce urease and utilize urea and L(+) sorbose as a substrate, which is different from all known Serratia reference strains . These results suggest that the six endophytic isolates represent a novel, non-pigmented subgroup of S . marcescens.

Curr Biol, 2001 Jun 5, 11(11), 809 - 21
A reverse genetic analysis of components of the Toll signaling pathway in Caenorhabditis elegans; Pujol N et al.; BACKGROUND: Both animals and plants respond rapidly to pathogens by inducing the expression of defense-related genes . Whether such an inducible system of innate immunity is present in the model nematode Caenorhabditis elegans is currently an open question . Among conserved signaling pathways important for innate immunity, the Toll pathway is the best characterized . In Drosophila, this pathway also has an essential developmental role . C . elegans possesses structural homologs of components of this pathway, and this observation raises the possibility that a Toll pathway might also function in nematodes to trigger defense mechanisms or to control development . RESULTS: We have generated and characterized deletion mutants for four genes supposed to function in a nematode Toll signaling pathway . These genes are tol-1, trf-1, pik-1, and ikb-1 and are homologous to the Drosophila melanogaster Toll, dTraf, pelle, and cactus genes, respectively . Of these four genes, only tol-1 is required for nematode development . None of them are important for the resistance of C . elegans to a number of pathogens . On the other hand, C . elegans is capable of distinguishing different bacterial species and has a tendency to avoid certain pathogens, including Serratia marcescens . The tol-1 mutants are defective in their avoidance of pathogenic S . marcescens, although other chemosensory behaviors are wild type . CONCLUSIONS: In C . elegans, tol-1 is important for development and pathogen recognition, as is Toll in Drosophila, but remarkably for the latter role, it functions in the context of a behavioral mechanism that keeps worms away from potential danger.

Shock, 2001 Aug, 16(2), 148 - 52
Comparison of translocation of different types of microorganisms from the intestinal tract of burned mice; Eaves-Pyles T et al.; The aim of this study was to compare the ability of various microorganisms to translocate from the intestine to the mesenteric lymph nodes (MLNs), liver, and spleen in a burned mouse model . Balb/c mice were gavaged with 1 x 10(9) or 1 x 10(10) of one of 11 different microorganisms . All animals were then given a 20% burn . Survival after 10 days showed no significant difference between any of the groups at the 10(10) dose . At the 10(9) dose, significantly higher survival rates were found in three of the 11 strains . Microbial translocation (gavage of 10(10) 111In-labeled organisms) and host's ability to kill translocated bacteria (viable bacteria in tissues) were measured followed by burn injury and sacrifice four hours later . Translocation and killing of Staphylococcus epidermidis and Escherichia coli was high in the MLNs compared with all other groups but translocation was lower to the liver . Klebsiella, Pseudomonas, and Serratia translocated more evenly to all the tissues . However, these groups showed very high clearance of bacteria in the liver and spleen except for Klebsiella and one strain of Pseudomonas in the spleen . Candida showed poor translocation to all of the tissues and high clearance . It is concluded that various strains of bacteria translocate from the intestine to a similar degree after injury, but the tissues to which they translocate and the rate at which they are killed are somewhat strain dependent.

Saudi Med J, 2000 Jun, 21(6), 550 - 3
Neonatal meningitis; Al-Harthi AA et al.; OBJECTIVE: To determine the prevalent bacterial agents of neonatal meningitis and their antibiotic susceptibility in a referral intensive care unit in Assir Central Hospital, Saudi Arabia, during the years 1993-1998 . METHODS: Records of newborn infants with positive cerebrospinal fluid culture during the period were retrospectively studied . RESULTS: There were 1473 nursery admissions, of which 32 episodes of meningitis occurred amongst 31 neonates . Klebsiella pneumoniae (31%) and Serratia marcescens (21%) were the main pathogens . The incidence of concurrent septicemia among these infants was 58% . Klebsiella pneumoniae appears to dominate in both early and late onset infections . The sex incidence was equal and the mortality rate was 48% . CONCLUSION: The survey identifies Klebsiella pneumoniae and Serratia sp . as the leading bacterial agents of neonatal meningitis in our environment . The relatively high frequency of Serratia infection in the present survey appears unique as this organism is comparatively rare in other reports across the globe . No Group B Streptococcus was isolated, which is in contrast to reports obtained in Europe, America and Australia where it is the predominant organism of neonatal sepsis or meningitis . Antibiogram identified imipenem and cefotaxime as the empirical antibiotics in infants with a clinical diagnosis of neonatal sepsis in our hospital; no more conventional use of ampicillin . In view of the changing bacterial pattern of infant infection with time even in the same environment, a periodic review of this subject is advocated.

Rev Argent Microbiol, 2001 Apr-Jun, 33(2), 65 - 74
{Escherichia coli: diversity of biochemical phenotypes in aquatic environments (Santa, Fe, Argentina)}; Emiliani F et al.; During certain environmental conditions, the floating aquatic vegetation, mainly represented by Eichhornia crassipes (water hyacinth) invade and even cover water courses assigned to recreational activities or to the supply of drinkable water . The rhizosphere of these plants constitutes an unknown biotope of bacteria of sanitary interest, possibly different from waters without vegetation and of the sediment of the same aquatic system . To verify such possibility, 206 isolated strains in MacConkey Agar (Difco) were typified and identified (78 from water, 65 from sediment and 63 from rhizosphere) using the API 20 E system (v . 4.0) and Apilab plus software (v 3.3.3), both of bioMerieux (Marcy-l'Etoile, France, 1998) . Nineteen different biochemical phenotypes from E . coli were found . The 79% of the population belonged to only 7 phenotypes; the 21% remaining, to the other 12 phenotypes . Twelve phenotypes did not share the biotopes, while only 4 were in the three . These results (and those obtained by other authors who used the API 20 E system in other biotopes) suggest that it would be possible to characterize the rhizosphere using those phenotypes that are found in smaller proportion . The greatest index of diversity (H) and evenness (E) were found in the rhizosphere (H = 2.903; E = 0.874) . The dendrogram (average distances and UPGMA method) reaffirms the dissimilarity in biochemical phenotypes of E . coli populations of the rhizosphere with regard to the other biotopes . The most abundant bacterial species in the three biotopes were E . coli, Klebsiella terrigena and K . pneumoniae, corresponding to 75.2% of the community . The rhizosphere differed from Serratia odorifera and from Klebsiella spp . because of its higher rate of isolation.

Mol Microbiol, 2001 Jul, 41(2), 439 - 50
Haemophore-mediated bacterial haem transport: evidence for a common or overlapping site for haem-free and haem-loaded haemophore on its specific outer membrane receptor; Letoffe S et al.; Bacterial extracellular haemophores also named HasA for haem acquisition system form an independent family of haemoproteins that take up haem from host haeme carriers and shuttle it to specific receptors (HasR) . Haemophore receptors are required for the haemophore-dependent haem acquisition pathway and alone allow free or haemoglobin-bound haem uptake, but the synergy between the haemophore and its receptor greatly facilitates this uptake . The three-dimensional structure of the Serratia marcescens holo-haemophore (HasASM) has been determined previously and revealed that the haem iron atom is ligated by tyrosine 75 and histidine 32 . The phenolate of tyrosine 75 is also tightly hydrogen bonded to the Ndelta atom of histidine 83 . Alanine mutagenesis of these three HasASM residues was performed, and haem-binding constants of the wild-type protein, the three single mutant proteins, the three double mutant proteins and the triple mutant protein were compared by absorption spectrometry to probe the roles of H32, Y75 and H83 in haem binding . We show that one axial iron ligand is sufficient to ligate haem efficiently and that H83 may become an alternative iron ligand in the absence of Y75 or both H32 and Y75 . All the single mutant proteins retained the ability to stimulate haemophore-dependent haem uptake in vivo . Thus, the residues H32, Y75 and H83 are not individually necessary for haem delivery to the receptor . The binding of haem-free and haem-loaded HasASM proteins to HasRSM-producing strains was studied . Both proteins bind to HasRSM with similar apparent Kd . The double mutant H32A-Y75A competitively inhibits binding to the receptor of both holo-HasASM and apo-HasASM, showing that there is a unique or overlapping site on HasRSM for the apo- and holo-haemophores . Thus, we propose a new mechanism for haem uptake, in which haem is exchanged between haem-loaded haemophores and unloaded haemophores bound to the receptor without swapping of haemophores on the receptor.

Proc Natl Acad Sci U S A, 2001 Jul 31, 98(16), 8979 - 84
Structural insights into the catalytic mechanism of a family 18 exo-chitinase; van Aalten DM et al.; Chitinase B (ChiB) from Serratia marcescens is a family 18 exo-chitinase whose catalytic domain has a TIM-barrel fold with a tunnel-shaped active site . We have solved structures of three ChiB complexes that reveal details of substrate binding, substrate-assisted catalysis, and product displacement . The structure of an inactive ChiB mutant (E144Q) complexed with a pentameric substrate (binding in subsites -2 to +3) shows closure of the "roof" of the active site tunnel . It also shows that the sugar in the -1 position is distorted to a boat conformation, thus providing structural evidence in support of a previously proposed catalytic mechanism . The structures of the active enzyme complexed to allosamidin (an analogue of a proposed reaction intermediate) and of the active enzyme soaked with pentameric substrate show events after cleavage of the glycosidic bond . The latter structure shows reopening of the roof of the active site tunnel and enzyme-assisted product displacement in the +1 and +2 sites, allowing a water molecule to approach the reaction center . Catalysis is accompanied by correlated structural changes in the core of the TIM barrel that involve conserved polar residues whose functions were hitherto unknown . These changes simultaneously contribute to stabilization of the reaction intermediate and alternation of the pKa of the catalytic acid during the catalytic cycle.

Am J Ophthalmol, 2001 Aug, 132(2), 257 - 8
Serratia Marcescens corneal ulcer as a complication of orthokeratology; Chen KH et al.; PURPOSE: To report a case of Serratia Marcescens corneal ulcer as a complication of orthokeratology treatment . METHODS: Case report . RESULTS: A 9-year-old male who underwent orthokeratology treatment for 6 months suffered from a corneal ulcer . The refractive state of lesion eye was -5.5D/-1.25D x 180 degrees, and visual acuity was hand motion at 30 cm . He wore a retainer lens, rigid gas permeable lens, overnight for 2 months before the corneal ulcer occurred . Ulcer became worse after tobramycin and gentamycin treatment for 2 days . After ciprofloxacin treatment, the ulcer healed and visual acuity recovered to 20/20 with spectacle correction . Cultures of the cornea tissue and contact lens storage solution both grew Serratia Marcescens, which was sensitive to ciprofloxacin . CONCLUSION: Overnight wearing of a rigid contact lens is a risk factor for a corneal ulcer.

FEMS Microbiol Lett, 2001 Jul 24, 201(2), 277 - 83
The Caulobacter crescentus outer membrane protein Omp58 (RsaF) is not required for paracrystalline S-layer secretion; Reichelt M et al.; To identify the outer membrane protein component of the Caulobacter crescentus CB2 surface-layer export machinery we used the Serratia marcescens LipD protein to find homologs in the CB2 genome . From two homologous sequences found, one encodes a putative OMP with a predicted molecular mass of 57.5 kDa, termed Omp58 (formerly RsaF) . Comparison of membrane protein profiles revealed a protein with an appropriate molecular mass present in wild-type, but not CB2 omp58::kanamycin, a mutant strain with an inactivated omp58 gene . Disruption of omp58 did not affect surface-layer production, suggesting that Omp58 is not involved in surface-layer protein secretion and, thus, may not be the outer membrane protein component of the C . crescentus surface-layer export system.

Antimicrob Agents Chemother, 2001 Aug, 45(8), 2331 - 9
Mutation in Serratia marcescens AmpC beta-lactamase producing high-level resistance to ceftazidime and cefpirome; Raimondi A et al.; Starting from a clinical isolate of Serratia marcescens that produced a chromosomally encoded AmpC beta-lactamase inducibly, we isolated by stepwise selection two laboratory mutants that showed high levels of resistance to some cephalosporins . The 98R mutant apparently overproduced the unaltered beta-lactamase constitutively, but the 520R mutant produced an altered enzyme, also constitutively . Ceftazidime and cefpirome MICs for the 520R mutant were much higher (512 and 64 microg/ml, respectively) than those for the 98R mutant (16 and 16 microg/ml, respectively) . Yet the MICs of cephaloridine and piperacillin for the 520R mutant were four- to eightfold lower than those for the 98R mutant . Cloning and sequencing of the ampC alleles showed that in the 520R mutant enzyme, the Thr64 residue, about two turns away from the active-site serine, was mutated to isoleucine . This resulted in a >1,000-fold increase in the catalytic efficiency (k(cat)/K(m)) of the mutated AmpC enzyme toward ceftazidime, whereas there was a >10-fold decrease in the efficiency of the mutant enzyme toward cefazolin and cephaloridine . The outer membrane permeability of the 520R strain to cephalosporins was also less than in the 98R strain, and the alteration of the kinetic properties of the AmpC enzyme together with this difference in permeability explained quantitatively the resistance levels of both mutant strains to most agents studied.

Clin Experiment Ophthalmol, 2001 Jun, 29(3), 157 - 60
Antimicrobial peptides: a potential role in ocular therapy; Aliwarga Y et al.; Bacterial pathogens are often involved in contact lens-related adverse responses . This study aimed to find antimicrobial peptides and proteins that effectively eradicate or inhibit ocular bacteria . The antimicrobials were screened against gram-negative and gram-positive bacteria originating from ocular sources . The viability of these ocular bacteria was measured after exposure to the peptides and proteins . Two conditions were used to grow bacteria, low nutrient phosphate-buffered saline and high nutrient tryptone soya broth . Samples were taken at different times up to 48 h . In low nutrient conditions, protamine was found to be the most effective against all strains . Melittin was very effectve against all strains except Serratia and one Pseudomonas isolate which were partially affected . In high nutrient condition, only melittin was effective in killing Staphylococcus aureus . Protamine and the combination of protamine and melittin had the greatest effect in eradicating the bacteria tested in low nutrient condition . Protamine alone and its combination with melittin may have potential therapeutic agents for ocular infections in an era of emerging antibiotic resistance.

Am Fam Physician, 2001 Jun 15, 63(12), 2413 - 20
Diagnosis and management of osteomyelitis; Carek PJ et al.; Acute osteomyelitis is the clinical term for a new infection in bone . This infection occurs predominantly in children and is often seeded hematogenously . In adults, osteomyelitis is usually a subacute or chronic infection that develops secondary to an open injury to bone and surrounding soft tissue . The specific organism isolated in bacterial osteomyelitis is often associated with the age of the patient or a common clinical scenario (i.e., trauma or recent surgery) . Staphylococcus aureus is implicated in most patients with acute hematogenous osteomyelitis . Staphylococcus epidermidis, S . aureus, Pseudomonas aeruginosa, Serratia marcescens and Escherichia coli are commonly isolated in patients with chronic osteomyelitis . For optimal results, antibiotic therapy must be started early, with antimicrobial agents administered parenterally for at least four to six weeks . Treatment generally involves evaluation, staging, determination of microbial etiology and susceptibilities, antimicrobial therapy and, if necessary, debridement, dead-space management and stabilization of bone.

Microbiology, 2001 Jul, 147(Pt 7), 1793 - 803
A Bacillus amyloliquefaciens ChbB protein binds beta- and alpha-chitin and has homologues in related strains; Chu HH et al.; A small (19.8 kDa) protein was identified in Bacillus amyloliquefaciens ALKO 2718 cultures during growth in the presence of yeast extract and chitin, but not with glucose . The protein targets beta-chitin best, then alpha-chitin, but barely any other polysaccharide . This described chitin-binding protein (ChbB) is the first of its type from a Bacillus strain and cross-reacts with antibodies raised against the Streptomyces alpha-chitin-binding protein CHB1 . Using reverse genetics, the chromosomal chbB gene of strain ALKO 2718 was identified, cloned and sequenced . ChbB shares several motifs with the alpha-chitin-binding proteins CHB1 and CHB2 of Streptomyces and CBP21 of Serratia marcescens predominantly targeting beta-chitin . Synthesis was repressed by glucose and the presence of cre boxes suggests catabolite control . Using PCR, Southern hybridization and anti-ChbB antibodies, the presence of a chbB gene, as well as of a ChbB protein homologue, was ascertained in several tested B . amyloliquefaciens strains, but not in Bacillus subtilis 168 . Contrary to B . subtilis 168, all B . amyloliquefaciens strains secreted varying amounts of enzymic activity, degrading carboxymethyl chitin coupled with Remazol brilliant violet.

Surg Today, 2001, 31(6), 497 - 501
Protective effect of a lipoxygenase inhibitor, nordihydroguaretic acid, on the ileal motor disturbances induced by Serratia marcescens endotoxin in rats; Ezberci F et al.; This study was conducted to examine the effects of peptidoleukotrienes on the ileal contractility disturbances induced by Serratia marcescens endotoxin in rats . Thirty-two male Wistar rats were divided into four groups (n = 8 each) . The first group was given only an anesthetic agent (control group); the second group was given the endotoxin (endotoxin group); the third group was given a lipoxygenase inhibitor, nordihydroguaretic acid (NDGA); and the fourth group was given NDGA 10 min before administration of the endotoxin (NDGA+endotoxin group) . The isolated ileum response was recorded in each group . Normal contractile activity was seen in the control group . After the endotoxin was given . the isolated ileum did not respond to 497acetylcholine (ACh) in the endotoxin group, but the contractile results of isolated ileum to ACh were similar to the control group results in both the NDGA and endotoxin+NDGA groups . The results of this study demostrate that leukotrienes may play a role in endotoxin-induced ileal contractility disturbances, and that the lipoxygenase inhibitor, NDGA, could be useful for the treatment of ileal motility disturbances induced by endotoxin.

Infect Control Hosp Epidemiol, 2001 May, 22(5), 303 - 5
Outbreak of Serratia marcescens infection in a neonatal intensive care unit; Prasad GA et al.; We report an outbreak of Serratia marcescens infection in the neonatal intensive care unit of a community hospital . The outbreak involved eight neonates, (five infected and three colonized), one of whom died . Pulsed-field gel electrophoresis confirmed that all isolates were identical strains . Cohorting and isolation of the infected neonates helped to control the outbreak . No environmental source of infection was found.

Life Sci, 2001 Mar 16, 68(17), 2025 - 36
Prodigiosin-induced apoptosis in human colon cancer cells; Montaner B et al.; Prodigiosin is a red pigment produced by various bacteria including Serratia marcescens . Colorectal cancer is one of the most frequent malignancies and one of the most frequent causes of cancer death in the Western world . Its treatment is far from satisfactory and the challenge to oncologists is to find novel chemical entities with less toxicity and greater effectiveness than those used in current chemotherapy . Here we characterize the apoptotic action of prodigiosin in colon cancer cells . DLD-1 and SW-620 human colon adenocarcinoma cells, NRK and Swiss-3T3 nonmalignant cells were assayed by the MTT assay, fragmentation pattern of DNA, Hoechst 33342 staining and study of PARP cleavage by Western blot, in order to characterize the prodigiosin-induced apoptosis . Prodigiosin was purified and its structure was confirmed . Metastatic SW-620 cells were more sensitive to prodigiosin (IC50: 275 nM) than DLD-1 . We did not observe a significant decrease in the viability of NRK cells . We confirmed that prodigiosin induces apoptosis in both cancer cell lines by the characteristic DNA laddering pattern and condensed nuclei or apoptotic bodies identified by fluorescence microscopy . These results indicate that prodigiosin induces apoptosis in colon cancer cells.

Proc Natl Acad Sci U S A, 2001 May 22, 98(11), 6021 - 6
The structures of anthranilate synthase of Serratia marcescens crystallized in the presence of (i) its substrates, chorismate and glutamine, and a product, glutamate, and (ii) its end-product inhibitor, L-tryptophan; Spraggon G et al.; The crystal structure of anthranilate synthase (AS) from Serratia marcescens, a mesophilic bacterium, has been solved in the presence of its substrates, chorismate and glutamine, and one product, glutamate, at 1.95 A, and with its bound feedback inhibitor, tryptophan, at 2.4 A . In comparison with the AS structure from the hyperthermophile Sulfolobus solfataricus, the S . marcescens structure shows similar subunit structures but a markedly different oligomeric organization . One crystal form of the S . marcescens enzyme displays a bound pyruvate as well as a putative anthranilate (the nitrogen group is ambiguous) in the TrpE subunit . It also confirms the presence of a covalently bound glutamyl thioester intermediate in the TrpG subunit . The tryptophan-bound form reveals that the inhibitor binds at a site distinct from that of the substrate, chorismate . Bound tryptophan appears to prevent chorismate binding by a demonstrable conformational effect, and the structure reveals how occupancy of only one of the two feedback inhibition sites can immobilize the catalytic activity of both TrpE subunits . The presence of effectors in the structure provides a view of the locations of some of the amino acid residues in the active sites . Our findings are discussed in terms of the previously described AS structure of S . solfataricus, mutational data obtained from enteric bacteria, and the enzyme's mechanism of action.

J Hosp Infect, 2001 May, 48(1), 13 - 9
Use of pulsed-field gel electrophoresis to investigate an outbreak of Serratia marcescens infection in a neonatal intensive care unit; Jang TN et al.; Serratia marcescens is a well-recognized hospital-acquired pathogen, which has been associated with a number of specific outbreaks, particularly in critically ill neonates . We used pulsed-field gel electrophoresis (PEGE) typing to analyse an outbreak in a neonatal intensive care unit (NICU) . We included samples from nine patients, three handwashes and ten environmental isolates from an outbreak (February to August 1999) in addition to four patient isolates from different wards of our hospital during the same time period . The clinical presentations of the outbreak included bacteraemia (four cases), pneumonia (three cases), umbilical wound infection (one case) and conjunctivitis (one case) . Nine outbreak isolates exhibited an identical PFGE fingerprint, while the epidemiologically unrelated strains demonstrated distinct patterns . Epidemiological investigation failed to reveal a common source of the outbreak, although the epidemic S . marcescens strain was isolated from hand-washes and doors of incubators . We concluded that cross-transmission via transient contamination of hands was the major route for this outbreak . Strict handwashing practices, the cohorting and isolation of colonized and infected patients, and the regular dis-infection of incubators are crucial steps for preventing the transmission of S . marcescens in an NICU . This PFGE method is highly discriminatory for the thorough epidemiological investigation of an outbreak of S . marcescens .

N Engl J Med, 2001 May 17, 344(20), 1491 - 7
Serratia liquefaciens bloodstream infections from contamination of epoetin alfa at a hemodialysis center; Grohskopf LA et al.; BACKGROUND: In a one month period, 10 Serratia liquefaciens bloodstream infections and 6 pyrogenic reactions occurred in outpatients at a hemodialysis center . METHODS: We performed a cohort study of all hemodialysis sessions on days that staff members reported S . liquefaciens bloodstream infections or pyrogenic reactions . We reviewed procedures and cultured samples of water, medications, soaps, and hand lotions and swabs from the hands of personnel . RESULTS: We analyzed 208 sessions involving 48 patients . In 12 sessions, patients had S . liquefaciens bloodstream infections, and in 8, patients had pyrogenic reactions without bloodstream infection . Sessions with infections or reactions were associated with higher median doses of epoetin alfa than the 188 other sessions (6500 vs . 4000 U, P=0.03) and were more common during afternoon or evening shifts than morning shifts (P=0.03) . Sessions with infections or reactions were associated with doses of epoetin alfa of more than 4000 U (multivariate odds ratio, 4.0; 95 percent confidence interval, 1.3 to 12.3) . A review of procedures revealed that preservative-free, single-use vials of epoetin alfa were punctured multiple times, and residual epoetin alfa from multiple vials was pooled and administered to patients . S . liquefaciens was isolated from pooled epoetin alfa, empty vials of epoetin alfa that had been pooled, antibacterial soap, and hand lotion . All the isolates were identical by pulsed-field gel electrophoresis . After the practice of pooling epoetin alfa was discontinued and the contaminated soap and lotion were replaced, no further S . liquefaciens bloodstream infections or pyrogenic reactions occurred at this hemodialysis facility . CONCLUSIONS: Puncturing single-use vials multiple times and pooling preservative-free epoetin alfa caused this outbreak of bloodstream infections in a hemodialysis unit . To prevent similar outbreaks, medical personnel should follow the manufacturer's guidelines for the use of preservative-free medications.

J Appl Microbiol, 2001 May, 90(5), 803 - 8
One-step purification of chitinase from Serratia marcescens NK1, a soil isolate; Nawani NN et al.; AIMS: A simple single step technique of gel filtration was developed for the purification of chitinase from Serratia marcescens NK1 . METHODS AND RESULTS: Chitinase from Ser . marcescens NK1 was purified to homogeneity by gel filtration chromatography with 9.2% recovery . The enzyme had a pH optimum of 6.2 and a temperature optimum of 47 degrees C . It was stable in a wide pH range of 3.0 to 10.0, retaining 60% activity at pH 3.0 and 65% activity at pH 10.5 . It retained 70% activity at 28 degrees C after 72 h and nearly 50% activity at 50 degrees C up to 24 h . CONCLUSION: The chitinase from Ser . marcescens NK1 can be efficiently purified in a single step by gel filtration chromatography . The chitinase of Ser . marcescens NK1, a soil isolate, is highly stable and as active as that of other reported isolates of Ser . marcescens . SIGNIFICANCE AND IMPACT OF THE STUDY: This purification scheme is advantageous because of its simplicity and can therefore be applied for the purification of other enzymes . The yield is sufficient for initial characterization studies of the enzyme, and an improved resolution can be obtained if the chromatography is done under fast flow systems.

Biochim Biophys Acta, 2001 Feb 9, 1545(1-2), 349 - 56
Enzyme activity determination on macromolecular substrates by isothermal titration calorimetry: application to mesophilic and psychrophilic chitinases; Lonhienne T et al.; Isothermal titration calorimetry has been applied to the determination of the kinetic parameters of chitinases (EC 3.2.1.14) by monitoring the heat released during the hydrolysis of chitin glycosidic bonds . Experiments were carried out using two different macromolecular substrates: a soluble polymer of N-acetylglucosamine and the insoluble chitin from crab shells . Different experimental temperatures were used in order to compare the thermodependence of the activity of two chitinases from the psychrophile Arthrobacter sp . TAD20 and of chitinase A from the mesophile Serratia marcescens . The method allowed to determine unequivocally the catalytic rate constant k(cat), the activation energy (E(a)) and the thermodynamic activation parameters (DeltaG(#), DeltaH(#), DeltaS(#)) of the chitinolytic reaction on the soluble substrate . The catalytic activity has also been determined on insoluble chitin, which displays an effect of substrate saturation by chitinases . On both substrates, the thermodependence of the activity of the psychrophilic chitinases was lower than that observed with the mesophilic counterpart.

Biochemistry (Mosc), 2001 Mar, 66(3), 323 - 7
Study of the mechanism of action of p-chloromercuribenzoate on endonuclease from the bacterium Serratia marcescens; Filimonova MN et al.; The mechanism of action of p-chloromercuribenzoate (PCMB) on Serratia marcescens nuclease was investigated . The analysis showed that PCMB forms complexes with DNA . Binding of C7H5O2Hg+ to DNA changes the secondary structure of the DNA . These changes alter the enzymatic activity of S . marcescens nuclease, which was previously found to be sensitive to the secondary structure of the substrates . The nuclease activity was either suppressed or stimulated in the presence of PCMB depending on the C7H5O2Hg+ to nucleotide equivalent ratio . Binding of C7H5O2Hg+ to DNA did not form an abortive enzyme-substrate complex . Binding of Mg2+ to the C7H5O2Hg-DNA complex caused appropriate changes in secondary structure of the substrate . Since Mg2+ and C7H5O2Hg+, though differing in the type of metal cation, are similar in their mechanisms of influence on enzymatic activity of S . marcescens nuclease, the identity of other metal-containing effectors in their mechanism of action on Serratia marcescens nuclease is assumed.

J Econ Entomol, 2001 Apr, 94(2), 362 - 6
Effects of Serratia marcescens on the F1 generation of laboratory-reared Heliothis virescens (Lepidoptera: Noctuidae); Inglis GD et al.; The effects of the bacterium Serratia marcescens (Bizio) was investigated on the F1 generation of laboratory-reared Heliothis virescens (F.) . There was no difference in adult male or female longevity (i.e., parental generation) for individuals inoculated with S . marcescens as larvae (Serratia treatment) and those that were free of the bacterium (control treatment) . However, the number of eggs laid and the prevalence of eclosion of eggs from Serratia treatment adults were reduced relative to control treatment adults . A very low number of F1 Serratia treatment eggs exhibited signs of infection, but a higher prevalence of mortality was observed for F1 larvae (n = 2,888) for the Serratia (3.5-4.6%) than for the control (1.1-1.5%) treatment . No S . marcescens was isolated from dead control larvae; whereas, 48 -54% of dead F1 larvae for the Serratia treatment were positive for the bacterium . However, there was no significant difference in larval weights between treatments . There were also no differences in either mortality or weight of F1 male pupae between treatments, but F1 female pupae were significantly smaller and prevalence of mortality was higher for the Serratia treatment . Serratia marcescens was not isolated from any of the control F1 pupae, but 6% of pupal cadavers for the Serratia treatment were positive for the bacterium . No S . marcescens was recovered from the meconia of any of the F1 adults (n = 2,600) regardless of treatment, and there were no differences in adult weights between treatments . Although sublethal effects of S . marcescens were detected, the impact and prevalence of the bacterium were tremendously reduced over the F1 generation in the absence of all but the most basic management strategies.

Histol Histopathol, 2001 Apr, 16(2), 415 - 21
Prodigiosin induces cell death and morphological changes indicative of apoptosis in gastric cancer cell line HGT-1; Diaz-Ruiz C et al.; Gastric cancer is one of the most frequent malignancies and its treatment is far from satisfactory . The challenge to oncologists is the characterization of novel chemical entities with greater effectiveness . Prodigiosin is a red pigment produced by various bacteria including Serratia marcescens . Here we characterize the apoptotic action of prodigiosin in human gastric carcinoma cell line (HGT-1) . Cells were assayed by the MTT assay, fragmentation pattern of DNA, Hoechst 33342 staining and study of actin microfilament architecture . Treatment of these cells with prodigiosin showed a constant decrease in viability by apoptosis . Morphological analysis of prodigiosin-treated cells demonstrated that prodigiosin induces cell shrinkage, chromatin condensation, reorganization of actin microfilament architecture, and detachment of cells from the cell culture substrate . Altogether these results suggest that prodigiosin induces apoptosis in HGT-1 human gastric cancer cells and raises the possibility of its use as a new chemotherapeutic drug.

J Mol Biol, 2001 Apr 27, 308(2), 311 - 23
Conformational flexibility in T4 endonuclease VII revealed by crystallography: implications for substrate binding and cleavage; Raaijmakers H et al.; The structure of the N62D mutant of the junction-resolving endonuclease VII (EndoVII) from phage T4 has been refined at 1.3 A, and a second wild-type crystal form solved and refined at 2.8 A resolution . Comparison of the mutant with the wild-type protein structure in two different crystal environments reveals considerable conformational flexibility at the dimer level affecting the substrate-binding cleft, the dimerization interface and the orientation of the C-terminal domains . The opening of the DNA-binding cleft, the orientation of the C-terminal domains relative to the central dimerization domain as well as the relative positioning of helices in the dimerization interface appear to be sensitive to the crystal packing environment . The highly unexpected rearrangement within the extended hydrophobic interface does change the contact surface area but keeps the number of hydrophobic contacts about the same and will therefore not require significant energy input . The conformational flexibility most likely is of functional significance for the broad substrate specificity of EndoVII . Binding of sulphate ions in the mutant structure and their positions relative to the active-site metal ions and residues known to be essential for catalysis allows us to propose a possible catalytic mechanism . A comparison with the active-site geometries of other magnesium-dependent nucleases, among them the homing endonuclease I-PpoI and Serratia endonuclease, shows common features, suggesting related catalytic mechanisms .

Microbios, 2001, 104(409), 159 - 66
Microbial contamination of water-soaked cotton gauze and its cause; Oie S et al.; Seven in-use cotton gauze samples and three cotton balls soaked in sterile distilled water in canisters were investigated 7 days after they were prepared in hospital . All samples were contaminated with bacteria including 10(6) to 10(7) colony forming units/ml of Pseudomonas aeruginosa . In vitro viability tests using cotton gauze and cotton balls soaked in sterile distilled water revealed rapid proliferation of P . aeruginosa, Serratia marcescens and Candida albicans . Since the cotton gauze and the cotton balls were soaked in water containing nutrients, such as protein and glucose, these materials may be readily contaminated with bacteria including P . aeruginosa . Thus, when using cotton gauze and cotton balls containing water, microbial contamination should be expected.

Cornea, 2001 Apr, 20(3), 306 - 8
Lomefloxacin is an effective treatment of experimental bacterial keratitis; Kowalski RP et al.; PURPOSE: Lomefloxacin was evaluated as a potential topical therapy for bacterial keratitis . METHODS: Lomefloxacin was compared with ciprofloxacin in different rabbit keratitis models . A total of 216 corneas were infected with Staphylococcus aureus (ciprofloxacin-susceptible and -resistant), Streptococcus viridans, Streptococcus pneumoniae, Pseudomonas aeruginosa, and Serratia marcescens and were treated with lomefloxacin (0.3%), ciprofloxacin (0.3% Ciloxan), and the control phosphate-buffered saline (PBS), respectively . The data were analyzed statistically comparing the decrease in the number of recovered viable bacteria . RESULTS: Compared with PBS-treated control corneas, the colony counts for all bacterial isolates were significantly reduced (p < 0.05) after topical treatment with either lomefloxacin or ciprofloxacin . For gram-positive bacteria, lomefloxacin and ciprofloxacin were equally effective . For gram-negative bacteria, lomefloxacin, while effective, was less so than ciprofloxacin under experimental conditions (p < 0.05) . CONCLUSION: Our data, using multiple bacterial keratitis models, suggest that lomefloxacin is promising for therapy of bacterial keratitis . Further clinical studies are needed to expand its use for keratitis therapy.

Biosci Biotechnol Biochem, 2001 Feb, 65(2), 338 - 47
LysR-type transcriptional regulator ChiR is essential for production of all chitinases and a chitin-binding protein, CBP21, in Serratia marcescens 2170; Suzuki K et al.; To identify the genes required for chitinase production by Serratia marcescens 2170, various Tn5 mutants somehow defective in chitinase production were isolated in a previous study . In order to identify the mutated gene in one of the chitinase-deficient mutants, N1, DNA regions flanking the Tn5 insertion were cloned and sequenced . Sequence comparison showed that the mutation occurred in the ORF located between chiB and cbp, which encode chitinase B and chitin-binding protein CBP21, respectively . The ORF encodes a 313-amino acid polypeptide which has significant similarity with various LysR-type transcriptional regulators, and thus the gene was designated chiR . Targeted mutagenesis confirmed that disruption of the chiR gene results in the phenotype of N1 . Gel mobility shift assays using partially purified ChiR protein demonstrated that this protein specifically binds to the intergenic region between chiR and cbp . These results strongly suggest that ChiR is a LysR-type transcriptional regulator which is essential for production of all chitinases and CBP21.

J Hosp Infect, 2001 Apr, 47(4), 301 - 7
Critical care unit outbreak of Serratia liquefaciens from contaminated pressure monitoring equipment; Harnett SJ et al.; Between October and December 1999, Serratia liquefaciens was isolated from 11 patients in an adult critical care unit . One patient was infected on two separate occasions . In total, there were 10 positive blood cultures and five positive intravascular catheter tips . Eight cases were clinically infected, three were possibly infected and one was not . All patients with clinical isolates received appropriate empirical antibiotic treatment and responded well . Environmental investigation revealed S . liquefaciens in syringes and connector tubing used to calibrate the intravascular line pressure monitoring equipment of eight patients . Three of these patients also had clinical isolates of S . liquefaciens . Analysis by pulsed-field gel electrophoresis found clinical and environmental isolates to be of the same strain . The most likely mode of transmission was a non-sterile sphygmomanometer tip used daily for calibration . Inadequate microbiological sampling methods may have limited detection of S . liquefaciens . Several other examples of poor infection control techniques were identified during the outbreak, notably lapses in hand hygiene during intravascular pressure monitoring . It was also observed that unlabelled multidose heparin and insulin vials were shared between patients and personal hand creams were used by staff . However, these were not directly implicated in the outbreak . The outbreak ended when poor infection control practices were corrected . Calibration syringes and connector tubing were discarded after a single use . The sphygmomanometer was replaced by a pneumatic pressure transducer tester with connector tube and the frequency of calibration reduced to a single test following line insertion only . The non-disposable tube was disinfected with alcohol wipes between patients .

Am J Infect Control, 2001 Apr, 29(2), 115 - 9
Serratia marcescens transmission in a pediatric intensive care unit: a multifactorial occurrence; Manning ML et al.; BACKGROUND: Fourteen patients in the pediatric cardiac intensive care unit (CICU) had > or =1 positive culture for a single strain of Serratia marcescens from April through December 1995 (study period) . OBJECTIVES: To identify risk factors for S marcescens infection or colonization in a pediatric CICU . METHODS: Retrospective case-control study . Assessment of CICU infection control practices and patient exposure to CICU health care workers (HCWs) . Epidemiologic-directed cultures of the environment and HCWs' hands were obtained . SETTING: Pediatric CICU . PATIENTS: Fourteen patients in the pediatric CICU had > or =1 positive culture for a single strain of S marcescens from April through December 1995 (study period) . CICU patients who did not have S marcescens infection or colonization during the study period were randomly selected as controls . RESULTS: A case patient was more likely than a noncase patient to have exposure to a single HCW (odds ratio {OR}, 19.5; 95% CI, 2.6-416; P<.003); however, this association was not adequately explained by epidemiologic or microbiologic studies . Interviews suggested that during the outbreak period, handwashing frequency among HCWs might have been reduced because of severe hand dermatitis . CONCLUSIONS: A combination of factors, including breaks in aseptic technique, reduced frequency of handwashing among HCWs before and between caring for patients, decreased attention to infection control practices, and environmental contamination may have indirectly contributed to this S marcescens infections outbreak.

J Biomed Sci, 2001 Mar-Apr, 8(2), 160 - 9
The role of RsmA in the regulation of swarming motility in Serratia marcescens; Ang S et al.; Swarming motility is a multicellular phenomenon comprising population migration across surfaces by specially differentiated cells . In Serratia marcescens, a network exists in which the flhDC flagellar regulatory master operon, temperature, nutrient status, and quorum sensing all contribute to the regulation of swarming motility . In this study, the rsmA (repressor of secondary metabolites) gene (hereafter rsmA(Sm)) was cloned from S . marcescens . The presence of multicopy, plasmid-encoded rsmA(Sm) expressed from its native promoter in S . marcescens inhibits swarming . Synthesis of N-acylhomoserine lactones, presumably by the product of smaI (a luxI homolog isolated from S . marcescens), was also inhibited . Knockout of rsmA(Sm) on the S . marcescens chromosome shortens the time before swarming motility begins after inoculation to an agar surface . A single copy of the chromosomal PrsmA(Sm)::luxAB reporter of rsmA(Sm) transcription was constructed . Using this reporter, the roles of the flhDC flagellar regulatory master operon, temperature and autoregulation in the control of rsmA(Sm) expression were determined . Our findings indicate that RsmA(Sm) is a component of the complex regulatory network that controls swarming .

Trends Microbiol, 2001 Apr, 9(4), 185 - 91
The tc genes of Photorhabdus: a growing family; Waterfield NR et al.; The toxin complex (tc) genes of Photorhabdus encode insecticidal, high molecular weight Tc toxins . These toxins have been suggested as useful alternatives to those derived from Bacillus thuringiensis for expression in insect-resistant transgenic plants . Although Photorhabdus luminescens is symbiotic with nematodes that kill insects, tc genes have recently been described from other insect-associated bacteria such as Serratia entomophila, an insect pathogen, and Yersinia pestis, the causative agent of bubonic plague, which has a flea vector . Here, recent advances in our understanding of the tc gene family are reviewed in view of their potential development as insect-control agents.

J Biol Chem, 2001 May 18, 276(20), 17507 - 14 Epub 2001 Feb 15.
The crystal structure of a novel mammalian lectin, Ym1, suggests a saccharide binding site; Sun YJ et al.; Ym1, a secretory protein synthesized by activated murine peritoneal macrophages, is a novel mammalian lectin with a binding specificity to GlcN . Lectins are responsible for carbohydrate recognition and for mediating cell-cell and cell-extracellular matrix interactions in microbes, plants, and animals . Glycosaminoglycan heparin/heparan sulfate binding ability was also detected in Ym1 . We report here the three-dimensional structure of Ym1 at 2.5-A resolution by x-ray crystallography . The crystal structure of Ym1 consists of two globular domains, a beta/alpha triose-phosphate isomerase barrel domain and a small alpha + beta folding domain . A notable electron density of sugar is detected in the Ym1 crystal structure . The saccharide is located inside the triose-phosphate isomerase domain at the COOH terminal end of the beta-strands . Both hydrophilic and hydrophobic interactions are noted in the sugar-binding site in Ym1 . Despite the fact that Ym1 is not a chitinase, structurally, Ym1 shares significant homology with chitinase A of Serratia marcescens . Ym1 and chitinase A have a similar carbohydrate binding cleft . This study provides new structure information, which will lead to better understanding of the biological significance of Ym1 and its putative gene members.

J Biotechnol, 2001 May 4, 87(2), 131 - 41
Immobilization of sugar-non-specific nucleases by utilizing the streptavidin--biotin interaction; Gast FU et al.; Due to their high enzymatic activity, the sugar-non-specific endonucleases from Serratia marcescens and Anabaena can be used for a number of applications, such as the removal of contaminating genetic material from biological preparations, footprinting studies, and the determination of nucleic acids in biochemical samples . These methods would benefit from immobilized nucleases . For this purpose, a single cysteine residue was added at the N-terminus of the Serratia and Anabaena nucleases and subsequently modified with a maleimide-biotin conjugate . Alternatively, a biotin acceptor domain was fused to the Anabaena nuclease, allowing biotinylation during expression in E . coli without a further chemical step . The attachment of biotin-modified nucleases to streptavidin-coated paramagnetic beads and to streptavidin-coated surface plasmon resonance sensor chips (to study interactions with substrate and inhibitor) worked well when aggregates present in the protein preparations were removed by ultrafiltration . These methods should be of general use for similar enzyme systems.

J Bacteriol, 2001 Apr, 183(8), 2634 - 45
Endophytic colonization of rice by a diazotrophic strain of Serratia marcescens; Gyaneshwar P et al.; Six closely related N2-fixing bacterial strains were isolated from surface-sterilized roots and stems of four different rice varieties . The strains were identified as Serratia marcescens by 16S rRNA gene analysis . One strain, IRBG500, chosen for further analysis showed acetylene reduction activity (ARA) only when inoculated into media containing low levels of fixed nitrogen (yeast extract) . Diazotrophy of IRBG500 was confirmed by measurement of 15N2 incorporation and by sequence analysis of the PCR-amplified fragment of nifH . To examine its interaction with rice, strain IRBG500 was marked with gusA fused to a constitutive promoter, and the marked strain was inoculated onto rice seedlings under axenic conditions . At 3 days after inoculation, the roots showed blue staining, which was most intense at the points of lateral root emergence and at the root tip . At 6 days, the blue precipitate also appeared in the leaves and stems . More detailed studies using light and transmission electron microscopy combined with immunogold labeling confirmed that IRBG500 was endophytically established within roots, stems, and leaves . Large numbers of bacteria were observed within intercellular spaces, senescing root cortical cells, aerenchyma, and xylem vessels . They were not observed within intact host cells . Inoculation of IRBG500 resulted in a significant increase in root length and root dry weight but not in total N content of rice variety IR72 . The inoculated plants showed ARA, but only when external carbon (e.g., malate, succinate, or sucrose) was added to the rooting medium.

Antimicrob Agents Chemother, 2001 Apr, 45(4), 1151 - 61
Novel carbapenem-hydrolyzing beta-lactamase, KPC-1, from a carbapenem-resistant strain of Klebsiella pneumoniae; Yigit H et al.; A Klebsiella pneumoniae isolate showing moderate to high-level imipenem and meropenem resistance was investigated . The MICs of both drugs were 16 microg/ml . The beta-lactamase activity against imipenem and meropenem was inhibited in the presence of clavulanic acid . The strain was also resistant to extended-spectrum cephalosporins and aztreonam . Isoelectric focusing studies demonstrated three beta-lactamases, with pIs of 7.2 (SHV-29), 6.7 (KPC-1), and 5.4 (TEM-1) . The presence of bla(SHV) and bla(TEM) genes was confirmed by specific PCRs and DNA sequence analysis . Transformation and conjugation studies with Escherichia coli showed that the beta-lactamase with a pI of 6.7, KPC-1 (K . pneumoniae carbapenemase-1), was encoded on an approximately 50-kb nonconjugative plasmid . The gene, bla(KPC-1), was cloned in E . coli and shown to confer resistance to imipenem, meropenem, extended-spectrum cephalosporins, and aztreonam . The amino acid sequence of the novel carbapenem-hydrolyzing beta-lactamase, KPC-1, showed 45% identity to the pI 9.7 carbapenem-hydrolyzing beta-lactamase, Sme-1, from Serratia marcescens S6 . Hydrolysis studies showed that purified KPC-1 hydrolyzed not only carbapenems but also penicillins, cephalosporins, and monobactams . KPC-1 had the highest affinity for meropenem . The kinetic studies also revealed that clavulanic acid and tazobactam inhibited KPC-1 . An examination of the outer membrane proteins of the parent K . pneumoniae strain demonstrated that the strain does not express detectable levels of OmpK35 and OmpK37, although OmpK36 is present . We concluded that carbapenem resistance in K . pneumoniae strain 1534 is mainly due to production of a novel Bush group 2f, class A, carbapenem-hydrolyzing beta-lactamase, KPC-1, although alterations in porin expression may also play a role.

Arthroscopy, 2001 Mar, 17(3), 290 - 297
Arthroscopic surgery for septic arthritis of the hip joint in 4 adults; Yamamoto Y et al.; PURPOSE: Arthroscopic surgery for septic coxarthritis has not become a well-established technique despite its minimally invasive nature . The authors performed arthroscopic surgery and intraoperative high-volume irrigation on 4 adult patients with septic coxarthritis . This minimally invasive procedure was successful in treating these patients, and there was no recurrence of arthritis or other complications . The purpose of this article is to introduce this 3-directional-approach method of arthroscopic surgery for septic coxarthritis . Type of Study: Case study of arthroscopic surgery for septic arthritis of the hip joint in 4 adults . METHODS: There were 3 women and 1 man with an average age of 58 years . The length of time from onset of symptoms to surgery averaged 36 days . One patient had diabetes; another had subarachnoid hemorrhage and was being treated with steroidal drugs . The etiologic agent was found to be Staphylococcus aureus infection in 2 patients, Serratia sp . in 1 patient, and group-B Streptococcus in 1 patient . Three-directional-approach arthroscopic surgery and intraoperative high-volume irrigation were performed using 20 to 25 L of physiologic saline on the 4 patients . Continuous postoperative intra-articular irrigation was not performed . RESULTS: Inflammatory reactions subsided within 4 weeks of surgery in 3 of the 4 patients and within 6 weeks in the other patient . At the time of the final examination, the postoperative follow-up period ranged from 1 to 6 years and none of the patients had ankylosis of the hip joint . CONCLUSIONS: Three-directional-approach arthroscopic surgery in combination with intraoperative large-volume irrigation is an effective technique for treating septic arthritis of the hip joint because the joint can be preserved and it is less invasive than other open arthrotomy techniques.

Epidemiol Mikrobiol Imunol, 2001 Feb, 50(1), 26 - 30
{Effect of subinhibitory levels of aminoglycosides and fluoroquinolines on hydrophobicity and motility of Serratia marcescens}; Majtan V et al.; The authors investigated the effect of subinhibitory quinolone concentrations (ciprofloxacin, enoxacin, norfloxacin, ofloxacin, pefloxacin) and aminoglycosides (amicacin, gentamicin, netilmicin, tobramycin) on the surface hydrophobicity and motility of the clinical isolate of Serratia marcescens . The hydrophobicity was evaluated by methods of adherence to the hydrocarbon xylene (BATH) in a salt-aggregation ammonium sulphate (SAT) test . The tested quinolones in subinhibitory concentrations inhibited the adherence of S . marcescens to xylene with the exception of 1/16 MIC ofloxacin where slight stimulation took place . The most marked inhibition of adherence was observed after the action of 1/4 MIC ciprofloxacin (to 13.2%) and pefloxacin (to 31.0%) as compared with the control . Among aminoglycosides netilmicin markedly inhibited the adherence over the whole range of concentrations, whereby 1/8 MIC suppressed it to 0.7% . With these data correlated also the results of the salt-aggregation test . The investigated antibiotics did not have a major effect on the motility of S . marcescens.

Environ Microbiol, 2000 Oct, 2(5), 542 - 54
Characterization of depth-related population variation in microbial communities of a coastal marine sediment using 16S rDNA-based approaches and quinone profiling; Urakawa H et al.; Depth-related changes in whole-community structure were evaluated in a coastal marine sediment using a molecular fingerprinting method, terminal restriction fragment length polymorphism (T-RFLP) analysis, and a chemotaxonomic technique (quinone profiling) . Dendrograms derived from both T-RFLP analysis and quinone profiling indicated a significant variation in microbial community structure between the 0-2 cm layer and deeper layers . This corresponded to the dramatic change in the redox potential, acid-volatile sulphide-sulphur and bacterial numbers observed at 0-2 cm and 2-4 cm depths . A significant change in the number of terminal restriction fragments (T-RFs) was also detected at this transition depth . However, the change in major T-RFs with depth was not seen in electropherograms . The population changes were primarily variations in minor ribotypes . Most quinone homologues were detected at all depths, although the quinone composition changed with depth . Therefore, quinone profiling also suggested that the depth-related variation was primarily attributable to minor bacterial groups rather than change in the major population structure . 16S rDNA clone library analysis revealed that clones belonging to the genera Vibrio and Serratia predominated as major bacterial groups at all depths . Our data suggested that the sediment community might result from sedimentation effects of sinking particles . Overall, our results demonstrated that the combined methods of T-RFLP analysis and quinone profiling were effective for assessing depth-related microbial populations.

Fresenius J Anal Chem, 2000 Dec, 368(7), 720 - 6
Voltammetric trace analysis of DNA and RNA; Reher S et al.; A voltammetric determination of DNA/RNA is described . The new aspect is the use of the extracellular endonuclease Serratia marcescens in the sample preparation . Using this enzyme it is possible to determine DNA/ RNA with a detection limit of 2-5 pg/mL . This satisfies the requirements of the WHO and the FDA.

CLAO J, 2001 Jan, 27(1), 16 - 22
Disinfection efficacy of contact lens care solutions against ocular pathogens; Miller MJ et al.; PURPOSE: Three commercially available products labeled as multi-purpose contact lens solutions, one multi-purpose disinfecting solution, and a hydrogen peroxide system were evaluated for antimicrobial activity according to the current International Organization for Standardization (ISO) and the U.S . Food and Drug Administration (FDA) stand-alone procedure for disinfecting products . One multi-purpose solution was selected to assess its antimicrobial activity against two human corneal isolates of Pseudomonas aeruginosa . METHODS: Products were challenged with bacteria and fungi, and following a specified period, aliquots of inoculated test solution were neutralized and plated on validated recovery media . After incubation the number of viable microorganisms was enumerated and mean log reductions determined . RESULTS: ReNu MultiPlus (Bausch & Lomb, Rochester, NY), AOSEPT (CIBA Vision Corporation, Duluth, GA), and Opti-Free Express with Aldox (Alcon Laboratories, Ft . Worth, TX) were the only lens care products that met the stand-alone criteria for all required microorganisms within their minimum recommended disinfection time . Of these, ReNu MultiPlus provided the greatest overall antimicrobial activity . ReNu MultiPlus demonstrated a significantly higher mean log reduction of Staphylococcus aureus and Serratia marcescens than Opti-Free Express . ReNu MultiPlus also gave a higher mean log reduction of S . aureus and S . marcescens than AOSEPT, and a higher mean log reduction of Candida albicans and Fusarium solani than AOSEPT, Complete Comfort Plus (Allergan, Irivine, CA), and Solo-Care (CIBA Vision Corp.) (at 4 hours) . Both Complete Comfort Plus and Solo-Care (at 4 hours) met the primary acceptance criteria for bacteria; however, neither product possessed enough antimicrobial activity to meet the minimum criteria for yeast or mold . ReNu Multiplus was effective against corneal isolates of P . aeruginosa . CONCLUSION: ReNu MultiPlus, AOSEPT, and Opti-Free Express met the requirements of the stand-alone primary criteria for disinfecting solutions . ReNu MultiPlus demonstrated the greatest overall disinfection efficacy, as well as excellent activity against clinical strains of P . aeruginosa.

Folia Microbiol (Praha), 2000, 45(1), 45 - 9
Postantibiotic effects of gentamicin and netilmicin on Serratia marcescens: effects on hydrophobicity and motility; Majtanova L et al.; The impact of postantibiotic effect (PAE) of aminoglycosides (gentamicin, netilmicin) on cell-surface hydrophobicity and motility of a clinical isolate Serratia marcescens was evaluated . For the induction of PAE 2x and 4xMIC concentrations of both antibiotics were used . Gentamicin and netilmicin induced a PAE of similar duration after 2xMIC concentration (2.7 and 2.8 h, respectively) . Both aminoglycosides demonstrated concentration-dependent PAE . At a concentration of 4xMIC they produced PAEs of 5.9 and 8.2 h, respectively . The evaluation of hydrophobic properties of S . marcescens after affecting PAE showed that both aminoglycosides inhibited adherence to xylene . This inhibition was also concentration-dependent . More expressive was netilmicin which inhibited the adhesion by 70.5% at 2xMIC and by 85.2% at 4xMIC . Netilmicin inhibited also the adhesion to nitrocellulose filter by 34.7% at 4xMIC . Exposure of the bacterial cells to suprainhibitory concentrations of both aminoglycosides resulted only in moderate inhibition of motility of strain tested compared to the unexposed cells.

Inorg Chem, 2000 Jun 12, 39(12), 2666 - 75
EPR and ligand field studies of iron superoxide dismutases and iron-substituted manganese superoxide dismutases: relationships between electronic structure of the active site and activity; Renault JP et al.; The problem of metal selectivity of iron/manganese superoxide dismutases (SODs) is addressed through the electronic structures of active sites using electron paramagnetic resonance and ligand field calculations . Studies of wild-type iron(III) SOD (FeSOD) from Escherichia coli and from Methanobacterium thermoautotrophicum and iron-substituted manganese(III) SOD (Fe(sub)MnSOD) from E . coli and from Serratia marcescens are reported . EPR spectroscopy of wild-type enzymes shows transitions within all three Kramers doublets identified by their g values . From the temperature dependence of the observed transitions, the zero-field splitting is found to be negative, D = -2 +/- 0.2 cm-1 . The electronic structure is typical of a distorted trigonal bipyramid, all the EPR features being reproduced by ligand field analysis . This unique and necessary electronic structure characterizes wild-type enzymes whatever their classification from the amino acid sequence into iron or manganese types, as E . coli FeSOD or M . thermoautotrophicum FeSOD . In iron-substituted manganese SODs, reduced catalytic activity is found . We describe how inhomogeneity of all reported substituted MnSODs might explain the activity decrease . EPR spectra of substituted enzymes show several overlapping components . From simulation of these spectra, one component is identified which shares the same electronic structure of the wild-type FeSODs, with the proportion depending on pH . Ligand field calculations were performed to investigate distortions of the active site geometry which induce variation of the excitation energy of the lowest quartet state . The corresponding coupling between the ground state and the excited state is found to be maximum in the geometry of the native SODs . We conjecture that such coupling should be considered in the electron-transfer process and in the contribution of the typical electronic structure of FeSOD to the activity.

Ear Nose Throat J, 2000 Dec, 79(12), 952 - 7
Need for tracheotomy is rare in patients with acute supraglottitis: findings of a retrospective study; Rizk SS et al.; We retrospectively reviewed the cases of 23 adults and six children who had been given a presumed diagnosis of acute supraglottitis between 1987 and 1997 . The most common symptoms in these patients were odynophagia, dysphagia, hoarseness, and fever . Stridor and drooling were also observed, primarily in the children . Fiberoptic laryngoscopy confirmed the presence of edema and erythema of the supraglottic structures in all patients . Blood cultures were positive for Hemophilus influenzae type b in three children and for Serratia marcescens in one adult . All other blood cultures were negative . All patients were treated with intravenous broad-spectrum antibiotics and humidified oxygen, and two-thirds received intravenous corticosteroids . Patients were monitored with pulse oximetry and serial fiberoptic laryngoscopy . Two patients required intubation; one had an epiglottic abscess, and the other had laryngeal edema so severe that vocal fold mobility could not be assessed . The length of stay in the intensive care unit ranged from 1 to 7 days (mean: 1.9) . All patients recovered and were discharged free of symptoms after 2 to 11 days of overall hospitalization (mean: 4.4).

J Hosp Infect, 2000 Dec, 46(4), 314 - 9
An outbreak of Serratia marcescens in two neonatal intensive care units; Jones BL et al.; Outbreaks of infection in neonatal intensive care units (NICUs) due to Serratia marcescens are well recognized . In some outbreaks no point source has been found, whereas in others cross-infection has been associated with contaminated ventilator equipment, disinfectants, hands and breast pumps . We report an outbreak due to S . marcescens that involved two geographically distinct NICUs . The outbreak occurred over a six week period; 17 babies were colonized, 12 at Glasgow Royal Maternity Hospital (GRMH) and five at the Queen Mothers Hospital (QMH) . At GRMH three babies developed septicaemia, of whom two died . The outbreak isolates were of the same serotype and phage type and were indistinguishable on the basis of restriction fragment length polymorphism analysis . During the outbreak, two babies shown consistently to be negative on screening, were transferred between the two units . In addition, two members of medical staff attended both units . In QMH no means of cross infection was identified . However, in GRMH the outbreak strain of S . marcescens was isolated from a laryngoscope blade and a sample of expressed breast milk .

J Bacteriol, 2001 Mar, 183(5), 1805 - 9
N-acyl-L-homoserine lactone-mediated regulation of the lip secretion system in Serratia liquefaciens MG1; Riedel K et al.; The analysis of Serratia liquefaciens MG1 'luxAB insertion mutants that are responsive to N-butanoyl-L-homoserine lactone revealed that expression of lipB is controlled by the swr quorum-sensing system . LipB is part of the Lip exporter, a type I secretion system, which is responsible for the secretion of extracellular lipase, metalloprotease, and S-layer protein.

J Bacteriol, 2001 Mar, 183(5), 1773 - 9
Cloning, sequences, and characterization of two chitinase genes from the Antarctic Arthrobacter sp . strain TAD20: isolation and partial characterization of the enzymes; Lonhienne T et al.; Arthrobacter sp . strain TAD20, a chitinolytic gram-positive organism, was isolated from the sea bottom along the Antarctic ice shell . Arthrobacter sp . strain TAD20 secretes two major chitinases, ChiA and ChiB (ArChiA and ArChiB), in response to chitin induction . A single chromosomal DNA fragment containing the genes coding for both chitinases was cloned in Escherichia coli . DNA sequencing analysis of this fragment revealed two contiguous open reading frames coding for the precursors of ArChiA (881 amino acids {aa}) and ArChiB (578 aa) . ArChiA and ArChiB are modular enzymes consisting of a glycosyl-hydrolase family 18 catalytic domain as well as two and one chitin-binding domains, respectively . The catalytic domain of ArChiA exhibits 55% identity with a chitodextrinase from Vibrio furnissii . The ArChiB catalytic domain exhibits 33% identity with chitinase A of Bacillus circulans . The ArChiA chitin-binding domains are homologous to the chitin-binding domain of ArChiB . ArChiA and ArChiB were purified to homogeneity from the native Arthrobacter strain and partially characterized . Thermal unfolding of ArChiA, ArChiB, and chitinase A of Serratia marcescens was studied using differential scanning calorimetry . ArChiA and ArChiB, compared to their mesophilic counterpart, exhibited increased heat lability, similar to other cold-adapted enzymes.

Microbiology, 2001 Feb, 147(Pt 2), 315 - 23
Properties of the major non-specific endonuclease from the strict anaerobe Fibrobacter succinogenes and evidence for disulfide bond formation in vivo; MacLellan SR et al.; DNase A is a non-specific endonuclease of Fibrobacter succinogenes . The enzyme was purified to homogeneity and its properties studied both in vitro and in vivo . Magnesium but not calcium was essential for nucleolytic activity . Manganese ions substituted for magnesium but were less stimulatory . DNase A activity was markedly inhibited by either NaCl or KCl at concentrations greater than 75 mM . The enzyme had a temperature optimum of 25 degrees C and a pH optimum of about 7.0 . Values for K:(m) and K:(cat) were determined to be 61 microM and 330 s(-1) respectively, with a catalytic efficiency approximately threefold greater than bovine pancreatic DNase I, but 10-fold less than the Serratia marcescens NucA . DNase A was localized to the periplasm and probably exists as a monomeric species . The enzyme possessed one or more disulfide bonds . In the reduced form it had an apparent mass of 33 kDa, while in the oxidized form it was 29 kDa as estimated by SDS-PAGE . Reduction of the disulfide bonds by dithiothreitol with or without subsequent alkylation by iodoacetamide strongly inactivated the enzyme . DNase A accumulated in vivo had an apparent mass of 29 kDa, indicating that it was in an oxidized form . This is the first indication in a strict anaerobe of a functional periplasmic disulfide bond forming system, phenotypically similar to Dsb systems in facultative and aerobic bacteria.

Med Microbiol Immunol (Berl), 1999 Nov, 188(2), 55 - 64
Study of the protective effects of hyperimmune immunoglobulins G and M against endotoxin in mice and rats; Nys M et al.; We prepared solutions of human IgM and IgG to various lipopolysaccharide (LPS) species . These were then tested, along with solutions of non-LPS specific human IgG or IgM, for their ability to confer passive immunity against experimental endotoxemia in two animal models . The immunoglobulins were first tested for an effect on the lethality induced by seven different LPSs in actinomycin-D sensitized mice, or by three different bacteria in normal mice . When the immunoglobulins were administered 1 h before challenge, a small protective effect was observed . This protection was dependent upon both the anti-LPS agent, the chemical composition of the LPS, or the strain of gram-negative bacteria used for injection . The anti-LPS IgM and IgG preparations reduced the mortality induced by Escherichia coli but not by Serratia marcescens or Klebsiella pneumoniae, indicating protection by strain-specific antibodies . When the antibodies were preincubated with LPS or bacteria for 30 min before administration, almost complete protection was seen . The influence of these immunoglobulin preparations or of human albumin (as a control) on the hypotensive and vascular-permeabilizing effects of LPS in rats was then studied . A dose-dependent inhibitory effect was observed with IgG preparations and albumin . At 200 mg/kg, anti-LPS IgG reduced the effects of LPS, while at 400 mg/kg, both anti-LPS and normal IgG preparations showed protection, as did human albumin used at the same dose . The IgM-enriched preparation worsened the initial hypotensive phase after LPS, whereas the anti-LPS IgM significantly reduced the second phase of the hypotension, but only at the largest dose of 400 mg/kg . In this second model using the rat, a clear difference between the activity of IgG and IgM was thus observed . We conclude that pretreatment with human immunoglobulins from large plasma pools modestly, but significantly, attenuated the effects of murine and rat Gram-negative sepsis, but that protection was incomplete . Our results suggest that single regimen intervention strategies may not be sufficient to influence the course of the disease.

Cutis, 2000 Dec, 66(6), 461 - 3
Cutaneous infection caused by Serratia marcescens; Marzano AV et al.; An 86-year-old woman presented with a chronic granulomatous skin lesion on the dorsal aspect of her left hand . Histologic examination showed pseudoepitheliomatous hyperplasia and a dense dermal infiltrate largely composed of lymphocytes and histiocytes . Abscess formation and fibroblastic proliferation were also present . Use of Fite, Giemsa, and periodic acid-Schiff stains did not show specific organisms . The gram-negative bacillus Serratia marcescens was the only microorganism isolated from all cultures performed . Trimethoprim-sulfamethoxazole, 960 mg every 12 hours for 20 days (orally), was given and resulted in complete disappearance of the lesion and negative culture findings . Cutaneous infection by S marcescens may represent a distinctive entity, whose clinical and possible pathogenic features are presented here.

Prikl Biokhim Mikrobiol, 2000 Nov-Dec, 36(6), 694 - 700
{Increase in the ecological danger upon the use of biocides for fighting corrosion induced by microorganisms}; Zhigletsova SK et al.; Five synergistic combinations of biocides were found, among which the combination of kathon + copper sulfate was the most efficient against Serratia marcescens . Depending on the ratio of these biocides, the synergistic effect of this pair allowed 4-20-fold decreases in the effective concentrations . Combinations of biocides with salts (carbonates and phosphates) that facilitate passivation of steel were found, which considerably decreased the corrosion losses of mild steel in comparison to isolated treatment with biocides or salts . The data showed that biocides must be added to corrosion-prone systems simultaneously with the beginning of their exploitation . Otherwise, considerably excessive amounts of biocides or their synergistic compositions are needed.

Int Microbiol, 2000 Mar, 3(1), 39 - 43
Rapid extracellular acidification induced by glucose metabolism in non-proliferating cells of Serratia marcescens; Sole M et al.; The addition of glucose or other sugars to resting cells of Serratia maurcescens induced rapid acidification of the extracellular medium . This acidification was due to the catabolism of sugars . The rate of acidification depended on the carbon source and its concentration . HPLC analysis of the supernatants demonstrated that the progressive fall in pH resulted from the rapid production of lactic, acetic, pyruvic and citric acids . Other microorganisms were tested for their ability to produce this rapid acidification of the medium . This study may provide a rapid and simple method for metabolism studies.

Turk J Pediatr, 2000 Jul-Sep, 42(3), 219 - 22
Serratia marcescens: an emerging microorganism in the neonatal intensive care unit; Aygun C et al.; As smaller babies survive in neonatal intensive care units, late-onset septicemia with unusual pathogens appears . Between 1 January and 31 December 1998, in Hacettepe University Ihsan Dogramaci Children's Hospital Neonatal Intensive Care Unit, seven infants had S . marcescens isolates . Four babies had septicemia with the microorganism . The case fatality rate was 50 percent in infants with S . marcescens septicemia . The combination of ceftazidime or imipenem with amikacin appears appropriate for the treatment of newborns with Serratia infection.

J Biol Chem, 2001 Mar 2, 276(9), 6468 - 72 Epub 2000 Dec 01.
Intracellular Ca(2+) mobilization and kinase activity during acylated homoserine lactone-dependent quorum sensing in Serratia liquefaciens; Werthen M et al.; Quorum sensing in Gram-negative bacteria involves acylated homoserine lactones (AHLs) and a transcription factor, activated by the AHLs . In this study, a possible involvement of intracellular Ca(2+) as second messenger and/or protein kinase activity during signal transduction is analyzed . When N-hexanoyl-l-homoserine lactone was added to a suspension of Fura-2-loaded Serratia liquefaciens, there was a decline in {Ca(2+)}(i), measured as a decrease in the Fura-2 fluorescence ratio . As controls, the addition of the signal molecule N-3-oxohexanoyl-l-homoserine lactone, which is not produced by S . liquefaciens, did not induce changes in {Ca(2+)}(i) . Using a protein kinase activity assay on AHL-stimulated cells, an increase in kinase activity after N-butanoyl-l-homoserine lactone stimulation of S . liquefaciens cells was detected, whereas the kinase activity induced by N-3-oxohexanoyl-l-homoserine lactone was not statistically significant . The conclusion from this study is that changes in {Ca(2+)}(i) are involved in quorum sensing signal transduction in the Gram-negative bacteria S . liquefaciens . We also conclude that kinase activity is induced in S . liquefaciens upon AHL stimulation . We suggest that the transient intracellular {Ca(2+)} changes and kinase activity, activated by the AHL signal, are critical for the quorum-sensing signal transduction.

Microbiology, 2000 Dec, 146 Pt 12, 3237 - 44
How Delisea pulchra furanones affect quorum sensing and swarming motility in Serratia liquefaciens MG1; Rasmussen TB et al.; Halogenated furanones produced by the benthic marine macroalga Delisea pulchra inhibit swarming motility of Serratia liquefaciens MG1 . This study demonstrates that exogenously added furanones control transcription of the quorum sensing regulated gene swrA in competition with the cognate signal molecule N:-butanoyl-L-homoserine lactone . This in turn results in reduced production of the surface-active compound serrawettin W2, which is crucial for surface translocation of the differentiated swarm cells . It is demonstrated that furanones interfere with interspecies communication during swarming of mixed cultures and that the mode of interference in quorum-sensing control and interspecies communication is not through inhibition of autoinducer synthesis.

Int J Med Microbiol, 2000 Oct, 290(6), 529 - 38
ShlB mutants of Serratia marcescens allow uncoupling of activation and secretion of the ShlA hemolysin; Yang FL et al.; The ShlB protein in the outer membrane of Serratia marcescens secretes hemolytic ShlA protein into the culture medium . In the absence of ShlB, nonhemolytic ShlA remains in the periplasm . ShlB mutants were isolated in which secretion was uncoupled from activation . Mutants with a tetrapeptide insertion after residues 136 or 224 of mature ShlB and a mutant with an insertion after residue 154 and a deletion secreted inactive ShlA . In vitro, secreted nonhemolytic ShlA was converted into hemolytic ShlA by isolated wild-type ShlB and by complementation with an N-terminal ShlA fragment of 255 residues (ShlA-255) . The isolation of secretion-competent, but activation-negative mutants indicates that secretion alone is not sufficient for activation of ShlA . Rather, ShlB is required for activation and secretion, and the mutants define sites in ShlB which are involved in activation . According to a predicted transmembrane model of ShlB, the mutations that retain secretion competence but abolish activation competence are located in the most prominent surface loop and the following transmembrane loop . In one tetrapeptide insertion mutant, ShlB-332, most of the ShlA remained cell-associated in an inactive form and low amounts (6%) were hemolytic . Secreted inactive ShlA(o) was completely degraded by trypsin, in contrast to hemolytic ShlA, which was cleaved into two fragments of 60 and 100 kDa . This result indicates that the conformational change from a highly trypsin-sensitive to a highly trypsin-resistant protein with only a single cleavage site in a polypeptide of 1,578 residues occurs upon activation of ShlA and not during secretion.

Transfusion, 2000 Nov, 40(11), 1308 - 12
Growth of bacteria in inoculated platelets: implications for bacteria detection and the extension of platelet storage; Brecher ME et al.; BACKGROUND: Recent reports from Europe have advocated the use of bacterial culturing of platelets on Day 2 or 3 of storage to extend the shelf life of platelets to 7 days, thereby reducing the outdating of platelets and preserving a limited medical resource . To assess the optimal timing, the necessary sensitivity, and the possible efficacy of bacterial detection, the bacterial growth characteristics were reviewed in 165 platelet units, each inoculated on the day of collection with one of the following organisms: Bacillus cereus, Pseudomonas aeruginosa, Klebsiella pneumoniae, Serratia marcescens, Staphylococcus aureus, and Staphylococcus epidermidis from four previously published studies . STUDY DESIGN AND METHODS: Quantitative culture data from inoculated platelet concentrates from five sites and four studies were combined into one database and analyzed for bacterial concentration thresholds (> or =10(1), > or =10(2), > or =10(3), > or =10(4), > or =10(5) CFU/mL) by day of storage . RESULTS: All examples of B . cereus, P . aeruginosa, K . pneumoniae, S . marcescens, and S . aureus had concentrations > or =10(2) CFU per mL by Day 3 after inoculation . By Day 4, all units with these organisms contained > or =10(5) CFU per mL . Units contaminated with S . epidermidis showed slower and more varied growth . By Day 3 after inoculation, 81.3 percent had 10(2) CFU per mL . By Day 4 after inoculation, 46 (95.8%) of 48 units had concentrations > or =10(2) CFU per mL . CONCLUSION: These experiments suggest that an assay capable of detecting 10(2) CFU per mL on Day 3 of storage would detect the vast majority of bacterially contaminated platelet units, prevent many cases of platelet-associated bacterial sepsis, and provide a scientific basis for the extension of the current platelet storage time . It would be expected that a rare, slow-growing organism could escape such a detection scheme.

Carbohydr Res, 2000 Oct 20, 329(1), 227 - 32
Structure of the acidic microcapsular glycan from the reference strain (C.D.C . 6320-58) for Serratia marcescens serotype O14:K12; Eserstam R et al.; The acidic polysaccharide from Serratia marcescens serogroup O14:K12 was analyzed by means of chemical studies and NMR spectroscopy and its repeating unit structure found to be carbohydrate sequence {see text} O-Acetyl groups are proposed to be present in non-stoichiometric amounts on O-6 on one of the hexose residues in the main chain.

Emerg Infect Dis, 2000 Nov-Dec, 6(6), 572 - 5
Trends in antimicrobial-drug resistance in Japan; Arakawa Y et al.; Multidrug resistance in gram-positive bacteria has become common worldwide . In Japan until recently, gram-negative bacteria such as Pseudomonas aeruginosa, Klebsiella pneumoniae, and Serratia marcescens were controlled by carbapenems, fluoroquinolones, and aminoglycosides . However, several of these microorganisms have recently developed resistance against many antimicrobial drugs.

J Biomed Sci, 2000 Nov-Dec, 7(6), 475 - 83
Role of flhDC in the expression of the nuclease gene nucA, cell division and flagellar synthesis in Serratia marcescens; Liu JH et al.; We investigated in Serratia marcescens the functions of the flhDC operon, which controls motility and cell division in enteric bacteria . Included in our evaluations were investigation of cell division, flagellar synthesis and regulation of the expression of nuclease (encoded by the nucA(Sm) gene, one of the virulence factors) . Interruption of the chromosomal flhDC operon in S . marcescens CH-1 resulted in aberrant cell division and loss of nuclease and flagella . Expression of nucA(Sm) and other mutated phenotypes was restored in the flhDC mutant by the induction of overexpression of flhDC in a multicopy plasmid . Multicopied flhDC also induced the formation of differentiated cells (polyploid aseptate cells with oversynthesis of peritrichous flagella) in broth culture using minimal growth medium . Expression of the flhDC operon showed positive autoregulation, and was growth phase dependent (upregulated in early log phase) . In addition, flhDC expression was inhibited when the temperature increased from 30 to 37 degrees C, and when osmolarity was increased, but was not influenced by glucose catabolite repression . These results show that FlhD/FlhC is a multifunctional transcriptional activator involved in the process of cell differentiation, swarming and virulence factor expression .

Epidemiol Infect, 2000 Aug, 125(1), 63 - 70
Interpretation of band differences to distinguish strains of Serratia marcescens by pulsed-field gel electrophoresis of XbaI DNA digests; Aucken HM et al.; The number of band differences in DNA macrorestriction profiles required to distinguish unrelated strains from an index strain varies in an outbreak with the species and restriction enzyme used . In order to define this difference for epidemiological studies of Serratia marcescens, we produced DNA fingerprints from 57 isolates of the organism using the restriction enzyme XbaI and pulsed-field gel electrophoresis (PFGE) . The isolates were selected on the basis of their epidemiology, serotype and phage-typing patterns to include 28 unrelated strains and 29 representatives from 2 distinct outbreaks . One of the outbreaks was prolonged . lasting for several years . Electrophoretic profiles consisting of 20 or more clearly resolved bands were obtained for all isolates . Twenty-six of the unrelated strains had unique profiles with over 10 band differences from all other strains, while 27 of the outbreak representatives could be assigned to the appropriate outbreak with confidence . The majority of the outbreak isolates had none or 2 band differences from the index profile, although 3 isolates differed by 5-7 bands . The 2 exceptions among the unrelated strains differed by 4 bands, and 3 phage typing reactions, and were isolated from London and Berlin 3 years apart, while the 2 exceptions among the outbreak collection had clearly unique profiles with over 20 band differences from each other and the outbreak profiles . Cluster analysis using Dice coefficient and UPGMA gave cut-off values of 75-78% similarity overall for related isolates, while the closest similarity for unrelated strains was 70% . The results of this study together with those of the 6 previous reports of PFGE for S . marcescens (which used either enzymes XbaI or SpeI) confirm that this technique is of value for this species and that with XbaI at least, most epidemiologically related strains will only differ by 3-4 bands . However, on occasion up to 7 band differences can be found within an apparent outbreak, which may be suggestive of genetic drift.

Acta Microbiol Immunol Hung, 2000, 47(4), 433 - 43
The value of pyrolysis mass spectrometry to investigate nosocomial outbreaks caused by Serratia marcescens; Nagy E et al.; Simultaneous outbreaks of S . marcescens infection going on in the Neonatal Intensive Care Unit and the Surgical Department of the same hospital were investigated by pyrolysis mass spectrometry (PyMS) . The PyMS analysis of the strains clearly demonstrated that the two outbreaks were caused by different strains . The 14 S . marcescens isolates from the first outbreak were closely related, with the exception of one environmental isolate, which did not harbour the ESBL plasmid, which was present in all other isolates . However, the phage type of all 14 isolates was the same . Among the 9 S . marcescens isolates from the second outbreak, PyMS clearly distinguished 3 that exhibited gentamicin resistance from the remaining 6 gentamicin-susceptible isolates . Phage typing was unhelpful in this case, as none of the isolates were typable . The PyMS typing of nosocomial outbreak strains can reach the level of discrimination approaching that achieved by molecular genetic analysis.

Tuber Lung Dis, 2000, 80(4-5), 217 - 28
Influence of relative humidity on particle size and UV sensitivity of Serratia marcescens and Mycobacterium bovis BCG aerosols; Ko G et al.; SETTING: A study of Serratia marcescens and BCG aerosols . OBJECTIVE: To evaluate the effect of relative humidity (RH) on (1) the particle size and (2) sensitivity of 254nm germicidal ultraviolet (UV) irradiation . METHODS: We built a RH controlled experimental chamber into which bacteria were aerosolized, exposed to varying amounts of UV irradiance over measured time periods, and quantitatively evaluated for viability . Aerosolized Serratia marcescens and bacille Calmette-Guerin (BCG) were subject to UV doses ranging from 57-829 microW . sec/cm(2), and sampled with a six-stage Andersen culture plate impactor at RHs ranging from 25-95% . RESULTS: Percent survival for both organisms was inversely related to UV dose . Serratia marcescens was more susceptible to UV than BCG under all conditions . More than 95% of the bacterial aerosol particles were 1.1-4.7 microm in aerodynamic diameter, and particles sizes increased from low (25-36%) to high (85-95%) RH . The count median diameter ranged from 1.9-2.6 microm for Serratia marcescens and from 2.2-2.7 microm for BCG as RH increased . For both Serratia marcescens and BCG, resistance to UV increased as RH increased . The UV resistance of both Serratia marcescens and BCG aerosols dramatically increased at RH higher than 85% . CONCLUSIONS: Our results indicate that differences in UV dose, kinds of microorganisms, airborne particle size and RH affect UV susceptibility . 2000 Harcourt Publishers Ltd.

FEMS Microbiol Ecol, 2000 Oct 1, 34(1), 63 - 71
Use of a chiA probe for detection of chitinase genes in bacteria from the Chesapeake Bay(1); Ramaiah N et al.; PCR primers specific for the chiA gene were designed by alignment and selection of highly conserved regions of chiA sequences from Serratia marcescens, Alteromonas sp., Bacillus circulans and Aeromonas caviae . These primers were used to amplify a 225 bp fragment of the chiA gene from Vibrio harveyi to produce a chiA gene probe . The chiA PCR primers and probe were used to detect the presence of the chiA gene in an assemblage of 53 reference strains and gave consistent results . Selected chiA fragments amplified by PCR were cloned and sequenced from nine known strains and from Chesapeake Bay isolates 6d and 11d . This confirmed the specificity and utility of the primers for detection of chiA-positive environmental strains . Over 1000 bacterial isolates from Chesapeake Bay water samples were tested for the presence of the chiA gene which was found to be present in 5-41% (average 21%) of the culturable bacterial community . The approach developed in this study was valuable for isolation and enumeration of chiA-positive bacteria in environmental samples.

Int J Med Microbiol, 2000 Mar, 290(1), 51 - 60
Molecular characterization of a novel siderophore-independent iron transport system in Yersinia; Saken E et al.; Enteropathogenic Yersinia enterocolitica can be divided into mouse lethal (biogroup 1 B serotypes O:8, O:13, O:20 and O:21) and mouse non-lethal (biogroups 2-4 serotypes O:3, O:5,27, O:9) strains . Mouse-lethality is associated with the presence of the high-pathogenicity island encoding the TonB-dependent ferric-yersiniabactin uptake system . The present study reports on a TonB-independent and non-siderophore yersiniae ferric uptake system, yfu . Genetic and functional characterization of the yfu determinant revealed high relationship to the periplasmic-binding-protein-dependent Serratia marcescens ferric uptake system sfu . The yfu locus is common to all Yersinia species pathogenic for humans . Gene targeting of the yfu locus has demonstrated its importance for ferric iron acquisition in vitro . However, yfu is not required for mouse virulence of Y . enterocolitica serotype O:8.

Biomol Eng, 2000 Oct, 17(1), 11 - 6
A broad-host-range expression vector series including a Ptac test plasmid and its application in the expression of the dod gene of Serratia marcescens (coding for ribulose-5-phosphate 3-epimerase) in Pseudomonas stutzeri; Graupner S et al.; A series of expression vectors for gram-negative bacteria was constructed which combine broad-host-range, inducible expression from the tac promoter and diverse antibiotic resistance determinants . The tac promoter activity and the repression by lacIq can be quantitated with a separate test plasmid in the strain to be studied . The dod gene of Serratia marcescens was expressed in Pseudomonas stutzeri and was shown to code for D-ribulose-5-phosphate 3-epimerase.

Antimicrob Agents Chemother, 2000 Nov, 44(11), 3061 - 8
A novel class A extended-spectrum beta-lactamase (BES-1) in Serratia marcescens isolated in Brazil; Bonnet R et al.; Serratia marcescens Rio-5, one of 18 extended-spectrum beta-lactamase (ESBL)-producing strains isolated in several hospitals in Rio de Janeiro (Brazil) in 1996 and 1997, exhibited a high level of resistance to aztreonam (MIC, 512 microgram/ml) and a distinctly higher level of resistance to cefotaxime (MIC, 64 microgram/ml) than to ceftazidime (MIC, 8 microgram/ml) . The strain produced a plasmid-encoded ESBL with a pI of 7.5 whose bla gene was not related to those of other plasmid-mediated Ambler class A ESBLs . Cloning and sequencing revealed a bla gene encoding a novel class A beta-lactamase in functional group 2be, designated BES-1 (Brazil extended-spectrum beta-lactamase) . This enzyme had 51% identity with chromosomal class A penicillinase of Yersinia enterocolitica Y56, which was the most closely related enzyme and 47 to 48% identity with CTX-M-type beta-lactamases, which were the most closely related ESBLs . In common with CTX-M enzymes, BES-1 exhibited high cefotaxime-hydrolyzing activity (k(cat), 425 s(-1)) . However, BES-1 differed from CTX-M enzymes by its significant ceftazidime-hydrolyzing activity (k(cat), 25 s(-1)), high affinity for aztreonam (K(i), 1 microM), and lower susceptibility to tazobactam (50% inhibitory concentration {IC(50)}, 0.820 microM) than to clavulanate (IC(50), 0.045 microM) . Likewise, certain characteristic structural features of CTX-M enzymes, such as Phe-160, Ser-237, and Arg-276, were observed for BES-1, which, in addition, harbored different residues (Ala-104, Ser-171, Arg-220, Gly-240) and six additional residues at the end of the sequence . BES-1, therefore, may be an interesting model for further investigations of the structure-function relationships of class A ESBLs.

Antimicrob Agents Chemother, 2000 Nov, 44(11), 3035 - 9
SME-type carbapenem-hydrolyzing class A beta-lactamases from geographically diverse Serratia marcescens strains; Queenan AM et al.; Three sets of carbapenem-resistant Serratia marcescens isolates have been identified in the United States: 1 isolate in Minnesota in 1985 (before approval of carbapenems for clinical use), 5 isolates in Los Angeles (University of California at Los Angeles {UCLA}) in 1992, and 19 isolates in Boston from 1994 to 1999 . All isolates tested produced two beta-lactamases, an AmpC-type enzyme with pI values of 8.6 to 9.0 and one with a pI value of approximately 9.5 . The enzyme with the higher pI in each strain hydrolyzed carbapenems and was not inhibited by EDTA, similar to the chromosomal class A SME-1 beta-lactamase isolated from the 1982 London strain S . marcescens S6 . The genes encoding the carbapenem-hydrolyzing enzymes were cloned in Escherichia coli and sequenced . The enzyme from the Minnesota isolate had an amino acid sequence identical to that of SME-1 . The isolates from Boston and UCLA produced SME-2, an enzyme with a single amino acid change relative to SME-1, a substitution from valine to glutamine at position 207 . Purified SME enzymes from the U . S . isolates had beta-lactam hydrolysis profiles similar to that of the London SME-1 enzyme . Pulsed-field gel electrophoresis analysis revealed that the isolates showed some similarity but differed by at least three genetic events . In conclusion, a family of rare class A carbapenem-hydrolyzing beta-lactamases first described in London has now been identified in S . marcescens isolates across the United States.

Diagn Microbiol Infect Dis, 2000 Sep, 38(1), 59 - 67
Ability of laboratories to detect emerging antimicrobial resistance in nosocomial pathogens: a survey of project ICARE laboratories; Steward CD et al.; A proficiency testing project was conducted among 48 microbiology laboratories participating in Project ICARE (Intensive Care Antimicrobial Resistance Epidemiology) . All laboratories correctly identified the Staphylococcus aureus challenge strain as oxacillin- resistant and an Enterococcus faecium strain as vancomycin-resistant . Thirty-one (97%) of 32 laboratories correctly reported the Streptococcus pneumoniae strain as erythromycin-resistant . All laboratories testing the Pseudomonas aeruginosa strain against ciprofloxacin or ofloxacin correctly reported the organism as resistant . Of 40 laboratories, 30 (75%) correctly reported resistant MICs or zone sizes for the imipenem- and meropenem-resistant Serratia marcescens . For the extended-spectrum beta-lactamase (ESBL)-producing strain of Klebsiella pneumoniae, 18 (42%) of 43 laboratories testing ceftazidime correctly reported ceftazidime MICs in the resistant range . These results suggest that current testing generally produces accurate results, although some laboratories have difficulty detecting resistance to carbapenems and extended-spectrum cephalosporins . This highlights the need for monitoring how well susceptibility test systems in clinical laboratories detect emerging resistance.

Br J Pharmacol, 2000 Oct, 131(3), 585 - 93
Prodigiosin from the supernatant of Serratia marcescens induces apoptosis in haematopoietic cancer cell lines; Montaner B et al.; The effects of supernatant from the bacterial strain Serratia marcescens 2170 (CS-2170) on the viability of different haematopoietic cancer cell lines (Jurkat, NSO, HL-60 and Ramos) and nonmalignant cells (NIH-3T3 and MDCK) was studied . We examined whether this cytotoxic effect was due to apoptosis, and we purified the molecule responsible for this effect and determined its chemical structure . Using an MTT assay we showed a rapid (4 h) decrease in the number of viable cells . This cytotoxic effect was due to apoptosis, according to the fragmentation pattern of DNA, Hoechst 33342 staining and FACS analysis of the phosphatidylserine externalization . This apoptosis was blocked by using the caspase inhibitor Z-VAD.fmk, indicating the involvement of caspases . Prodigiosin is a red pigment produced by various bacteria including S . marcescens . Using mutants of S . marcescens (OF, WF and 933) that do not synthesize prodigiosin, we further showed that prodigiosin is involved in this apoptosis . This evidence was corroborated by spectroscopic analysis of prodigiosin isolated from S . marcescens . These results indicate that prodigiosin, an immunosuppressor, induces apoptosis in haematopoietic cancer cells with no marked toxicity in nonmalignant cells, raising the possibility of its therapeutic use as an antineoplastic drug.

J Biochem (Tokyo), 2000 Oct, 128(4), 673 - 8
Substrate recognition mechanism of prolyl aminopeptidase from Serratia marcescens; Ito K et al.; Molecular cloning of the gene and the crystal structure of the prolyl aminopeptidase {EC 3.4.11.5} from Serratia marcescens have been studied by us {J . Biochem . 122, 601-605 (1997); ibid . 126, 559-565 (1999)} . Through these studies, Phe139, Tyr149, Glu204, and Arg136 were estimated to be concerned with substrate recognition . To elucidate the details of the mechanism for the substrate specificity, the site-directed mutagenesis method was applied . The F139A mutant showed an 80-fold decrease in catalytic efficiency (k(cat)/K(m)), but the Y149A mutant did not show a significant change in catalytic efficiency . The catalytic efficiency of the E204Q mutant was about 4% of that of the wild type . The peptidase activity of the mutant (R136A) was markedly decreased, however, arylamidase activity with Pyr-bNA was retained as in the wild-enzyme . From these results, it was clarified that the pyrrolidine ring and the amino group of proline at the S1 site were recognized by Phe139 and Glu204, respectively . P1' of a substrate was recognized by Arg136 . On the other hand, the enzyme had two cysteine residues . Mutants C74A and C271A were inhibited by PCMB, but the double mutated enzyme (C74/271A) was resistant to it.

Appl Environ Microbiol, 2000 Oct, 66(10), 4193 - 9
Seasonal population dynamics and interactions of competing bacteriophages and their host in the rhizosphere; Ashelford KE et al.; We describe two prolonged bacteriophage blooms within sugar beet rhizospheres ensuing from an artificial increase in numbers of an indigenous soil bacterium . Further, we provide evidence of in situ competition between these phages . This is the first in situ demonstration of such microbial interactions in soil . To achieve this, sugar beet seeds were inoculated with Serratia liquefaciens CP6RS or its lysogen, CP6RS-ly-phi 1 . These were sown, along with uninoculated seeds, in 36 field plots arranged in a randomized Latin square . The plots were then sampled regularly over 194 days, and the plants were assayed for the released bacteria and any infectious phages . Both the lysogen and nonlysogen forms of CP6RS survived equally well in situ, contradicting earlier work suggesting lysogens have a competitive disadvantage in nature . A Podoviridae phage, identified as phi CP6-4, flourished on the nonlysogen-inoculated plants in contrast to those plants inoculated with the lysogen . Conversely, the Siphoviridae phage phi CP6-1 (used to construct the released lysogen) was isolated abundantly from the lysogen-treated plants but almost never on the nonlysogen-inoculated plants . The uninoculated plants also harbored some phi CP6-1 phage up to day 137, yet hardly any phi CP6-4 phages were found, and this was consistent with previous years . We show that the different temporal and spatial distributions of these two physiologically distinct phages can be explained by application of optimal foraging theory to phage ecology . This is the first time that such in situ evidence has been provided in support of this theoretical model.

Toxicol Lett, 2000 Aug 16, 116(3), 237 - 42
Cytotoxicity of prodigiosin and benznidazole on V79 cells; da Silva Melo P et al.; The cytotoxicity of prodigiosin, an antibiotic and potential trypanocide produced by Serratia marcescens, and Benznidazole, a trypanocidal drug, were assayed on V79 fibroblast cell line . Three independent endpoints for cytotoxicity were evaluated; namely, the nucleic acid content (NAC), MTT reduction and neutral red uptake (NRU) . IC(50) values of 1-20 microM were obtained for prodigiosin in the NRU, MTT and NAC tests . Prodigiosin had greater trypanocidal activity (IC(50)=5 microM) than Nifurtimox (IC(50)=150 microM) a known trypanocide drug used in Chagas' disease therapy . Benznidazole was less toxic (IC(50)=2000 microM) than prodigiosin (IC(50)=1-20 microM) in V79 cells based on the MTT and NAC assays . Benznidazole stimulated the NRU until 2 mM . Indeed, the cell viability measured with the NRU was higher at all concentrations of benznidazole tested than that measured by MTT reduction and NAC assays.

Prikl Biokhim Mikrobiol, 2000 Jul-Aug, 36(4), 402 - 11
{Isolation and properties of extracellular lipase of native (B-10) and mutant (M-1) Serratia marcescens strains}; Duzhak AB et al.; The cultivation conditions of wild-type strain V-10 and mutant strain M-1 (overproducer of endonuclease and chitinase) of Serratia marcescens optimal for extracellular lipase biosynthesis were determined . The strain V-10 displayed the maximal lipase yield (840 AU/ml) after 10-12 h of cultivation; the strain M-1 (33 AU/ml), after 25-30 h . The data showed that extracellular lipases from V-10 and M-1 can be precipitated in a weakly acid medium (pH 5.0 and 4.5, respectively) . This property was used to obtain partially purified lipase preparations . The effect of the ionic composition of the reaction mixture on the activities of these enzymatic preparations was studied . Both preparations displayed highest activities in weakly alkaline media (pH 8.0); however, the wild-type strain lipase displayed a higher thermal stability and stability at alkaline pH compared with M-1 lipase . Both lipases were activated by various anionic and nonionic surfactants and inactive in the presence of cetyltrimethylammonium bromide.

Microb Drug Resist, 2000 Summer, 6(2), 111 - 7
Evidence of an efflux pump in Serratia marcescens; Berlanga M et al.; Spontaneous mutants resistant to fluoroquinolones were obtained by exposing Serratia marcescens NIMA (wild-type strain) to increasing concentrations of ciprofloxacin both in liquid and on solid media . Frequencies of mutation ranged from 10(-7) to 10(-9) . Active expulsion of antibiotic was explored as a possible mechanism of resistance in mutants as well as changes in topoisomerase target genes . The role of extrusion mechanisms in determining the emergence of multidrug-resistant bacteria was also examined . Mutants resistant to high concentrations of fluoroquinolones had a single mutation in their gyrA QRDR sequences, whereas the moderate resistance in the rest of mutants was due to extrusion of the drug.

J Hosp Infect, 2000 Aug, 45(4), 255 - 62
Intensive care unit design and environmental factors in the acquisition of infection; O'Connell NH et al.; The incidence of infection in the intensive care unit (ICU) is one of the highest in the hospital and yet facilities to prevent infection are often inadequate in this important clinical area . Many antibiotic-resistant bacteria such as methicillin-resistant Staphylococcus aureus (MRSA), Serratia marcescens and vancomycin-resistant enterococci (VRE), may survive and persist in the environment leading to recurrent outbreaks . A number of professional and scientific bodies in the UK, the USA and Europe have published guidelines on the design and layout of ICUs . All emphasize the importance of adequate isolation facilities (at least one cubicle for every six beds), sufficient space around each bed (20 m2), wash hand basins between every other bed, ventilation including positive and negative pressure ventilation for high risk patients and sufficient storage and utility space . Common sense and considerations of safety and comfort should guide decisions on floors, walls etc . Appropriate cleaning and disinfection programmes are essential to render the ICU relatively pathogen free and compliance with handwashing is imperative in minimizing infection in this high-risk area . Infection control teams should support ICU personnel in their efforts to upgrade facilities and help ensure that this is a priority when resources are limited.

Curr Microbiol, 2000 Oct, 41(4), 267 - 70
Killing of flies in electrocuting insect traps releases bacteria and viruses; Urban JE et al.; Electrocuting insect traps (EIT) are popular devices frequently used by homeowners and food handlers attempting to localize the control of flying insects, including the ubiquitous house fly (Musca domestica L.) . The traps contain a visual attractant and a high-voltage metal grid . Upon contact with the grids, the insects are disintegrated by the high voltage . As part of a systematic evaluation of EITs and their role in infectious disease spread, we quantitated spread of bacteria and a bacterial virus during electrocution of house flies . We loaded flies with Serratia marcescens or with the Escherichia coli phage PhiX174 and placed sprayed or fed flies into a room containing an EIT . While flies were being electrocuted, liberated particles and bacteria were assayed via agar plates or via air filtration samplers . Sprayed flies released one of every 10,000 of the added bacteria or viruses, and fed flies released one of every 1,000,000 of the consumed bacteria or viruses . Results of our studies suggest EITs could play a role in the spread of infectious disease agents, but the potential is influenced by the insect's route of contamination.

Proteins, 2000 Nov 1, 41(2), 202 - 10
Functional aspects of the heme bound hemophore HasA by structural analysis of various crystal forms; Arnoux P et al.; The protein HasA from the Gram negative bacteria Serratia marcescens is the first hemophore to be described at the molecular level . It participates to the shuttling of heme from hemoglobin to the outer membrane receptor HasR, which in turn releases it into the bacterium . HasR alone is also able to take up heme from hemoglobin but synergy with HasA increases the efficiency of the system by a factor of about 100 . This iron acquisition system allows the bacteria to survive with hemoglobin as the sole iron source . Here we report the structures of a new crystal form of HasA diffracting up to 1.77A resolution as well as the refined structure of the trigonal crystal form diffracting to 3.2A resolution . The crystal structure of HasA at high resolution shows two possible orientations of the heme within the heme-binding pocket, which probably are functionally involved in the heme-iron acquisition process . The detailed analysis of the three known structures reveals the molecular basis regulating the relative affinity of the heme/hemophore complex.

Chemotherapy, 2000 Sep-Oct, 46(5), 315 - 21
Antibiotic susceptibility of Serratia marcescens and Serratia liquefaciens; Traub WH; BACKGROUND: Over a period of 20 years, a total of 1,603 Serratia isolates were recovered from clinical specimens and examined for susceptibility to 29 antimicrobial drugs using the Bauer-Kirby agar disk diffusion test . Serratia marcescens was recovered most frequently (n = 1,409), followed by S . liquefaciens (n = 172); other Serratia species were scarce . During the 2-decade observation period there occurred 35 putative episodes/clusters of nosocomial cross-infection and 1 pseudo-outbreak due to S . marcescens, but none due to S . liquefaciens . METHODS: The antimicrobial susceptibility data for S . marcescens and S . liquefaciens were subdivided into two observation periods: I = 1980-1993, and II = 1993-1999 . The crude data (series A) obtained for S . marcescens were corrected in two ways: by the omission of repetitive patient isolates (series B) and the additional removal of outbreak isolates except for index case isolates (series C) . RESULTS AND CONCLUSIONS: Comparison of data obtained in series IC and IIC disclosed an increase in the susceptibility of S . marcescens to ampicillin + sulbactam, cefotaxime, chloramphenicol, doxycycline, fosfomycin, gentamicin, piperacillin, piperacillin + tazobactam, timentin and tobramycin during observation period II . Conversely, there was a decrease in susceptibility to ciprofloxacin, nalidixic acid and trovafloxacin, and slightly diminished susceptibility to norfloxacin and ofloxacin during observation period II as compared with the previous period . The crude data obtained for S . liquefaciens required no correction, as there were only a few repeat isolates . There was an increase in susceptibility to ampicillin, ampicillin + sulbactam, cefuroxime, doxycycline, fosfomycin, nitrofurantoin and polymyxin B (clear inhibition zones) . However, there was an inexplicable decrease in susceptibility to piperacillin + tazobactam . Cocarde growth around polymyxin B disks was noted with 55.8% of the S . marcescens isolates as compared with 6.8% of the S . liquefaciens isolates . Slime around fluoroquinolone inhibition zones was produced by 83.4% of the S . marcescens isolates . Slime production around carbapenem inhibition zones was noted with 52% of the S . liquefaciens isolates, but with only a single isolate of S . marcescens .

Transfusion, 2000 Aug, 40(8), 931 - 5
Transfusion-related sepsis due to Serratia liquefaciens in the United States; Roth VR et al.; BACKGROUND: Severe, often fatal, transfusion reactions due to bacterial contamination of blood components continue to occur . Serratia liquefaciens, an unusual human pathogen, is a recently recognized potential cause of transfusion-related sepsis . CASE REPORTS: Five episodes of transfusion-related sepsis and endotoxic shock due to S . liquefaciens were reported to the CDC from July 1992 through January 1999 . One episode has been described . The remaining four, all fatal, are described here: three associated with RBC transfusion and one associated with transfusion of platelets . In each instance, the source of contamination could not be found . The implicated units tended to be older (mean RBC age 28 days), and visual discoloration was noted in each RBC unit, although usually in retrospect . CONCLUSION: S . liquefaciens is an increasingly recognized cause of transfusion-related sepsis and is associated with a high mortality rate . S . liquefaciens can contaminate both RBCs and platelets, but the mechanism(s) of contamination remain unknown . Increased attention to pretransfusion visual inspection may avert the transfusion of some S . liquefaciens-contaminated RBC units . However, more sensitive rapid diagnostic tests are needed to further reduce the risk of transfusion-related sepsis and endotoxic shock.

J Bacteriol, 2000 Sep, 182(18), 5127 - 38
Plasmid-located pathogenicity determinants of Serratia entomophila, the causal agent of amber disease of grass grub, show similarity to the insecticidal toxins of Photorhabdus luminescens; Hurst MR et al.; Serratia entomophila and Serratia proteamaculans cause amber disease in the grass grub Costelytra zealandica (Coleoptera: Scarabaeidae), an important pasture pest in New Zealand . Larval disease symptoms include cessation of feeding, clearance of the gut, amber coloration, and eventual death . A 115-kb plasmid, pADAP, identified in S . entomophila is required for disease causation and, when introduced into Escherichia coli, enables that organism to cause amber disease . A 23-kb fragment of pADAP that conferred disease-causing ability on E . coli and a pADAP-cured strain of S . entomophila was isolated . Using insertion mutagenesis, the pathogenicity determinants were mapped to a 17-kb region of the clone . Sequence analysis of the 17-kb region showed that the predicted products of three of the open reading frames (sepA, sepB, and sepC) showed significant sequence similarity to components of the insecticidal toxin produced by the bacterium Photorhabdus luminescens . Transposon insertions in sepA, sepB, or sepC completely abolished both gut clearance and cessation of feeding on the 23-kb clone; when recombined back into pADAP, they abolished gut clearance but not cessation of feeding . These results suggest that SepA, SepB, and SepC together are sufficient for amber disease causation by S . entomophila and that another locus also able to exert a cessation-of-feeding effect is encoded elsewhere on pADAP.

Antimicrob Agents Chemother, 2000 Sep, 44(9), 2304 - 9
Functional analysis of the active site of a metallo-beta-lactamase proliferating in Japan; Haruta S et al.; An R-plasmid-mediated metallo-beta-lactamase was found in Klebsiella pneumoniae DK4 isolated in Japan in 1991 . The nucleotide sequence of its structural gene revealed that the beta-lactamase termed DK4 was identical to the IMP-1 metallo-beta-lactamase which was mediated by a chromosomal gene of Serratia marcescens TN9106 isolated in Japan in 1991 (E . Osano et al., Antimicrob . Agents Chemother . 38:71-78, 1994) . The dose effect of DK4 beta-lactamase production on the resistance levels indicated a significant contribution of the enzyme to bacterial resistance to all the beta-lactams except monobactams . The enzymatic characteristics of the DK4 beta-lactamase and its kinetic parameters for nine beta-lactams were examined . The DK4 beta-lactamase was confirmed to contain 2 mol of zinc per mol of enzyme protein . The apoenzyme that lacked the two zincs was structurally unstable, and the activities of only 30% of the apoenzyme molecules could be restored by the addition of 1 mM zinc sulfate . The substitution of five conserved histidines (His28, His86, His88, His149, His210) and a cysteine (Cys168) for an alanine indicated that His86, His88, and His149 served as ligands to one of the zincs and that Cys168 played a role as a ligand to the second zinc . Both zinc molecules contribute to the enzymatic process . Mutant enzymes that lack only one of these retained some activity . Additionally, a conserved aspartic acid at position 90 was replaced by asparagine . This mutant enzyme showed an approximately 1,000 times lower k(cat) value for cephalothin than that of the wild-type enzyme but retained the two zincs even after dialysis against zinc-free buffer . The observed effect of pH on the activity suggested that Asp90 functions as a general base in the enzymatic process.

J Biotechnol, 2000 Jul 14, 80(3), 277 - 83
Analysis of the chiB gene of Serratia liquefaciens; Woytowich AE et al.; A 4.6-kb EcoRI/BglII fragment of Serratia liquefaciens genomic DNA has been sequenced and within this fragment the chiB gene has been identified and characterized . The chiB ORF encodes a polypeptide with a deduced molecular mass of 52-kDa and the translational product in vitro has chitinase, but not chitobiase activity . Alignment of the predicted Chib 499 amino acid sequence indicated a chitin-binding and a catalytic domain that shares homology to the chitinase family 18 domain, to the Chib polypeptide of Serratia marcescens QMB1466 (93.6%), a human chitinase and several bacterial chitinases . This chiB gene sequence transcription/translation in Escherichia coli may be blocked by a RNA folding mechanism thus controlling the chitin utilization regulon in S . liquefaciens.

Can J Microbiol, 2000 Aug, 46(8), 716 - 22
Role of the outer membrane in the accumulation of quinolones by Serratia marcescens; Berlanga M et al.; Accumulation of four quinolones by Serratia marcescens was measured fluorometrically . The passage of quinolones through the outer membrane was studied in both lipopolysaccharide-deficient and porin-deficient mutants . The lipopolysaccharide (LPS) layer formed a partially effective barrier for highly hydrophobic quinolones such as nalidixic acid . Quinolones with a low relative hydrophobicity coefficient seemed to pass preferentially through the water-filled Omp3 porin channels . Results were confirmed when Omp3 was cloned in a porin-defective Escherichia coli.

J Antimicrob Chemother, 2000 Aug, 46(2), 279 - 82
Salicylate induction of phenotypic resistance to quinolones in Serratia marcescens; Berlanga M et al.; The influence of salicylic acid on the permeability and susceptibility of Serratia marcescens to both nalidixic acid and ciprofloxacin was studied, as well as the effect of salicylate on outer membrane proteins and lipopolysaccharide . As salicylic acid concentration increased, ciprofloxacin accumulation decreased with a concomitant, previously observed, reduction in the porin content of the outer membrane . Resistance to ciprofloxacin and nalidixic acid was enhanced when bacteria grew in the presence of salicylic acid.

Cornea, 2000 Jul, 19(4), 517 - 20
Colorimetric indicators of microbial contamination in corneal preservation medium; Chu YI et al.; PURPOSE: To compare acid-base and oxidation-reduction indicators and to investigate the effect of buffer and temperature on the colorimetric detection of microbial growth in corneal preservation media . METHODS: Corneal preservation media containing gentamicin, without or with HEPES buffer, were prepared with either phenol red or AlamarBlue indicators (AccuMed International, Westlake, OH, U.S.A.) . Both media were inoculated with Staphylococcus aureus, Streptococcus sanguis, Pseudomonas aeruginosa, Serratia marcescens, or Candida albicans and then incubated at 4 degrees C, 22 degrees C, or 35 degrees C . The pH or percent reduction were determined hourly for eight hours, then daily for one week . RESULTS: The length of time before a confirmed change in pH or reduction occurred varied by microorganism, storage temperature, and buffering capacity . At 4 degrees C, none of the microorganisms caused a detectable pH change in buffered medium within one day after inoculation, although two bacterial species reduced AlamarBlue within four hours . At 22 degrees C and 35 degrees C, all bacteria except P . aeruginosa produced a pH shift within a few hours, and all tested bacterial species reduced AlamarBlue . For bacteria producing detectable pH changes, HEPES-buffered medium took longer to change than medium without HEPES . C . albicans was not detectable in HEPES-buffered medium at any temperature by phenol red and was only detectable by AlamarBlue after 2-3 days at 22 degrees C and 35 degrees C . CONCLUSION: Acidic shifts in refrigerated corneal preservation medium do not occur during contamination by several microorganisms . AlamarBlue, a redox indicator, is more sensitive than phenol red in detecting some bacteria . C . albicans is not reliably detected by pH or redox indicators.

Ophthalmology, 2000 Aug, 107(8), 1497 - 502
Shifting trends in bacterial keratitis in south Florida and emerging resistance to fluoroquinolones; Alexandrakis G et al.; OBJECTIVE: To study the distribution, current trends, and patterns of resistance to antimicrobial agents of bacterial keratitis isolates in South Florida . DESIGN: Retrospective, observational, case series . PARTICIPANTS: The microbiology records of all patients with bacterial keratitis seeking treatment at the Bascom Palmer Eye Institute from January 1, 1990 through December 31, 1998 were reviewed . MAIN OUTCOME MEASURES: In vitro laboratory minimum inhibitory concentration testing of the corneal isolates to the fluoroquinolones (ofloxacin and ciprofloxacin) and to the aminoglycosides (tobramycin and gentamicin) was performed using the Vitek (Automatic Microbial System Biomerieux Vitek, Inc., Hazelwood, Missouri) method . RESULTS: During this 9-year period, 2920 consecutive corneal cultures were obtained, and a pathogen was recovered in 1468 cultures (50%) . The number of corneal ulcers scraped, positive cultures, recovered bacterial isolates, and ratio of gram-positive to gram-negative isolates per year remained approximately equal throughout the study period . Staphylococcus aureus and Pseudomonas aeruginosa represented 19.4% and 25.7%, respectively, of the total bacterial isolates during this period . However, we documented a gradual increase in the number of S . aureus keratitis isolates (29% of gram-positive organisms in 1990 versus 48% in 1998, P = 0.01) coupled with a decrease in the number of P . aeruginosa isolates (54% of gram-negative organisms in 1990 versus 46% in 1998) . A decrease in the incidence of contact lens-associated keratitis and P . aeruginosa isolates in this group of patients was documented . Serratia marcescens and P . aeruginosa were most commonly isolated in contact lens-associated keratitis (18% each) . There was increasing laboratory resistance of S . aureus keratitis isolates to the fluoroquinolones (11% in 1990 to 28% in 1998), but resistance patterns to the aminoglycosides remained unchanged . There was a three-fold increase in the percentage of resistant S . aureus isolates to fluoroquinolones between 1990 and 1994 and between 1995 and 1998 . Both fluoroquinolones and aminoglycosides exhibited low in vitro effectiveness against P . aeruginosa throughout the study period . CONCLUSIONS: The increased recovery of S . aureus keratitis isolates and decreased laboratory effectiveness against fluoroquinolones to these pathogens present an important therapeutic challenge.

Ophthalmology, 2000 Aug, 107(8), 1483 - 91
Endogenous bacterial endophthalmitis: an east Asian experience and a reappraisal of a severe ocular affliction; Wong JS et al.; PURPOSE: To report 32 eyes of 27 patients with endogenous bacterial endophthalmitis seen over a 4 year period . Features and outcomes of this condition in the current series and the cases reported in the literature from 1986-1998 were reviewed . DESIGN: Retrospective noncomparative case series . PARTICIPANTS: All patients with this condition seen at the three participating general hospitals were included . INTERVENTION: A review of the systemic and ocular characteristics, therapeutic methods, and final outcomes in patients afflicted with this condition . MAIN OUTCOME MEASURES: Features studied included patients' demographic characteristics, microbiology, source of infection, ocular features, therapeutic interventions, final visual and anatomic outcomes . RESULTS: Nineteen (70%) of the 27 incriminating organisms in this case series were gram negative microbes, with Klebsiella pneumoniae infections alone being responsible in 16 (60%) cases . Hepatobiliary tract infection was the source of bacteremia in 13 (48%) patients . Only nine (28%) eyes obtained good final visual acuity (20/120 or better), and two eyes were enucleated/eviscerated . A literature review of 209 patients with endogenous endophthalmitis over a 12 year period showed a similar increase in the frequency of gram negative microbes as the responsible organism, especially among the East Asian population . Overall, 22% had bilateral involvement; two thirds of patients had predisposing factor(s) or underlying illness(es), and diabetes mellitus was present in 46% . Thirty-four percent of all eyes obtained counting finger or better final vision, and 16% had their eyes eviscerated or enucleated . Infections with virulent organisms (gram negative rods, SERRATIA:, BACILLUS:) usually denoted a grave visual prognosis; however, a media that was not opaque on presentation was usually associated with a good prognosis . CONCLUSION: Metastatic ocular infection is not uncommon despite the availability of modern antibiotic therapy . Among the East Asian population, the patient at highest risk is a diabetic patient with Klebsiella pneumoniae hepatobiliary infection . In contrast, in the Caucasian population, this condition occurs in predisposed patients with gram-positive bacteremia arising from endocarditis or skin/joint infections . The final visual outcome in patients with endogenous bacterial endophthalmitis in the recent 12 years has not differed significantly from five decades ago.

J Insect Physiol, 2000 Nov 1, 46(11), 1481 - 1487
Insect cellular reactions to the lipopolysaccharide component of the bacterium Serratia marcescens are mediated by eicosanoids; Bedick JC et al.; Nodulation, which begins with the formation of cellular microaggregates, is the predominant cellular defense reaction to bacterial infections in insects . We suggested that these reactions to bacterial infections are mediated by eicosanoids . The lipopolysaccharide (LPS) component of some bacterial cells stimulates defense reactions in mammals and insects . Here, we report on experiments designed to test the hypothesis that eicosanoids mediate microaggregation reactions to LPS . Injections of LPS (purified from the bacterium, Serratia marcescens) into larvae of the tenebrionid beetle, Zophobas atratus, stimulated microaggregation reactions in a dose-dependent manner . Treatments with eicosanoid-biosynthesis inhibitors immediately prior to LPS challenge sharply reduced the microaggregation responses . Separate treatments with specific inhibitors of phospholipase A(2), cyclooxygenase and lipoxygenase reduced microaggregation, supporting our view that microaggregate formation involves lipoxygenase and cyclooxygenase products . The inhibitory influence of dexamethasone was apparent within 30min after injection, and microaggregation was significantly reduced, relative to control insects, over the following 90min . The dexamethasone effects were reversed by treating LPS-injected insects with the eicosanoid precursor, arachidonic acid . These findings indicate that cellular defense reactions to a specific component of bacterial cells are mediated by eicosanoids, and open up new possibilities for dissecting detailed hemocytic actions in insect immune reactions to bacterial infections.

Microbios, 2000, 102(402), 79 - 88
Effect of suprainhibitory concentrations of quinolones on hydrophobicity and motility of Serratia marcescens; Majtan V et al.; The effect of suprainhibitory concentrations of quinolones (ciprofloxacin, enoxacin and norfloxacin) on the growth, hydrophobicity and motility of a nosocomial pathogen Serratia marcescens was studied . A postantibiotic effect (PAE) was induced by 2x of 4x MIC concentrations for 0.5 h . By using the 2x MIC concentrations all three quinolones induced equally long PAE approximately 1 h . The longest PAE of 5.4 h at 4x MIC concentration was induced by enoxacin . The results obtained showed that suprainhibitory concentrations of quinolones significantly stimulated the adhesion of S . marcescens to xylene, with the exception of enoxacin, which inhibited the adhesion to 61.2% at 4x MIC concentration . These results correlated with those in the salt aggregation test . The adhesion of strains to nitrocellulose filters did not influence the aftereffect of suprainhibitory concentrations of quinolones . Exposure of bacterial cells to suprainhibitory concentrations of ciprofloxacin and norfloxacin caused a reduction in motility, while this effect was more distinct at 4x MIC concentration . The results suggest that any consideration of postantibiotic effects should include the residual antibiotic effects on virulence factors, in addition to the defined suppression of bacterial regrowth.

J Mol Biol, 2000 Jul 14, 300(3), 611 - 7
Structures of chitobiase mutants complexed with the substrate Di-N-acetyl-d-glucosamine: the catalytic role of the conserved acidic pair, aspartate 539 and glutamate 540; Prag G et al.; The catalytic domain of chitobiase (beta-N-1-4 acetylhexosaminidase) from Serratia marcescens, is an alpha/beta TIM-barrel . This enzyme belongs to family 20 of glycosyl hydrolases in which a conserved amino acid pair, aspartate-glutamate, is present (Asp539-Glu540) . It was proposed that catalysis by this enzyme family is carried out by glutamate 540 acting as a proton donor and by the acetamido group of the substrate as a nucleophile . We investigated the role of Asp539 and Glu540 by site-directed mutagenesis, biochemical characterization and by structural analyses of chitobiase -substrate co-crystals . We found that both residues are essential for chitobiase activity . The mutations, however, led to subtle changes in the catalytic site . Our results support the model that Glu540 acts as the proton donor and that Asp539 acts in several different ways . Asp539 restrains the acetamido group of the substrate in a specific orientation by forming a hydrogen bond with N2 of the non-reduced (-1) sugar . In addition, this residue participates in substrate binding . It is also required for the correct positioning of Glu540 and may provide additional negative charge at the active site . Thus, these biochemical and structural studies provide a molecular explanation for the functional importance and conservation of these residues .

Zh Mikrobiol Epidemiol Immunobiol, 1999 May-Jun, (3), 16 - 20
{The effect of the cultivation conditions on the growth and pigmentation of Serratia marcescens}; Andreeva IN et al.; The influence of cultivation conditions on the growth and pigmentation of S . marcescens was studied . The cultures under study grew in media containing glycerin, glucose or acetate and organic or mineral nitrogen . Pigment formation occurred in a medium with organic nitrogen and glycerin or acetate, but not glucose . Sodium chloride inhibited the growth of cultures, but at a concentration not exceeding 4-5% increased the accumulation of prodigiosin . Prodigiosin was accumulation by the culture growing at 28 degrees C, while at 37 degrees C no accumulation of the pigment occurred . The illumination of the growing culture with visible light decreased the intensity of its pigmentation . Prodigiosin apparently plays an important role in the metabolism of S . marcescens and is linked with the energy exchange of the cell.

J Appl Microbiol, 2000 Jun, 88(6), 952 - 60
Diversity of antifungal and plant-associated Serratia plymuthica strains; Berg G; A total of 21 plant-associated Serratia plymuthica strains were characterized phenotypically by their nutritional patterns, susceptibility to antibiotics, antifungal and haemolytic properties, and genotypically by denaturing gradient gel electrophoresis (DGGE) of PCR-amplified 16S rDNA, PCR fingerprints using BOX primers (BOX-PCR) and pulsed-field gel electrophoresis (PFGE) after digestion with SpeI . All of the investigated strains demonstrated antifungal activity in vitro against fungal pathogens while only six strains produced the antifungal antibiotic prodigiosin . Haemolytic activity and antibiotic resistance patterns were investigated to assess the risk associated with the use of isolates in plant protection . The strains were haemolytic at human-relevant temperatures . The level of resistance to antibiotics was low . This work shows that BOX-PCR and PFGE are useful fingerprinting methods to characterize Ser . plymuthica strains, although the discriminatory effect between the two methods differed . Computer-assisted analysis of phenotypic and genotypic features demonstrated relationships between the origin of isolation, the production of prodigiosin and the molecular fingerprint.

Eur J Clin Microbiol Infect Dis, 2000 Apr, 19(4), 248 - 53
Clinical and microbiological survey of Serratia marcescens infection during HIV disease; Manfredi R et al.; Clinical charts of 2,398 consecutive HIV-infected patients hospitalized over an 8-year period were reviewed retrospectively to identify all cases of Serratia infection and to evaluate the occurrence and outcome of these cases according to several epidemiological . clinical, and laboratory parameters . Seventeen of 2,398 (0.71%) patients developed Serratia marcescens infections: nine had septicaemia, six had pneumonia, one had a lymph node abscess, and one had cellulitis . All patients were severely immunocompromised, as evidenced by a mean CD4+ lymphocyte count of < 70 cells/microl and a frequent diagnosis of AIDS (13 patients) . When compared with other disease localizations, septicaemia was related to a significantly lower CD4+ cell count and a more frequent occurrence of neutropaenia . Antibiotic, corticosteroid, or cotrimoxazole treatment was frequently carried out during the month preceding disease onset . Hospital-acquired Serratia spp . infection was more frequent than community-acquired infection and was significantly related to AIDS, neutropaenia, and sepsis . Antimicrobial sensitivity testing showed complete resistance to ampicillin and cephalothin but elevated susceptibility to ureidopenicillins, second- and third-generation cephalosporins, aminoglycosides, quinolones, and cotrimoxazole . An appropriate antimicrobial treatment attained clinical and microbiological cure in all cases, in absence of related mortality or relapses . Since only 13 episodes of HIV-associated Serratia spp . infection have been described until now in nine different reports (7 patients with pneumonia, 3 with sepsis, 1 with endophthalmitis, 1 with perifolliculitis, and 1 with cholecystitis), our series represents the largest one dealing with Serratia marcescens infection during HIV disease . Serratia marcescens may be responsible for appreciable morbidity among patients with HIV disease, especially when a low CD4 + cell count, neutropaenia, and hospitalization are present . The clinician and the microbiologist facing a severely immunocompromised HIV-infected patient with a suspected bacterial disease should consider the Serratia spp . organisms . In fact, a rapid diagnosis and an adequate and timely treatment can avoid disease relapses and mortality.

Proc Natl Acad Sci U S A, 2000 May 23, 97(11), 5842 - 7
Structure of a two-domain chitotriosidase from Serratia marcescens at 1.9-A resolution; van Aalten DM et al.; In this paper, we describe the structure of chitinase B from Serratia marcescens, which consists of a catalytic domain with a TIM-barrel fold and a 49-residue C-terminal chitin-binding domain . This chitinase is the first structure of a bacterial exochitinase, and it represents one of only a few examples of a glycosyl hydrolase structure having interacting catalytic and substrate-binding domains . The chitin-binding domain has exposed aromatic residues that contribute to a 55-A long continuous aromatic stretch extending into the active site . Binding of chitin oligomers is blocked beyond the -3 subsite, which explains why the enzyme has chitotriosidase activity and degrades the chitin chain from the nonreducing end . Comparison of the chitinase B structure with that of chitinase A explains why these enzymes act synergistically in the degradation of chitin.

Biochemistry, 2000 May 23, 39(20), 6219 - 27
Role of beta Arg211 in the active site of human beta-hexosaminidase B; Hou Y et al.; Tay-Sachs or Sandhoff disease results from a deficiency of either the alpha- or the beta-subunits of beta-hexosaminidase A, respectively . These evolutionarily related subunits have been grouped with the "Family 20" glycosidases . Molecular modeling of human hexosaminidase has been carried out on the basis of the three-dimensional structure of a bacterial member of Family 20, Serratia marcescens chitobiase . The primary sequence identity between the two enzymes is only 26% and restricted to their active site regions; therefore, the validity of this model must be determined experimentally . Because human hexosaminidase cannot be functionally expressed in bacteria, characterization of mutagenized hexosaminidase must be carried out using eukaryotic cell expression systems that all produce endogenous hexosaminidase activity . Even small amounts of endogenous enzyme can interfere with accurate K(m) or V(max) determinations . We report the expression, purification, and characterization of a C-terminal His(6)-tag precursor form of hexosaminidase B that is 99.99% free of endogenous enzyme from the host cells . Control experiments are reported confirming that the kinetic parameters of the His(6)-tag precursor are the same as the untagged precursor, which in turn are identical to the mature isoenzyme . Using highly purified wild-type and Arg(211)Lys-substituted hexosaminidase B, we reexamine the role of Arg(211) in the active site . As we previously reported, this very conservative substitution nevertheless reduces k(cat) by 500-fold . However, the removal of all endogenous activity has now allowed us to detect a 10-fold increase in K(m) that was not apparent in our previous study . That this increase in K(m) reflects a decrease in the strength of substrate binding was confirmed by the inability of the mutant isozyme to efficiently bind an immobilized substrate analogue, i.e., a hexosaminidase affinity column . Thus, Arg(211) is involved in substrate binding, as predicted by the chitobiase model, as well as catalysis.

Rev Invest Clin, 2000 Jan-Feb, 52(1), 39 - 43
Parenteral infusions as culture media from a viewpoint of nosocomial bacteremia; Macias AE et al.; OBJECTIVE: To assess the growth patterns of selected organisms in common parenteral solutions, in order to ascertain implications for nosocomial bacteremia . DESIGN: A microbial suspension of approximately 300 CFU/mL was sequentially inoculated into common parenteral infusions from three different manufacturers and incubated at room temperature . Initially, 11 bacterial isolates and one Candida species from clinical specimens were studied . Eight gram-negative rods (GNR) were tested at varying pH's . Species variability was examined by testing an additional 39 isolates . RESULTS: The eight GNR grew in Ringer's lactate (RL) from two manufacturers and only two grew in dextrose 5% in water (D5/W) (Klebsiella pneumoniae and Serratia marcescens) . No organism grew in saline or dextrose 5% in saline . The gram-positive cocci and Candida did not grow in any solution . No significant changes in growth were found after modifying the pH of solutions . Significant inter- and intra-species growth variability was noted . CONCLUSIONS: RL is a good culture media for GNR and D5/W is a poor culture media with the exception of some bacteria of the Tribe Klebsielleae . We recommend to follow high standards of nursing practice for administering intravenous infusions and to avoid nutrient-containing solutions for prolonged parenteral use, when possible.

Bone Marrow Transplant, 2000 Apr, 25(8), 873 - 7
An outbreak of multiply resistant Serratia marcescens: the importance of persistent carriage; Knowles S et al.; An outbreak of multi-resistant Serratia marcescens involving 24 patients occurred in a bone marrow transplant and oncology unit, from September 1998 to June 1999, of whom 14 developed serious infection . This is the first such outbreak described in a BMT unit . All isolates demonstrated the same antimicrobial susceptibility pattern and were the same unusual serotype O21:K14 . The antimicrobial susceptibility profile showed reduced susceptibility to ciprofloxacin, gentamicin and piperacillin-tazobactam . As the latter two antimicrobials are part of our empiric therapy for febrile neutropenia, they were substituted with meropenem and amikacin during the outbreak . Investigation revealed breaches in infection control practices . Subsequently, the outbreak was contained following implementation of strict infection control measures . A prominent feature of the outbreak was prolonged carriage in some patients . These patients may have acted as reservoirs for cross-infection . This report also indicates that patients who become colonised with Serratia marcescens may subsequently develop invasive infection during neutropenic periods.

FEMS Immunol Med Microbiol, 2000 Jun, 28(2), 143 - 9
Clinical relevance and virulence factors of pigmented Serratia marcescens; Carbonell GV et al.; Pigmented Serratia marcescens isolated in a Brazilian hospital were studied with respect to frequency of isolation, serotyping, antibiotic resistance and virulence factors . The serotype most frequent was O6:K14 (53%) and all isolates were resistant to ampicillin, cephalothin and tetracycline . The majority of the isolates (92%) were resistant to the action of human serum and all produced cytotoxins on Vero, CHO, HEp-2 and HeLa cells . These isolates were virulent for mice (LD(50)=10(7) bacteria ml(-1)) and showed virulence factors, but were isolated with low frequency (3 . 4%) and caused infection in only 31% of cases . Analysis of serotyping, phage typing and chromosomal DNA revealed at least 13 unrelated strains among pigmented S . marcescens . In conclusion, this work describes a low frequency of isolation of pigmented S . marcescens from clinical specimens, indicating that non-pigmented strains are clinically more significant.

Invest Ophthalmol Vis Sci, 2000 May, 41(6), 1438 - 47
PCR-RFLP-mediated detection and speciation of bacterial species causing endophthalmitis; Okhravi N et al.; PURPOSE: To determine the usefulness of polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) in the identification and speciation of bacteria causing endophthalmitis . METHODS: PCR-RFLP was performed on 53 strains of 14 bacterial species (eight Gram positive and five Gram negative) collected from both keratitis and endophthalmitis patients . Two pairs of oligonucleotide primers based on the 16S rDNA gene were used to PCR-amplify 1.2- and 1.0-kb fragments of bacterial genomic DNA . RFLPs within the PCR product were used to speciate the organisms . RESULTS: The sensitivity of the nested PCR amplification reaction was one organism . All bacteria tested could be identified and speciated using RFLP analysis except for Escherichia coli and Serratia marcescens, which could not be interdifferentiated using RFLP . Molecular analysis of two vitreous samples from two eyes with typical signs of bacterial endophthalmitis confirmed the presence of E . coli in the vitreous from a culture-positive case with E . coli endophthalmitis and revealed the presence of Staphylococcus epidermidis in the vitreous of a culture-negative case . CONCLUSIONS: It is expected that this technique will provide a useful laboratory tool for future microbiologic diagnosis of patients presenting with endophthalmitis, especially for those eyes that prove culture negative.

Lett Appl Microbiol, 2000 May, 30(5), 419 - 21
RAPD-fingerprinting of Serratia marcescens after formaldehyde inactivation of DNase activity; Polyzou A et al.; Serratia marcescens strains commonly cause hospital outbreaks . A random amplified polymorphic DNA (RAPD) assay was applied to the epidemiology of Ser . marcescens using formaldehyde fixation and boiling of bacterial cells for DNA extraction . The method preserved bacterial DNA and gave optimal results of RAPD-fingerprinting, facilitating the investigation of hospital infections caused by Ser . marcescens.

Br J Dermatol, 2000 Apr, 142(4), 784 - 8
Neutrophilic eccrine hidradenitis secondary to infection with Serratia marcescens; Combemale P et al.; Neutrophilic eccrine hidradenitis (NEH) is a rare dermatosis which usually develops after administration of chemotherapeutic treatments . An infective origin is exceptional . We report a patient, previously operated on for ependymoma, who presented with an eruption typical of NEH even though he had not received chemotherapy . Culture of a skin biopsy revealed Serratia marcescens . The dermatosis improved after antibiotic therapy but recurred twice and culture again isolated S . marcescens; electron microscopy revealed cytoplasmic inclusions within neutrophils, suggestive of bacteria . The disease improved every time with appropriate antibiotic therapy . An infective aetiology for NEH is rare: three such cases have been reported, of which one was due to S . marcescens . The originality of our case is the recurrence of the disease on three occasions with the same bacterium isolated on each occasion, with disease remission after antibiotic therapy . This case confirms that infections may be a possible cause of NEH and underlines the necessity to search for infective agents, especially in patients immunocompromised by haematopoietic malignancies and/or chemotherapeutic treatments.

J Bacteriol, 2000 May, 182(10), 2680 - 6
Assessment of flhDC mRNA levels in Serratia liquefaciens swarm cells; Tolker-Nielsen T et al.; We reported previously that artificial overexpression of the flhDC operon in liquid-grown Serratia liquefaciens resulted in the formation of filamentous, multinucleated, and hyperflagellated cells that were indistinguishable from surface-induced swarm cells (L . Eberl, G . Christiansen, S . Molin, and M . Givskov, J . Bacteriol . 178:554-559, 1996) . In the present report we show by means of reporter gene measurements, Northern analysis, and in situ reverse transcription-PCR that the amount of flhDC mRNA in surface-grown swarm cells does not exceed the maximum level found in nondifferentiated, vegetative cells . This suggests that surface-induced S . liquefaciens swarm cell differentiation, although dependent on flhDC gene expression, does not occur through elevated flhDC mRNA levels.

Acta Crystallogr D Biol Crystallogr, 2000 May, 56 ( Pt 5), 567 - 72
Atomic structure of the Serratia marcescens endonuclease at 1.1 A resolution and the enzyme reaction mechanism; Shlyapnikov SV et al.; The three-dimensional crystal structure of Serratia marcescens endonuclease has been refined at 1.1 A resolution to an R factor of 12.9% and an R(free) of 15.6% with the use of anisotropic temperature factors . The model contains 3694 non-H atoms, 715 water molecules, four sulfate ions and two Mg(2+)-binding sites at the active sites of the homodimeric protein . It is shown that the magnesium ion linked to the active-site Asn119 of each monomer is surrounded by five water molecules and shows an octahedral coordination geometry . The temperature factors for the bound Mg(2+) ions in the A and B subunits are 7.08 and 4.60 A(2), respectively, and the average temperature factors for the surrounding water molecules are 12.13 and 10.3 A(2), respectively . In comparison with earlier structures, alternative side-chain conformations are defined for 51 residues of the dimer, including the essential active-site residue Arg57 . A plausible mechanism of enzyme function is proposed based on the high-resolution S . marcescens nuclease structure, the functional characteristics of the natural and mutational forms of the enzyme and consideration of its structural analogy with homing endo-nuclease I-PpoI.

Biochem J, 2000 May 1, 347 Pt 3, 815 - 9
Endonuclease activity in lipocalins; Yusifov TN et al.; Several lipocalins contain conserved amino acid sequences similar to the phosphodiester bond cleavage domain of sugar non-specific magnesium-dependent nucleases of the Serratia marcescens type . His-89 and Glu-127 of the S . marcescens endonuclease are believed to have a role in the active catalytic site by the attack of a water molecule at the phosphorus atom of the bridging phosphate . Tear lipocalin contains both amino acids in analogous regions, and is active as a nuclease . Two forms of beta-lactoglobulin contain only Glu-134 (analogous to Glu-127 of the Serratia nuclease) yet retain nuclease activity equal to or greater than that of tear lipocalin . However, retinol-binding protein lacks both of these motifs and shows no detectable activity . DNA-nicking activity is decreased by 80% in the mutant of tear lipocalin that replaces Glu-128 but is unchanged by mutations of His-84 . The endonuclease activity of tear lipocalin is dependent on the bivalent cations Mg(2+) or Mn(2+) but is decreased at high concentrations of NaCl . These findings indicate that some lipocalins have non-specific endonuclease activity similar in characteristics to the Mg(2+)-dependent nucleases and related to the conserved sequence LEDFXR (where 'X' denotes 'any other residue'), in which the glutamic residue seems to be important for activity.

Am Surg, 2000 Mar, 66(3), 223 - 8
Tornado disaster in rural Georgia: triage response, injury patterns, lessons learned; Millie M et al.; Our objective was to characterize the medical response and injury patterns from a recent tornado disaster in rural southeastern Georgia . We conducted a retrospective review of 11 patients treated at a Level I trauma center after sustaining injuries due to an April 9, 1998 F3 tornado . Data were obtained from trauma registry and medical records . Of 11 victims, 8 (73%) were male . Ages ranged from 5 to 54 years . Two patients were triaged directly by military helicopter, six arrived as secondary triage from local rural hospitals (2 by air, 4 by ground), and three arrived by delayed secondary transfer . Six patients were thrown by the tornado, and five were struck by flying debris . All victims were either in exposed areas or mobile homes . Injuries by anatomic region included the chest (45%), abdomen (27%), extremity (91%), and head (45%) . Nine (82%) of the patients required surgical intervention . These included three laparotomies, one thoracotomy, six orthopedic procedures, and one neurosurgical procedure . The average Injury Severity Score (ISS) was 23 . Among patients who were thrown mean ISS was 31; among those struck by debris, mean ISS was 12 . Hemodynamically significant pelvic fractures occurred in three patients (27%) . The major complication, sepsis due to Serratia marcescens was seen in three patients, all of whom had been thrown and had clinically significant wound contamination . Both patients who died had Serratia sepsis and multiorgan system failure . The injuries and inclement weather characteristic of tornado disasters stress regional trauma triage responses, cause significant injury, and disrupt communities . Injury patterns involve multiple systems and require coordinated efforts among caretakers . Infectious complications are common and frequently involve Gram-negative bacilli and are associated with soil-contaminated wounds . Trauma severity increases if the victim is thrown rather than struck by flying debris.

Protein Sci, 2000 Mar, 9(3), 544 - 51
The X-ray structure of a chitinase from the pathogenic fungus Coccidioides immitis; Hollis T et al.; The X-ray structure of chitinase from the fungal pathogen Coccidioides immitis has been solved to 2.2 A resolution . Like other members of the class 18 hydrolase family, this 427 residue protein is an eight-stranded beta/alpha-barrel . Although lacking an N-terminal chitin anchoring domain, the enzyme closely resembles the chitinase from Serratia marcescens . Among the conserved features are three cis peptide bonds, all involving conserved active site residues . The active site is formed from conserved residues such as tryptophans 47, 131, 315, 378, tyrosines 239 and 293, and arginines 52 and 295 . Glu171 is the catalytic acid in the hydrolytic mechanism; it was mutated to a Gln, and activity was abolished . Allosamidin is a substrate analog that strongly inhibits the class 18 enzymes . Its binding to the chitinase hevamine has been observed, and we used conserved structural features of the two enzymes to predict the inhibitors binding to the fungal enzyme.

Appl Environ Microbiol, 2000 Apr, 66(4), 1711 - 4
Expression of the antifeeding gene anfA1 in Serratia entomophila requires rpoS; Giddens SR et al.; The rpoS gene of Serratia entomophila BC4B was cloned and used to create rpoS-mutant strain BC4BRS . Larvae of the New Zealand grass grub Costelytra zealandica infected with BC4BRS became amber colored but continued to feed, albeit to a lesser extent than infected larvae . Subsequently, we found that expression of the antifeeding gene anfA1 in trans was substantially reduced in BC4BRS relative to that in the parental strain BC4B . Our data show that a functional rpoS gene is vital for full expression of anfA1 and for development of the antifeeding component of amber disease.

Infect Control Hosp Epidemiol, 2000 Mar, 21(3), 196 - 9
Nosocomial Serratia marcescens infections associated with extrinsic contamination of a liquid nonmedicated soap; Sartor C et al.; OBJECTIVE: To determine the role of nonmedicated soap as a source of Serratia marcescens nosocomial infections (NIs) in hospital units with endemic S marcescens NI and to examine the mechanisms of soap colonization . SETTING: University-affiliated tertiary-care hospitals . METHODS: A prospective case-control study and an environmental investigation were performed to assess the relationship between S marcescens NIs in hospital units and S marcescens-contaminated soap . Soap-bottle use and handwashing practices were reviewed . Cultures of healthcare workers' (HCWs) hands were obtained before and after hand washing with soap . RESULTS: 5 of 7 hospital units with S marcescens NIs had soap bottles contaminated with S marcescens, compared to 1 of 14 other units (P=.006) . After hand washing with an S marcescens-contaminated soap pump, HCWs' hands were 54 times more likely to be contaminated with S marcescens (P<.001) . CONCLUSIONS: Extrinsic contamination of a non-medicated liquid soap by S marcescens resulted in handborne transmission of S marcescens NIs by HCWs in our setting . This finding led to the application of strict guidelines for nonmedicated soap use and to the reinforcement of alcoholic hand disinfection.

Mem Inst Oswaldo Cruz, 2000 Mar-Apr, 95(2), 227 - 9
Identification of environmental Serratia plymuthica strains with the new combo panels type 1S; Vivas J et al.; Automated systems are required when numerous samples need to be processed, offering both high through put and test of a multiple simultaneously . This study was performed to compare the MicroScan WalkAway automated identification system in conjunction with the new MicroScan Combo Neg Panels Type 1S with conventional biochemical methods for identifying ten environmental Serratia plymuthica strains . High correlation between both methods were observed for all the 21 tests evaluated, and the MicroScan system was found capable of correctly identifying all S . plymuthica strains tested . In all tests, the percentage of correlation was 100%, except in raffinose test (91%).

Electrophoresis, 2000 Feb, 21(3), 526 - 30
High-efficiency passive elution of bacterial lipopolysaccharides from polyacrylamide gels; Pupo E et al.; We recently described a method for recovering polyacrylamide-gel-separated bacterial lipopolysaccharides (LPS) based on the sensitive on-gel LPS detection (1-10 ng/band) with zinc-imidazole followed by passive elution from 32 microm average size gel microparticles into water . With this procedure, the recovery of rough- or semismooth-type LPS after 3 h elution is about 70-80%, while that of smooth LPS is only about 10% . Here we evaluated whether a simple replacement of water with other eluents would enhance the passive diffusion of LPS . We found that solutions of the detergents sodium dodecyl sulfate (SDS), sodium deoxycholate (DOC) and Triton X-100, or mixtures of the organic solvents acetonitrile and triethylamine and water, increased the recovery of a smooth LPS band from Vibrio cholerae O1 in a concentration-dependent manner . Furthermore, a quantitative recovery of rough or smooth LPS from V . cholerae O1, Escherichia coli O111:B4, E . coli K-235, or Serratia marcescens was feasible in 1% SDS or DOC after 3 h or in 5% triethylamine after only 2 min . A simple dilution of SDS or DOC or evaporation of triethylamine rendered the eluted LPS preparations compatible with biochemical activity determination, as tested by Limulus amebocyte lysate assay . Thus, this improved micropurification method may be a suitable interface between analytical gel electrophoresis and further characterization or use of LPS.

J Mol Biol, 2000 Mar 24, 297(2), 521 - 34
Mechanism of DNA cleavage by the DNA/RNA-non-specific Anabaena sp . PCC 7120 endonuclease NucA and its inhibition by NuiA; Meiss G et al.; A structural model of the DNA/RNA non-specific endonuclease NucA from Anabaena sp . PCC7120 that has been obtained on the basis of the three-dimensional structure of the related Serratia nuclease, suggests that the overall architecture of the active site including amino acid residues H124, N155 and E163 (corresponding to H89, N119 and E127 in Serratia nuclease) is similar in both nucleases . Substitution of these residues by alanine leads to a large reduction in activity (<0.1 %), similarly as observed for Serratia nuclease demonstrating that both enzymes share a similar mechanism of catalysis with differences only in detail . NucA is inhibited by its specific polypeptide inhibitor with a K(i) value in the subpicomolar range, while the related Serratia nuclease at nanomolar concentrations is only inhibited at an approximately 1000-fold molar excess of NuiA . The artificial chromophoric substrate deoxythymidine 3',5'-bis-(p-nitrophenyl phosphate) is cleaved by NucA as well as by Serratia nuclease . Cleavage of this analogue by NucA, however, is not inhibited by NuiA, suggesting that small molecules gain access to the active site of NucA in the enzyme-inhibitor complex under conditions where cleavage of DNA substrates is completely inhibited . The active site residue E163 seems to be the main target amino acid for inhibition of NucA by NuiA, but R93, R122 and R167 (corresponding to K55, R87, R131 in Serratia nuclease) are also involved in the NucA/NuiA interaction . NuiA deletion mutants show that the structural integrity of the N and C-terminal region of the inhibitor is important for complex formation with NucA and inhibition of nuclease activity . Based on these results a mechanism of DNA cleavage by NucA and its inhibition by NuiA is proposed .

Jpn J Antibiot, 2000 Jan, 53(1), 1 - 25
{In vitro activities of carbapenem antibiotics against the various clinical isolates}; Kashitani F et al.; The annual changes of antibacterial activities of beta-lactam antibiotics, mainly carbapenem antibiotics, were investigated against 5 bacterial species, S . aureus (MSSA), methicillin-resistant S . aureus (MRSA), Klebsiella pneumoniae, Serratia marcescens, Pseudomonas aeruginosa, which had been isolated from the clinical materials at Toho University Omori Hospital during the period of 1995 to 1997 . In addition, antibacterial activities against other main bacterial strains isolated from the clinical materials during 1997 were also determined . The five bacterial species on which annual changes of the sensitivity were investigated did not show any remarkable trend to increase in resistance to the carbapenem antibiotics tested . The antibacterial activities of the carbapenem antibiotics against MRSA were weak, and MIC90 values were between 25 and 50 micrograms/ml . In S . marcescens and P . aeruginosa on which high resistance by the production of metallo-beta-lactamase has become a problem in recent years, there were no remarkable changes in annual changes of sensitivities . Especially, MIC90 valuses of the carbapenem antibiotics against P . aeruginosa were between 12.5 and 25 micrograms/ml, 4 to 8 times better than that of PIPC, like the case of CAZ . Furthermore, the carbapenem antibiotics showed strong antibacterial activities against clinically important 16 bacterial species, from Gram-positive to Gram-negative bacteria.

J Antimicrob Chemother, 2000 Mar, 45(3), 271 - 6
In vitro antibacterial activity and mechanism of action of J-111,225, a novel 1beta-methylcarbapenem, against transferable IMP-1 metallo-beta-lactamase producers; Nagano R et al.; IMP-1 beta-lactamase, a class B zinc metallo-enzyme encoded by the transferable bla(IMP) gene, is known to confer high-level resistance to carbapenems as well as to penicillins and cephalosporins . J-111, 225 is a novel 1beta-methylcarbapenem with a structurally unique side chain comprising a trans-3,5-disubstituted pyrrolidinylthio moiety at the C2 position . It inhibited 17 Serratia marcescens and two Pseudomonas aeruginosa IMP-1-producing clinical isolates at a concentration of 32 mg/L (range 4-32 mg/L) . It showed synergy with imipenem against IMP-1-producing S . marcescens BB5886 and P . aeruginosa GN17203 with minimal FIC indices of 0.38 and 0.5, respectively . J-111,225 was more resistant than imipenem to hydrolysis by class B metallo-beta-lactamases . In kinetic studies, J-111,225 inhibited the IMP-I enzyme with a K(i) of 0.18 microM when imipenem was used as a substrate . In contrast, J-111,225 was the substrate for hydrolysis by other class B beta-lactamases such as Bacteroides fragilis CcrA, Stenotrophomonas maltophilia L1 and Bacillus cereus type II enzyme with respective K(m) values of 11, 10 and 148 microM . The greater antibacterial activity of J-111,225 against IMP-1-producing bacteria may result from its unique interaction with the beta-lactamase.

Appl Environ Microbiol, 2000 Mar, 66(3), 890 - 4
Simultaneous enhancement of thermostability and catalytic activity of phospholipase A(1) by evolutionary molecular engineering; Song JK et al.; The thermal stability and catalytic activity of phospholipase A(1) from Serratia sp . strain MK1 were improved by evolutionary molecular engineering . Two thermostable mutants were isolated after sequential rounds of error-prone PCR performed to introduce random mutations and filter-based screening of the resultant mutant library; we determined that these mutants had six (mutant TA3) and seven (mutant TA13) amino acid substitutions . Different types of substitutions were found in the two mutants, and these substitutions resulted in an increase in nonpolar residues (mutant TA3) or in differences between side chains for polar or charged residues (mutant TA13) . The wild-type and mutant enzymes were purified, and the effect of temperature on the stability and catalytic activity of the enzymes was investigated . The melting temperatures of the TA3 and TA13 enzymes were increased by 7 and 11 degrees C, respectively, compared with the melting temperature of the wild-type enzyme . Thus, we found that evolutionary molecular engineering was an effective and efficient approach for increasing thermostability without compromising enzyme activity.

Biochem J, 2000 Mar 15, 346 Pt 3, 799 - 804
Cloning and characterization of a novel nuclease from shrimp hepatopancreas, and prediction of its active site; Wang WY et al.; Approximately 95% of the amino acid sequence of a shrimp (Penaeus japonicus) nuclease was derived from protease-digested peptides . A 1461-base cDNA for the nuclease was amplified and sequenced with degenerate primers based on the amino acid sequence and then specific primers by 3' and 5' RACE (rapid amplification of cDNA ends) . It contains an open reading frame encoding a putative 21-residue signal peptide and a 381-residue mature protein . The N-terminus of the enzyme is pyroglutamate, deduced from composition and matrix-assisted laser desorption ionization-time-of-flight MS analyses, and confirmed by a glutamine residue in the cDNA sequence . The enzyme has 11 Cys residues, forming five intramolecular disulphides . The eleventh Cys residue was linked to a thiol compound with an estimated molecular mass of between 500 and 700 Da . A sequence similarity search revealed no homologous proteins but residues 205-255 shared a conserved active-site motif within a distinct group of nucleases . His(211) in this conserved motif was shown to be very important in catalysis by site-specific modification with (14)C-labelled iodoacetate . The shrimp nuclease, previously designated DNase I, does indeed possess a low level of hydrolytic activity towards RNA in the presence of Mg(2+) and Ca(2+) . The conservation of functionally important residues during distant evolution might imply that the catalytic mechanisms are similar in these nucleases, which should be classified in one subfamily . Finally, an active-site structure for shrimp nuclease was proposed on the basis of published structural data and the results of mutational and biochemical analyses of Serratia nuclease.

Am J Ophthalmol, 2000 Feb, 129(2), 247 - 8
Localized infection by Serratia marcescens simulating a conjunctival neoplasm; Shields JA et al.; PURPOSE: To report a Serratia marcescens infection that clinically simulated a conjunctival neoplasm . METHOD: Case report . RESULTS: A healthy 80-year-old man without contact lenses presented with a pink-yellow conjunctival mass that resembled a solid neoplasm . Stains and cultures of material that exuded from the mass during surgery revealed S . marcescens . Histopathology disclosed an epithelial-lined cyst with macrophages containing S . marcescens . CONCLUSION: Although S . marcescens usually affects the eye as a keratoconjunctivitis in patients with contact lenses, it can also present as a mass simulating a neoplasm in a patient who does not wear contact lenses.

J Chromatogr B Biomed Sci Appl, 2000 Jan 14, 737(1-2), 13 - 23
Two-step fast protein liquid chromatographic purification of the Serratia marcescens hemolysin and peptide mapping with mass spectrometry; Hertle R et al.; The pore forming toxin of Serratia marcescens (ShlA) is secreted and activated by an outer membrane protein (ShlB) . Activation of inactive ShlA (termed ShlA*) by ShlB is dependent on phosphatidylethanolamine (PE) . Activation may be a covalent modification of ShlA . To test this hypothesis, the responsible activation domain (in the N-terminal 255 amino acids of ShlA) was isolated from whole bacteria with 8 M urea in an inactive form (ShlA-255*) and from the culture supernatant in an active form (ShlA-255), followed by a two-step purification by anion-exchange chromatography and gel permeation chromatography . Comparison of a tryptic peptide map of both forms with subsequent electrospray mass spectrometry (ES-MS) and sequencing by tandem ES-MS revealed no modification . These data imply that ShlB presumably imposes a conformation on ShlA-255 that triggers activity.

J Bacteriol, 2000 Mar, 182(5), 1257 - 63
Identification of a chitin-binding protein secreted by Pseudomonas aeruginosa; Folders J et al.; One of the major proteins secreted by Pseudomonas aeruginosa is a 43-kDa protein, which is cleaved by elastase into smaller fragments, including a 30-kDa and a 23-kDa fragment . The N-terminal 23-kDa fragment was previously suggested as corresponding to a staphylolytic protease and was designated LasD (S . Park and D . R . Galloway, Mol . Microbiol . 16:263-270, 1995) . However, the sequence of the gene encoding this 43-kDa protein revealed that the N-terminal half of the protein is homologous to the chitin-binding proteins CHB1 of Streptomyces olivaceoviridis and CBP21 of Serratia marcescens and to the cellulose-binding protein p40 of Streptomyces halstedii . Furthermore, a short C-terminal fragment shows homology to a part of chitinase A of Vibrio harveyi . The full-length 43-kDa protein could bind chitin and was thereby protected against the proteolytic activity of elastase, whereas the degradation products did not bind chitin . The purified 43-kDa chitin-binding protein had no staphylolytic activity, and comparison of the enzymatic activities in the extracellular medium of a wild-type strain and a chitin-binding protein-deficient mutant indicated that the 43-kDa protein supports neither chitinolytic nor staphylolytic activity . We conclude that the 43-kDa protein, which was found to be produced by many clinical isolates of P . aeruginosa, is a chitin-binding protein, and we propose to name it CbpD (chitin-binding protein D).

J Math Biol, 2000 Jan, 40(1), 27 - 63
The interaction of thin-film flow, bacterial swarming and cell differentiation in colonies of Serratia liquefaciens; Bees MA et al.; The rate of expansion of bacterial colonies of S . liquefaciens is investigated in terms of a mathematical model that combines biological as well as hydrodynamic processes . The relative importance of cell differentiation and production of an extracellular wetting agent to bacterial swarming is explored using a continuum representation . The model incorporates aspects of thin film flow with variable suspension viscosity, wetting, and cell differentiation . Experimental evidence suggests that the bacterial colony is highly sensitive to its environment and that a variety of mechanisms are exploited in order to proliferate on a variety of surfaces . It is found that a combination of effects are required to reproduce the variation of bacterial colony motility over a large range of nutrient availability and medium hardness.

J Food Prot, 2000 Jan, 63(1), 123 - 5
Evaluation of the Petrifilm rapid coliform count plate method for coliform enumeration from surimi-based imitation crab slurry; Chung KS et al.; The 3M Petrifilm rapid coliform count (RCC) plate method was compared with two conventional methods, namely violet red bile agar (VRBA) and desoxycholate lactose agar (DLA), for enumerating coliforms . The VRBA plating method is a reference method in the Bacteriological Analytical Manual and the DLA plating method is the method recommended by the Food Sanitation Law of Korea for enumeration of coliforms . Serratia sp., a coliform that was isolated from frozen surimi, was incubated in surimi-based imitation crab (SBIC) slurries and enumerated on the Petrifilm RCC, VRBA, and DLA plates . Results from the Petrifilm RCC plate were not significantly different from results from VRBA or DLA plates at P < 0.05 level . The correlation coefficient for Petrifilm RCC plates versus the VRBA method and for Petrifilm RCC plates versus the DLA method were 0.994 and 0.996, respectively . With the Petrifilm RCC plate method, we were able to estimate presumptive coliforms (except Serratia sp.) after 14 h and to enumerate confirmed coliforms (including Serratia sp.) after 24 h.

J Formos Med Assoc, 1999 Dec, 98(12), 851 - 4
Necrotizing fasciitis caused by Serratia marcescens in two patients receiving corticosteroid therapy; Huang JW et al.; Necrotizing fasciitis (NF), a devastating soft tissue infection, is rarely attributed to Serratia marcescens . We here report two patients with S . marcescens NF, both of whom had underlying renal disease and had been receiving corticosteroid therapy . The first patient, a 40-year-old man with systemic lupus erythematosus and uremia on prednisolone therapy, developed fulminant cellulitis and septic shock 1 month after a skin biopsy for cutaneous vasculitis of the left foot . The cellulitis evolved to NF, and blood and necrotic tissue cultures both grew S . marcescens . The patient completely recovered after debridement and ceftazidime therapy . The second patient, a 73-year-old man receiving prednisolone therapy for nephrotic syndrome, developed right leg cellulitis that evolved to NF . Blood and necrotic tissue cultures both grew S . marcescens . After aggressive debridement and ciprofloaxcin therapy, the NF improved . However, the patient died of aspiration pneumonia and massive gastrointestinal bleeding 1 month later . These findings illustrate that S . marcescens should be considered as a potential pathogen causing NF in susceptible hosts.

Microbiology, 1999 Dec, 145 ( Pt 12), 3557 - 64
Oocydin A, a chlorinated macrocyclic lactone with potent anti-oomycete activity from Serratia marcescens; Srobel G et al.; A unique chlorinated macrocyclic lactone, termed oocydin A, was isolated from a strain of Serratia marcescens growing as an epiphyte on Rhyncholacis pedicillata, an aquatic plant native to the Carrao river of the Venezuelan-Guyanan region of South America . The lactone has a molecular mass of 470 Da, and contains one atom of chlorine, a carboxyl group and a tetrahydrofuran ring internal to a larger macrocyclic ring . MICs of approximately 0.03 microg ml(-1) were noted for oocydin A against such phytopathogenic oomycetes as Pythium ultimum, Phytophthora parasitica, Phytophthora cinnamomi and Phytophthora citrophora . With regard to the true fungi, oocydin A had either minimal or no effect against certain Fungi Imperfecti (including several pathogens of humans), two ascomycetes and a basidiomycete . Oocydin A may have potential as an antimycotic in agricultural applications and especially for crop protection.

Arch Biochem Biophys, 2000 Jan 15, 373(2), 352 - 60
Allosteric signal transmission involves synergy between discrete structural units of the regulatory subunit of aspartate transcarbamoylase; Liu L et al.; Previous studies have shown that the S5' beta-strand (r93-r97) of the regulatory polypeptides of the aspartate transcarbamoylases (ATCases) from Serratia marcescens and Escherichia coli are responsible for their diverged allosteric regulatory patterns, including conversion of CTP from an inhibitor in E . coli to an activator in S . marcescens . Similarly, mutation of residues located in the interface between the allosteric and the zinc domains resulted in conversion of the ATP responses of the E . coli enzyme from activation to inhibition, suggesting that this interface not only mediates but also discriminates the allosteric responses of ATP and CTP . To further decipher the roles and the interrelationships of these regions in allosteric communication, allosteric-zinc interface mutations (Y77F and V106A) have been introduced into both the native and the S5' beta-strand chimeric backgrounds . While the significance of this interface in the allosteric regulation has been confirmed, there is no direct evidence supporting the presence of distinct pathways for the ATP and CTP signals through this interface . The analysis of the mutational effects reported here suggested that the S5' beta-strand transmits the allosteric signal by modulating the hydrophobic allosteric-zinc interface rather than disturbing the allosteric ligand binding . Intragenic suppression by substitutions in the hydrophobic interface between the allosteric and the zinc domains of the regulatory chains resulted in the partial recovery of allosteric responses in the EC:rS5'sm chimera and reduced the activation by ATP in the Sm:rS5'ec chimera . Thus, it seems that there is a synergy between these two structural units .

FEMS Microbiol Lett, 2000 Jan 1, 182(1), 131 - 5
Evidence on the presence of two distinct alkaline phosphatases in Serratia marcescens; Bhatti AR et al.; Certain strains of Serratia marcescens synthesized two different types of alkaline phosphatase (APase), constitutive (CAPase) and inducible (IAPase) APases, in low phosphate medium . Synthesis of the IAPase was repressed in the presence of high phosphate . Purification and separation of these electrophoretically distinct APases was achieved by using fractional (NH(4))(2)SO(4) precipitation, adsorption on a DEAE-cellulose column and elution of enzymes by a linear sodium chloride gradient . Starch gel electrophoresis of certain fractions revealed the separation of not only IAPase from CAPase but its separation into four distinct isozymes . CAPase gave maximum enzyme activity around pH 9.5, whereas for IAPase a broad range of enzyme activity was found between pH 8.5 and 10.5 . Reversible inactivation at low pH occurred for IAPase but very little with CAPase . CAPase was more thermolabile than IAPase at 95 degrees C . The two APases were found to be distinct in their kinetic as well as immunological properties, suggesting two distinct enzyme species.

Int J Occup Saf Ergon, 1998, 4(3), 287 - 297
Method for Evaluating Germicidal Ultraviolet Inactivation of Biocontaminated Surfaces; Gorsuch EL et al.; Safety issues related to work-site conditions often deal with potential worker exposure to infectious airborne microorganisms due to their dissemination in indoor air and contamination of surfaces . Germicidal ultraviolet (GUV) radiation is used in health-care settings and other occupational environments for microbial inactivation . In this study, a new methodology for determining the efficiency of GUV microbial inactivation of surfaces was developed and evaluated . The method utilizes identical chambers in which test microorganisms are irradiated on agar surfaces at different humidity and irradiation intensity levels . The effects of GUV intensity and exposure time on microbial inactivation were examined for Micrococcus luteus and Serratia marcescens . It was found that at low humidity levels (20-25%) both organisms can be inactivated with at least 95% efficiency if the GUV intensity exceeds 50 micro W/cm2 for at least 3-5 min (corresponding to a dose of 10 mJ/cm2) . The radiation dose needed for effective inactivation of S . marcescens, as measured by a UV meter near the microbial sample, was found not to be affected by the humidity level, whereas that of M . luteus increased at higher humidities . The findings of this study can be used to determine sufficient GUV inactivation doses for occupational environments with various microbial contaminations.

FEBS Lett, 1999 Dec 10, 463(1-2), 1 - 2
Structural parsimony in endonuclease active sites: should the number of homing endonuclease families be redefined?
Kuhlmann UC, Moore GR, James R, Kleanthous C, Hemmings AM.
Homing endonucleases are classified into four families based on active site sequence motifs . Through structural comparisons we have found structural similarities between the endonuclease domain of colicin E9, an H-N-H motif-containing enzyme, and both the non-specific nuclease from Serratia and I-PpoI, a His-Cys box-containing homing endonuclease . Our comparison identifies conservation at the heart of all three enzyme active sites and so argues for a re-classification of H-N-H and His-Cys box homing endonucleases as a single family . We suggest the 'betabetaalpha-Me family' of homing enzymes to reflect the three elements of secondary structure and the metal ion that define the motif.

J Microbiol Immunol Infect, 1997 Nov, 30(4), 242 - 54
Population cell differentiation of Serratia marcescens on agar surface and in broth culture; Lai HC et al.; The bacterium Serratia marcescens shows population surface migration (swarming) phenomenum on an LB swarming plate, and differentiated cells can be observed at the swarming front . How the cell population differentiates during swarming on the agar surface is not known, neither is it clear whether cells with differentiated characteristics can be observed in broth culture . To monitor the population cell differentiation in a highly sensitive way without cell destruction, experiments were designed using bacterial luciferase genes luxAB as the reporter genes to allow direct monitoring of the differentiating cells through bioluminescence . An isogenic S . marcescens strain was constructed with luxAB under the control of the promoter of flagellin gene hag (phag::luxAB) . Patterns of cell differentiation were monitored either by direct X-ray film exposure and/or by Autolumat luminometer detection . Results show that population cell differentiation on the agar surface occurs first in a temporal and then spatial way during colonial growth . It was also found that cells harvested from both the spreading agar plate and broth culture showed differentiation patterns similar to those from swarming cells, suggesting that the agar surface culture may not be essential for the formation of differentiated cells.

Antimicrob Agents Chemother, 1999 Dec, 43(12), 2904 - 9
Biochemical characterization of novel tetrahydrofuranyl 1beta-methylcarbapenems: stability to hydrolysis by renal dehydropeptidases and bacterial beta-lactamases, binding to penicillin binding proteins, and permeability properties; Yang Y et al.; The biochemical properties of tetrahydrofuranyl (THF) carbapenems, carbapenems with THF substituents, were evaluated with respect to enzyme stability, binding to penicillin-binding proteins (PBPs), and penetration into gram-negative organisms . THF carbapenems showed increased stability to hog renal dehydropeptidases (DHPs) compared to that of imipenem or meropenem and were more stable to human DHP than imipenem (<10% hydrolysis compared to that for imipenem) . THF carbapenems were stable to hydrolysis by all serine beta-lactamases tested . CL 191,121, a prototype THF carbapenem, was more stable to hydrolysis by carbapenem-hydrolyzing serine beta-lactamases such as IMI-1 and Sme-1 than imipenem, with a relative k(cat) value of <20% for imipenem . Similar to imipenem and meropenem, THF carbapenems were not stable to the metallo beta-lactamases CcrA and L1 . However, CL 191,121 bound to all Staphylococcus aureus PBPs at concentrations that were less than or equal to the MICs . The THF carbapenems bound to PBPs from Escherichia coli and Pseudomonas aeruginosa, with the highest affinities being for PBPs 2 and 4, as noted with imipenem . The affinities for PBPs 1a and 1b in E . coli were reduced for the THF carbapenems compared to that for imipenem, even though the MICs of the THF carbapenems for E . coli strains were lower than those of imipenem . The penetrability of the THF carbapenems into Serratia marcescens S6, which produces the Sme-1 carbapenem-hydrolyzing beta-lactamase, was 2.4 to 7.8 times less than that of imipenem . Compounds CL 190,294 and CL 188,624 showed good penetrability, with permeability coefficient values comparable to those of the rapidly penetrating agents cephaloridine, imipenem, meropenem, and biapenem . Decreased penetration into wild-type P . aeruginosa was suggested by the high MICs of the THF carbapenems (MICs, 16 to 32 microg/ml), despite equivalent or better binding to P . aeruginosa PBPs than that of imipenem . However, the MICs of the THF carbapenems for wild-type P . aeruginosa compared to that for an OprD2 mutant generally varied no more than 2-fold, but those of imipenem and other carbapenems differed 16-fold . These data indicated that THF carbapenems do not appear to enter through protein OprD2 . In conclusion, the THF carbapenems exhibited stability to hydrolysis by renal DHPs and serine beta-lactamases, exhibited strong binding to essential PBPs from E . coli and S . aureus, and penetrated gram-negative enteric bacteria at rates comparable to those for meropenem and biapenem.

Parasitology, 1999 Oct, 119 ( Pt 4), 395 - 404
Evidence from two planorbid snails of a complex and dedicated response to digenean (echinostome) infection; Adema CM et al.; The planorbid snail Biomphalaria glabrata responded to exposure to either the compatible digenetic trematode Echinostoma paraensei or the incompatible species Echinostoma trivolvis by producing increased amounts of several distinctive plasma polypeptides . These polypeptides characteristically precipitated from plasma when mixed with secreted-excreted products (SEP) of sporocysts or rediae from either digenean species . In contrast, control snails, or snails that had been wounded or infected with bacteria (Serratia marcesens or Staphylococcus epidermidis) showed no obvious plasma alterations and no precipitates formed when their plasma was mixed with SEP . Another planorbid species, Helisoma trivolvis, which displays reverse compatibility for the echinostome species used, also responded to exposure to both echinostomes by increased production of plasma polypeptides that precipitated in the presence of SEP . With some individual variation, these 2 snail species synthesized SEP-reactive plasma polypeptides forming diffuse bands centred at 53, 65, 80-120 and 200 kDa (the latter absent in Helisoma trivolvis) . The 53 kDa polypeptides had not been observed before, whereas the others have been noted from B . glabrata . The diffuse 65 kDa band was strongly bound by anti-fibrinogen antibodies, supportive of earlier studies indicating it contains fibrinogen-related domains . The other specified polypeptides were also bound by these antibodies raising the possibility that they too contain fibrinogen domains . The results are suggestive of a general ability of these 2 planorbid snails to detect the presence of echinostomes even if the latter are subsequently incapable of development . The complex response they then mount, one not evoked by other challenges such as wounding or bacterial infection, may represent a dedicated response to a frequently encountered group of pathogenic parasites, the digeneans (echinostomes).

J Microbiol Methods, 1999 Dec, 39(1), 59 - 78
Species-specific detection of hydrocarbon-utilizing bacteria; Wilson VL et al.; Rapid detection and quantitative assessment of specific microbial species in environmental samples is desirable for monitoring changes in ecosystems and for tracking natural or introduced microbial species during bioremediation of contaminated sites . In the interests of developing rapid tests for hydrocarbon-degrading bacteria, species-specific PCR primer sets have been developed for Pseudomonas aeruginosa, Stentrophomonas (Xanthomonas) maltophilia, and Serratia marsescens . Highly variable regions of the 16S rRNA gene were used to design these primer sets . The amplification products of these primer sets have been verified and validated with hemi-nested PCR and with ligase chain reaction (LCR) techniques, and have been applied to the analyses of environmental water samples . These species-specific primer sets were also chosen to amplify in conjunction with a universal set of PCR primers chosen from highly conserved neighboring sequences in the same gene . These multiplex or competitive PCR procedures enable testing with an internal marker and/or the quantitative estimation of the relative proportion of the microbial community that any one of these species occupies . In addition, this universal PCR primer set amplified the same size amplicon from a wide spectrum of procaryotic and eucaryotic organisms and may have potential in earth biota analyses.

J Clin Microbiol, 1999 Dec, 37(12), 4167 - 9
Molecular epidemiology of a cluster of cases due to Klebsiella pneumoniae producing SHV-5 extended-spectrum beta-lactamase in the premature intensive care unit of a Hungarian hospital; Szabo D et al.; Fifteen nosocomial cases of extended-spectrum beta-lactamase-producing Klebsiella pneumoniae occurred among 132 neonates in a premature intensive care unit in Hungary in June through November 1998 . Fourteen strains were indistinguishable by molecular biological typing and harbored the same single conjugative extended-spectrum beta-lactamase-encoding plasmid that was spontaneously found in a Serratia marcescens strain in the same patient.

CLAO J, 1999 Oct, 25(4), 213 - 7
Antimicrobial comparison of a new multi-purpose disinfecting solution to a 3% hydrogen peroxide system; Rosenthal RA et al.; PURPOSE: We compared the antimicrobial activity of a new multi-purpose disinfection solution (OPTI-FREE EXPRESS with ALDOX) to a 3% hydrogen peroxide disinfecting system . The antimicrobial ingredients in the new solution are polyquaternium-1 and myristamidopropyl dimethylamine . METHODS: The solutions were tested for antimicrobial activity against Staphylococcus sp.., Pseudomonas aeruginosa, Serratia marcescens, Candida albicans, Fusarium solani, and two Acanthamoeba species and were evaluated according to the primary criteria of the FDA and ISO contact lens disinfection procedures . RESULTS AND CONCLUSIONS: OPTI-FREE EXPRESS with ALDOX (EXPRESS MPDS) Multi-Purpose Disinfecting Solution provided a multiple spectrum of antimicrobial activity and met the FDA and ISO primary Stand Alone Test criteria for disinfection of contact lenses . EXPRESS MPDS showed disinfection activity in the range of a 3% hydrogen peroxide system . Unlike the 3% hydrogen peroxide system, it retarded contamination during storage.

Curr Eye Res, 1999 Dec, 19(6), 525 - 32
Serratia marcescens keratitis: strain-specific corneal pathogenesis in rabbits; Hume EB et al.; PURPOSE . The purpose of this study was to develop an animal model of Serratia keratitis that is suitable to demonstrate the pathology of specific strains . METHODS . Serratia marcescens ocular strains 93-1399-1 and 94-EI-185-2, and an environmental strain (ATCC 14041) were characterized in vitro in terms of their motility, metabolic profiles, ribotypes, and protease production . The strains were then analyzed in the rabbit intrastromal injection model . Slit lamp examination (SLE) and enumeration of bacteria in the cornea was conducted every 6 hours for 30 hours post-infection . In vivo motilities were analyzed by quantification of bacteria in the peripheral and central areas of infected rabbit corneas . RESULTS . All strains were similar in their metabolic activity and production of extracellular proteases . The ocular isolates were distinct from the environmental strain in their ribotyping patterns and in their motility . Each strain grew logarithmically in the cornea up to 6 hours post-infection . SLE scores increased from 0 to 30 hours post-infection for strains ATCC 14041 and 93-1399-1, while the SLE score of strain 94-EI-185-2 reached its maximum at 18 hours post-infection . Strain-specific differences in pathology were noted from 18 to 30 hours post-infection . Strain 94-EI-185-2 produced iritis but only mild corneal changes . Strain 93-1399-1 produced a severe corneal infiltrate encompassing the entire corneal surface as well as severe conjunctival inflammation and iritis . Strain ATCC 14041 produced a localized, severe, exudative corneal abscess that contained infecting bacteria . CONCLUSIONS . A rabbit model of Serratia keratitis was developed in which bacterial growth kinetics and strain-specific ocular pathologic changes were reproducible.

Nucleosides Nucleotides, 1999 Sep, 18(9), 1945 - 60
Application of oligonucleoside methylphosphonates in the studies on phosphodiester hydrolysis by Serratia endonuclease; Srivastava TK et al.; The endonuclease from Serratia marcescens is a non-specific enzyme that cleaves single and double stranded RNA and DNA . It accepts a phosphorylated pentanucleotide as a minimal substrate which is cleaved in the presence of Mg2+ at the second phosphodiester linkage . The present study is aimed at understanding the role of electrostatic and hydrogen bond interactions in phosphodiester hydrolysis . Towards this objective, six pentadeoxyadenylates with single stereoregular methylphosphonate substitution within this minimal substrate (2a-4b) were synthesized following a protocol described here . These modified oligonucleotides were used as substrates for the Serratia nuclease . The enzyme interaction studies revealed that the enzyme failed to hydrolyze any of the methylphosphonate analogues suggesting the importance of negative charge and/or hydrogen bond acceptors in binding and cleavage of its substrate . Based on these results and available site-directed mutagenesis as well as structural data, a model for nucleic acid binding by Serratia nuclease is proposed.

Biochem J, 1999 Nov 1, 343 Pt 3, 587 - 96
The third chitinase gene (chiC) of Serratia marcescens 2170 and the relationship of its product to other bacterial chitinases; Suzuki K et al.; The third chitinase gene (chiC) of Serratia marcescens 2170, specifying chitinases C1 and C2, was identified . Chitinase C1 lacks a signal sequence and consists of a catalytic domain belonging to glycoside hydrolase family 18, a fibronectin type III-like domain (Fn3 domain) and a C-terminal chitin-binding domain (ChBD) . Chitinase C2 corresponds to the catalytic domain of C1 and is probably generated by proteolytic removal of the Fn3 and ChBDs . The loss of the C-terminal portion reduced the hydrolytic activity towards powdered chitin and regenerated chitin, but not towards colloidal chitin and glycol chitin, illustrating the importance of the ChBD for the efficient hydrolysis of crystalline chitin . Phylogenetic analysis showed that bacterial family 18 chitinases can be clustered in three subfamilies which have diverged at an early stage of bacterial chitinase evolution . Ser . marcescens chitinase C1 is found in one subfamily, whereas chitinases A and B of the same bacterium belong to another subfamily . Chitinase C1 is the only Ser . marcescens chitinase that has an Fn3 domain . The presence of multiple, divergent, chitinases in a single chitinolytic bacterium is perhaps necessary for efficient synergistic degradation of chitin.

FEMS Microbiol Lett, 1999 Oct 15, 179(2), 289 - 96
Inhibition of IMP-1 metallo-beta-lactamase and sensitization of IMP-1-producing bacteria by thioester derivatives(dagger); Hammond GG et al.; IMP-1 metallo-beta-lactamase is a transferable carbapenem-hydrolyzing enzyme found in some clinical isolates of Pseudomonas aeruginosa, Serratia marcescens and Klebsiella pneumoniae . Bacteria that express IMP-1 show significantly reduced sensitivity to carbapenems and other beta-lactam antibiotics . A series of thioester derivatives has been shown to competitively inhibit purified IMP-1 . As substrates for IMP-1, the thioesters yielded thiol hydrolysis products which themselves were reversible competitive inhibitors . The thioesters also increased sensitivity to the carbapenem L-742,728 in an IMP-1-producing laboratory stain of Escherichia coli, but will need further modification to improve their activity in less permeable organisms such as Pseudomonas and Serratia . Nonetheless, the thioester IMP-1 inhibitors offer an encouraging start to overcoming metallo-beta-lactamase-mediated resistance in bacteria.

Appl Environ Microbiol, 1999 Oct, 65(10), 4543 - 8
Effect of milk proteins on adhesion of bacteria to stainless steel surfaces; Barnes LM et al.; Stainless steel coupons were treated with skim milk and subsequently challenged with individual bacterial suspensions of Staphylococcus aureus, Pseudomonas fragi, Escherichia coli, Listeria monocytogenes, and Serratia marcescens . The numbers of attached bacteria were determined by direct epifluorescence microscopy and compared with the attachment levels on clean stainless steel with two different surface finishes . Skim milk was found to reduce adhesion of S . aureus, L . monocytogenes, and S . marcescens . P . fragi and E . coli attached in very small numbers to the clear surfaces, making the effect of any adsorbed protein layer difficult to assess . Individual milk proteins alpha-casein, beta-casein, kappa-casein, and alpha-lactalbumin were also found to reduce the adhesion of S . aureus and L . monocytogenes . The adhesion of bacteria to samples treated with milk dilutions up to 0.001% was investigated . X-ray photoelectron spectroscopy was used to determine the proportion of nitrogen in the adsorbed films . Attached bacterial numbers were inversely related to the relative atomic percentage of nitrogen on the surface . A comparison of two types of stainless steel surface, a 2B and a no . 8 mirror finish, indicated that the difference in these levels of surface roughness did not greatly affect bacterial attachment, and reduction in adhesion to a milk-treated surface was still observed . Cross-linking of adsorbed proteins partially reversed the inhibition of bacterial attachment, indicating that protein chain mobility and steric exclusion may be important in this phenomenon.

J Microbiol Immunol Infect, 1998 Dec, 31(4), 245 - 8
Serratia marcescens renal abscess with endophthalmitis: a case report; Lin MF et al.; A renal abscess, caused by Serratia marcescens with endophthalmitis in a 68-year-old diabetic female, is described . Endophthalmitis presented with visual loss, conjunctiva injection and lid edema with eye pain . Right costovertebral knocking pain was also noted . Sonography and computed tomography of abdomen showed a 4 cm hypoechoic lesion in the middle portion of the right kidney with marginal enhancement after contrast media injection . Percutaneous abscess drain was performed . Pus culture from the drain tube revealed S . marcescens, yet, vitreous cultures yielded no growth, which was ascribed to previous antibiotics use . Although vitrectomy, fortified eye drops, intravitreal and systemic intravenous antibiotics were administered, the visual function was still lost . To our knowledge, this is the first reported case of S . marcescens renal abscess complicated with endophthalmitis.

Aust N Z J Ophthalmol, 1999 Jun-Aug, 27(3-4), 228 - 30
Bacterial invasion of corneal epithelial cells; Vallas V et al.; PURPOSE: The normal ocular surface is frequently colonized by commensal gram-positive species . Gram-negative bacteria are often implicated in corneal infection and inflammation, particularly in association with soft contact lens wear . The aim of this study was to elucidate possible mechanisms of virulence in ocular bacteria . METHODS: The susceptibility of a human corneal epithelial cell line to bacterial invasion and association was evaluated using the gentamicin exclusion assay . Organisms tested included isolates from corneal ulcers, corneal inflammation and ocular sites in asymptomatic individuals . RESULTS: The commensal, non-pathogenic bacterium Staphylococcus epidermidis and some pathogenic strains of Serratia marcescens did not invade corneal epithelial cells . In contrast, pathogenic strains of Pseudomonas aeruginosa associated with and invaded corneal epithelial cells . CONCLUSIONS: The increased association of P . aeruginosa, compared to other bacterial types, might be a reason for the more frequent association of this bacterium with contact-lens-associated microbial keratitis.

Appl Environ Microbiol, 1999 Sep, 65(9), 4227 - 9
Identification of bacterial species associated with the sheep scab mite (Psoroptes ovis) by using amplified genes coding for 16S rRNA; Hogg JC et al.; This was the first molecular study of the bacterial flora of the sheep scab mite (Psoroptes ovis) . A sequence analysis of genes coding for 16S rRNA revealed that Serratia marcescens and bacteria closely related to Staphylococcus intermedius or Staphylococcus chromogens and Alloiococcus otitidis were present . These bacteria were associated with skin lesions, dermatitis, and otitis media caused by P . ovis.

Zentralbl Bakteriol, 1999 Jul, 289(3), 249 - 63
Characterization of nosocomial Serratia marcescens isolates: comparison of Fourier-transform infrared spectroscopy with pulsed-field gel electrophoresis of genomic DNA fragments and multilocus enzyme electrophoresis; Irmscher HM et al.; A total of 66 Serratia marcescens isolates from 46 patients was investigated by macrorestriction using XbaI followed by pulsed-field gel electrophoresis . 7 restriction fragment patterns attributable to more than one patient and 9 individual patterns were identified . The isolates were additionally characterized by multilocus enzyme electrophoresis and Fourier-transform infrared spectroscopy . The macrorestriction patterns and the multilocus enzyme electrophoresis patterns corresponded fairly well while the classifications derived from these methods were not completely congruent . The grouping achieved by Fourier-transform infrared spectroscopy on the basis of high (> 1000) and moderately high heterogeneity values (300) was consistent with the macrorestriction results . Grouping on a lower heterogeneity level did not contribute to further discrimination . In general, Fourier-transform infrared spectroscopy was less discriminatory than the two other methods, but easier to perform . Therefore, laboratories equipped with the necessary devices may use it to rapidly select bacterial isolates for macrorestriction or other well established characterization procedures.

J Biochem (Tokyo), 1999 Sep, 126(3), 559 - 65
Crystal structure of prolyl aminopeptidase from Serratia marcescens; Yoshimoto T et al.; Prolyl aminopeptidase from Serratia marcescens specifically catalyzes the removal of N-terminal proline residues from peptides . We have solved its three-dimensional structure at 2.3 A resolution by the multiple isomorphous replacement method . The enzyme consists of two contiguous domains . The larger domain shows the general topology of the alpha/beta hydrolase fold, with a central eight-stranded beta-sheet and six helices . The smaller domain consists of six helices . The catalytic triad (Ser113, His296, and Asp268) is located near the large cavity at the interface between the two domains . Cys271, which is sensitive to SH reagents, is located near the catalytic residues, in spite of the fact that the enzyme is a serine peptidase . The specific residues which make up the hydrophobic pocket line the smaller domain, and the specificity of the exo-type enzyme originates from this smaller domain, which blocks the N-terminal of P1 proline.

Diagn Microbiol Infect Dis, 1999 Aug, 34(4), 263 - 8
Comparative evaluation of an automated ribotyping instrument versus pulsed-field gel electrophoresis for epidemiological investigation of clinical isolates of bacteria; Hollis RJ et al.; A collection of bacterial isolates were typed using the Ribo-Printer Microbial Characterization System (Qualicon, Wilmington, DE, USA), an automated ribotyping system, and pulsed-field gel electrophoresis (PFGE) . Grouping patterns, discrimination, and typeability were compared . The collection consisted of 411 isolates of bacteria from 32 medical centers . The isolates included a total of 18 species (both Gram-positive and Gram-negative), covering the range of concern to a laboratory performing epidemiological investigations . The patterns of groups obtained by both typing systems were similar for all species examined . Ribotyping provided less discrimination than PFGE, especially for Serratia marcescens, and Pseudomonas aeruginosa . All strains were typed by the Ribo-Printer, but 2.75% were not typeable by PFGE . The Ribo-Printer has proven to be a valuable primary typing method for a high-volume laboratory, even for those species for which it provides a lesser degree of discrimination than PFGE.

Mol Plant Microbe Interact, 1999 Aug, 12(8), 748 - 51
Expression of a Serratia marcescens chitinase gene in Sinorhizobium fredii USDA191 and Sinorhizobium meliloti RCR2011 impedes soybean and alfalfa nodulation; Krishnan HB et al.; A gene encoding chitinase from Serratia marcescens BJL200 was cloned into a broad-host-range vector (pRK415) and mobilized into Sinorhizobium fredii USDA191 . Chitinolytic activity was detected in S . fredii USDA191 transconjugants that carried the S . marcescens chiB gene . Chitinase-producing S . fredii USDA191 formed nodules on soybean cultivar McCall . However, there was a delay in nodule formation and a marked decrease in the total number of nodules formed by the chitinase-producing S . fredii in comparison with the wild-type strain . Expression of chitinase in S . meliloti RCR2011 also impeded alfalfa nodulation . Thin-layer chromatography of 14C-labeled Nod factors from chitinase-producing S . fredii USDA191 revealed hydrolysis of lipochitooligosaccharides.

Proc Natl Acad Sci U S A, 1999 Aug 3, 96(16), 8931 - 6
Crystal structure and mechanism of histone acetylation of the yeast GCN5 transcriptional coactivator; Trievel RC et al.; The yeast GCN5 (yGCN5) transcriptional coactivator functions as a histone acetyltransferase (HAT) to promote transcriptional activation . Here, we present the high resolution crystal structure of the HAT domain of yGCN5 and probe the functional importance of a conserved glutamate residue . The structure reveals a central protein core associated with AcCoA binding that appears to be structurally conserved among a superfamily of N-acetyltransferases, including yeast histone acetyltransferase 1 and Serratia marcescens aminoglycoside 3-N-acetyltransferase . A pronounced cleft lying above this core, and flanked by N- and C-terminal regions that show no sequence conservation within N-acetyltransferase enzymes, is implicated by cross-species conservation and mutagenesis studies to be a site for histone substrate binding and catalysis . Located at the bottom of this cleft is a conserved glutamate residue (E173) that is in position to play an important catalytic role in histone acetylation . Functional analysis of an E173Q mutant yGCN5 protein implicates glutamate 173 to function as a general base for catalysis . Together, a correlation of the yGCN5 structure with functionally debilitating yGCN5 mutations provides a paradigm for understanding the structure/function relationships of the growing number of transcriptional regulators that function as histone acetyltransferase enzymes.

Antimicrob Agents Chemother, 1999 Aug, 43(8), 1924 - 31
A novel type of AmpC beta-lactamase, ACC-1, produced by a Klebsiella pneumoniae strain causing nosocomial pneumonia; Bauernfeind A et al.; A Klebsiella pneumoniae strain resistant to oxyimino cephalosporins was cultured from respiratory secretions of a patient suffering from nosocomial pneumonia in Kiel, Germany, in 1997 . The isolate harbors a bla resistance gene located on a transmissible plasmid . An Escherichia coli transconjugant produces a beta-lactamase with an isoelectric point of 7.7 and a resistance phenotype characteristic of an AmpC (class 1) beta-lactamase except for low MICs of cephamycins . The bla gene was cloned and sequenced . It encodes a protein of 386 amino acids with the active site serine of the S-X-X-K motif at position 64, as is characteristic for class C beta-lactamases . Multiple alignment of the deduced amino acid sequence with 21 other AmpC beta-lactamases demonstrates only very distant homology, reaching at maximum 52.3% identity for the chromosomal AmpC beta-lactamase of Serratia marcescens SR50 . The beta-lactamase of K . pneumoniae KUS represents a new type of AmpC-class enzyme, for which we propose the designation ACC-1 (Ambler class C-1).

J Basic Microbiol, 1999, 39(3), 197 - 211
Two genes in prophage y of Serratia marcescens with functional counterparts in prophage Psi tested by Mu insertions as to order and homology; Steiger H et al.; Two special genes carried in pairs by the native prophages y and psi of Serratia marcescens HY, with functionally rather similar counterparts each, were assigned to restriction fragments and tested for homology . The y genes any and sky, as well as the psi genes anp and skp, are specifically activated by infection of HY cells with kappa phage . The kappa genes exerting this effect are tay for y and tap for psi . By means of tay and tap mutants, insertions of phage Mu DNA in the relevant parts of y and psi prophage, respectively, could be discovered . These insertions and subsequent deletions of Mu were the basis of our studies . The use of Mu was made possible by the isolation of an HY variant giving appropriate plaques with Mu particles of the G(-) type . In the case of another HY variant, Mu plaque formation depended on the presence of a host range mutation isolated by its ability to allow plaque formation on E . coli C, an indicator only for G(-) particles . Unexpectedly, this HY strain was an indicator of both G(-) and G(+) particles, but unfortunately had become adsorption resistant to y and psi . As an accessory result, it provided evidence for a second restriction/modification system . In both cases the O-specific polysaccharides were reduced . The main results of our paper concerning the two pairs of y and psi genes are as follows: the orders any-sky and anp-skp correspond with each other in y and psi; the sky gene, just as the skp gene, lies near one prophage end . However, despite the similarity in function and order, these genes are not homologous, in contrast to any and anp, which are at least partially homologous . The homologous regions of y and psi amount to only about 0.5 kbp . Another observation was that bacteria with a Mu insertion near the skp end of psi prophage were no longer cured of psi when infected with kappa tay-l, in contrast to the efficient curing observed with an ordinary psi prophage.

J Am Acad Dermatol, 1999 Aug, 41(2 Pt 2), 319 - 21
Painful red nodules of the legs: a manifestation of chronic infection with gram-negative organisms; Nieves DS et al.; Skin infection secondary to gram-negative organisms is uncommon and is typically limited to persons who are immunocompromised . When these do occur, they are acute, progressive, and severe . Here we report 2 cases of painful red nodules that presented with a waxing and waning course over a long period . One case is that of a 45-year-old healthy white man who developed Serratia marcescens infection in 1 leg . The other case is that of a 78-year-old man with chronic lymphocytic leukemia treated with prednisone who developed infection of the leg secondary to Pseudomonas aeruginosa . In the first case, symptoms were present for 2 years before definitive diagnosis and treatment . In the second case, 4 months elapsed . Ultimately, both patients responded to antibiotic therapy and recovered . These cases illustrate an unusual presentation of chronic red painful nodules of the leg secondary to infection with gram-negative organisms and underscore the importance of culture even when infection seems unlikely.

Arch Insect Biochem Physiol, 1999, 41(4), 225 - 32
Prostaglandin production in response to a bacterial infection in true armyworm larvae
Jurenka RA, Pedibhotla VK, Stanley DW.
Prostaglandin levels were determined by fluorometric HPLC analysis of hemolymph collected from larvae of the true armyworm, Pseudaletia unipuncta, that had been injected with bacteria . Prostaglandins were extracted and derivatized with the fluorogenic compound 9-anthryldiazomethane and detected by fluorescence-HPLC . One of the prostaglandins produced was identified as prostaglandin F(2alpha) based on HPLC retention time . The chemical identity of prostaglandin F(2alpha) was confirmed by isolation and derivatization followed by gas chromatography mass spectrometry analysis . Larvae injected with heat-killed bacteria, Serratia marcescens, produced about 4 times as much prostaglandin F(2alpha) as larvae injected with saline . In a separate experiment, larvae injected with bacteria and the prostaglandin precursor arachidonic acid produced still higher levels of prostaglandin F(2alpha) . The production of prostaglandin was inhibited with phenidone, a dual cyclooxygenase and lipoxygenase inhibitor . These data indicate that bacterial injections stimulate increased eicosanoid biosynthesis in true armyworms, particularly biosynthesis of prostaglandin F(2alpha) . Our findings add considerable support to the hypothesis that eicosanoids mediate insect cellular immune reactions to bacterial infections . Arch .

Lancet, 1999 Jul 17, 354(9174), 181 - 5
Incidence of contact-lens-associated microbial keratitis and its related morbidity; Cheng KH et al.; BACKGROUND: The incidence of contact-lens-associated microbial keratitis is uncertain and its related morbidity in the general population of contact-lens wearers is not known . We examined these issues in a prospective epidemiological study . METHODS: We surveyed all practising ophthalmologists in the Netherlands to identify all new cases of microbial keratitis reported during a 3-month period in 1996 . Follow-up telephone calls were made to examine ocular morbidity . We undertook annual nationwide telephone surveys between 1994 and 1997 to estimate the prevalence of contact-lens wear . FINDINGS: Of 440 ophthalmologists contacted, 379 provided information . There were 92 cases of microbial keratitis; 17 used daily-wear rigid gas-permeable lenses, 63 daily-wear soft lenses, and 12 extended-wear soft lenses . The estimated annualised incidence of microbial keratitis was 1.1 per 10,000 (95% CI 0.6-1.7) users of daily-wear rigid gas-permeable lenses, 3.5 per 10,000 (2.7-4.5) users of daily-wear soft lenses, and 20.0 per 10,000 (10.3-35.0) users of extended-wear soft lenses (p<0.00001 for comparison between all groups), Five of the 92 patients achieved a final visual acuity of 20/70 or less . Pseudomonas and Serratia spp were the organisms most commonly isolated . Pseudomonas keratitis accounted for the largest mean diameter of corneal ulcers, the highest mean number of days in hospital, the greatest number of mean outpatients visits, and the poorest visual acuity outcome . INTERPRETATION: The incidence of microbial keratitis among users of extended-wear soft contact lenses in the Netherlands is similar to that reported in the USA during 1989 . Awareness of risk factors and improvement in contact-lens materials have not led to a decrease in incidence . Overnight wear should be strongly discouraged.

Mol Microbiol, 1999 Aug, 33(3), 546 - 55
Interactions of HasA, a bacterial haemophore, with haemoglobin and with its outer membrane receptor HasR; Letoffe S et al.; The major mechanism by which bacteria acquire free or haemoglobin-bound haem involves direct binding of haem to specific outer membrane receptors . Serratia marcescens and Pseudomonas aeruginosa have an alternative system, which involves an extracellular haemophore, HasA, that captures free or haemoglobin-bound haem and shuttles it to a specific cell surface outer membrane receptor, HasR . Both haem-free (apoprotein) and haem-loaded (holoprotein) HasA bind to HasR, evidence for direct protein-protein interactions between HasA and HasR . HasA binding to HasR takes place in a tonB mutant . TonB is thus required for a step subsequent to HasA binding.

J Biotechnol, 1999 Jun 11, 72(1-2), 103 - 14
Cloning and expression of the gene encoding phospholipase A1 from Serratia sp . MK1 in Escherichia coli; Song JK et al.; The gene encoding extracellular phospholipase A1 of Serratia sp . MK1 was cloned from a genomic DNA library . Formation of transparent halos on the PCY agar plates was used to identify E . coli carrying the phospholipase A1 gene . A 4.2 kb EcoRI fragment was isolated and sequenced . From nucleotide sequences and expression of various plasmids, two open reading frames (plaA and plaS) involved in efficient expression of phospholipase A1 in natural and recombinant host were identified . Extracellular phospholipase A1 activity was identified as the gene product of plaA encoding 321 amino acids with a predicted MW of 33,400 . Analysis of the amino acid sequence revealed significant homology (around 70%) to phospholipase A1 of Serratia liquefaciens and Yersinia enterocolitica . The sequence, -Gly-X1-Ser-X2-Gly-, known as a lipase-specific consensus sequence was also found in the bacterial phospholipase A1 . PlaS encoding a protein of 224 amino acids showed no enzymatic activity, but might be necessary for the efficient expression of phospholipase A1 in E . coli . To further improve the production of phospholipase A1 as a soluble and active form in E . coli, the effect of some parameters was examined . Surprisingly, a higher yield of soluble and active phospholipase A1 could be obtained under the combined conditions of a lower temperature, an enriched medium, and a lower-strength promoter.

Microbios, 1998, 96(385), 157 - 63
Biosynthesis of endochitinase of Serratia marcescens; Gabdrakhmanova LA et al.; The growth of a mutant strain of Serratia marcescens with high chitinase activity and the biosynthesis of endochitinase by this strain were investigated . The study was carried out using semisynthetic culture medium without inducers and culture medium containing colloidal chitin as a sole nitrogen and carbon source, with and without mitomycin C . The mutant strain, unlike the native one, was shown to produce endochitinase and to secrete the enzyme into the medium during the growth on culture medium without the inducers, chitin and mitomycin C . During growth on the medium with chitin the mutant strain differed from the native one with a short lag-phase of growth, the early appearance of endochitinase in the culture liquid and a high level of endochitinase activity . The difference between the strains disappeared after the addition of mitomycin C, an inducer of the cell SOS-response, to the culture medium containing chitin . Specific endochitinase activity of S . marcescens mutant strain grown on various culture media had two maxima, namely at the beginning and at the end of the stationary phase . Mitomycin C increased the specific activity in a second peak of endochitinase activity during the growth of the mutant strain.

EMBO J, 1999 Jul 1, 18(13), 3521 - 32
Crystal structure of the histone acetyltransferase domain of the human PCAF transcriptional regulator bound to coenzyme A; Clements A et al.; The human p300/CBP-associating factor, PCAF, mediates transcriptional activation through its ability to acetylate nucleosomal histone substrates as well as transcriptional activators such as p53 . We have determined the 2.3 A crystal structure of the histone acetyltransferase (HAT) domain of PCAF bound to coenzyme A . The structure reveals a central protein core associated with coenzyme A binding and a pronounced cleft that sits over the protein core and is flanked on opposite sides by the N- and C-terminal protein segments . A correlation of the structure with the extensive mutagenesis data for PCAF and the homologous yeast GCN5 protein implicates the cleft and the N- and C-terminal protein segments as playing an important role in histone substrate binding, and a glutamate residue in the protein core as playing an essential catalytic role . A structural comparison with the coenzyme-bound forms of the related N-acetyltransferases, HAT1 (yeast histone acetyltransferase 1) and SmAAT (Serratia marcescens aminoglycoside 3-N-acetyltransferase), suggests the mode of substrate binding and catalysis by these enzymes and establishes a paradigm for understanding the structure-function relationships of other enzymes that acetylate histones and transcriptional regulators to promote activated transcription.

Acta Neurochir (Wien), 1999, 141(5), 525 - 8
An easy and safe method to store and disinfect explanted skull bone; Schultke E et al.; In our department extensive decompression craniectomies became the treatment of choice for patients with massive cerebral oedema following either trauma or acute cerebral infarction . The remarkable survival rates of this neurosurgical technique created the problem of adequate vault defect reconstruction . To evaluate the biological safety of using stored autologous skull flaps for this purpose, we compared three different disinfection methods . Skull bone fragments stored at -21 degrees C for different periods of time were artificially contaminated with clinically relevant strains of Serratia marcescens, Enterococcus faecium and Staphylococcus aureus . As potential methods for disinfection we tested immersion in 3% H2O2, boiling in normal saline for 15 and 30 minutes and a special process of steam disinfection at a temperature of 75 degrees C for 20 minutes . We were able to demonstrate that only steam disinfection completely eliminated the bacterial strains tested . Refrigeration plus steam disinfection of autologous skull bone prior to re-implantation seems to offer reliable safety for its use for defect closure . It is available at reasonable cost in many hospitals and does not require a bone bank.

Minerva Med, 1999 Jan-Feb, 90(1-2), 33 - 7
{Pefloxacin in the treatment of the bone and joint infections}; Maiello A et al.; BACKGROUND: To assess efficacy and tolerability of pefloxacin in association with other antibiotics in the treatment of acute and chronic bone and joint infections . METHODS: From January to December 1997, all the outpatients with diagnosis of acute or chronic bone and joint infections have been enrolled in a perspective study . If possible a cultural or histopathological study was performed . Treatment response was evaluated with radiological and clinical chemistry parameters . RESULTS: Fifteen patients {10 males, 5 females; mean age 40.7 +/- 15 years (range 15-71)} have been studied . They had 5 knee septic arthritis, 1 sacroileitis, 1 hip septic arthritis, 4 long bone osteomyelitis, 1 sterum osteomyelitis, 3 spondilitis . Three patients were HIV infected . Twelve were acute infections, 3 chronic ones . Overall, 7 were hematogenous infections, 6 subsequent to elective surgery, 1 post-traumatic thighbone osteomyelitis, 1 osteomyelitis by external fixation device . Isolates were S . aureus in 5 cases, P . mirabilis in 1 case, S . aureus+ Serratia marcescens in 1 . In the remaining part cultural tests were negative . Pefloxacin was administered i.v . or orally at the dose of 400 mg/bid for a mean time of 114 +/- 74.5 days (range 30-270) in association with other chemotherapic agents . Ten good recoveries, 3 partial and 2 no responses were observed . CONCLUSIONS: Pefloxacin resulted to be useful in the treatment of acute and chronic bone and joint infections . No severe side effect was observed during the treatment.

J Bacteriol, 1999 Jul, 181(13), 3880 - 5
Characterization of a dam mutant of Serratia marcescens and nucleotide sequence of the dam region; Ostendorf T et al.; The DNA of Serratia marcescens has N6-adenine methylation in GATC sequences . Among 2-aminopurine-sensitive mutants isolated from S . marcescens Sr41, one was identified which lacked GATC methylation . The mutant showed up to 30-fold increased spontaneous mutability and enhanced mutability after treatment with 2-aminopurine, ethyl methanesulfonate, or UV light . The gene (dam) coding for the adenine methyltransferase (Dam enzyme) of S . marcescens was identified on a gene bank plasmid which alleviated the 2-aminopurine sensitivity and the higher mutability of a dam-13::Tn9 mutant of Escherichia coli . Nucleotide sequencing revealed that the deduced amino acid sequence of Dam (270 amino acids; molecular mass, 31.3 kDa) has 72% identity to the Dam enzyme of E . coli . The dam gene is located between flanking genes which are similar to those found to the sides of the E . coli dam gene . The results of complementation studies indicated that like Dam of E . coli and unlike Dam of Vibrio cholerae, the Dam enzyme of S . marcescens plays an important role in mutation avoidance by allowing the mismatch repair enzymes to discriminate between the parental and newly synthesized strands during correction of replication errors.

Mol Microbiol, 1999 Jun, 32(6), 1212 - 25
The haemolysin-secreting ShlB protein of the outer membrane of Serratia marcescens: determination of surface-exposed residues and formation of ion-permeable pores by ShlB mutants in artificial lipid bilayer membranes; Konninger UW et al.; The ShlB protein in the outer membrane of Serratia marcescens is the only protein known to be involved in secretion of the ShlA protein across the outer membrane . At the same time, ShlB converts ShlA into a haemolytic and a cytolytic toxin . Surface-exposed residues of ShlB were determined by reaction of an M2 monoclonal antibody with the M2 epitope DYKDDDDK inserted at 25 sites along the entire ShlB polypeptide . The antibody bound to the M2 epitope at 17 sites in intact cells, which indicated surface exposure of the epitope, and to 23 sites in isolated outer membranes . Two insertion mutants contained no ShlB(M2) protein in the outer membrane . The ShlB derivatives activated and/or secreted ShlA . To gain insights into the secretion mechanism, we studied whether highly purified ShlB and ShlB deletion derivatives formed pores in artificial lipid bilayer membranes . Wild-type ShlB formed channels with very low single channel conductance that rarely assumed an open channel configuration . In contrast, open channels with a considerably higher single channel conductance were observed with the deletion mutants ShlB(Delta65-186), ShlB(Delta87-153), and ShlB(Delta126-200) . ShlB(Delta126-200) frequently formed permanently open channels, whereas the conductance caused by ShlB(Delta65-186) and ShlB(Delta87-153) did not assume a stationary value, but fluctuated rapidly between open and closed configurations . The results demonstrate the orientation of large portions of ShlB in the outer membrane and suggest that ShlB may function as a specialized pore through which ShlA is secreted.

Structure Fold Des, 1999 May, 7(5), 497 - 507
Crystal structure of an aminoglycoside 6'-N-acetyltransferase: defining the GCN5-related N-acetyltransferase superfamily fold; Wybenga-Groot LE et al.; BACKGROUND: The predominant mechanism of antibiotic resistance employed by pathogenic bacteria against the clinically used aminoglycosides is chemical modification of the drug . The detoxification reactions are catalyzed by enzymes that promote either the phosphorylation, adenylation or acetylation of aminoglycosides . Structural studies of these aminoglycoside-modifying enzymes may assist in the development of therapeutic agents that could circumvent antibiotic resistance . In addition, such studies may shed light on the development of antibiotic resistance and the evolution of different enzyme classes . RESULTS: The crystal structure of the aminoglycoside-modifying enzyme aminoglycoside 6'-N-acetyltransferase type li (AAC(6')-li) in complex with the cofactor acetyl coenzyme A has been determined at 2.7 A resolution . The structure establishes that this acetyltransferase belongs to the GCN5-related N-acetyltransferase superfamily, which includes such enzymes as the histone acetyltransferases GCN5 and Hat1 . CONCLUSIONS: Comparison of the AAC(6')-li structure with the crystal structures of two other members of this superfamily, Serratia marcescens aminoglycoside 3-N-acetyltransferase and yeast histone acetyltransferase Hat1, reveals that of the 84 residues that are structurally similar, only three are conserved and none can be implicated as catalytic residues . Despite the negligible sequence identity, functional studies show that AAC(6')-li possesses protein acetylation activity . Thus, AAC(6')-li is both a structural and functional homolog of the GCN5-related histone acetyltransferases.

Microbiology, 1999 May, 145 ( Pt 5), 1209 - 16
The NucE and NucD lysis proteins are not essential for secretion of the Serratia marcescens extracellular nuclease; Strych U et al.; The nuclease of Serratia marcescens is an extracellular protein encoded by the nucA gene . Pre-nuclease carries a typical 21-amino-acid N-terminal signal sequence that interacts with the Sec machinery to allow the translocation of nuclease to the periplasm . In Escherichia coli the nuclease remains in the periplasm; however, S . marcescens has the capacity to secrete nuclease extracellularly . The nucC operon carrying the nucEDC genes of S . marcescens has been identified previously . NucC is a transcriptional activator necessary for expression of nuclease as well as the extracellular bacteriocin 28b . NucE resembles and can act as a bacteriophage holin, whereas NucD has homology to bacteriophage lysozyme-like proteins . When present on a multicopy plasmid, the nucC operon, and specifically the nucED genes, appeared to allow extracellular secretion of nuclease from E . coli . Here experiments are reported which demonstrate that, when the nucC operon was placed in the E . coli chromosome in single copy, nuclease secretion was lost and nuclease remained periplasmic . The converse experiment, deletion of the nucE and nucD genes from the chromosome of S . marcescens, likewise had no effect on nuclease secretion by S . marcescens . It is concluded therefore that NucD and NucE are not necessary for nuclease secretion.

J Hosp Infect, 1999 May, 42(1), 37 - 43
Epidemiological analysis of imipenem-resistant Serratia marcescens in hospitalized patients; Troillet N et al.; Our objective was to examine epidemiological characteristics of hospitalized patients with imipenem-resistant Serratia marcescens . We performed a case-control study using data collected from computerized databases and chart review . Molecular typing by pulsed field gel electrophoresis of available isolates was performed . One hundred and ten patients had Serratia spp isolated during the 23-month study period . Twelve were infected or colonized with S . marcescens resistant or of intermediate susceptibility to imipenem . Eleven of the 12 patients were detected during a seven-month period between August 1994 and February 1995, suggesting the possible occurrence of an outbreak . However, the patients were admitted to different wards and services and, in eight patients, imipenem-resistant S . marcescens were isolated within 48 h or admission . None of the patients had epidemiological links within other institutions . The 12 cases were not more likely to have been exposed to beta-lactam antibiotics, including imipenem, than patients with imipenem-susceptible isolates . Six isolates were available for typing by PFGE; three were indistinguishable or closely related whereas each of the other three isolates were unique . In conclusion both the prevalence of imipenem-resistant S . marcescens and its unusual epidemiologic characteristics warrant further study.

Nat Struct Biol, 1999 Jun, 6(6), 516 - 20
The crystal structure of HasA, a hemophore secreted by Serratia marcescens; Arnoux P et al.; Free iron availability is strongly limited in vertebrate hosts, making the iron acquisition by siderophores inappropriate . Pathogenic bacteria have developed various ways to use the host's iron from iron-containing proteins . Serratia marcescens can use the iron from hemoglobin through the secretion of a hemophore called HasA, which takes up the heme from hemoglobin and shuttles it to the receptor HasR, which in turn, releases heme into the bacterium . We report here the first crystal structure of such a hemophore, bound to a heme group at two different pH values and at a resolution of 1.9 A . The structure reveals a new original fold and suggests a hypothetical mechanism for both heme uptake and release.

Antisense Nucleic Acid Drug Dev, 1999 Apr, 9(2), 171 - 81
Enzymatic assignment of diastereomeric purity of stereodefined phosphorothioate oligonucleotides; Koziolkiewicz M et al.; Enzymatic hydrolysis of stereoregular oligodeoxyribonucleoside phosphorothioates (PS-oligos) synthesized via the oxathiaphospholane method has been used for assignment of their diastereomeric purity . For this purpose, two well-known enzymes of established diastereoselectivity, nuclease P1 and snake venom phosphodiesterase (svPDE) have been used . However, because of some disadvantageous properties of svPDE, a search for other {Rp}-specific endonucleases was undertaken . Extracellular bacterial endonuclease isolated from Serratia marcescens accepts PS-oligos as substrates and hydrolyzes phosphorothioate bonds of the {Rp} configuration, whereas internucleotide {Sp}-phosphorothioates are resistant to its action . Cleavage experiments carried out with the use of unmodified and phosphorothioate oligonucleotides of different sequences demonstrate that the Serratia nuclease is more selective in recognition and hydrolysis of oligodeoxyribonucleotides than previously reported . The substrate specificity exhibited by the enzyme is influenced not only by the nucleotide sequence at the cleavage site but also by the length and base sequence of flanking sequences . The Serratia nuclease can be useful for analysis of diastereomeric purity of stereodefined phosphorothioate oligonucleotides, but because of its sequence preferences, the use of this enzyme in conjunction with svPDE is more reliable.

Can J Microbiol, 1999 Jan, 45(1), 88 - 91
A basal-defined medium for the study of proteolytic activity of Serratia marcescens; Bromke BJ et al.; A simple defined basal medium is presented for the study of proteolytic activity, induction and repression, and protease purification with Serratia marcescens . Since the medium contains no protein, it does not interfere with or present artifact to protein assays, column chromatography, or electrophoresis . The medium consists of the basal salts and buffer medium of Bromke and Hammel (1979) plus a carbon-energy source such as glycerol, calcium chloride for the cation requirement for protease activity, and an amino acid, preferably leucine . Growth parameters and proteolytic activities are presented for unsupplemented medium and for the medium supplemented with each of 18 amino acids . Unsupplemented medium completes the logarithmic phase in 12.5 h of incubation and has a constitutive level of proteolytic activity . Supplementation with any amino acid, except cysteine and tryptophan, increases significantly the proteolytic activity, but has a varied effect on growth parameters.

Biotechnol Appl Biochem, 1999 Jun, 29 ( Pt 3), 263 - 8
Purification and characterization of a levanbiose-producing levanase from Pseudomonas sp . No . 43; Jung Kang E et al.; A levanbiose-accumulating levanase from Pseudomonas sp . No . 43 was purified to a homogeneous state by (NH4)2SO4 fractionation and by chromatography on DEAE-Toyopearl 650 M and phenyl-Toyopearl 650 M columns . The molecular mass and isoelectric point of the enzyme were estimated to be 36 kDa and 5.7 respectively; the optimal pH and temperature for the enzyme reaction were pH 7.0 and 40 degrees C respectively . The purified enzyme was stable in the pH range 6.0-8.0 at 20 degrees C and stable up to 50 degrees C at pH 7.0 . The enzyme's activity was inhibited by MnCl2, CoCl2, AlCl3, EDTA and potassium permanganate . The levanase was specific towards the 2, 6-beta-D-fructosidic linkages of levan and did not hydrolyse other polysaccharides among those examined . The enzyme is an exohydrolase of levan and produced levanbiose as a sole product; the limits of hydrolysis of levans from Zymomonas mobilis and Serratia sp . were 65% and 80% respectively.

Prikl Biokhim Mikrobiol, 1999 Jan-Feb, 35(1), 20 - 4
{Polydispersity of Serratia marcescens nuclease at optimal pH values}; Filimonova MN et al.; Treatment with dimethyl suberimidate, a cross-linking bifunctional agent, showed that Sm1 and Sm2 nucleases of Serratia marcescens B10M1 are polydisperse in solution and consist of monomers and dimers at the level of pH optimal for the enzyme activity . The data suggest that nucleases from the strain B10M1 and any other strain are polydisperse at pH optimum if their amino acid sequences are identical.

J Mol Biol, 1999 May 21, 288(5), 975 - 87
The active site of Serratia endonuclease contains a conserved magnesium-water cluster; Miller MD et al.; Serratia endonuclease is an important member of a class of magnesium dependent nucleases that are widely distributed in nature . Here, we describe the location and geometry of a magnesium-water cluster within the active site of this enzyme . The sole protein ligand of the magnesium atom is Asn119; this metal ion is also associated with five water molecules to complete an octahedral coordination complex . These water molecules are very well ordered and there is no evidence of rotational disorder or motion . Glu127 and His89 are located nearby and each is hydrogen bonded to water molecules in the coordination sphere . Asp86 is not chelated to the magnesium or its surrounding water molecules . Results of kinetics and site-specific mutagenesis experiments suggest that this metal-water cluster contains the catalytic metal ion of this enzyme . All residues which hydrogen bond to the water molecules that coordinate the magnesium atom are conserved in nucleases homologous to Serratia endonuclease, suggesting that the water cluster is a conserved feature of this family of enzymes . We offer a detailed structural comparison to one other nuclease, the homing endonuclease I-PpoI, that has recently been shown, in spite of a lack of sequence homology, to share a similar active site geometry to Serratia endonuclease . Evidence from both of these structures suggests that the magnesium of Serratia nuclease participates in catalysis via an inner sphere mechanism .

J Mol Biol, 1999 May 7, 288(3), 377 - 90
The DNA/RNA non-specific Serratia nuclease prefers double-stranded A-form nucleic acids as substrates; Meiss G et al.; A steady-state kinetic analysis of the cleavage of the oligonucleotides d(CGCTTTTTTGC) (d(y)), d(GCAAAAAAGCG) (d(r)), r(CGCUUUUUUGC) (r(y)) and r(GCAAAAAAGCG) (r(r)) in single and double-stranded form by the extracellular Serratia marcescens endonuclease, in conjunction with structural data from a circular dichroism spectroscopic analysis of these substrates, suggests that oligonucleotides adopting the A-conformation are preferred over those adopting the B-conformation as substrates . Relative catalytic efficiencies (kcat/KM) for the cleavage of the homo- and heteroduplexes follow the order r(r).r(y) (1.0)>r(r).d(y) (0.9)>d(r) . r(y) (0.7)>d(r).d(y) (0.3) . The purine-rich single-stranded oligonucleotides r(r) and d(r), are cleaved more efficiently than the pyrimidine-rich oligonucleotides, r(y) and d(y), presumably because they adopt helical structures with pronounced base stacking . Except for the double-stranded oligodeoxynucleotide substrate, the individual strands are cleaved more efficiently when incorporated into a duplex, than in a single-stranded form . Cleavage experiments with various polynucleotides, including a viroid RNA and a specifically designed 167 bp DNA, confirm that double-stranded A-form nucleic acids are preferentially attacked by Serratia nuclease . In an attempt to analyze the basis of these preferences, we have mutated the amino acid residues Tyr76 and Trp123 of Serratia nuclease . These residues are located close to the active site and are conserved in all members of the Serratia nuclease family, suggesting that they could be involved in substrate binding, e.g . by stacking interactions with the bases, which could lead to the cleavage preferences observed . However, only effects on the activity, but no change of the sequence or substrate preferences, were detected upon substitution of these amino acid residues, ruling out any involvement of these residues in the A-form preference of Serratia nuclease .

Anim Behav, 1999 Jan, 57(1), 117 - 124
Evidence for adaptive changes in egg laying in crickets exposed to bacteria and parasites; Adamo SA; Animals should increase their present reproductive output if their chances for future reproduction are low . However, an animal's ability to make this adjustment may be constrained by the physiological mechanisms mediating the response . To examine this hypothesis, I infected 2- and 5-week-old female crickets, Acheta domesticus, with either a pathogen (the bacterium Serratia marcescens) that induces antimicrobial immune responses, or a parasite (larvae of the parasitoid fly, Ormia ochracea) that induces an encapsulation immune response . Females of both age groups infected with bacteria laid more eggs the day after injection than did saline-injected crickets . A similar increase was elicited by injecting components of the bacterial cell wall (lipopolysaccharides) . The bacteria-induced increase in egg laying (1) was not the result of physical stress, (2) did not appear to be a nonspecific response to the infection, and (3) was probably not mediated by octopamine . Females did not increase egg laying when infested with O . ochracea, even though this parasitoid invariably kills its host . Injections of Sephadex beads, which induced an immune response similar to that created by the parasitoids, also had no effect on egg laying . These results are consistent with the hypotheses that crickets can increase egg laying in response to infection and that increased egg output correlates with the activation of some, but not all, immune responses .

New Microbiol, 1999 Apr, 22(2), 91 - 8
Fatty acid profiles in pigmented and non-pigmented strains of S . marcescens; Pizzimenti FC et al.; Wild, pigmented strains of Serratia marcescens and their non-pigmented mutants were compared on the basis of fatty acid profiles and lipid content . Classic biochemical tests show only minor differences, as well as fatty acid ratio C18:C16 . The total amount of lipid synthesized and the saturated/unsaturated fatty acids ratio disclose a sharp total lipid reduction and a high percentage of unsaturated fatty acids in the pigmented strains, placing them in separated clusters compared with the nonpigmented mutants . It is hypothesized that the synthesis of the polyacetate required for the completion of the prodigiosin molecule may result in waste of methyl groups and thus affect the total amount of lipids.

Biosens Bioelectron, 1999 Mar 15, 14(3), 341 - 51
Evaluation of a dielectrophoretic bacterial counting technique; Brown AP et al.; Dielectrophoresis, an electrokinetic migration of particles, can occur in non-uniform alternating electric fields and is dependent upon the dielectric nature of the cells and their suspending medium . An enumeration system utilising this phenomenon is described, which has the potential to count particles selectively, including different bacterial or eukaryotic cell species and even sub-populations of different cell viability states or sizes . Relationships were observed between suspension concentrations and the extent of dielectrophoretic (DEP) collection for polystyrene latex beads, pure bacterial samples and mixtures of bacterial species including Escherichia coli, Serratia marcescens, Pseudomonas aeruginosa and Bacillus subtilis . A similar relationship was utilised for polystyrene latex as a calibration line to enable the concentration of particles in a suspension to be determined according to the level of DEP collection . The particle concentration of an unknown test sample was found to lie within the predicted concentration range determined on the basis of DEP collection . In addition, the predicted limits were found only to deviate between -6.2 and +6.9% from the mean particle concentration.

Appl Environ Microbiol, 1999 May, 65(5), 1959 - 65
Characterization of six bacteriophages of serratia liquefaciens CP6 isolated from the sugar beet phytosphere
Ashelford KE, Fry JC, Bailey MJ, Jeffries AR, Day MJ.
Six phages (PhiCP6-1 to PhiCP6-6) that are commonly found in the phytosphere of sugar beet (Beta vulgaris var . Amethyst) were investigated, and their relative impacts on their host (Serratia liquefaciens CP6) were compared . There were fundamental differences between the two most abundant predators of CP6 (PhiCP6-1 and PhiCP6-4) . Like PhiCP6-2 and PhiCP6-5, PhiCP6-1 belonged to the family Siphoviridae, while PhiCP6-4 exhibited the morphology of the family Podoviridae . The other phages were members of the family Myoviridae . DNA-DNA cross-hybridization revealed that PhiCP6-1 and PhiCP6-4 had little common DNA, although all of the other phages exhibited some genetic similarity . Like PhiCP6-2, PhiCP6-3, and PhiCP6-5, PhiCP6-1 was capable of forming a lysogenic association with its host, while PhiCP6-4 and PhiCP6-6 appeared to be entirely virulent . Single-step growth curve experiments revealed that PhiCP6-4 had a much shorter latent period and a smaller burst size than PhiCP6-1 . Also, PhiCP6-1 could transduce a number of host chromosomal markers with transfer frequencies of 2.9 x 10(-9) to 3.9 x 10(-7), whereas PhiCP6-4 could not transduce S . liquefaciens CP6 genes . When viewed in the context of the strikingly different temporal niches of these phages, our data provide an insight into how bacteriophage interactions with their hosts might reflect the natural ecology of bacteriophages . Our data also illustrate how the potential for gene transfer changes over time in an environment that supports several different phages.

Pediatr Infect Dis J, 1999 Apr, 18(4), 357 - 60
Use of real time pulsed field gel electrophoresis to guide interventions during a nursery outbreak of Serratia marcescens infection; Hoyen C et al.; BACKGROUND: Pulsed field gel electrophoresis (PFGE) is a commercially available technique that can establish clonal relationships among many common hospital-derived organisms with a high degree of accuracy and can yield results in a sufficiently short time to guide interventions during an outbreak investigation . METHODS: The CHEF Genomic Bacterial DNA Plug Kit (Bio-Rad) was applied to an unfolding nursery outbreak of Serratia marcescens infections according to the manufacturer's guidelines . Bacterial genomic DNA was digested with XbaI or SpeI and separated on 1% agarose gels, and the isolates were grouped by restriction endonuclease patterns according to established standards . RESULTS: S . marcescens was isolated from nine patients in an intensive care nursery during an 8-week period . Initial PFGE analysis performed after identification of the first eight patients, when closure of the nursery was imminent, revealed that the epidemic was caused by two groups of four isolates each . In both instances the group was geographically contained, and the nursery remained open . A second PFGE analysis indicated that a ninth S . marcescens isolate, recovered in Week 8, was genetically unrelated to the other two . Surveillance during an additional 6 weeks revealed no new cases, and the epidemic was declared over . No cases of invasive S . marcescens infection were identified during the subsequent 10 months . CONCLUSION: Real-time PFGE determined that an apparent nursery outbreak of S . marcescens infection was, in fact, caused by three genetically distinct strains . This information allowed the nursery to remain open after other appropriate infection control measures had been imposed.

Infect Control Hosp Epidemiol, 1999 Apr, 20(4), 233 - 6
Investigation of a nosocomial outbreak due to Serratia marcescens in a maternity hospital; Berthelot P et al.; OBJECTIVES: To investigate an outbreak of Serratia marcescens in a maternity hospital (November 1994 to May 1995) . DESIGN: Retrospective analysis of epidemiological data and prospective study of systematic bacteriological samples from patients and environment, with genotyping of strains by arbitrarily primed polymerase chain reaction . SETTING: A private maternity hospital, Saint-Etienne, France . RESULTS: In the neonatal unit, 1 newborn developed a bacteremia, and 36 were colonized in stools with S marcescens . As the colonization of some newborns was shown to occur only a few hours after delivery, the inquiry was extended to other maternity wards, where 8 babies and 4 mothers were found to be colonized . Environmental sampling led to the isolation of S marcescens from a bottle of enteral feed additive in the neonatal unit and from the transducers of two internal tocographs in the delivery rooms . The genotyping of 27 strains showed two different profiles: a major epidemic profile shared by 22 strains (18 from babies of the neonatal unit, 2 from babies of other units, and 2 from breast milk) and another profile shared by 5 strains (2 from transducers of internal tocographs, 2 from babies, and 1 from a mother) . The strain isolated from lipid enteral feeding was not available for typing . Although this source of contamination was removed soon from the neonatal unit, the outbreak stopped only when infection control measures were reinforced in the delivery rooms, including the nonreuse of internal tocographs . CONCLUSIONS: In delivery rooms, the quality of hygiene needs to be as high as in surgery rooms to prevent nosocomial colonization or infection of neonates at birth.

Arch Esp Urol, 1999 Mar, 52(2), 105 - 11
{Bartolomeo Bizio and the phenomenon of "purpurine polenta": unknown history of Serratia marcescens infections}; Aragona F; The present article describes the observations and experiments of Bartolomeo Bizio on a typical food of northern Italy known as "polenta", corn flour boiled in water and salt, on which purpurine stains would appear at high temperature and moisture . Due to these experiments and investigative work, Bizio is considered to be the father of modern bacteriology and bacterial biochemistry.

Eur J Biochem, 1999 Apr, 261(2), 562 - 8
NMR studies of the C-terminal secretion signal of the haem-binding protein, HasA; Izadi-Pruneyre N et al.; HasA is a haem-binding protein which is secreted under iron-deficiency conditions by the gram-negative bacterium Serratia marcescens . It is a monomer of 19 kDa (187 residues) able to bind free haem as well as to capture it from haemoglobin . HasA delivers haem to a specific outer-membrane receptor HasR and allows the bacteria to grow in the absence of any other source of iron . It is secreted by a signal peptide-independent pathway which involves a C-terminal secretion signal and an ABC (ATP-binding cassette) transporter . The C-terminal region of the secretion signal containing the essential secretion motif is cleaved during or after the secretion process by proteases secreted by the bacteria . In this work, we study by 1H NMR the conformation of the C-terminal extremity of HasA in the whole protein and that of the isolated secretion signal peptide in a zwitterionic micelle complex that mimicks the membrane environment . We identify a helical region followed by a random-coil C-terminus in the peptide-micelle complex and we show that in both the whole protein and the complex, the last 15 residues containing the motif essential for secretion are highly flexible and unstructured . This flexibility may be a prerequisite to the recognition of HasA by its ABC transporter . We determine the cleavage site of the C-terminal extremity of the protein and analyse the effect of the cleavage on the haem acquisition process.

Br J Plast Surg, 1998 Dec, 51(8), 640 - 1
Leech-borne Serratia marcescens infection following complex hand injury; Pereira JA et al.; Leeches are commonly used in the postoperative course of plastic surgical operations where there is venous congestion in a pedicled or free flap . They provide a temporary relief to venous engorgement whilst venous drainage is re-established . It is known that leeches can carry Aeromonas hydrophila infection, and a second or third generation cephalosporin antibiotic has traditionally been given as prophylaxis against infection . We report a new observation that leeches can carry Serratia marcescens and give rise to clinically significant infection . The implication for prophylaxis and treatment of leech-associated cellulitis is discussed.

J Hosp Infect, 1999 Mar, 41(3), 219 - 22
Serratia marcescens pseudobacteraemia in neonates associated with a contaminated blood glucose/lactate analyzer confirmed by molecular typing; Neal TJ et al.; Three episodes of Serratia marcescens pseudobacteraemia occurred on a neonatal intensive care unit . Following the first two cases, one full term and one pre-term infant, the source was identified as a glucose/lactate analyzer . Blood culture and environmental isolates of the organisms involved were indistinguishable when subjected to pulsed-field gel electrophoresis of Spe 1 digests and PCR ribotyping . Failure to recognize pseudobacteraemia in neonates results in inappropriate therapy for the individual and increased antibiotic pressures on the unit . Attention to the possibility of cross infection when using automated analyzers is required to minimize the risks of true or pseudoinfection to patients.

Anesth Analg, 1999 Apr, 88(4), 936 - 8
The effect of lidocaine on bacterial growth in propofol; Vidovich MI et al.; Extrinsically contaminated propofol has been associated with multiple infectious complications . Injection of propofol is associated with pain that is diminished by the addition of lidocaine . Lidocaine has antibacterial properties at high concentrations, but low concentrations of lidocaine (0.1%) have not been studied . We examined the growth rates of Staphylococcus aureus, Serratia marcescens, Pseudomonas aeruginosa, and Candida albicans in propofol containing disodium edeteate with and without added lidocaine 0.1% 2, 5, and 24 h after inoculation . There was no significant difference in the number of colony-forming units between propofol with and without added lidocaine at any time after inoculation . Implications: The addition of lidocaine to propofol in concentrations clinically effective in reducing pain on injection had no effect on microbial growth . Adherence to strict aseptic technique is further emphasized.

Antimicrob Agents Chemother, 1999 Apr, 43(4), 890 - 901
Structure of In31, a blaIMP-containing Pseudomonas aeruginosa integron phyletically related to In5, which carries an unusual array of gene cassettes; Laraki N et al.; The location and environment of the acquired blaIMP gene, which encodes the IMP-1 metallo-beta-lactamase, were investigated in a Japanese Pseudomonas aeruginosa clinical isolate (isolate 101/1477) that produced the enzyme . In this isolate, blaIMP was carried on a 36-kb plasmid, and similar to the identical alleles found in Serratia marcescens and Klebsiella pneumoniae clinical isolates, it was located on a mobile gene cassette inserted into an integron . The entire structure of this integron, named In31, was determined . In31 is a class 1 element belonging to the same group of defective transposon derivatives that originated from Tn402-like ancestors such as In0, In2, and In5 . The general structure of In31 appeared to be most closely related to that of In5 from pSCH884, suggesting a recent common phylogeny for these two elements . In In31, the blaIMP cassette is the first of an array of five gene cassettes that also includes an aacA4 cassette and three original cassettes that have never been described in other integrons . The novel cassettes carry, respectively, (i) a new chloramphenicol acetyltransferase-encoding allele of the catB family, (ii) a qac allele encoding a new member of the small multidrug resistance family of proteins, and (iii) an open reading frame encoding a protein of unknown function . All the resistance genes carried on cassettes inserted in In31 were found to be functional in decreasing the in vitro susceptibilities of host strains to the corresponding antimicrobial agents.

Biotechnol Bioeng, 1998 Sep 5, 59(5), 640 - 6
Metabolic engineering of Serratia marcescens with the bacterial hemoglobin gene: alterations in fermentation pathways; Wei ML et al.; Serratia marcescens was transformed with plasmid vector pUC8 or pUC8 containing the bacterial (Vitreoscilla) hemoglobin gene (vgb) on either a 2.3-kb fragment (pUC8:15) or 1.4-kb fragment (pUC8:16) of Vitreoscilla DNA . The vgb-bearing strains were compared with the pUC8 transformant and untransformed S . marcescens with respect to growth in Luria-Bertani (LB) broth supplemented with glucose or casein acid hydrolysate . Growth (on a viable cell basis) was similar to that in unsupplemented LB . Total acid excretion (as estimated by medium pH) was similar for all strains in both LB plus 2% casein acid hydrolysate and LB without additions . Acid excretion in LB plus 2% glucose was somewhat greater at up to 10 h in culture for the two vgb-bearing strains; from 10 to 26 h in culture, the pHs of these cultures continued to decrease (to 4.1-4.2), whereas those of the non-vgb-bearing strains returned to near the starting pH (7.4-7.8) . Concomitantly, after 26 h of culture in LB plus 2% glucose, the non-vgb-bearing strains had produced about 15 times as much acetoin and about three to four times as much 2,3-butanediol as the vgb-bearing strains . In general, for all strains, much more acetoin and 2,3-butanediol were produced in LB plus 2% glucose than in unsupplemented LB . The exception was acetoin production by the strain bearing vgb on plasmid pUC8:15; after 26 h of culture in LB without supplementation it was between three and four times that of the other strains, and about 50% higher than its level in LB plus 2% glucose . When grown with the 2% casein acid hydrolysate supplement, the strain bearing vgb on plasmid pUC8:15 produced much more acetoin and 2,3-butanediol than the other strains after 26 hours in culture . The results confirm that vgb can significantly alter carbon metabolism and suggest that the use of vgb technology for directed metabolic engineering may be a complicated process, depending in part on medium composition .

Biotechnol Bioeng, 1998 Feb 20, 57(4), 477 - 83
Genetic engineering of Serratia marcescens with bacterial hemoglobin gene: effects on growth, oxygen utilization, and cell size; Wei ML et al.; The bacterial hemoglobin from Vitreoscilla has been shown to increase growth yield and yield of genetically engineered product in Escherichia coli . To test the generality of this phenomenon, the approximately 560-bp bacterial (Vitreoscilla) hemoglobin gene (vgb) (including the native promoter), cloned into the vector pUC8 in two constructs containing about 1650 and 850 bp, respectively, of Vitreoscilla DNA downstream of vgb, was transformed into Serratia marcescens . After several transfers of the transformants on selective media, both plasmids became stable in this host and the resulting strains produced hemoglobin . Both transformants were compared, regarding growth in liquid Luria-Bertani (LB) medium, with untransformed S . marcescens and S . marcescens transformed with pUC8 . The vgb-bearing strains had about 5 times lower maximum viable cell numbers than the strains without hemoglobin, but the former also had late log or early stationary phase cells that were 5-10 times larger than those of the latter . Further, on a dry cell mass basis the presence of vgb inhibited cell growth in liquid media . In contrast, growth of the vgb-bearing strains on LB plates based on cell mass (determined from colony size) was markedly enhanced compared with that of the pUC8 transformant . Respiration of the vgb-bearing strains was lower than that of the strains without vgb on a cell mass basis . These results show that the presence of vgb can have idiosyncratic effects and is not always an aid to cell growth so that its use for genetic engineering must be tested on a case by case basis .

Infect Control Hosp Epidemiol, 1999 Mar, 20(3), 192 - 5
Long-lasting contamination of a vitrectomy apparatus with Serratia marcescens; Kappstein I et al.; OBJECTIVE: To investigate the contamination of a vitrectomy apparatus with Serratia marcescens . DESIGN: Descriptive microbiological and molecular environmental study . SETTING: An 1,800-bed university hospital . RESULTS: S . marcescens was found inside the vitrectomy apparatus at the pressure transducer . Molecular typing by randomly amplified polymorphic DNA-automated laser fluorescence analysis and pulsed-field gel electrophoresis identified a single pattern for all strains isolated from the apparatus . Surprisingly, the contaminating strain was identical to two strains of S . marcescens isolated nearly 2 years earlier from two patients who were involved in a small outbreak of acute postoperative endophthalmitis following cataract surgery at another hospital . The emergency vitrectomies in these patients were performed at our hospital with the same apparatus that was found to be contaminated 2 years later . CONCLUSION: Performing a systematic environmental search for the assumed bacterial reservoir within the system of the vitrectomy apparatus finally made it possible to find and eliminate the nidus for the gram-negative rod . Molecular typing demonstrated that all isolates belonged to a single genotype, and revealed unexpectedly a link to two vitrectomies performed 2 years earlier . The data support the hypothesis that the source of the contamination was one of these patients, and thus contamination of the apparatus was present for almost 2 years.

J Microbiol Methods, 1999 Feb, 35(1), 31 - 5
Clinical correlation of a skin antisepsis model; McDonnell G et al.; The use of pigskin as a test substrate for evaluating topical antimicrobial activity has been developed . Simulated handwashing protocols with this in vitro model in parallel with in vivo studies have been evaluated, based on an ASTM method for the clinical evaluation of a healthcare personnel handwash . Using Serratia marcescens as the test organism, similar log reductions were observed using the in vitro model when compared to in vivo efficacy . Results suggest that this model can be used as a reliable indicator of antiseptic efficacy on the skin . The use of sterilized skin simplifies the use of this model for both efficacy and skin-pathogen interaction studies.

J Bacteriol, 1999 Mar, 181(6), 1883 - 91
Genetic analysis of the Serratia marcescens N28b O4 antigen gene cluster; Saigi F et al.; The Serratia marcescens N28b wbbL gene has been shown to complement the rfb-50 mutation of Escherichia coli K-12 derivatives, and a wbbL mutant has been shown to be impaired in O4-antigen biosynthesis (X . Rubires, F . Saigi, N . Pique, N . Climent, S . Merino, S . Alberti, J . M . Tomas, and M . Regue, J . Bacteriol . 179:7581-7586, 1997) . We analyzed a recombinant cosmid containing the wbbL gene by subcloning and determination of O-antigen production phenotype in E . coli DH5alpha by sodium dodecyl sulfate-polyacrylamide electrophoresis and Western blot experiments with S . marcescens O4 antiserum . The results obtained showed that a recombinant plasmid (pSUB6) containing about 10 kb of DNA insert was enough to induce O4-antigen biosynthesis . The same results were obtained when an E . coli K-12 strain with a deletion of the wb cluster was used, suggesting that the O4 wb cluster is located in pSUB6 . No O4 antigen was produced when plasmid pSUB6 was introduced in a wecA mutant E . coli strain, suggesting that O4-antigen production is wecA dependent . Nucleotide sequence determination of the whole insert in plasmid pSUB6 showed seven open reading frames (ORFs) . On the basis of protein similarity analysis of the ORF-encoded proteins and analysis of the S . marcescens N28b wbbA insertion mutant and wzm-wzt deletion mutant, we suggest that the O4 wb cluster codes for two dTDP-rhamnose biosynthetic enzymes (RmlDC), a rhamnosyltransferase (WbbL), a two-component ATP-binding-cassette-type export system (Wzm Wzt), and a putative glycosyltransferase (WbbA) . A sequence showing DNA homology to insertion element IS4 was found downstream from the last gene in the cluster (wbbA), suggesting that an IS4-like element could have been involved in the acquisition of the O4 wb cluster.

CLAO J, 1999 Jan, 25(1), 52 - 6
Comparative antimicrobial efficacy of multi-purpose lens care solutions using the FDA's revised guidance document for industry: stand-alone primary criteria; Lever AM et al.; PURPOSE: We evaluated six single-bottle, multi-purpose lens care solutions and a two component lens care system for disinfection efficacy according to the stand-alone primary criteria within the recently published U.S . Food and Drug Administration (FDA) Guidelines . METHODS: One-tenth mL of 1 x 10(8) colony forming units (CFU)/mL of bacterial and fungal challenge organisms was added to each test solution . Following a specified period (e.g., each manufacturer's labeled minimum disinfection time), aliquots of inoculated test solution were neutralized and plated on validated recovery media . After incubation the number of viable microorganisms were enumerated and mean log reductions determined . RESULTS: ReNu and ReNu MultiPlus met the FDA's acceptance criteria for stand-alone disinfectants against all challenge organisms: Staphylococcus aureus, Serratia marcescens, Pseudomonas aeruginosa, Candida albicans, and Fusarium solani . Opti-Free Express failed to meet the FDA's stand-alone disinfectant acceptance criteria for S . aureus, S . marcescens and C . albicans and Opti-Free Express with Opti-Free Supraclens failed to meet the acceptance criteria for either S . aureus and C . albicans . Opti-One failed to meet the FDA's stand-alone disinfectant acceptance criteria for C . albicans and F . solani . Both Complete and Solo-Care failed to meet the FDA's acceptance criteria for C . albicans . CONCLUSIONS: This evaluation provides a direct comparison of antimicrobial activity (based on stand-alone criteria) for commercially available multi-purpose lens care solutions at their labeled minimum disinfection times . The results of this study should be considered when selecting appropriate lens care systems for patients.

J Protein Chem, 1999 Jan, 18(1), 137 - 46
Synthesis and biochemical characterization of obligatory dimers of the sugar non-specific nuclease from Serratia marcescens using specifically designed bismaleimidoalkanes as SH-specific crosslinking reagents; Franke I et al.; The genetically engineered S140C variant of the homodimeric nuclease from Serratia marcescens was crosslinked across the dimer interface at the Cys 140 residues using bifunctional SH-specific 1,1'-alkanediyl-bis-pyrrole-2,5-diones of different lengths . These bismaleimidoalkanes were synthesized by the condensation of n-alkyldiamines with maleic anhydride and subsequent cyclization with acetic anhydride and sodium acetate . Bismaleimidohexane (BMH) which gave the best crosslinking yield was used to produce in preparative amounts crosslinked Serratia nuclease . The crosslinked protein has the same secondary structure and exhibits the same guanidinium chloride unfolding behavior as the wild type enzyme or the non-covalently linked S 140C variant . In contrast, in thermal unfolding experiments the crosslinked dimer behaves differently from the wild type enzyme or the non-covalently linked S140C variant . CD-spectra recorded during temperature rise showed only minor changes of the secondary structure composition for the wild type enzyme and the non-covalently linked S140C variant, whereas in the case of the crosslinked S140C dimer a distinct increase of the CD effect was observed corresponding to an increase in alpha-helix . Our results demonstrate that bismaleimidoalkanes are very well suited to covalently link subunits of proteins, provided suitably located cysteine residues are present.

Biosens Bioelectron, 1999 Jan 1, 14(1), 1 - 7
Biochemical oxygen demand sensor using Serratia marcescens LSY 4; Kim MN et al.; A microbial biochemical oxygen demand (BOD) sensor consisting of Serratia marcescens LSY 4 and an oxygen electrode was prepared for estimation of the biochemical oxygen demand . The response of the BOD sensor was insensitive to pH in the range of pH 6.0-8.0, and the baseline drift of the signal was nearly absent even in unbuffered aqueous solution . Because heavy metal ions were precipitated from the phosphate buffer solution, unbuffered solution was used to investigate the effect of the concentration of heavy metal ions on the sensor response . Contrary to previous studies, not only Cu2+ and Ag+ but also Cd2+ and Zn2+ significantly decreased the response of the BOD sensor in unbuffered solution . Graft polymerization of sodium styrene sulfonate on the surface of the porous teflon membrane was carried out to absorb the heavy metal ions permeating through the membrane . Tolerance against Zn2+ was induced for S . marcescens LSY 4 to make the cells less sensitive to the presence of heavy metal ions . The membrane modification and the Zn2+ tolerance induction showed some positive effects in such a way that they reduced the inhibitory effects of Zn2+ and Cd2+ on the sensitivity of the BOD sensor . However, they had no effect on the protection of the cells against the interference of Cu2+ and Ag+ on the performance of the sensor.

FEBS Lett, 1999 Jan 25, 443(2), 209 - 14
Cleavage experiments with deoxythymidine 3',5'-bis-(p-nitrophenyl phosphate) suggest that the homing endonuclease I-PpoI follows the same mechanism of phosphodiester bond hydrolysis as the non-specific Serratia nuclease; Friedhoff P et al.; We show here that two nucleases, Serratia nuclease and I-PpoI, with contrasting specificities, i.e . non-specific vs . highly sequence specific, share a structurally similar active site region with conservation of the catalytically relevant histidine and asparagine residues . On the basis of a comparison of the available structures and biochemical data for wild type and mutant variants of Serratia nuclease and I-PpoI we propose that both enzymes have a common catalytic mechanism, a proposition that is supported by our finding that both enzymes accept deoxythymidine 3',5'-bis-(p-nitrophenyl phosphate) as a substrate and cleave it in an identical manner . According to this mechanism a histidine residue functions as a general base and Mg2+ bound to an asparagine residue as a Lewis acid in phosphodiester bond cleavage.

Infect Immun, 1999 Feb, 67(2), 817 - 25
Cytotoxic action of Serratia marcescens hemolysin on human epithelial cells; Hertle R et al.; Incubation of human epithelial cells with nanomolar concentrations of chromatographically purified Serratia marcescens hemolysin (ShlA) caused irreversible vacuolation and subsequent lysis of the cells . Vacuolation differed from vacuole formation by Helicobacter pylori VacA . Sublytic doses of ShlA led to a reversible depletion of intracellular ATP . Restoration to the initial ATP level was presumably due to the repair of the toxin damage and was inhibited by cycloheximide . Pores formed in epithelial cells and fibroblasts without disruption of the plasma membrane, and the pores appeared to be considerably smaller than those observed in artificial lipid membranes and in erythrocytes and did not allow the influx of propidium iodide or trypan blue . All cytotoxic effects induced by isolated recombinant ShlA were also obtained with exponentially growing S . marcescens cells . The previously suggested role of the hemolysin in the pathogenicity of S . marcescens is supported by these data.

Appl Environ Microbiol, 1999 Jan, 65(1), 169 - 74
In situ population dynamics of bacterial viruses in a terrestrial environment
Ashelford KE, Day MJ, Bailey MJ, Lilley AK, Fry JC.
Predation by bacteriophages is thought to control bacterial numbers and facilitate gene transfer among bacteria in the biosphere . A thorough understanding of phage population dynamics is therefore necessary if their significance in natural environments is to be fully appreciated . Here we describe the in situ population dynamics of three separate phage populations predating on separate bacterial species, living on the surface of field-grown sugar beet (Beta vulgaris var . Amethyst), as recorded over a 9-month period . The distributions of the three phage populations were different and fluctuated temporally in 1996 (peak density, approximately 10(3) PFU g-1) . One of these populations, predating on the indigenous phytosphere bacterium Serratia liquefaciens CP6, consisted of six genetically distinct DNA phages that varied in relative abundance to the extent that an apparent temporal succession was observed between the two most abundant phages, PhiCP6-1 and PhiCP6-4.

J Biol Chem, 1999 Jan 8, 274(2), 825 - 32
On the advantage of being a dimer, a case study using the dimeric Serratia nuclease and the monomeric nuclease from Anabaena sp . strain PCC 7120; Franke I et al.; The extracellular endonucleases from Serratia marcescens and Anabaena sp . are members of a family of nonspecific endonucleases . In contrast to the monomeric Anabaena nuclease, the Serratia nuclease is a dimer of two identical subunits . To find out whether the two active sites of the Serratia nuclease function independently of each other and what the advantage of being a dimer for this enzyme might be, we produced (i) dimers in which the two subunits were cross-linked, (ii) heterodimers consisting of a wild type and an inactive mutant subunit which were also cross-linked, and (iii) monomeric variants which are unable to dimerize . The monomeric H184R variant and the cross-linked S140C variant exhibit the same activity as the wild type enzyme, while the cross-linked heterodimer with one inactive subunit shows only half of the activity of the wild type enzyme, demonstrating functional independence of the two subunits of the Serratia nuclease . On the other hand at low enzyme and substrate concentrations dimeric forms of the Serratia nuclease are relatively more active than monomeric forms or the monomeric Anabaena nuclease in cleaving polynucleotides, not, however, oligonucleotides, which is correlated with the ability of dimeric forms of the Serratia nuclease to form large enzyme-substrate networks with high molecular weight DNA and to cleave polynucleotides in a processive manner . We conclude that in the natural habitat of Serratia marcescens where the supply of nutrients may become growth limiting the dimeric nuclease can fulfil its nutritive function more efficiently than a monomeric enzyme.

Infect Control Hosp Epidemiol, 1998 Dec, 19(12), 924 - 8
Epidemiological analysis defining concurrent outbreaks of Serratia marcescens and methicillin-resistant Staphylococcus aureus in a neonatal intensive-care unit; Campbell JR et al.; OBJECTIVE: To describe the epidemiology, interventions, and molecular typing methods used during the investigation and control of concurrent outbreaks of Serratia marcescens and methicillin-resistant Staphylococcus aureus (MRSA) infections in a neonatal intensive-care unit (NICU) . SETTING: A 206-bed women's and infants' hospital with a 48-bed NICU . DESIGN: A 22-week, prospective, descriptive study of all NICU infants with S marcescens or MRSA infection or colonization . Repetitive polymerase chain reaction (rep PCR) and pulsed-field gel electrophoresis (PFGE), respectively, were applied to the typing of S marcescens and MRSA isolates . INTERVENTIONS: Infants with S marcescens or MRSA infection or colonization were placed in isolation; all other infants were cohorted . A multidisciplinary task force implemented education for all hospital and medical staff regarding policies essential for outbreak control . Changes in physical setting and patient contact procedure were required to promote adherence to existing policies . RESULTS: Two premature infants had S marcescens infection, and five were colonized; rep PCR verified that both invasive and three of five colonizing isolates were related genotypically . Five bacteremic and 10 MRSA-colonized infants were identified; PFGE confirmed that 12 of the isolates had similar electrophoretic patterns . S marcescens infection was eliminated from the NICU 3 weeks after interventions were initiated . MRSA infections also were eliminated, and MRSA colonization fell to below pre-outbreak rates within 8 weeks . Despite a 100% increase in NICU patient days per month during the subsequent 2 years, no further clusters of S marcescens or MRSA infection have occurred . CONCLUSIONS: Concurrent outbreaks of S marcescens and MRSA in an NICU were confirmed by genotyping of strains . Control was achieved by isolation and cohorting of patients and strict adherence to NICU policies and procedures.

Microbios, 1998, 95(381), 109 - 15
Appearance of fosfomycin resistant Rahnella aquatilis clinically isolated in Japan; O'Hara K et al.; Among recent clinical isolates in Japan, strain CU264 was discovered which formed unusual colonies . This strain was identified as Rahnella aquatilis which is usually found in water . The antibiotic susceptibilities against tetracycline, carbenicillin, chloramphenicol, streptomycin, kanamycin, gentamicin, sulphonamide, neomycin, fosfomycin, rifampicin, norfloxacin and nalidixic acid, were investigated . The result demonstrated that the strain was highly resistant to fosfomycin only . It was further shown that this resistance was transmissible with low frequency to Serratia marcescens whereas it was not transmissible to Escherichia coli.

Curr Microbiol, 1999 Feb, 38(2), 71 - 9
Characterization of porins isolated from the outer membrane of Serratia liquefaciens; Nitzan Y et al.; A major outer membrane protein with an apparent molecular weight of 42 kDa was purified from Serratia liquefaciens grown on Brain Heart Infusion medium . The same protein was obtained when the cells were grown on a synthetic medium supplemented with 2% glucose . The amino acid composition of this protein revealed it to be hydrophilic . The pore-forming ability of the 42-kDa protein was determined by the liposome swelling assay . This assay demonstrated that the protein forms nonspecific channels with a diameter between 1.16 and 1.6 nm . An additional protein with a molecular weight of 47 kDa was obtained on synthetic medium supplemented with maltose . This protein exhibited specific pore-forming ability to maltose and maltodextrins, but was also permeable to other compounds, according to their size . When bacteria were grown on Nutrient Broth medium, two outer membrane proteins with molecular weights of 41 kDa and 42 kDa were produced by the bacteria . All three types of proteins represent monomers of respective oligomers . The monomers did not exhibit pore-forming ability when incorporated into liposomes . We, therefore, propose that the oligomer is the functional unit of a porin capable of forming permeability channels in the outer membrane of Serratia liquefaciens . These results indicate that S . liquefaciens contains several porins exhibiting specific osmoregulation or that are induced by a specific nutrient, where the 42-kDa outer membrane protein of this bacterium is certainly a major porin.

Biochemistry (Mosc), 1998 Nov, 63(11), 1299 - 301
Regulation of activity of chloroperoxidase from Serratia marcescens; Burd VN et al.; The influence of various factors on the activity of chloroperoxidase from Serratia marcescens was investigated . The enzyme is active only in acetate-containing buffers within the pH range 4.2-5.8 . F-, Cu2+, {Fe(CN)6}4+, and {Fe(CN)6}3+ inhibit the enzyme . The chloroperoxidase is thermostable and resistant to the effect of lower alcohols.

J Med Microbiol, 1998 Dec, 47(12), 1105 - 13
Antibiotic resistance and putative virulence factors of Serratia marcescens with respect to O and K serotypes; Aucken HM et al.; Serratia marcescens serotypes O6:K14, O8:K14 and O28:K28 are common in the natural environment, but rare in hospitals . Serotypes O14:K14 and O27:K14 predominate among clinical strains, but not in the environment, suggesting that the latter serotypes may be more suited for survival in the clinical setting . Consequently, 469 epidemiologically distinct strains of S . marcescens were tested for various putative virulence factors and analysed for associations with serotype . The factors positively associated with serotype O14:K14 were agglutination of five different species of red blood cells and expression of type 1 fimbriae . These were found in 63% and 53% of O14:K14 strains, respectively, compared with 7% and 12% of the three 'environmental serotypes' . Almost a quarter of the collection expressed the mannose-resistant haemagglutinin indicative of type 3 fimbriae, but this was not associated with any serotype . The production of DNAase, haemolysin, lipase, lecithinase, proteases and siderophores was almost universal and showed no serotype correlations . Almost half of the strains (46%) were resistant to serum and serotypes O27:K14 and O6:K14 were strongly associated with this characteristic . Serotype O27:K14 was also associated with higher proportions of antibiotic-resistant strains than other serotypes, but the same was not true of serotype O14:K14 . All three 'environmental serotypes' were associated with low frequencies of antibiotic resistance; <12% were resistant to gentamicin, carbenicillin or piperacillin, or any combination of these three, compared with 20-25% of O14:K14 strains and >42-51% of O27:K14 strains . Pigment production was strongly associated with serotype . None of the O14:K14 or O27:K14 strains produced prodigiosin, but frequencies for the three 'environmental serotypes' ranged from 31% of O28:K28 strains to 85% of O6:K14 strains . The results of this study suggest that the adherence capability of S . marcescens strains may play a role in the colonisation of hospital patients, while the production of prodigiosin is a marker of environmental origin.

J Med Microbiol, 1998 Dec, 47(12), 1097 - 104
Different O and K serotype distributions among clinical and environmental strains of Serratia marcescens; Aucken HM et al.; Recent revision of the O serotyping scheme for Serratia marcescens has allowed the definitive serological identification of a collection of 511 epidemiologically distinct strains in terms of both lipopolysaccharide (O) antigens and capsular (K) antigens . High levels of typability were achieved, 88% and 91% respectively, with only 2% failing to type with either method . In most cases, non-typability was due to a lack of antigen, i.e., the strains produced only rough LPS or were acapsular, suggesting that typability would be little improved by the discovery of additional serotypes . The distribution of the 58 O:K serotypes was very uneven, with O14:K14 accounting for 30% of the 423 clinical strains in the collection, but only 5% of the 88 non-clinical, environmental strains . Thus, the prevalence of O14:K14 strains in hospitals is not reflected in the environment . Similar conclusions were valid for O27:K14, O21:K3 and O21:K14 strains, as well as those with rough lipopolysaccharide . Conversely, the proportions of O6:K3, O6:K14, O8:K14 or O28:K28 strains were significantly lower among the clinical collection than among their environmental counterparts (12% in total rather than 65%) . This suggests that O14:K14 may have a selective advantage in colonising or infecting hospitalised patients and, therefore, that the O14 and K14 polysaccharides themselves may contribute towards the apparent pathogenicity of these serotypes.

Eye, 1998, 12 ( Pt 4), 714 - 6
A comparison of skin storage methods for oculoplastic surgery; Baldeschi L et al.; PURPOSE: To assess the level of contamination of full-thickness skin grafts stored with or without an antibiotic cover . METHODS: Full-thickness skin grafts were harvested from 40 bilateral upper lid blepharoplasties . Before surgery the face was sterilised, the head of the patient was packed with sterile, single-use surgical drapes and the whole face was left exposed . The harvested full-thickness skin grafts were conserved in sterile containers at 4 degrees C for 6 days, rolled in gauze moistened with either 4 ml of sterile saline solution (group I) or with 4 ml of gentamicin solution (2 mg/ml) (group II) . The degree of contamination, expressed in colony forming units (CFU), was evaluated on days 2, 3, 4, 5 and 6 . Identification of the microorganisms was done to species level following standard procedures and commercial methods . RESULTS: In group I 2 grafts (5%) were negative during the whole observation period while the other 38 grafts (95%) presented a degree of contamination ranging from 10(2) to 10(4) CFU . Microorganisms isolated were: Staphylococcus epidermidis (24 cases), Staphylococcus aureus (5 cases), Staphylococcus saprophyticus (2 cases), Pseudomonas aeruginosa (4 cases), Serratia liquefaciens (1 case) and Klebsiella oxytoca (2 cases) . In group II, 26 grafts (65%) were negative during the whole observation time while in 14 cases (35%) a few colonies (3 to 6) of Candida albicans were isolated on day 2 and remained constant in number for the whole observation time . CONCLUSIONS: The storage of full-thickness skin graft with an antibiotic cover is more reliable than the storage of full-thickness skin graft without an antibiotic cover.

Eur J Clin Microbiol Infect Dis, 1998 Sep, 17(9), 629 - 36
Repeated epidemics caused by extended-spectrum beta-lactamase-producing Serratia marcescens strains; Luzzaro F et al.; An outbreak of Serratia marcescens involving 42 patients admitted to the general intensive care unit of the Hospital of Varese, Italy, occurred from March 1994 to August 1995 . The causative strains were resistant to oxyimino-cephalosporins and monobactams due to their production of an extended-spectrum beta-lactamase . Another outbreak caused by Serratia marcescens strains had occurred in the same unit a few months earlier, from February to October 1993, with the strains involved producing a novel TEM-derived extended-spectrum beta-lactamase . In order to verify whether there were any relationships between isolates from the two epidemics, the strains and their enzymes were characterized . Biochemical data and gene amplification experiments showed that the isolates of the second outbreak harbored a non-conjugative plasmid of approximately 48 kb, codifying for the production of an SHV-derived extended-spectrum beta-lactamase with pI 8.2 . Restriction fragment length polymorphism analysis of total genomic DNA by pulsed-field gel electrophoresis of Serratia marcescens isolates unambiguously identified two different bacterial clones responsible for the two epidemics . Epidemiological and microbiological investigations demonstrated the long persistence of Serratia marcescens strains and their circulation in other hospital wards, thus suggesting their possible role as a long-term reservoir for further epidemic spread.

Int J Infect Dis, 1998 Jul-Sep, 3(1), 36 - 8
Bullous cellulitis caused by Serratia marcescens; Cooper CL et al.; Bullous cellulitis is a distinctive form of cellulitis most often caused by beta hemolytic streptococci . This report describes a case of bullous cellulitis caused by Serratia marcescens in an elderly diabetic woman with peripheral vascular disease . A discussion of this ubiquitous, nosocomial pathogen follows.

J Bacteriol, 1998 Dec, 180(23), 6384 - 8
N-Acyl-L-homoserine lactone autoinducers control production of an extracellular lipopeptide biosurfactant required for swarming motility of Serratia liquefaciens MG1; Lindum PW et al.; A nonswarming Serratia liquefaciens mutant deficient in serrawettin W2 production was constructed by transposon mutagenesis . Sequence homology indicated that insertion had occurred in gene swrA, which encodes a putative peptide synthetase . Expression of swrA is controlled by quorum sensing.

FEMS Microbiol Lett, 1998 Nov 1, 168(1), 111 - 7
Purification, characterization and immunochemical properties of a novel 60-kDa protein of Vibrio anguillarum strains; Mutharia LM et al.; Vibrio anguillarum strains expressed increased amounts of a novel 60-kDa protein when cells were grown at physiologically elevated temperatures . The relative amounts of the 60-kDa protein were unaltered by changes in osmolarity or ionic concentration of the growth medium in cells grown at optimal growth temperatures . The N-terminal amino acid sequence analysis of the V . anguillarum 60-kDa protein showed extensive (94-89%) sequence identity with the 60-kDa heat shock protein of Yersinia enterocolitica and with Serratia rubidaea GroEL protein . Monoclonal antibodies against the Y . enterocolitica chaperonin reacted with the 60-kDa protein from V . anguillarum strains, and with a temperature-induced protein of similar molecular mass in other Gram-negative pathogens of fish.

J Bacteriol, 1998 Nov, 180(22), 6064 - 7
An upstream sequence element required for NucC-dependent expression of the Serratia marcescens extracellular nuclease; Winslow RH et al.; The Serratia marcescens extracellular nuclease gene, nucA, is positively regulated by the product of the nucC gene . In this study, the upstream region required for NucC-dependent nuclease expression was defined by using fusions to the gene encoding chloramphenicol acetyltransferase (cat) . This sequence includes an element of hyphenated dyad symmetry identified previously as the binding site for the P2 Ogr family of activators . Footprint analysis confirmed that members of this family of activator proteins bind to this site, protecting a region between -76 and -59 relative to the start of transcription . The activator binding site in the nucA promoter lies one turn of the helix upstream from the corresponding sites in the P2 and P4 late promoters . The effects of deletions between the downstream end of the activator binding site and the putative -35 region are consistent with a strict helical phasing requirement for activation.

Curr Microbiol, 1998 Dec, 37(6), 380 - 6
Mass balance studies with 14C-labeled 2,4,6-trinitrotoluene (TNT) mediated by an Anaerobic desulfovibrio species and an Aerobic serratia species; Drzyzga O et al.; Investigations were carried out to evaluate the level of incorporation of radiolabeled 2,4,6-trinitrotoluene (TNT) and metabolites into the bacterial biomass of two different bacterial species after cometabolically mediated TNT transformation . Biotransformation experiments with 14C-TNT indicated that TNT was not mineralized; however, carbon derived from TNT became associated with the cells . It was found that more than 42% of the initially applied radiolabel was associated with the cell biomass after cometabolic 14C-TNT transformation with the strictly anerobic Desulfovibrio species strain SHV, whereas with the strictly aerobic Serratia plymuthica species strain B7, 32% of cell-associated 14C activity was measured . The remainder of the radiolabel was present in the supernatants of the liquid cultures in the form of different TNT metabolites . Under anoxic conditions with the Desulfovibrio species, TNT was ultimately transformed to 2,4,6-triaminotoluene (TAT) and both diaminonitrotoluene isomers, whereas under oxic conditions with the Serratia species, TNT was converted to hydroxylaminodinitrotoluenes and aminodinitrotoluenes, with 4-amino-2,6-dinitrotoluene (4ADNT) being the major end product . In both culture supernatants, small amounts of very polar, radiolabeled, but unidentified metabolites were detected . At the end of the experiments approximately 92% and 96% of the originally applied radioactivity was recovered in the studies with the Serratia and Desulfovibrio species, respectively.

Infect Control Hosp Epidemiol, 1998 Oct, 19(10), 791 - 4
An outbreak of Serratia marcescens infections related to contaminated chlorhexidine; Vigeant P et al.; An outbreak of Serratia marcescens infections occurred in a university tertiary-care hospital . Alcohol-free chlorhexidine solutions were contaminated with S marcescens . The majority of patient and chlorhexidine strains had similar pulsed field-gel electrophoresis banding patterns . Chlorhexidine was recalled, and the rate of S marcescens isolation returned to baseline . Chlorhexidine without alcohol should not be used as an antiseptic.

J Am Osteopath Assoc, 1998 Sep, 98(9), 505 - 7
Serratia odorifera biogroup I: an emerging pathogen; Cook MA et al.; Gram-negative bacteremia is a common cause of infection in hospitalized patients . Serratia sepsis is known to cause clinically significant morbidity and mortality . The most common species involved is Serratia marcescens . Clinicians have been uncertain as to the role of Serratia odorifera biogroup 1 as a human pathogen because most isolates have not been associated with invasive disease . In previous publications, 12 cases have been described in which S odorifera biogroup 1 caused sepsis . These observations verify the organism's role as a human pathogen.

Kansenshogaku Zasshi, 1998 Aug, 72(8), 845 - 8
{Serratia marcescens brain abscess in a newborn}; Sakata H et al.; The patient was born by emergency cesarean section for fetal distress at 35 weeks gestation with a weight of 2740 g . The early neonatal course was complicated by transient tachypnea and renal failure . He was receiving oxygen and diureticus in incubator for 5 days and his condition was very improved on day 5 . On day 7 he became lethargy and there was inability to tolerate feeding . Investigation of the cerebrospinal fluid revealed 8,000 leukocytes/microliter . S . marcescens was grown from cultures of both blood and cerebrospinal fluid . Treatment was started with cefotaxime and ampicillin every 6 hour . On day 14 the CT showed a brain abscess located parietooccipitally on the left side and diffuse infarction on the right side . On day 14 and 23 recurrence of increased leukocytes in the cerebrospinal fluid, high values of serum CRP and deterioration of clinical symptoms were observed . It is thought that the episodes show rupture of the abscess into the lateral ventricle . On day 55 surgical drainage was performed for the hydrocephalus . On day 110 the abscess was not found in the brain CT scan . His psychomotor development 3 years later was equivalent to two years old and he had secondary epilepsy.

Res Microbiol, 1998 Feb, 149(2), 137 - 43
Typing of nosocomial strains of Serratia marcescens: comparison of pulsed-field gel electrophoresis of macrorestriction fragments with biotyping, esterase typing and ribotyping; Chetoui H et al.; Fifty nosocomial isolates of Serratia marcescens, collected in six Belgian hospitals between 1986 and 1990, were characterized by using pulsed-field gel electrophoresis (PFGE) with XbaI . The results were compared with those previously obtained by three other methods: biotyping, esterase electrophoresis typing and ribotyping with EcoRI and HindIII . Macrorestriction analysis (42 PFGE groups) and esterase typing (42 zymotypes) proved to be the most discriminating, followed by ribotyping (28 ribotypes) and biotyping (10 biochemical profiles) . Biotyping would serve as a screen to identify isolates, due to its accessibility . Esterase typing provided a reliable tool to make subdivisions within biotypes because of congruence between biochemical groups and esterase patterns . Additional discrimination was still achieved by ribotyping and PFGE . It is concluded that the combined results of these four markers were useful for distinguishing all epidemic and sporadic isolates.

J Mol Biol, 1998 Oct 2, 282(4), 891 - 901
Temperature effects on the allosteric responses of native and chimeric aspartate transcarbamoylases; Liu L et al.; Although structurally very similar, the aspartate transcarbamoylases (ATCase) of Serratia marcescens and Escherichia coli have distinct allosteric regulatory patterns . It has been reported that a S . marcescens chimera, SM : rS5'ec, in which five divergent residues (r93 to r97) of the regulatory polypeptide were replaced with their Escherichia coli counterparts, possessed E . coli-like regulatory characteristics . The reverse chimera EC:rS5'sm, in which the same five residues of E . coli have been replaced with their S . marcescens counterpart, lost both heterotrophic and homotropic responses . These results indicate that the r93-r97 region is critical in defining the ATCase allosteric character . Molecular modeling of the regulatory polypeptides has suggested that the replacement of the S5' beta-strand resulted in disruption of the allosteric-zinc interface . However, the structure-function relationship could be indirect, and the disruption of the interface could influence allostery by altering the global energy of the enzyme . Studies of the temperature-sensitivity of the CTP response demonstrate that it is possible to convert CTP inhibition of the SM:rS5'ec chimera at high temperature to activation below 10 degreesC . Nonetheless, the temperature response of the native S . marcescens ATCase suggests a strong entropic effect that counteracts the CTP activation . Therefore, it is suggested that the entropy component of the coupling free energy plays a significant role in the determination of both the nature and magnitude of the allosteric effect in ATCase .

Biochem J, 1998 Sep 15, 334 ( Pt 3), 731 - 41
Prodigiosins uncouple lysosomal vacuolar-type ATPase through promotion of H+/Cl- symport; Ohkuma S et al.; We reported previously {Kataoka, Muroi, Ohkuma, Waritani, Magae, Takatsuki, Kondo, Yamasaki and Nagai (1995) FEBS Lett . 359, 53-59} that prodigiosin 25-C (one of the red pigments of the prodigiosin group produced by micro-organisms like Streptomyces and Serratia) uncoupled vacuolar H+-ATPase, inhibited vacuolar acidification and affected glycoprotein processing . In the present study we show that prodigiosin, metacycloprodigiosin and prodigiosin 25-C, all raise intralysosomal pH through inhibition of lysosomal acidification driven by vacuolar-type (V-)ATPase without inhibiting ATP hydrolysis in a dose-dependent manner with IC50 values of 30-120 pmol/mg of protein . The inhibition against lysosomal acidification was quick and reversible, showing kinetics of simple non-competitive (for ATP) inhibition . However, the prodigiosins neither raised the internal pH of isolated lysosomes nor showed ionophoric activity against H+ or K+ at concentrations where they strongly inhibited lysosomal acidification . They required Cl- for their acidification inhibitory activity even when driven in the presence of K+ and valinomycin, suggesting that their target is not anion (chloride) channel(s) . In fact, the prodigiosins inhibited acidification of proteoliposomes devoid of anion channels that were reconstituted from lysosomal vacuolar-type (V-)ATPase and Escherichia coli phospholipids . However, they did not inhibit the formation of an inside-positive membrane potential driven by lysosomal V-ATPase . Instead, they caused quick reversal of acidified pH driven by lysosomal V-ATPase and, in acidic buffer, produced quick acidification of lysosomal pH, both only in the presence of Cl- . In addition, they induced swelling of liposomes and erythrocytes in iso-osmotic ammonium salt of chloride but not of gluconate, suggesting the promotion of Cl- entry by prodigiosins . These results suggest that prodigiosins facilitate the symport of H+ with Cl- (or exchange of OH- with Cl-) through lysosomal membranes, resulting in uncoupling of vacuolar H+-ATPase.

Cell, 1998 Aug 21, 94(4), 439 - 49
Crystal structure of a GCN5-related N-acetyltransferase: Serratia marcescens aminoglycoside 3-N-acetyltransferase; Wolf E et al.; The X-ray structure of a canonical GCN5-related N-acetyltransferase (GNAT), Serratia marcescens aminoglycoside 3-N-acetyltransferase, bound to coenzyme A (CoA) has been determined at 2.3 A resolution . The single domain alpha/beta protein resembles a cupped right hand wrapped around a cylinder and consists of a highly curved, six-stranded beta sheet of mixed polarity that is sandwiched between four alpha helices . The structure includes all four conserved GNAT motifs (C, D, A, and B) and represents the catalytic core of this large enzyme superfamily . Acetyl CoA recognition is mediated by a betaalpha structure derived from GNAT motif A, which presents an invariant Arg/Gln-X-X-Gly-X-Gly/Ala segment for hydrogen bonding with the cofactor . Motif B contributes acidic residues to the binding site for the positively charged antibiotic substrate.

Dig Dis Sci, 1998 Aug, 43(8), 1657 - 64
Role of active oxygen species and lipid peroxidation in mepirizole-induced duodenal ulcers in rats; Iinuma S et al.; The role of active oxygen species and lipid peroxidation in the pathogenesis of duodenal ulcers induced by mepirizole was investigated in rats . Oral administration of mepirizole (200 mg/kg) resulted in ulcer lesions in the proximal duodenum . Thiobarbituric acid-reactive substances (TBA-reactive substances), an indicator of lipid peroxidation, also significantly increased in the duodenal mucosa . Myeloperoxidase (MPO) activity in the duodenal mucosa, a sign of polymorphonuclear leukocyte (PMN) accumulation, significantly increased . Combination treatment with polyethylene glycol-modified Serratia Mn-SOD and catalase significantly decreased the size of the ulcers and TBA-reactive substances in the duodenal mucosa . Allopurinol, a xanthine oxidase inhibitor, also reduced the size of duodenal ulcers . Both the size of the ulcers and the increase in TBA-reactive substances in the duodenal mucosa were significantly lower in PMN-depleted rats . Mepirizole increased the surface expression of adhesion molecule CD18 on PMNs in vitro . These results suggest that lipid peroxidation, mediated by active oxygen species generated from xanthine oxidase and PMNs, plays an important role in the pathogenesis of duodenal ulcers induced by mepirizole.

Microbiology, 1998 Aug, 144 ( Pt 8), 2189 - 94
Involvement of chitinases of Bacillus thuringiensis during pathogenesis in insects; Sampson MN et al.; Bacillus thuringiensis subsp . israelensis IPS78 and B . thuringiensis subsp . aizawai HD133 both secreted exochitinase activity when grown in a medium containing chitin . Allosamidin, a specific chitinase inhibitor, inhibited activity from both strains, with IC50 values of about 50 microM with colloidal chitin as substrate and between 1 and 10 microM with 4-methylumbelliferyl-diacetylchitobioside and 4-methylumbelliferyl-triacetylchitotrioside as substrates . The involvement of these chitinolytic activities during pathogenesis in insects has been investigated with B . thuringiensis subsp . israelensis IPS78 against larvae of the midge Culicoides nubeculosus, and with B . thuringiensis subsp . aizawai HD133 against caterpillars of the cotton leafworm Spodoptera littoralis . Presence of 100 microM allosamidin increased the LD50 by factors of 1.3 and 1.4, respectively, demonstrating a role for bacterial chitinases in the attack on the insects . Presence of chitinase A from Serratia marcescens considerably decreased the values for LD50 confirming previous observations with different systems of the potentiation of entomopathogenesis of B . thuringiensis by exogenous chitinases . The most likely action of the endogenous chitinases of B . thuringiensis is to weaken the insects' peritrophic membranes, allowing more ready access of the bacterial toxins to the gut epithelia . Addition of exogenous chitinases will then increase this effect . Complementary cross-infection experiments, strain HD133 against midge larvae and strain IPS78 against caterpillars, were performed to investigate the pathogen/host specificities of the effects . Results showed that much higher concentrations of bacteria were required to achieve even low mortalities, and addition of chitinase A gave no increase in death rate.

Int J Immunopharmacol, 1998 Jan-Mar, 20(1-3), 1 - 13
T-cell specific immunosuppression by prodigiosin isolated from Serratia marcescens; Han SB et al.; Prodigiosin was isolated from the culture broth of Serratia marcescens B-1231 . This compound inhibited the T-cell mediated immune responses such as concanavalin-A induced proliferation, mixed lymphocyte response, local graft vs host reaction and T-dependent antibody response at non-toxic concentrations . However, prodigiosin did not affect B-cell mediated immune functions such as lipopolysaccharide-induced proliferation and-activated polyclonal antibody production at the same concentrations . Prodigiosin did not cause death in vitro to lymphocytes at effective concentrations (< 100 nM) and also did not show toxicity in vivo to lymphoid organs at effective dosages (10 and 30 mg/kg) . The pharmacological potencies were comparable to the activities of other T-cell specific immunosuppressants such as cyclosporin A and FK-506 . In conclusion, it might be suggested that prodigiosin could be used as an immunosuppressant in clinical and immunological studies.

Biochem Mol Biol Int, 1998 Jul, 45(4), 725 - 33
Streptokinase secretion by Serratia marcescens signaled by the C-terminal 41 amino acid segment of metalloprotease; Kim KS et al.; In order to investigate the secretion signal of Serratia marcescens metalloprotease (SMP) and examine the ability of the secretion signal to secrete foreign proteins, hybrid genes encoding the passenger-SMP C-terminal segments were constructed . As a passenger protein, streptokinase (SK) deprived of its signal peptide was used . Three kinds of SMP C-terminal segments containing 41, 80, or 220 amino acid residues were fused to the C-terminus of SK as secretion signals . The SK-SMP chimeric proteins containing 41 or 220 amino acid segments of the SMP C-terminus were secreted into the culture medium by the SMP transporter of S . marcescens . This result suggests that cytoplasmic SK is secreted into the external medium by the C-terminal segments of SMP and also shows that the smallest, 41 amino acid segment of the SMP C-terminus functions as a secretion signal of foreign proteins as well as SMP.

FEMS Microbiol Lett, 1998 Aug 1, 165(1), 1 - 13
Serratia marcescens and its extracellular nuclease; Benedik MJ et al.; Serratia marcescens produces an endonuclease with extraordinarily high specific activity that is released into the surrounding medium . This enzyme has been the focus of studies on gene regulation, protein secretion, endonuclease action, and protein structure; it has also been found to have many applications in biotechnology . Here we briefly review these different facets of research regarding the Serratia nuclease and summarize the current state of knowledge about this enzyme.

Arch Physiol Biochem, 1998 Aug, 105(4), 347 - 57
Effects of Ca2+ ions on survival, growth, and cell size in Serratia marcescens SMG40 exposed to mecillinam; Gratia JP; Serratia marcescens strain SMG40 is sensitive to mecillinam killing at concentrations approaching those required for rod-to-sphere conversion . After a 1 h exposure to mecillinam, the type of response was found to depend on the conditions of post-incubation . Whereas they lysed soon after transfer to a tenfold-diluted broth, treated cells stopped dividing and enlarged impressively without immediate lysis when they were transferred to a complete low-agar medium and incubated at 30 degrees C . More remarkably, the presence of Ca2+ cations in any post-incubation medium definitely protected treated cells from lysis, enabled them to divide as spheres, and prevented enlargement . These survival-promoting and size-limiting effects were reversible upon elimination of Ca2+ from the medium . They were observable at far lower ionic concentrations than those required for osmotic stabilization . The growth rate depended on the Ca2+ concentration (from 10 microM) and on the presence of other supplements . Na+ cations also exerted a protective effect but acted differently from Ca2+ ions; the effects of Na+ and Ca2+ ions appeared as synergistic . A physiological activity of calcium is suggested for this bacterial strain, resulting in a RodA-like mecillinam resistant phenotype.

Mol Microbiol, 1998 Jun, 28(6), 1223 - 34
Isolation and characterization of an extracellular haem-binding protein from Pseudomonas aeruginosa that shares function and sequence similarities with the Serratia marcescens HasA haemophore; Letoffe S et al.; The major mechanism by which bacteria acquire free or haemoglobin-bound haem involves direct binding to specific outer membrane receptors . Serratia marcescens also secretes a haem-binding protein, HasA, which functions as a haemophore that catches haem and shuttles it to a cell surface specific outer membrane receptor, HasR . We report the isolation and characterization of hasAp, a gene from Pseudomonas aeruginosa . HasAp is an iron-regulated extracellular haem-binding protein that shares about 50% identity with HasA . HasAp is required for P . aeruginosa utilization of haemoglobin iron . It can replace HasA for HasR-dependent haemoblobin acquisition in a system reconstituted in Escherichia coli . HasAp, like HasA, lacks a signal peptide and is secreted by an ABC transporter . These findings show that haemophore-dependent haem acquisition is not unique to S . marcescens.

J Biol Chem, 1998 Jul 31, 273(31), 19618 - 24
Structural and functional characterization of Streptomyces plicatus beta-N-acetylhexosaminidase by comparative molecular modeling and site-directed mutagenesis; Mark BL et al.; We have sequenced the Streptomyces plicatus beta-N-acetylhexosaminidase (SpHex) gene and identified the encoded protein as a member of family 20 glycosyl hydrolases . This family includes human beta-N-acetylhexosaminidases whose deficiency results in various forms of GM2 gangliosidosis . Based upon the x-ray structure of Serratia marcescens chitobiase (SmChb), we generated a three-dimensional model of SpHex by comparative molecular modeling . The overall structure of the enzyme is very similar to homology modeling-derived structures of human beta-N-acetylhexosaminidases, with differences being confined mainly to loop regions . From previous studies of the human enzymes, sequence alignments of family 20 enzymes, and analysis of the SmChb x-ray structure, we selected and mutated putative SpHex active site residues . Arg162 --> His mutation increased Km 40-fold and reduced Vmax 5-fold, providing the first biochemical evidence for this conserved Arg residue (Arg178 in human beta-N-acetylhexosaminidase A (HexA) and Arg349 in SmChb) as a substrate-binding residue in a family 20 enzyme, a finding consistent with our three-dimensional model of SpHex . Glu314 --> Gln reduced Vmax 296-fold, reduced Km 7-fold, and altered the pH profile, consistent with it being the catalytic acid residue as suggested by our model and other studies . Asp246 --> Asn reduced Vmax 2-fold and increased Km only 1.2-fold, suggesting that Asp246 may play a lesser role in the catalytic mechanism of this enzyme . Taken together with the x-ray structure of SmChb, these studies suggest a common catalytic mechanism for family 20 glycosyl hydrolases.

FEMS Microbiol Lett, 1998 Jul 1, 164(1), 69 - 75
Serratia liquefaciens swarm cells exhibit enhanced resistance to predation by Tetrahymena sp; Ammendola A et al.; Tetrahymena sp . was found to graze extensively on Serratia liquefaciens MG1 swim cells (1.5-3 microns long rods) resulting in the rapid elimination of the bacterial strain . However, when S . liquefaciens cells are exposed to certain surfaces they differentiate into elongated, highly motile swarm cells and these cells were found to be grazing-resistant provided their length exceeded 15 microns.

Infect Immun, 1998 Aug, 66(8), 3941 - 51
Phospholipase A of Yersinia enterocolitica contributes to pathogenesis in a mouse model; Schmiel DH et al.; Some isolates of Yersinia enterocolitica exhibit phospholipase activity, which has been linked to lecithin-dependent hemolysis (M . Tsubokura, K . Otsoki, I . Shimohira, and H . Yamamoto, Infect . Immun . 25:939-942, 1979) . A gene encoding Y . enterocolitica phospholipase was identified, and analysis of the nucleotide sequence revealed two tandemly transcribed open reading frames . The first, yplA, has 74% identity and 85% similarity to the phospholipase A found in Serratia liquefaciens . Though the other, yplB, was less similar to the downstream accessory protein found in S . liquefaciens, the organization in both species is similar . Subsequently, a yplA-null Y . enterocolitica strain, YEDS10, was constructed and demonstrated to be phospholipase negative by plate and spectrophotometric assays . To ascertain whether the phospholipase has a role in pathogenesis, YEDS10 was tested in the mouse model . In experiments with perorally infected BALB/c mice, fewer YEDS10 organisms were recovered from the mesenteric lymph nodes and Peyer's patches (PP) than the parental strain at 3 or 5 days postinfection . Furthermore, bowel tissue and PP infected with YEDS10 appeared to be less inflamed than those infected with the parental strain . When extremely high doses of both the parental and YEDS10 strains were given, similar numbers of viable bacteria were recovered from the PP and mesenteric lymph nodes on day 3 . However, the numbers of foci and the extent of inflammation and necrosis within them were noticeably less for YEDS10 compared to the parental strain . Together these findings suggest that Y . enterocolitica produces a phospholipase A which has a role in pathogenesis.

J Forensic Sci, 1998 Jul, 43(4), 797 - 805
Six forensic entomology cases: description and commentary; Benecke M; Insects are known to be useful in estimating the postmortem interval (PMI) . Here several cases are reported which show that a wide range of applications in medicolegal questions and hygiene together or apart from estimating the PMI can be answered by use of forensic entomology techniques, including close observation of larval development . Case 1 describes how blowfly larvae fell from a putrefied corpse, hid, and finally emerged from pupae three months after disinfection and renovation . In case 2, the entomological state of the decomposed corpse of a heroin user is described . Case 3 deals with a single adult Protophormia terranovae found in the skull of a partially mummified woman . Case 4 reports the finding of Serratia marcescens bacteria in red Muscina stabulans pupae which were found on a 5-day-old corpse . In case 5, blowfly eggs on the corpse of another heroin user are interpreted as an indication of the decedent being laid outside at night after his death in a flat . Case 6 deals with the finding of Parasarcophaga argyrostoma, which in Cologne might be an indicator species which tells if a corpse was lying outside at least for some time.

Kyobu Geka, 1998 Jul, 51(7), 609 - 11
{Treatment of mediastinal infection by continuous closed irrigation with an antibiotic solution in a new bone baby}; Tamura M et al.; The patient was a three-week-old girl . Four days after thoracic surgery, mild fever developed, and turbid fluid was drained from the incision . Culture of the discharge showed Pseudomonas aeruginosa and Serratia marcescens . Debridement was immediately performed and continuous closed irrigation with an antibiotic solution started and maintained for 17 days . During this period, the upper half of the body was elevated . Ten days after irrigation started culture of the drainage fluid became negative . We emphasize early diagnosis, and the usefulness of continuous closed irrigation with an antibiotic solution in neonates.

Vet Immunol Immunopathol, 1998 May 15, 63(1-2), 83 - 103
Listeria monocytogenes and Serratia marcescens infections as models for Th1/Th2 immunity in laboratory cats; Pedersen NC et al.; Five species of bacteria known to be naturally-occurring pathogens of cats were screened for their ability to grow in feline macrophages in vitro, and to induce antibodies and delayed type hypersensitivity (DTH) responses in vivo . Two of these organisms, L . monocytogenes and S . marcescens, were selected for further study based on clear-cut differences in their in vitro and in vivo behavior . Listeria was macrophage tropic, induced DTH, and evoked poor antibody responses post-recovery, whereas Serratia remained extracellular, did not induce a DTH reaction, and produced high titer of antibodies . Young specific pathogen free cats were then inoculated subcutaneously into the drainage areas of the right and left popliteal and auricular lymph nodes with either L . monocytogenes or S . marcescens . Each of the four lymph nodes were then removed in sequence over a two week period, weighed, cultured for viable bacteria, and RNA extracted for Th1/Th2 cytokine mRNA quantitation . Antibody responses and delayed type hypersensitivity responses were also measured . Identical to pilot studies, cats infected with Serratia developed very high levels of antibody compared to Listeria infected cats but no DTH, while Listeria infected cats produced negligible or low titers of antibodies and strong DTH . Immunity to Listeria occurred around 168 h post infection as evidenced by the disappearance of living bacteria from the nodes, while immunity to Serratia took over 264 h . Pronounced lymph node hyperplasia occurred in both infections, but persisted longer for Serratia . Enlargement of Serratia infected nodes was associated with marked follicular, primary and secondary germinal center and medullary hyperplasia . Germinal center formation in Listeria stimulated nodes was much less intense and dense accumulations of macrophages dissected between follicles downward from the subcapsular sinuses . Although functional and histologic studies showed a clear-cut cell-mediated vs . humoral response in the respective Listeria and Serratia infections, preferential cytokine mRNA upregulation was observed for only two of the five major Th1/Th2 cytokines measured . Interferon-gamma, a Th1 cytokine, was much more elevated in the Listeria stimulated nodes, but TNF-alpha (also a Th1 cytokine) was more elevated in Serratia infected nodes . Interleukin-12, an important Th1 cytokine, was elevated to equal levels in both infections as were the Th2 cytokines IL-4 and IL-10.

J Hosp Infect, 1998 Jun, 39(2), 135 - 41
An outbreak of an unusual strain of Serratia marcescens in two Dublin hospitals; Herra CM et al.; We describe a serious outbreak of infection caused by a strain of Serratia marcescens in two Dublin hospitals which occurred over an 11 week period and affected a total of 15 patients . A contaminated bed-pan macerator in the Intensive Care Unit of one hospital was identified as the possible source of infection and spread of the organism probably occurred via hand transmission by hospital personnel and via patient transfer to a second hospital . All isolates of S . marcescens involved in the outbreak had the same antimicrobial susceptibility pattern, with reduced susceptibility to gentamicin, cefotaxime and ciprofloxacin . Epidemiological typing revealed that the strains of S . marcescens isolated in the outbreak were of an uncommon serotype, O21:K14, and using pulsed-field gel electrophoresis, XbaI DNA macrorestriction profiles clustered at 90% similarity . The DNA patterns of the outbreak strain were also highly similar to S . marcescens isolates of the same serotype recovered from a separate Dublin hospital during the same time period as the outbreak described here . In addition, the isolates clustered at 82% similarity with strains of the same serotype from a retrospective collection of S . marcescens isolates from various hospitals in the Dublin area, indicating that these may be genetic variants of the same strain . Although the outbreak was brought under control following implementation of infection control measures, a significant number of similar O:21 isolates of S . marcescens have since been identified in four Dublin hospitals . These results suggest the unique spread of a single strain of S . marcescens in Dublin hospitals.

J Parasitol, 1998 Jun, 84(3), 529 - 33
The specificity of behavioral fever in the cricket Acheta domesticus; Adamo SA; When infected, some insects can raise their body temperature by moving to warmer areas . This behavioral fever response can help the host overcome infection . However, not all parasites and pathogens are equally susceptible to increases in host temperature . Elevating the temperature of the cricket Acheta domesticus from room temperature (22 C) to 33 C did not reduce the survival of parasitoid flies or reduce the number of gregarine gut protozoans, and crickets infested with these parasites showed no increase in their temperature preference . Warmer temperatures (33 C) did not increase the survival of crickets infected with the bacterium Serratia marcescens, and infected crickets did not prefer warmer temperatures . However crickets infected with the intracellular parasite Rickettsiella grylli were more likely to survive when the host was exposed to warmer temperatures . Crickets infected with R . grylli increased their preferred temperature from 26 C to 32 C . In A . domesticus, behavioral fever may be a specific response induced by relatively few pathogens and parasites . Behavioral fever in insects may differ in this respect from fever in mammals that can be elicited by a wide variety of parasites and pathogens.

Am J Clin Pathol, 1998 Jun, 109(6), 743 - 7
Lack of efficacy for conventional gamma irradiation of platelet concentrates to abrogate bacterial growth; Huston BM et al.; The maximum storage time for platelet concentrates is 5 days, owing to the higher risk bacterial contamination with longer storage . The expiration date could potentially be extended if a rapid system to detect microbial contamination or a safe sterilization technique could be developed and easily implemented . Gamma irradiation has decreased bacterial contamination in food products . Conventional doses of gamma irradiation were tested for their efficacy in decreasing bacterial growth during the 5-day platelet shelf life . An initial pilot study determined that bacteria suspended in normal saline at concentrations of 1 to 2 x 10(7) colony-forming units per milliliter showed a dose-related susceptibility to gamma irradiation . Subsequently, four platelet concentrates were pooled, inoculated with a known concentration of Staphylococcus autreus or Serratia marcescens, and divided . The concentrates were exposed to varying amounts of gamma irradiation, ie, no irradiation (control), 25, 50, and 75 Gy, and subjected to typical blood bank storage conditions . The platelet concentrates were sampled daily for 7 consecutive days to monitor bacterial growth by quantitative cultures . An inverse linear dose-related extinction of bacteria was evident in the pilot study with an extrapolated total kill in the 100 to 150 Gy range . There is no difference in bacterial growth with S aureus using irradiation levels from 0 to 75 Gy . A 1-day delay in bacterial growth at 75 Gy was found with S marcescens compared with units irradiated with 0 through 50 Gy . Exposure of bacteria-contaminated platelet concentrates on storage day zero to gamma irradiation at levels up to 75 Gy is ineffective at sterilizing the platelet concentrates . Higher levels of irradiation may be effective in sterilizing platelet concentrates . Function, survival, and sterility after higher than conventional levels of irradiation need further study.

Biosci Biotechnol Biochem, 1998 Apr, 62(4), 667 - 71
Purification and partial characterization of purine nucleoside phosphorylase from Serratia marcescens; Choi HS; Purine nucleoside phosphorylase (PNP) was purified to homogeneity . The molecular weight of the enzyme was 170,000 . The enzyme consisted of six subunits, each with a molecular weight of 27,000 . Serratia PNP had ten times the affinity for adenosine and deoxyadenosine than for inosine and deoxyinosine in a pattern characteristic of bacterial PNP . 1-Methylinosine and 1-methylguanosine, which have no affinity for mammalian PNP, bound Serratia PNP . In terms of Kcat/K(m), the substrate specificities were in the descending order of guanosine, inosine, and adenosine . When inosine or deoxyinosine was used as a variable substrate, a biphasic reciprocal plot with upward curvature was observed . The values of the Hill coefficient were 1.2 and 1.1 for inosine and deoxyinosine, respectively . Positive cooperativity seemed to be involved in the binding of inosine and deoxyinosine to the enzyme.

Rev Invest Clin, 1998 Jan-Feb, 50(1), 13 - 8
{Case-control study of an outbreak of S . marcescens in a neonatal intensive care unit}; Miranda-Novales MG et al.; OBJECTIVE: To analyze an outbreak of Serratia marcescens in a neonatal intensive care unit and identify the risk factors associated to the development of infection . MATERIAL AND METHODS: It was a case-control study from March to July 1995 . Factors included were age, sex, intravascular devices, nebulizers, mechanical ventilation, use of total parenteral nutrition (TPN), underlying diseases, surgical interventions, tubes, previous antimicrobial treatment and days of exposure . The associations were explored using the odds ratio . RESULTS: 24 cases and 30 controls were included . In the univariate analysis the significant risk factors (OR,IC) were use of central venous catheter (4.57, 1.01-23.5), days of use of TPN (4.38, 1.03-16.5), days of previous antimicrobial treatment (4.87, 1.60-22) and days of exposure (2.7, 2.65-27.6) . In the multivariate analysis the significant risk factors were previous antimicrobial treatment (3.98, 2.36-18.2), days of previous antimicrobial treatment (6.76, 3.02-24.6) and days of use of TPN (4.87, 1.67-15.6) . CONCLUSIONS: The significant risk factors in our study were previous antimicrobial treatment, days of antimicrobial and days of use of TPN.

Med Arh, 1995, 49(3-4), 87 - 9
{Aerobic wound infections during the war}; Seric K et al.; We presented the results of causative agents of wounds aerobic infections obtained during the first three months of third war year in Bosnia . We isolated mostly Staphylococcus aureus (54%), Pseudomonas aeruginosa (25%) and Serratia marcensens (20%) . Other aerobic causative agents of wounds were established in less percent . The most frequent infections were detected in swaba specimens received from Orthopaedic, Traumathological, Plastical, Vasculary and Clinic for Pulmonary Diseases . In discussion we compared our results to data from 1st and 2nd world war and wars in Algeria, Corea, Vietnam and Israel.

Ophthalmic Surg Lasers, 1998 Apr, 29(4), 345 - 7
Bacterial contamination of the pressure receiver of a vitrectomy machine; Janknecht P et al.; On a routine sterility check, the authors found bacteria in their vitrectomy machine . Serratia marcescens was detected in the pressure receiver of a roller pump vitrectomy machine . The authors improved the machine by installing a millipore filter in front of the receiver that prevents bacteria from entering it without interfering with the pressure measurements . The origin of Serratia was probably a patient with endophthalmitis who was operated on long before the routine check . Although this appears to be the first report of a bacterial contamination of a vitrectomy machine, the results of testing show that this situation is indeed possible . The authors strongly recommend routine checks of the equipment and suggest mounting an antibacterial filter.

Transfus Med, 1998 Mar, 8(1), 15 - 8
Fatal reaction to transfusion of red-cell concentrate contaminated with Serratia liquefaciens; Boulton FE et al.; A 60-year-old woman undergoing surgery died from endotoxic shock and DIC after receiving a 19-day-old unit of optimal additive red-cell concentrate found contaminated with Serratia liquefaciens . No source of contamination could be found . This normally free-living organism is usually of low pathogenicity . It is a very unusual contaminant of stored donated blood, although it appears to be on the increase . When transfused, blood contaminated with S . liquefaciens always causes severe morbidity and is associated with a high death rate . This is the fifth report in the English literature.

Int J Immunopharmacol, 1997 Aug, 19(8), 443 - 9
Modulation of the immune response of Balb/c mice against Leishmania major by imuvert; Taha SM et al.; This study investigated the effect of Imuvert, a biological response modifier derived from Serratia marcescens, on the progression of Leishmania major infection in Balb/c mice . A single 100 micrograms Imuvert injection was significantly protective in Balb/c mice when challenged 28 days later in the footpad with 5 x 10(5) stationary phase L . major promastigotes . Intraperitoneal (i.p.) and intravenous (i.v.) immunization of mice with heat-killed stationary phase L . major promastigotes significantly reduced lesion development following challenge with L . major promastigotes . Subcutaneous (s.c.) immunization had no protective effect . A single 100 micrograms Imuvert injection significantly reduced lesion development in s.c . immunized mice, but had a lesser effect in mice immunized by i.p . and i.v . routes . Balb/c mice receiving four Imuvert injections 14, 7, 2 and 1 day prior to footpad challenge with L . major promastigotes were not protected, but rather displayed significant exacerbation of infection . Our results suggest the possibility that Imuvert could be useful in stimulating a protective response against L . major when given along with s.c . vaccine, a realistic route for vaccinating humans in contrast to either i.v . or i.p . routes . Since the protective response in Balb/c mice against L . major is dependent on the stimulation of Th1 cells, it is suggested that the observed adjuvant effect of Imuvert given with s.c . vaccine perhaps is due to changes in immunological responses in such a direction.

FEBS Lett, 1998 Apr 3, 425(3), 517 - 22
Genetic engineering, production and characterisation of monomeric variants of the dimeric Serratia marcescens endonuclease; Franke I et al.; The Serratia nuclease is a non-specific endonuclease which cleaves single- and double-stranded RNA and DNA . It is a member of a large family of related endonucleases, most of which are dimers of identical subunits, with the notable exception of the Anabaena nuclease which is a monomer . In order to find out whether the dimer state of the Serratia nuclease is essential for its function we have produced variants of this nuclease which based on the crystal structure (Miller, M.D . and Krause, K.L . (1996), Protein Science 5, 24-33) were expected to be unable to dimerise . We demonstrate here that these variants, H184A, H184N, H184T and H184R, are monomers and have the same secondary structure, stability towards chemical denaturation and activity as the wild-type enzyme . This allows to conclude that the dimeric state is not essential for the catalytic function of the Serratia nuclease . In contrast, the S179C variant which is also a monomer shows little activity, presumably because this amino acid substitution changes the structure of the enzyme.

What Is Biofilm?, What Is Genome?, What Is Botulism?, What Is MIC?, What Is Pcr?, o, Microbe, c, Bacteriology, c, Microbes, o, Bacterium, s, Microorganisms, i, Bacteria, i, Antibiotics, n, Prokaryotes, c, Prokaryotes, a, Penicillin, o, Prokaryotes, e, Yeasts, o, Bacteriological, n, Candida albicans, e, Yeasts, r, Staphylococcus aureus, o, Microorganisms, a, Escherichia coli, n, Penicillin, r, Penicillin, c, Microorganisms, a, Yeasts, e, Streptococcal, c, Bacillus, s, Lactococci, c, Bactericidal

Scientific Publications - Work Done by Microbiology Reader Bioscreen C
Agricultural Microbiology Anaerobic Microbiology Antimicrobial Susceptibility Artificial Atmosphere Bioassay of Antibiotics Biofilm Microbiology Bioreactor Technology Biotechnology Cell Biology Clinical Microbiology Environmental Microbiology Experiments with Yeast	Fermentation Food Microbiology Functional Genomics Gene Technology Growth Media Development Growth Rate and Lag Time Industrial Microbiology Medical/Pharmaceutical Field Microbiological Assay Microbiological Research Microbiology of Cosmetics go to a specific theme...	Military Microbiology Molecular Microbiology Mutagenicity and Genotoxicity Oral Microbiology Patents Postantibiotic Studies Soil Microbiology Spore Microbiology Veterinary Microbiology Waste/Wastewater Treatment Water Microbiology Wine Microbiology

� 2005 Transgalactic Ltd (manufacturer of Bioscreen C software) | Privacy Statement | P.O. Box 1393, 00101 Helsinki, Finland, phone: +358 9 85172920, fax: +358 9 8749481, e-mail: microbiology@bionewsonline.com

Last modified: May 25, 2005