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