Aeromonades

Clin Infect Dis, 1998 Aug, 27(2), 332 - 44
Evolving concepts regarding the genus Aeromonas: an expanding Panorama of species, disease presentations, and unanswered questions; Janda JM et al.; It has been almost 10 years since a major review on the association of Aeromonas with human disease has been published . During that period the number of valid species in the genus has grown to 14, with a new family (Aeromonadaceae) established to house this genus . Despite this explosion in the number of new genomospecies, only five (Aeromonas hydrophila, A . caviae, A . veronii, A . jandaei, and A . schubertii) are currently recognized as human pathogens . New syndromes attributed to this genus include hemolytic uremic syndrome, burn-associated sepsis, and a variety of respiratory tract infections, including epiglottitis . Convincing evidence suggests that some aeromonads do cause gastroenteritis, but it is presently unclear whether many of the strains isolated from feces are involved in diarrheal disease . Many questions regarding this genus remain unanswered.

J Food Prot, 1998 Apr, 61(4), 414 - 8
Survival of Aeromonas hydrophila in fresh tomatoes (Lycopersicum esculentum Mill) stored at different temperatures and treated with chlorine; Velazquez LC et al.; This study examines the survival of two Aeromonas hydrophila strains (A . hydrophila ATCC 7965 {strain A} and A . hydrophila isolated from food {strain B} on the surface and core tissue of fresh tomatoes stored at different temperatures and the efficacy of chlorine treatment on their survival . Counts of A . hydrophila on the surface of tomatoes stored at 25 and 35 degrees C were significantly higher between days 1 and 4 for both strains as compared to results obtained at 6 degrees C . Core tissue counts of A . hydrophila cells on tomatoes dipped in a cellular suspension at 25 degrees C and stored at 25 degrees C were significantly higher (P < 0.05) than counts obtained with dip suspensions at 6 or 35 degrees C . In chopped tomatoes stored at 25 and 35 degrees C, populations of aerobic mesophiles showed significant increases after 96 and 70 h, respectively . The populations of both A . hydrophila strains in chopped tomatoes stored at 6 degrees C increased significantly after 96 h, while at 25 and 35 degrees C the counts increased in the first hours of incubation . Viable counts of A . hydrophila on the surface and central tissue of tomatoes significantly decreased (P < 0.05) when the samples were dipped for 2 min in chlorine at a concentration of 50 ppm (50 microgram/ml) . The results suggest that tomatoes should be kept at low temperatures during storage, shipping, and retail stocking and that chlorine at a concentration of 50 ppm should be used to reduce the levels of A . hydrophila.

J Formos Med Assoc, 1998 Jul, 97(7), 498 - 502
Aeromonas hydrophila sepsis presenting as meningitis and necrotizing fasciitis in a man with alcoholic liver cirrhosis; Lin CS et al.; Aeromonas hydrophila is rarely reported as a causative organism of meningitis in humans . A 39-year-old man with alcoholic liver cirrhosis was admitted with a 2-day history of fever, chills, and confusion . Laboratory data revealed leukocytosis with granulocytosis, marked impairment of renal and liver function, and an elevated serum ammonia level . A . hydrophila was isolated from both blood and cerebrospinal fluid samples . Skin and soft-tissue lesions, consisting of bullae and necrotizing fasciitis, were found in the lower left leg 2 days after admission . Cultures of the bullous fluid, subcutaneous tissue, and fascia all yielded A . hydrophila . Pathologic examination revealed extensive necrosis . Although the patient was appropriately managed with antibiotics, debridement, and fasciotomies, his clinical status rapidly deteriorated, resulting in death 3 days after admission.

Dis Aquat Organ, 1998 Feb 26, 32(1), 49 - 69
Occurrence and significance of atypical Aeromonas salmonicida in non-salmonid and salmonid fish species: a review; Wiklund T et al.; Bacterial strains of Aeromonas salmonicida included in the recognized subsp . acromogenes, subsp . masoucida, and subsp . smithia in addition to the large number of strains not included in any of the described subspecies are referred to as atypical A . salmonicida . The atypical strains form a very heterogeneous group with respect to biochemical characteristics, growth conditions, and production of extracellular proteasess . Consequently, the present taxonomy of the species A . salmonicida is rather ambiguous . Atypical A . salmonicida has been isolated from a wide range of cultivated and wild fish species, non-salmonids as well as salmonids, inhabiting fresh water, brackish water and marine environments in northern and central Europe, South Africa, North America, Japan and Australia . In non-salmonid fish species, infections with atypical strains often manifest themselves as superficial skin ulcerations . The best known diseases associated with atypical A . salmonicida are carp Cyprinus carpio erythrodermatitis, goldfish Carassius auratus ulcer disease, and ulcer disease of flounder Platichthys flesus, but atypical strains are apparently involved in more disease outbreaks than previously suspected . Macroscopical and microscopical studies of ulcerated fish indicate internal organs are infrequently invaded by atypical A . salmonicida . This view is supported by the fact that atypical strains are irregularly isolated from visceral organs of ulcerated fish . High mortality caused by atypical A . salmonicida has been observed in populations of wild non-salmonids and farmed salmonids, although the association between the mortality in the wild fish stocks and atypical A . salmonicida has not always been properly assessed . In injection experiments the pathogenicity of the atypical strains examined showed large variation . An extacellular A-layer has been detected in different atypical strains, but virulence mechanisms different from those described for (typical) A . salmonicida subsp . salmonicida, for example an extracellular metallo-protease and a different iron utilization mechanism, have been described . Limited information is available about the ecology, spread and survival of atypical strains in water . The commonly used therapeutic methods for the control of diseases in farmed fish caused by atypical A . salmonicida are generally effective against the atypical strains . Resistance to different antibiotics and transferable plasmid encoding multiple drug resistance have been observed in atpical A . salmonicida . Studies aimed at producing a vaccine against atypical strains are in progress.

Burns, 1998 Jun, 24(4), 350 - 3
Aeromonas hydrophila in burn patients; Skoll PJ et al.; Burn wound infection with Aeromonas hydrophila appears to be very uncommon . This study reports on nine cases of A . hydrophila in burn patients treated over a 21 month period at the New Somerset Hospital Burn Unit . The average age of the patients was 31 years (range 24-60 years) and the average TBSA was 33% (range 16-51%) . All patients had positive wound cultures for A . hydrophila, obtained on admission or shortly thereafter . One patient also had a positive blood culture . Two patients with small partial thickness burns did not receive antibiotic therapy, and made an uneventful recovery with topical therapy alone . The other seven patients developed clinical signs of septicaemia and required parenteral antibiotics, in addition to topical therapy . One patient died of ARDS, but the other eight recovered and were discharged . No patient had evidence of myonecrosis . Small, superficial burns which culture A . hydrophila can be treated by topical therapy alone . Large and/or deep burns, require antibiotic therapy and debridement of all necrotic tissue, particularly when myonecrosis is present . The antibiotics of choice are the aminoglycosides or the quinolones.

Zentralbl Hyg Umweltmed, 1998 Jun, 201(2), 199 - 203
The maximum growth temperature and human pathogenicity of psychrotrophic aeromonads; Schubert RH et al.; Determination of the maximum growth temperature of Aeromonas strains isolated from clinical material and endowed with pronounced propensity for adhesion to intestinal cells has demonstrated that all strains still grow at 39 degrees C, with this holding true for the majority of strains also at 40 degrees C . Since Aeromonas isolated obtained from water evidence to a large extent a markedly lower maximum growth temperature, the 39 degrees C growth criterion is a characteristic of Aeromonas strains isolated from clinical material.

Rev Cubana Med Trop, 1997, 49(2), 84 - 5
{Comparative study of 4 methods for identifying species of the genus Aeromonas}; Longa A et al.; It is given an explanation of the results obtained with the following methods: AEROKEY II, AEROKEY II + Abbot's scheme, Api 20 NE, and the Biolog System . The study was conducted with 38 strains of Aeromonas isolated from children under 5 with acute diarrheal disease (ADD) . The AEROKEY II + Abbot's scheme proved to be the best identification method.

Rev Cubana Med Trop, 1997, 49(1), 43 - 5
{Application of pyrazinamidase activity for the identification of Aeromonas species}; Bravo L et al.; 70 Aeromonas strains isolated from patients with acute diarrheal disease were classified into species by using the CAMP factor test and the Pyrazinamidase activity . It is stressed the high percent of coincidence between both tests, which are easy to make at the clinical microbiology laboratories.

FEMS Immunol Med Microbiol, 1998 Jun, 21(2), 131 - 7
Possible virulence factors of Aeromonas spp . from food and water; Granum PE et al.; Thirty-one isolates of Aeromonas spp . from food and water in Norway were classified and tested for possible virulence factors including cytotoxins (tissue cultures, PCR), enterotoxins (PCR) and invasion ability (Caco-2 cells) . Five different species were recorded, A . caviae (9/31), A . hydrophila (15/31), A . schubertii (3/31), A . trota (3/31) and A . veronii biovar veronii (1/31) . One of the A . hydrophila strains was probably responsible for a small outbreak of food poisoning caused by ingestion of raw fermented fish . All the A . hydrophila strains produced and secreted cytotoxins at 37 degrees C, as well as two A . trota strains and the single A . veronii biovar veronii strain . In some cases increased cytotoxin secretion was observed under osmotic stress . The majority of the A . caviae strains which produced cytotoxins at 30 degrees C were unable to produce and/or secrete cytotoxins at 37 degrees C . One A . schubertii strain and one A . caviae strain were invasive.

Dis Aquat Organ, 1998 Jun 19, 33(2), 87 - 92
Siderophore production by Aeromonas salmonicida subsp . salmonicida . Lack of strain specificity; Fernandez AI et al.; Siderophore production, presence of iron-regulated outer membrane proteins and siderophore specificity was determined among 17 isolates of Aeromonas salmonicida subsp . salmonicida obtained from Spain and Scotland . All grew in the presence of ethylenediamine di(o-hydroxyphenylacetic acid) (EDDA) and siderophore production was detected using chrome azurol S (CAS) agar, confirming the presence of a high-affinity siderophore iron-uptake mechanism . The Arnow test confirmed that all isolates produced a catechol siderophore . Cross-feeding assays with indicator bacteria showed the absence of anguibactin, enterobactin, 2,3-dihydroxybenzoic acid (DHBA) and the hydroxamate siderophore, aerobactin, in the iron-restricted supernants of a representative isolate which cross fed 15/17 A . salmonicida isolates tested . Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) showed the presence of the same 2 major iron-regulated outer membrane proteins (IROMPs) in all isolates when grown in iron-restricted conditions and siderophore strain specificity as assessed by cross-feeding experiments was not apparent . Thus, with respect to IROMP and siderophore production A . salmonicida appears to be a homogeneous species.

Lett Appl Microbiol, 1998 May, 26(5), 352 - 4
False-positive coliform reaction mediated by Aeromonas in the Colilert defined substrate technology system; Landre JP et al.; The Colilert defined substrate technology system allows specific, one-step detection of both coliforms and Escherichia coli while claiming to suppress the influence of non-coliform heterotrophs . The Colilert assay was examined in order to determine whether organisms from the genus Aeromonas could interfere and cause production of a false-positive coliform result as aquatic Aeromonas are known to constitute a fraction of the heterotrophic population found in drinking water . Results obtained clearly demonstrate that Aeromonas sp . can elicit a positive coliform type reaction at very low densities . Cell suspensions as low as 1 x 10(1) cells 10 ml-1 were observed to yield a positive reaction using Colilert reagent 4 weeks short of shelf-life expiry . Use of aged Colilert for monitoring water quality could lead to overestimation of coliforms as Aeromonas have been identified in many treated drinking water supplies.

Lett Appl Microbiol, 1998 May, 26(5), 347 - 51
Bactericidal effect of chlorine on motile Aeromonas spp . in drinking water supplies and influence of temperature on disinfection efficacy; Sisti M et al.; The susceptibility of toxigenic Aeromonas spp . to free chlorine in drinking water supplies, and the influence of environmental temperature on the bactericidal activity of the oxidant, were evaluated . The results showed inactivation curves characterized by an initial phase of rapid reduction of viable cells followed by a slow inactivation of bacteria . The effect of the chlorine compound was markedly influenced by water temperature . At a summer water temperature (20 degrees C), the efficacy of the chlorine concentrations tested was found to be two to three times lower compared to that found at a winter temperature (5 degrees C) . Resistance was moderately, but significantly, greater in Aer . hydrophila vs Aer . caviae and Aer . sobria, but all Aeromonas spp . were more susceptible than Escherichia coli . Selective pressure with free chlorine did not produce Aeromonas cells with higher levels of chlorine resistance.

Infect Immun, 1998 Aug, 66(8), 3825 - 31
Activation of the complement classical pathway (C1q binding) by mesophilic Aeromonas hydrophila outer membrane protein; Merino S et al.; The mechanism of killing of Aeromonas hydrophila serum-sensitive strains in nonimmune serum by the complement classical pathway has been studied . The bacterial cell surface component that binds C1q more efficiently was identified as a major outer membrane protein of 39 kDa, presumably the porin II described by D . Jeanteur, N . Gletsu, F . Pattus, and J . T . Buckley (Mol . Microbiol . 6:3355-3363, 1992), of these microorganisms . We have demonstrated that the purified form of porin II binds C1q and activates the classical pathway in an antibody-independent manner, with the subsequent consumption of C4 and reduction of the serum total hemolytic activity . Activation of the classical pathway has been observed in human nonimmune serum and agammaglobulinemic serum (both depleted of factor D) . Binding of C1q to other components of the bacterial outer membrane, in particular to rough lipopolysaccharide, could not be demonstrated . Activation of the classical pathway by this lipopolysaccharide was also much less efficient than activation by the outer membrane protein . The strains possessing O-antigen lipopolysaccharide bind less C1q than the serum-sensitive strains, because the outer membrane protein is less accessible, and are resistant to complement-mediated killing . Finally, a similar or identical outer membrane protein (presumably porin II) that binds C1q was shown to be present in strains from the most common mesophilic Aeromonas O serogroups.

Infect Immun, 1998 Aug, 66(8), 3501 - 9
Role of a cytotoxic enterotoxin in Aeromonas-mediated infections: development of transposon and isogenic mutants; Xu XJ et al.; Transposon and marker exchange mutagenesis were used to evaluate the role of Aeromonas cytotoxic enterotoxin (Act) in the pathogenesis of diarrheal diseases and deep wound infections . The transposon mutants were generated by random insertion of Tn5-751 in the chromosomal DNA of a diarrheal isolate SSU of Aeromonas hydrophila . Some of the transposon mutants had dramatically reduced hemolytic and cytotoxic activities, and such mutants exhibited reduced virulence in mice compared to wild-type Aeromonas when injected intraperitoneally (i.p.) . Southern blot data indicated that transposition in these mutants did not occur within the cytotoxic enterotoxin gene (act) . The transcription of the act gene was affected drastically in the transposon mutants, as revealed by Northern blot analysis . The altered virulence of these transposon mutants was confirmed by developing isogenic mutants of the wild-type Aeromonas by using a suicide vector . In these mutants, the truncated act gene was integrated in place of a functionally active act gene . The culture filtrates from isogenic mutants were devoid of hemolytic, cytotoxic, and enterotoxic activities associated with Act . These filtrates caused no damage to mouse small intestinal epithelium, as determined by electron microscopy, whereas culture filtrates from wild-type Aeromonas caused complete destruction of the microvilli . The 50% lethal dose of these mutants in mice was 1.0 x 10(8) when injected i . p., compared to 3.0 x 10(5) for the wild-type Aeromonas . Reintegration of the native act gene in place of the truncated toxin gene in isogenic mutants resulted in complete restoration of Act's biological activity and virulence in mice . The animals injected with a sublethal dose of wild-type Aeromonas or the revertant, but not the isogenic mutant, had circulating toxin-specific neutralizing antibodies . Taken together, these studies clearly established a role for Act in the pathogenesis of Aeromonas-mediated infections.

Eur J Epidemiol, 1998 Apr, 14(3), 305 - 10
Clonal identification of Aeromonas hydrophila strains using randomly amplified polymorphic DNA analysis; Talon D et al.; The suitability of arbitrary primer polymerase chain reaction (RAPD) as a typing technique was evaluated by comparing it with pulsed-field gel electrophoresis (PFGE) to characterize Aeromonas hydrophila strains isolated from a cluster of hospital-acquired infections . Five isolates from patients and 10 isolates from the water supply were compared to 10 epidemiologically unrelated strains isolated from patients and rivers . Two methods were used to prepare DNA and two primers (AP3 and AP5) were selected . The discriminatory power was better with the extractive DNA preparation than the boiling method . The discrimination of closely related from less related strains by PCR using AP3 was consistent with that by PFGE: water supply of Cholet hospital contaminated with Aeromonas species was not the source of the cluster of hospital infections and only two patients were infected with clonally-related strains . RAPD using primer AP3 was simpler, cheaper, and quicker to perform than pulsed-field gel electrophoresis and is well suited for the epidemiological study of A . hydrophila isolates.

Dis Aquat Organ, 1998 May 14, 33(1), 73 - 5
Generation and preliminary characterization of monoclonal antibodies directed to glycerophospholipid:cholesterol acyltransferase (GCAT) native epitopes of Aeromonas salmonicida; Lachmann I et al.; Four monoclonal antibodies (MAbs) directed to native glycerophospholipid:cholesterol acyltransferase (GCAT) epitopes of Aeromonas salmonicida were isolated using an esterase capture assay . The molecular mass of this MAb-defined antigen was estimated to be 26 kDa in SDS-PAGE . Three different epitope specificities of these MAbs were demonstrated . It was shown that all 4 MAbs recognize GCAT in culture filtrates of the strain MT004 excluding the simultaneous trapping of other components . None of the MAbs react with the denatured GCAT in Western blots.

Appl Environ Microbiol, 1998 Jul, 64(7), 2473 - 8
Molecular cloning, nucleotide sequence, and expression in Escherichia coli of a hemolytic toxin (aerolysin) gene from Aeromonas trota; Khan AA et al.; Aeromonas trota AK2, which was derived from ATCC 49659 and produces the extracellular pore-forming hemolytic toxin aerolysin, was mutagenized with the transposon mini-Tn5Km1 to generate a hemolysin-deficient mutant, designated strain AK253 . Southern blotting data indicated that an 8.7-kb NotI fragment of the genomic DNA of strain AK253 contained the kanamycin resistance gene of mini-Tn5Km1 . The 8.7-kb NotI DNA fragment was cloned into the vector pGEM5Zf(-) by selecting for kanamycin resistance, and the resultant clone, pAK71, showed aerolysin activity in Escherichia coli JM109 . The nucleotide sequence of the aerA gene, located on the 1.8-kb ApaI-EcoRI fragment, was determined to consist of 1,479 bp and to have an ATG initiation codon and a TAA termination codon . An in vitro coupled transcription-translation analysis of the 1.8-kb region suggested that the aerA gene codes for a 54-kDa protein, in agreement with nucleotide sequence data . The deduced amino acid sequence of the aerA gene product of A . trota exhibited 99% homology with the amino acid sequence of the aerA product of Aeromonas sobria AB3 and 57% homology with the amino acid sequences of the products of the aerA genes of Aeromonas salmonicida 17-2 and A . sobria 33.

Sci Total Environ, 1998 Jun 18, 214, 153 - 64
Effects of mercuric chloride and sodium selenite on some immune responses of blue gourami, Trichogaster trichopterus (Pallus); Low KW et al.; The immunotoxicological effects of mercuric chloride and sodium selenite on blue gourami were studied . Some immune responses ranging from non-specific to specific were investigated . These include tissue lysozyme activity, kidney lymphocyte proliferation and plasma agglutinating antibody titre against bacteria . After 2 weeks of chronic exposure, 0.09 mg/l of Hg2+ alone induced a significant increase of kidney lysozyme activity of 4196.3 +/- 1171.0 U/g, but it decreased to 1577.4 +/- 902.4 U/g when exposed simultaneously to equiconcentration of selenium . Plasma lysozyme activity was also increased by co-administration of Hg2+ and SeO3(2-) . The level of plasma agglutinating antibody against Aeromonas hydrophila L37 was lowered in the chemical-treated fish . This indicates that the fish immunity was impaired by action of mercury and selenium . However, the in vitro lymphocyte proliferation test shows that mercury concentration lower than 0.045 mg/l Hg2+ enhanced the mitotic rate of kidney lymphocytes by approximately 30% . A high concentration of mercury caused irreversible damaging effects on con A-induced lymphoblastogenesis . In contrast, the inhibitory effect of low concentrations of mercury could be removed by washing . On the other hand, selenium showed a suppressive effect on the lymphocyte proliferation even at 0.5 mg/l.

Cell Mol Life Sci, 1998 May, 54(5), 467 - 75
Antimicrobial activity in the skin of the channel catfish Ictalurus punctatus: characterization of broad-spectrum histone-like antimicrobial proteins; Robinette D et al.; Three antibacterial proteins were isolated from acid extracts of channel catfish (Ictalurus punctatus) skin by cation exchange chromatography and reverse-phase high-pressure liquid chromatography . The molecular masses of the proteins were 15.5, 15.5 and 30 kD as determined by SDS-polyacrylamide gel electrophoresis . Mass spectrometry, amino acid composition and amino acid sequence data suggest that the most abundant protein is closely related to histone H2B . The H2B-like protein was inhibitory to Aeromonas hydrophila and Saprolegnia spp., which are important bacterial and fungal pathogens of fish . These findings suggest that histones may be important defensive molecules in fish.

Curr Microbiol, 1998 Jul, 37(1), 70 - 3
Purification and characterization of an arylamine N-acetyltransferase from the bacteria Aeromonas hydrophilia; Chung JG; N-acetyltransferase from Aeromonas hydrophilia was purified by ultrafiltration, DEAE-Sephacel, gel filtration chromatography on Sephadex G-100, and DEAE-5pw on high performance liquid chromatography, as judged by sodium dodecyl sulfate-polyacrylamine gel electrophoresis (SDS-PAGE) on a 12.% (wt/vol) slab gel . The enzyme had a molecular mass 44.9 kDa . The purified enzyme was thermostable at 37 degrees C for 1 h with a half-life 28 min at 37 degrees C, and displayed optimum activity at 37 degrees C and pH 7.0 . The Km and Vmax values for 2-aminofluorene were determined to be 0 . 896 mM and 2.456 nmol/min/mg protein, respectively . Among a series of divalent cations and salts, Zn2+, Ca2+, and Fe2+ were demonstrated to be the most potent inhibitors.

Ann Trop Med Parasitol, 1998 Mar, 92(2), 213 - 7
Aeromonas hydrophila soft-tissue infection as a complication of snake bite: report of three cases; Jorge MT et al.; Aeromonas hydrophila soft-tissue infection has been associated with fish and reptile bites . There have bee three recent cases from Brazil of abscesses complicating snake bites in which A . hydrophila was isolated from the purulent exudates . One of the snakes responsible for the bites was a specimen of Bothrops moojeni, and the others were most probably also lance-headed vipers . These snakes have a local necrotizing, myotoxic, oedema-inducing venom that must have favoured the multiplication in the injured tissue of A . hydrophila strains, which were probably present in the mouth, fangs or venom of the snakes . The use of a tourniquet by two of the patients probably worsened the local envenoming, and contributed to the occurrence of soft-tissue infection . The patients had a good outcome after the abscesses were incised and drained, and after being treated with chloramphenicol . Chloramphenicol appears to be a good alternative for the empirical treatment of soft-tissue infection complicating snake bite in Brazil, because: it is active against the majority of the anaerobic and aerobic bacteria found in these abscesses, including A . hydrophila; it can be administered by the oral route; and its is inexpensive . Suitable alternatives are cotrimoxazole or fluoroquinolones, to which aeromonads are usually susceptible in vitro, associated with antibiotics, such as clindamycin and metronidazole, with an anti-anaerobic spectrum.

Vet Immunol Immunopathol, 1998 Feb 27, 61(2-4), 369 - 78
Immunostimulatory effects of dimerized lysozyme (KLP-602) on the nonspecific defense mechanisms and protection against furunculosis in salmonids; Siwicki AK et al.; Utilization of natural immunostimulants in fish culture offers a wide range of attractive methods for inducing and building protection against diseases . Lysozyme is an enzyme with bacteriolytic properties and is ubiquitous in its distribution among living organisms . This enzyme has antiviral, antibacterial and anti-inflammatory properties . In nature, lysozyme is found as a monomer . Lysozyme dimer is significantly less toxic than its monomer, and its high biological activity has been ascertained in cases of both viral and bacterial infections . In our study, we examined the influence of dimerized lysozyme (KLP-602) on the nonspecific cellular and humoral defense mechanisms and protection against furunculosis in rainbow trout (Oncorhynchus mykiss) . We have analyzed the immunomodulatory effects of KLP-602 after experimental infection by Aeromonas salmonicida . Application of dimerized lysozyme (KLP-602) by injection stimulated the cellular and humoral defense mechanisms and provided protection against furunculosis . By contrast, mortality rate was reduced to 45% (one injection) and 25% (three injections) using 10 or 100 microg/kg KLP-602 . Mortality in the untreated control group was 85%.

Comp Immunol Microbiol Infect Dis, 1998 Jan, 21(1), 43 - 9
Aeromonas hydrophila septicaemia in a grey seal (Halichoerus grypus) from the Baltic Sea: a case study; Krovacek K et al.; Aeromonas hydrophila septicaemia in a grey seal (Halichoerus grypus) from the Swedish part of the Baltic Sea is reported . The pathogen was isolated from both lung and spleen specimens . All of the A . hydrophila isolates produced haemolysin and Vero active cytotoxin . The aerolysin gene was found in all tested isolates as evidenced by the polymerase chain reaction (PCR) technique . Also, all isolates tested showed identical patterns of biochemical and antibiotic resistance . As Aeromonas spp . commonly occur in aquatic environments, we suggest that organisms from this genus may also play an important role as opportunistic pathogens in morbillivirus infected seals.

Can J Microbiol, 1998 Feb, 44(2), 103 - 8
Phenotypic identification of Aeromonas genomospecies from clinical and environmental sources; Borrell N et al.; A collection of 983 Aeromonas isolates from environmental and clinical sources have been identified to the genomospecies level . A phenotypic method identified 93% of the strains . The use of citrate and the production of acid from sorbitol enabled the members of the Aeromonas hydrophila complex to be separated . The most common genomospecies from intestinal sources were Aeromonas veronii biotype sobria and Aeromonas caviae . The former, together with A . hydrophila, was the most frequently isolated species of extraintestinal origin . Most pathogenic species were very prevalent in environmental samples, with A . veronii biotype sobria being the most common in lakes and reservoirs (41.5%) and in treated drinking water (25.0%), and A . caviae was the most common in sea water (26.0%) and milk products (35.5%) . Aeromonas hydrophila (18.1%) was the second most prevalent species isolated in untreated drinking water . Since Aeromonas infections are generally regarded as a water- and food-borne diseases, the high environmental prevalence of these pathogenic genomospecies should be regarded as an important threat to public health.

Infect Immun, 1998 May, 66(5), 1990 - 8
Defined deletion mutants demonstrate that the major secreted toxins are not essential for the virulence of Aeromonas salmonicida; Vipond R et al.; The importance of the two major extracellular enzymes of Aeromonas salmonicida, glycerophospholipid: cholesterol acyltransferase (GCAT) and a serine protease (AspA), to the pathology and mortality of salmonid fish with furunculosis had been indicated in toxicity studies . In this study, the genes encoding GCAT (satA) and AspA (aspA) have been cloned and mutagenized by marker replacement of internal deletions, and the constructs have been used for the creation of isogenic satA and aspA mutants of A . salmonicida . A pSUP202 derivative (pSUP202sac) carrying the sacRB genes was constructed to facilitate the selection of mutants . The requirement of serine protease for processing of pro-GCAT was demonstrated . Processing involved the removal of a short internal fragment . Surprisingly, pathogenicity trials revealed no major decrease in virulence of the A . salmonicida delta satA::kan or A . salmonicida delta aspA::kan mutants compared to the wild-type parent strains when Atlantic salmon (Salmo salar L.) were challenged by intraperitoneal injection . Moreover, using a cohabitation model, which more closely mimics the natural disease, there was also no significant decrease in the relative cumulative mortality following infection with either of the deletion mutants compared to the parent strain . Thus, although these two toxins may confer some competitive advantage to A . salmonicida, neither toxin is essential for the very high virulence of A . salmonicida in Atlantic salmon . This first report of defined deletion mutations within any proposed extracellular virulence factor of A . salmonicida raises crucial questions about the pathogenesis of this important fish pathogen.

Infect Immun, 1998 May, 66(5), 1813 - 21
Molecular characterization of the Aeromonas hydrophila aroA gene and potential use of an auxotrophic aroA mutant as a live attenuated vaccine; Hernanz Moral C et al.; The aroA gene of Aeromonas hydrophila SO2/2, encoding 5-enolpyruvylshikimate 3-phosphate synthase, was cloned by complementation of the aroA mutation in Escherichia coli K-12 strain AB2829, and the nucleotide sequence was determined . The nucleotide sequence of the A . hydrophila aroA gene encoded a protein of 440 amino acids which showed a high degree of homology to other bacterial AroA proteins . To obtain an effective attenuated live vaccine against A . hydrophila infections in fish, the aroA gene was inactivated by the insertion of a DNA fragment containing a kanamycin resistance determinant and reintroduced by allelic exchange into the chromosome of A . hydrophila AG2 by means of the suicide vector pSUP202 . The A . hydrophila mutant AG2 aroA::Ka(r) was highly attenuated when inoculated intraperitoneally into a rainbow trout, with a 50% lethal dose of >2 x 10(8) CFU . The mutants were not recoverable from the internal organs after 48 h postinoculation . Immunohistochemical studies demonstrated that immunopositive materials, but not whole cells, reacting with a polyclonal antiserum against A . hydrophila were present in the kidney and spleen 9 days postinjection . Vaccination of rainbow trout with the AroA mutant as a live vaccine conferred significant protection against the wild-type strain of A . hydrophila.

FEMS Immunol Med Microbiol, 1998 Mar, 20(3), 219 - 29
Analysis of the interaction of Aeromonas caviae, A . hydrophila and A . sobria with mucins; Ascencio F et al.; Aeromonas species are known to be involved in human gastrointestinal diseases . These organisms colonize the gastrointestinal tract . Aeromonas hydrophila, A . caviae, and A . sobria have been demonstrated microscopically to adhere to animal cell lines that express mucous receptors, but quantitative studies of adherence to mucosal components such as mucin have not been published to date . Purified bovine submaxillary gland, hog gastric mucin, and fish skin mucin were used as a model to study mucin-binding activity among A . caviae, A . hydrophila, and A . sobria strains . Our findings revealed that binding of radiolabeled and enzyme-conjugated mucins to Aeromonas cells varied depending on the labeling procedure . The highest binding was observed when the three mucin preparations were labeled with horseradish peroxidase . Binding of the various horseradish peroxidase-labeled mucins by A . caviae, A . hydrophila, and A . sobria cells is a common property among Aeromonas species isolated from human infections, diseased fish, and from environmental sources . The proportion of Aeromonas strains which bind the various horseradish peroxidase-labeled mucins was significantly higher for A . hydrophila than for A . caviae and A . sobria . Bacterial cell-surface extracts containing active mucin-binding components recognized the horseradish peroxidase-labeled mucins . The molecular masses of the mucin-binding proteins were estimated by SDS-PAGE and Western blot as follows: A . caviae strain A4812 (95 and 44 kDa); A . hydrophila strain 48748 (97, 45, 33 and 22 kDa); and A . sobria strain 48739 (95 and 43 kDa) . Mucin interaction with Aeromonas cells was also studied in terms of growth in mucin-rich media . The culture conditions greatly influence the expression of A . hydrophila mucin-binding activity.

Zentralbl Hyg Umweltmed, 1998 Feb, 200(5-6), 571 - 4
Detection of psychotrophic aeromonads in drinking water; Schubert RH; In the context of evaluating their pathogenic relevance, culture on solid media is the only approach presently suitable for culture of psychotrophic aeromonads from drinking water . In this respect, a check must be effected to ensure that the culture medium cannot engender selective culture losses for individual species . For this reason, media to which e.g . ampicillin has been added are unsuitable.

Antimicrob Agents Chemother, 1998 Feb, 42(2), 436 - 9
Nucleotide and amino acid sequences of the metallo-beta-lactamase, ImiS, from Aeromonas veronii bv . sobria; Walsh TR et al.; The Aeromonas veronii bv . sobria metallo-beta-lactamase gene, imiS, was cloned . The imiS open reading frame extends for 762 bp and encodes a protein of 254 amino acids with a secreted modified protein of 227 amino acids and a predicted pI of 8.1 . To confirm the predicted sequence, purified ImiS was digested and the resulting peptides were identified, yielding an identical sequence for ImiS, with 98% identity to CphA . Both possessed the putative active-site sequence Asn-Tyr-His-Thr-Asp at positions 88 to 92, which is unique to the Aeromonas metallo-beta-lactamases.

Arch Microbiol, 1998 Mar, 169(3), 239 - 48
Reduction of diverse electron acceptors by aeromonas hydrophila
Knight V V, Blakemore R.
Aeromonas hydrophila ATCC 7966 grew anaerobically on glycerol with nitrate, fumarate, Fe(III), Co(III), or Se(VI) as the sole terminal electron acceptor, but did not ferment glycerol . Final cell yields were directly proportional to the amount of terminal electron acceptor provided . Twenty-four estuarine mesophilic aeromonads were isolated; all reduced nitrate, Fe(III), or Co(III), and five strains reduced Se(VI) . Dissimilatory Fe(III) reduction by A . hydrophila may involve cytochromes . Difference spectra obtained with whole cells showed absorption maxima at wavelengths characteristic of c-type cytochromes (419, 522, and 553 nm) . Hydrogen-reduced cytochromes within intact cells were oxidized by the addition of Fe(III) or nitrate . Studies with respiratory inhibitors yielded results consistent with a respiratory chain involving succinate (flavin-containing) dehydrogenase, quinones and cytochromes, and a single Fe(III) reductase . Neither anaerobic respiration nor dissimilatory metal reduction by members of the genus Aeromonas have been reported previously.

FEMS Microbiol Lett, 1997 Nov 15, 156(2), 199 - 204
RFLP-PCR analysis of the aroA gene as a taxonomic tool for the genus Aeromonas; Cascon Soriano A et al.; The aroA gene has been identified as a target in screening for the presence of most Aeromonas species so far described by PCR . Synthetic oligonucleotide primers of 24 and 25 nucleotides were used by PCR assay to amplify a sequence of the aroA gene, which encodes 3-phosphoshikimate-1-carboxyvinyltransferase, a key enzyme of aromatic amino acids and folate biosynthetic pathway . A 1236-bp DNA fragment, representing most of the aroA gene, according to the nucleotide sequence of A . salmonicida, was amplified from all Aeromonas species tested, which represented most of the 14 hybridization groups . HaeII digestion of the 1236-bp fragment generated a restriction fragment length polymorphisms which could be used as a powerful tool for identification of aeromonads to the genus level.

J Pak Med Assoc, 1997 Dec, 47(12), 305 - 8
Isolation and identification of Aeromonas species from human stools; Ahmed A et al.; One thousand and three diarrhoeal stool samples were processed in our laboratory during the period 1996/1997 for the presence of enteric pathogens especially Aeromonas spp., which has emerged as a new agent causing diarrhoea . Ampicillin sheep blood agar was found to be the best medium for the isolation of Aeromonas spp . from stool specimens . Enteric pathogens were found in 200 (20%) stools, of which Aeromonas spp . was the second commonest pathogen isolated amounting to 21% of isolates . This study clearly indicates that Aeromonas spp . must be looked for in every diarrhoeal stool samples, specially in children below 10 years of age . Isolation and identification is cost effective and easy, if the given protocol is observed.

Haematologica, 1997 Nov-Dec, 82(6), 692 - 4
Acute rhabdomyolysis and myonecrosis complicating aeromonas bacteremia in neutropenic patients with hematologic malignancies: report of two cases; Martino R et al.; Infections by Aeromonas spp . are a rare cause of systemic infection in normal and immunocompromised hosts . We report the cases of two patients with acute non-lymphoblastic leukemia who developed septic shock by Aeromonas species with unusual soft-tissue complications . One patient who was undergoing consolidation chemotherapy developed septic shock by Aeromonas hydrophila with rhabdomyolysis and subsequent soft-tissue destruction consistent with myonecrosis . She recovered with combination antibiotic therapy and supportive care . The second patient developed neutropenia due to ganciclovir treatment for post-allogeneic transplant cytomegalovirus antigenemia . He developed a rapidly progressive septic shock due to Aeromonas sobria with rhabdomyolysis, multi-organ failure and bilateral lower limb myonecrosis, and died within 48 hours . The portal of entry was not identified in either case . These cases confirm the potentially aggressive nature of these bacteria in neutropenic cancer patients with an unusual tendency to produce muscular and soft-tissue destruction.

Int J Food Microbiol, 1997 Sep 16, 38(2-3), 111 - 6
Effects of temperature, medium composition, pH, salt and dissolved oxygen on haemolysin and cytotoxin production by Aeromonas hydrophila isolated from oyster; Tsai GJ et al.; The effects of temperature, medium composition, pH, salt content and dissolved oxygen (DO) on the production of haemolysin and cytotoxin by one strain of Aeromonas hydrophila isolated from oyster were investigated . Four media were tested: brain heart infusion broth (BHIB), casamino acid-yeast extract broth (CAYEB), nutrient broth (NB), and trypticase soy broth (TSB) . BHIB was the best for toxin production even though the growth rates for Aeromonas hydrophila in all of these media were quite similar . Aeromonas hydrophila could produce haemolysin and cytotoxin at 37, 28 and 5 degrees C; however, the toxins were produced faster and were more stable at 28 degrees C than at 37 degrees C . Although Aeromonas hydrophila itself is tolerant to 5% (w/v) salt in BHIB and a pH range of pH 5.5 to 10.0, the production of haemolysin and cytotoxin was apparently decreased in the presence of 1-5% (w/v) NaCl or when the pH of the medium was greater or less than 7.2 . The DO values in the culture medium during the stationary growth phase also seemed to affect toxin production; greater quantities of toxins were produced when the DO values were higher.

New Microbiol, 1998 Jan, 21(1), 23 - 30
Virulence factors in Aeromonas spp and their association with gastrointestinal disease; Schiavano GF et al.; Culture filtrates of eight Aeromonas strains isolated from the feces of 487 subjects (292 diarrhoeic patients and 195 asymptomatic subjects) were tested for toxin production in CHO and McCoy cells, and adhesion and invasive ability in Caco-2 cells . Among these isolates, three Aeromonas sobria and one Aeromonas caviae strains possessed virulence-associated properties . Toxin production was the most common of the three virulence properties . Two A . caviae were associated, in the absence of other diarrhoeagenic agents, with gastroenteritis; however, a virulence marker (cytotoxin) was recognized only in one strain . Two strains of A . sobria isolated from subjects with gastroenteritis were shown to be associated with one (cytotoxicity) or two (adhesion and invasive abilities) virulence factors, respectively . However, a third strain of A . sobria, although cytotoxic and invasive, was isolated from an asymptomatic subject . The results show that Aeromonas spp may act as human enteric pathogens, but also indicate that the significance of several putative virulence factors, such as production of cytotoxin and the capacity to adhere to and invade mammalian cells, remains controversial in explaining the enteropathogenesis of Aeromonads and therefore needs further studies.

J Cell Biol, 1998 Feb 9, 140(3), 525 - 40
A pore-forming toxin interacts with a GPI-anchored protein and causes vacuolation of the endoplasmic reticulum; Abrami L et al.; In this paper, we have investigated the effects of the pore-forming toxin aerolysin, produced by Aeromonas hydrophila, on mammalian cells . Our data indicate that the protoxin binds to an 80-kD glycosyl-phosphatidylinositol (GPI)-anchored protein on BHK cells, and that the bound toxin is associated with specialized plasma membrane domains, described as detergent-insoluble microdomains, or cholesterol-glycolipid "rafts." We show that the protoxin is then processed to its mature form by host cell proteases . We propose that the preferential association of the toxin with rafts, through binding to GPI-anchored proteins, is likely to increase the local toxin concentration and thereby promote oligomerization, a step that it is a prerequisite for channel formation . We show that channel formation does not lead to disruption of the plasma membrane but to the selective permeabilization to small ions such as potassium, which causes plasma membrane depolarization . Next we studied the consequences of channel formation on the organization and dynamics of intracellular membranes . Strikingly, we found that the toxin causes dramatic vacuolation of the ER, but does not affect other intracellular compartments . Concomitantly we find that the COPI coat is released from biosynthetic membranes and that biosynthetic transport of newly synthesized transmembrane G protein of vesicular stomatitis virus is inhibited . Our data indicate that binding of proaerolysin to GPI-anchored proteins and processing of the toxin lead to oligomerization and channel formation in the plasma membrane, which in turn causes selective disorganization of early biosynthetic membrane dynamics.

Microbiology, 1998 Feb, 144 ( Pt 2), 299 - 307
Internalization of Aeromonas hydrophila by fish epithelial cells can be inhibited with a tyrosine kinase inhibitor; Tan E et al.; Aeromonas hydrophila is a Gram-negative bacterium that is pathogenic in fish, causing motile aeromonad septicaemia . It can enter (invade) fish cells, and survive as an intracellular parasite . The host-pathogen interaction and signal transduction pathway were studied by screening signal transduction inhibitors using carp epithelial cells and a virulent strain of the bacterium, PPD134/91 . Genistein, a tyrosine kinase inhibitor, postponed internalization of A . hydrophila into host cells, suggesting that tyrosine phosphorylation plays a role in internalization . In contrast, staurosporine, a protein kinase C inhibitor, and sodium orthovanadate, a protein tyrosine phosphatase inhibitor, accelerated internalization of PPD134/91 . Other virulent strains of A . hydrophila were also examined and it is likely that all strains, irrespective of serogroup, use the same signalling pathway to facilitate bacterial uptake.

Appl Environ Microbiol, 1997 Oct, 63(10), 3770 - 5
Further characterization of Renibacterium salmoninarum extracellular products; Barton TA et al.; Renibacterium salmoninarum, the agent of bacterial kidney disease in salmonids, releases high concentrations of extracellular protein in tissues of infected fish . The extracellular protein consists almost entirely of a 57-kDa protein and derivatives of degradation and aggregation of the same molecule . The 57-kDa protein and its derivatives were fractionated into defined ranges of molecular mass . Separated fractions continued to produce degradation and aggregation products . One-dimensional electrophoretic separation of extracellular protein revealed a number of proteolytically active bands from > 100 to approximately 18 kDa associated with various 57-kDa protein derivatives in the different molecular mass fractions . Two-dimensional separation of extracellular protein showed that continued degradation and aggregation, similar both in location and behavior to some of the 57-kDa protein derivatives, was also displayed by the proteolytically active bands after their separation . Effects of reducing agents and sulfhydryl group proteinase inhibitors indicated a common mechanism for the proteolytically active polypeptides characteristic of a thiol proteinase . The results suggested that the 57-kDa protein and some of its derivatives undergo autolytic cleavage, releasing a proteolytically active polypeptide(s) of at least 18 kDa . Soluble polysaccharide-like material also was detected in extracellular products and tissue from infected fish . Antiserum to the polysaccharide-like material cross-reacted with O-polysaccharide of the fish pathogen Aeromonas salmonicida, suggesting some structural similarity between these polysaccharides . The polysaccharide and the proteolytic activity associated with the 57-kDa protein derivatives should be investigated with respect to the pathogenesis of R . salmoninarum infections.

Curr Microbiol, 1998 Jan, 36(1), 19 - 23
Experimental pathogenicity of aeromonas spp . for the zebra mussel, dreissena polymorpha
Maki JS, Patel G, Mitchell R.
Experiments were conducted to determine whether species of Aeromonas were pathogenic to the zebra mussel Dreissena polymorpha . A . jandaei, A . veronii, and A . media, identified with Biolog, were originally isolated from dead zebra mussels . When inoculated into living mussels, these bacteria resulted in the mortality of the bivalves . Two additional species, A . salmonicida salmonicida (ATCC 33678) and A . hydrophila (ATCC 7966), were also demonstrated to be pathogenic to the mussels . In addition to the pathogenicity, the data also suggest that the zebra mussels may be an important reservoir for these bacteria in freshwater environments.

Appl Environ Microbiol, 1998 Feb, 64(2), 549 - 54
Gene cloning, nucleotide sequencing, and purification and characterization of the low-specificity L-threonine aldolase from Pseudomonas sp . strain NCIMB 10558; Liu JQ et al.; A low-specificity L-threonine aldolase (L-TA) gene from Pseudomonas sp . strain NCIMB 10558 was cloned and sequenced . The gene contains an open reading frame consisting of 1,041 nucleotides corresponding to 346 amino acid residues . The gene was overexpressed in Escherichia coli cells, and the recombinant enzyme was purified and characterized . The enzyme, requiring pyridoxal 5'-phosphate as a coenzyme, is strictly L specific at the alpha position, whereas it cannot distinguish between threo and erythro forms at the beta position . In addition to threonine, the enzyme also acts on various other L-beta-hydroxy-alpha-amino acids, including L-beta-3,4-dihydroxyphenylserine, L-beta-3,4-methylenedioxyphenylserine, and L-beta-phenylserine . The predicted amino acid sequence displayed less than 20% identity with those of low-specificity L-TA from Saccharomyces cerevisiae, L-allo-threonine aldolase from Aeromonas jandaei, and four relevant hypothetical proteins from other microorganisms . However, lysine 207 of low-specificity L-TA from Pseudomonas sp . strain NCIMB 10558 was found to be completely conserved in these proteins . Site-directed mutagenesis experiments showed that substitution of Lys207 with Ala or Arg resulted in a significant loss of enzyme activity, with the corresponding disappearance of the absorption maximum at 420 nm . Thus, Lys207 of the L-TA probably functions as an essential catalytic residue, forming an internal Schiff base with the pyridoxal 5'-phosphate of the enzyme to catalyze the reversible aldol reaction.

Zh Mikrobiol Epidemiol Immunobiol, 1995 Jul-Aug, (4), 9 - 12
{Bacteria of the genus Aeromonas as the causative agents of saprophytic infection}; Pogorelova NP et al.; The bacteriological study of feces from 458 patients with acute enteric diseases revealed that in 3.2% of cases (in summer in 8.1% of cases) the disease was caused by Aeromonas . In Aeromonas strains isolated from river water in the Volga delta, from fish and from raw meat the same pathogenicity factors occurred as in strains isolated from patients (hemolysin, DNA-ase, protease, lecithinase, amylase, adhesins, capacity of binding Congo red).

J Bacteriol, 1998 Feb, 180(3), 667 - 73
Expression and characterization of (R)-specific enoyl coenzyme A hydratase involved in polyhydroxyalkanoate biosynthesis by Aeromonas caviae; Fukui T et al.; Complementation analysis of a polyhydroxyalkanoate (PHA)-negative mutant of Aeromonas caviae proved that ORF3 in the pha locus (a 402-bp gene located downstream of the PHA synthase gene) participates in PHA biosynthesis on alkanoic acids, and the ORF3 gene is here referred to as phaJ(Ac) . Escherichia coli BL21(DE3) carrying phaJ(Ac) . under the control of the T7 promoter overexpressed enoyl coenzyme A (enoyl-CoA) hydratase, which was purified by one-step anion-exchange chromatography . The N-terminal amino acid sequence of the purified hydratase corresponded to the amino acid sequence deduced from the nucleotide sequence of phaJ(Ac) except for the initial Met residue . The enoyl-CoA hydratase encoded by phaJ(Ac) exhibited (R)-specific hydration activity toward trans-2-enoyl-CoA with four to six carbon atoms . These results have demonstrated that (R)-specific hydration of 2-enoyl-CoA catalyzed by the translated product of phaJ(Ac) is a channeling pathway for supplying (R)-3-hydroxyacyl-CoA monomer units from fatty acid beta-oxidation to poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) biosynthesis in A . caviae.

Kansenshogaku Zasshi, 1997 Nov, 71(11), 1172 - 4
{Detection of the thermostable lipase gene (lipAH) in clinical isolates of Aeromonas hydrophila belonging to the major O serogroups O11, O16 and O34}; Shibata M et al.; On the basis of DNA hybridization data and phenotypes, most pathogenic strains of Aeromonas hydrophila are grouped into hybridization group 1 (HG1) . These pathogenic strains secret the theromostable lipase, and it's gene (lipAH) has been cloned and sequenced . The present study was performed to identify the pathogenic strains of A . hydrophila by the polymerase chain reaction (PCR) technique to detect the lipAH . Synthetic oligonucleotide primers (lipAH-ns-1 and -na-1) were used in the PCR . The PCR identified 80% of lipAH-positive strains, consisting of seven of the 11 O11 strains (64%), 13 of the 15 O16 strains (87%) and 25 of the 30 O34 strains (83%) in clinical isolates of A . hydrophila used in this study.

Folia Microbiol (Praha), 1997, 42(4), 385 - 9
Virulence factors-pathogenicity relationships for Aeromonas species from clinical and food isolates; Pin C et al.; The presence of virulence factors in 96 Aeromonas strains isolated from food and clinical samples was studied . Neither cytotoxic activity and hydrophobicity, not the presence of pili or an extra surface layer made it possible to establish differences between food and clinical strains . Statistical studies showed that cytotoxin production was associated with a positive Voges-Proskauer reaction, inability to ferment arabinose and a positive lysine decarboxylation . Therefore, when comparing cytotoxic clinical and food strains with lysine decarboxylation phenotype, there was a significant difference (p < 0.05) between the two groups . The association of a cytotoxin production and lysine decarboxylation character should thus be considered as a possible virulence marker.

J Basic Microbiol, 1997, 37(6), 403 - 5
Effect of amino acids on the production and activities of cephalosporin C acylase and penicillin V acylase from Aeromonas species ACY 95; Dehpande BS et al.; Amino acids altered the production and activities of cephalosporin C acylase and penicillin V acylase from Aeromonas species ACY 95 to a varying degree . DL-Tryptophan enhanced the cephalosporin C acylase formation by 222% while suppressed the penicillin V acylase formation by 68%.

Arch Latinoam Nutr, 1997 Mar, 47(1), 44 - 6
{Prevalence of Aeromonas spp . in surface water}; Hernandez P et al.; Some Aeromonas strains are well recognized enteropathogens according to microbiological, clinical, immunological and epidemiological evidence . The main source of infection seems to be untreated water, these microorganisms can be found in virtually all aquatic environments . Additionally, some Aeromonas, which include enterotoxigenic strains, are capable of rapid growth at 5 degrees C and even of producing toxins . Vegetable products irrigated with contaminated water may reach critical Aeromonas levels after being kept under refrigeration, this could represent a public health risk when they are consumed as uncooked salads . This study was pursued to evaluate such risk . Surface water samples were streaked on starch ampicillin and inositol-brilliant green-bile salts agar dishes . In addition, 100 ml of each sample were filtered through a 0.45 micron Millipore membrane filter . The filters were incubated on alkaline peptone water as enrichment media during 24 h at 35 degrees C . Enrichment broth was then streaked on the selective agars above mentioned . Isolates from both tests were identified using the API 20 E System . The prevalence of Aeromonas strains in the analyzed samples was 17.8% . A higher isolation rate was observed after the enrichment technique . Starch ampicillin agar showed a higher recuperation rate . A Veronii biotype sobria (formerly A . sobria) was isolated with higher frequency . Since this species has been associated with the greatest virulence, the use of contaminated water to irrigate vegetable products that are to be kept under refrigeration and consumed without ulterior cooking may represent a risk to the public health.

Lett Appl Microbiol, 1997 Nov, 25(5), 363 - 6
Reappraisal of the effect of temperature on the growth kinetics of Aeromonas salmonicida; Guerin-Faublee V et al.; The effect of temperature (1-34 degrees C) on the maximum specific growth rate of Aeromonas salmonicida could not be described by the classical growth models; for some strains, two optimal temperatures at 23 degrees C and 30 degrees C were observed, as well as an unexpected increase in the pseudolag time above 27 degrees C . This could be explained by the presence of two subsets, notably S-layer+ and S-layer- sub-populations . The A- cells had higher growth parameters (Topt and mu opt) than the A+ cells and were selected by subcultures above 30 degrees C . Yet the relative proportion of A+ cells did not explain all the variation of mu max versus temperature, and the growth kinetics of an Aer . salmonicida isolate remained unpredictable.

J Appl Microbiol, 1997 Nov, 83(5), 542 - 51
Pathogenicity of atypical Aeromonas salmonicida in Atlantic salmon compared with protease production; Gunnlaugsdottir B et al.; The pathogenicity of extracellular products (ECPs) from 24 atypical Aeromonas salmonicida strains was studied with respect to: lethality in Atlantic salmon, pathogenic effect in muscle, haemolytic activity, cytotoxicity in two fish cell lines and proteolytic activities . Furthermore, the relationship between lethality of ECPs and mortality caused by bacterial challenge was examined . Correlation was demonstrated between the pathogenic properties and proteolytic activities of the ECPs . Cytolytic (GCAT) activity comparable with that of the typical reference strain used (NCMB 1102) was not detected in ECPs of any of the atypical strain tested . An extracellular metallo-caseinase, AsaP1, was linked with lethal toxicity and a strong pathogenic effect . Furuncular-like lesions were produced by ECPs containing AsaP1 activity . One strain produced a lethal toxin which was neither caseinolytic nor with GCAT comparable activity . The examined atypical strains form at least three distinct groups based on different virulence mechanisms and extracellular proteases.

Arch Biochem Biophys, 1997 Nov 15, 347(2), 201 - 7
Determination of the amino acid sequence of the plant cytolysin enterolobin; Fontes W et al.; The cytolytic seed protein enterolobin from seeds of Enterolobium contortisiliquum was purified by using FPLC on a Mono Q column giving a single peak in capillary electrophoresis . The complete amino acid sequence of the plant cytolysin was determined by an automated method, yielding a molecular mass of 54,806 Da . Databank searches and sequence alignment demonstrated a high degree of sequence identity and similarity between enterolobin and bacterial aerolysins from Aeromonas hydrophila and A . sobria . Several key residues involved in oligomerization of A . hydrophila aerolysin are conserved in enterolobin . Circular dichroism measurements and structural predictions revealed that enterolobin is very rich in beta sheet, like aerolysin . Light-scattering studies revealed that enterolobin oligomerizes as a hexamer at pH levels below 7.0 . NaCl concentrations above 50 mM caused dimerization of enterolobin . Dithiothreitol did not cause oligomerization .

Aust N Z J Ophthalmol, 1997 Nov, 25(4), 299 - 300
Aeromonas sobria endophthalmitis; Lee LR et al.; BACKGROUND: Aeromonas sobria causes a rare Gram-negative bacterial water-borne infection . It has been found in waters of North Queensland and South-east Asia . Of all Aeromonas species, A . sobria is the most virulent and invasive and has been reported to cause soft tissue infection and corneal ulcer . METHODS: A 14-year-old Caucasian male from North Queensland presented following a penetrating eye injury in which a water bird (cormorant species) had pecked his eye while he was fishing . A fulminant endophthalmitis developed despite treatment with intravenous, intravitreal and topical antibiotics and initial wound repair . Enucleation was performed . RESULTS: Aeromonas sobria was isolated from the vitreous aspirate . CONCLUSION: Aeromonas sobria infection should be suspected in water-contaminated penetrating eye injuries . The prognosis in this case was poor.

J Med Microbiol, 1997 Oct, 46(10), 833 - 8
Influence of iron, growth temperature and plasmids on siderophore production in Aeromonas hydrophila; Naidu AJ et al.; Aeromonas hydrophila strains obtained from diarrhoeal samples of human patients (19 isolates) and freshwater ponds (11 isolates) were analysed for siderophore production . Both clinical and environmental isolates showed significantly increased siderophore production under iron-limiting conditions both at 28 degrees C and at 37 degrees C . Clinical isolates consistently produced higher levels of siderophores than did the environmental isolates . The role of plasmids in moderating siderophore production was studied after curing with acridine orange . Treatment with acridine orange for 24 h removed the larger plasmids but the smaller plasmids (< 5 MDa), more common in the environmental isolates, were resistant to curing . As found in the untreated isolates, the cured clinical isolates produced higher mean levels of siderophores than the cured environmental isolates . Siderophore production in A . hydrophila was significantly influenced by iron-limiting cultural conditions and the source of isolates, but plasmid content and growth temperature at 28 degrees C or 37 degrees C had little effect on production . The basis for the greater production of siderophores in clinical isolates than in environmental isolates needs further study.

Am J Gastroenterol, 1997 Nov, 92(11), 2104 - 6
Aeromonas sobria-associated left-sided segmental colitis; Deutsch SF et al.; Aeromonas species, once thought pathogenic only in immunocompromised hosts, have more recently been found to be associated with many different infections in previously healthy individuals . The most common site of these infections is the gastrointestinal tract . We describe a 67-yr-old woman who presented with abdominal pain and bloody diarrhea and was diagnosed with left-sided, segmental colitis due to Aeromonas sobria, which was proven by stool culture . Extensive work-up for ischemic colitis was unremarkable, and after treatment with antibiotics, the patient's symptoms resolved, and follow-up colonoscopy failed to reveal any evidence of residual colitis or inflammatory bowel disease . Our report supports the view that Aeromonas species need to be considered in the differential diagnosis of colitis, and we believe it to be the first report of left-sided, segmental colitis secondary to Aeromonas sobria infection.

Appl Environ Microbiol, 1997 Nov, 63(11), 4534 - 42
Development and application of monoclonal antibodies for in situ detection of indigenous bacterial strains in aquatic ecosystems; Faude UC et al.; Strain-specific monoclonal antibodies (MAbs) were developed for three different bacterial isolates obtained from a freshwater environment (Lake Plusssee) in the spring of 1990 . The three isolates, which were identified by molecular methods, were as follows: Cytophaga johnsonae PX62, Comamonas acidovorans PX54, and Aeromonas hydrophila PU7718 . These strains represented three species that were detected in high abundance during a set of mesocosm experiments in Lake Plusssee by the direct analysis of low-molecular-weight RNAs from bacterioplankton . We developed one MAb each for the bacterial isolates PX54 and PU7718 that did not show any cross-reactivity with other bacterial strains by immunofluorescence microscopy . Each MAb recognized the general lipopolysaccharide fraction of the homologous strain . These MAbs were tested successfully for their ability to be used for the in situ detection and counting of bacteria in lake water by immunofluorescence microscopy . During the spring of 1993, A . hydrophila PU7718 showed a depth distribution in Lake Plusssee with a pronounced maximum abundance at 6 m, whereas Comamonas acidovorans PX54 showed a depth distribution with a maximum abundance at the surface . The application of these MAbs to the freshwater samples enabled us to determine the cell morphologies and microhabitats of these strains within their natural environment . The presence of as many as 8,000 cells of these strains per ml in their original habitats 3 years after their initial isolation demonstrated the persistence of individual strains of heterotrophic bacteria over long time spans in pelagic habitats.

Enzyme Microb Technol, 1997 Nov 15, 21(7), 472 - 8
Expression and characterization of the recombinant gene encoding chitinase from Aeromonas caviae; Lin CS et al.; The gene encoding a chitinase from Aeromonas caviae was cloned by PCR techniques . Its recombinant gene expression was performed using pET20b(+) in Escherichia coli BL21 (DE3) . The recombinant chitinase with the extra 33 and 13 amino acids in its N- and C-termini, respectively, was purified to near homogeneity using His-Tag affinity chromatography . The recombinant chitinase was found to be present in both the culture medium and the cytoplasm . A single protein band on the native polyacrylamide gel was confirmed by both the activity staining and protein staining . The optimum pH and temperature of the recombinant chitinase were determined to be 6.25-6.5 and 42.5 degrees C, respectively . It was stable within the pH range of 5-7 . Significant activity stimulation by Cu2+ and inhibition by Fe3+ and Hg2+ were observed . Detergents such as SDS and Triton X-100 strongly inhibited the enzyme activity . Substrates such as 4-methylumbelliferyl-N,N'-diacetylchitobioside and 4-methylumbelliferyl-N,N',N"-triacetylchitotriose were hydrolyzed by the recombinant chitinase; however, 4-methylumbelliferyl-N-acetylglucosaminide was not cleaved during the activity assay periods . When chitin power was suspended in buffer with the chitinase (pH 6.5 and 42.5 degrees C), N-acetylchitooligosaccharides {(GlcNAc)n, n = 1-4} were detected at 24 h.

Gene, 1997 Oct 15, 199(1-2), 225 - 9
Cloning and sequence analysis of the gene (eprA1) encoding an extracellular protease from Aeromonas hydrophila; Chang TM et al.; A gene (eprA1) encoding the extracellular protease of Aeromonas hydrophila AH1 has been cloned and sequenced . Nucleotide sequence analysis of eprA1 predicted a single open reading frame (ORF) of 1038 bp encoding a 346 amino acid (aa) polypeptide, with a potential 21-aa signal peptide . When the eprA1 gene was expressed in minicells, one major band of approx . 37 kDa was identified, while protease activity staining experiments identified a caseinolytic band of approx . 29 kDa determined by SDS-PAGE analysis of the minicells . The deduced C-terminal aa region (Arg-290 to Gly-313) showed sequence homology to partial C-terminal sequences of other zinc metalloproteases including Penicillium citrinum metalloprotease (PlnC), Aspergillus oryzae metalloprotease (NpII), Aspergillus flavus metalloprotease (MepA), and Aspergillus fumigatus metalloprotease (Mep20), particularly with respect to zinc-binding residues.

Lett Appl Microbiol, 1997 Oct, 25(4), 269 - 73
Toxicity of crude extracellular products of Aeromonas hydrophila in tilapia, Tilapia nilotica; Khalil AH et al.; Extracellular products (ECP) secreted from Aeromonas hydrophila with haemolytic and proteolytic activity were studied with respect to temperature and time of incubation as well as the lethal toxicity on tilapia, Tilapia nilotica . The highest production of the haemolysin product was achieved when Aer . hydrophila was grown at 35 degrees C for 30 h . Tilapia erythrocyte was found to be more susceptible than sheep erythrocyte for determining the haemolytic activity . The haemolytic activity against tilapia erythrocyte was completely inactivated after heating the ECP at 60 degrees C for 10 min or 55 degrees C for 15 min . The proteolytic activity was maximized when the bacterium was grown at 30 degrees C for 36 h . Complete inactivation of the protease enzyme was performed after heating the ECP at 80 degrees C for 10 min or 70 degrees C for 15 min . Aeromonas hydrophila was found to produce haemolytic and proteolytic exotoxin lethal to tilapia (LD50 2.1 x 10(4) cell/fish), as well as heat stable unknown virulent factors that were responsible for 20% mortality . The lethality of ECP was decreased by heating and completely inactivated by boiling at 100 degrees C for 10 min.

Microb Pathog, 1997 Oct, 23(4), 241 - 7
Aeromonas spp . possess at least two distinct type IV pilus families; Barnett TC et al.; Type IV pili have been purified from strains of most of the Aeromonas species associated with gastroenteritis (A . veronii biovar sobria, A . hydrophila, A . trota and A . caviae) . They appear to be a related family (molecular mass of pilin 19 to 23 kDa) with a tendency to bundle-formation . Hence, we have designated them 'bundle-forming pili' (Bfp) . A type IV pilus biogenesis gene cluster (tapABCD) recently cloned from a strain of A . hydrophila, however, encoded a 17 kDa pilin which differed significantly in its N-terminal amino acid sequence from the Bfp pilins . This paper describes the cloning of part (tapA and approximately 20% of tapB) of a homologous pilin gene cluster from a Bfp-positive strain of A . veronii biovar sobria, and presents evidence that the entire pilin gene cluster (tapABCD) is present in this strain . The predicted N-terminal amino acid sequence of the pilin encoded by the A . veronii biovar sobria tapA differed markedly from the corresponding sequence of its Bfp pilin, and those of the Bfp purified from other Aeromonas strains and species . Probing with tapA and tapD genes showed that these Bfp-positive Aeromonas strains also possessed the Tap gene cluster . TapA proteins of A . veronii biovar sobria and A . hydrophila shared 53% identity and 63% homology . We conclude that Aeromonas species are potentially able to express at least two distinct families of type IV pili (Bfp and Tap) .

Shock, 1997 Oct, 8(4), 276 - 83
Differences in eicosanoid and cytokine production between injury/hemorrhage and bacteremic shock in the pig; Foex BA et al.; Plasma concentrations of the eicosanoids leukotriene (LT)B4, LTC4D4E4, thromboxane (TX)A2 and prostaglandin (PG)I2, and tumor necrosis factor (TNF) were measured during acute bacteremic shock and injury/hemorrhage in two porcine models . As TXA2 and PGI2 are rapidly metabolized, we measured their stable metabolites TXB2 and 6-keto-PGF1 alpha . Bacteremic shock was induced by a graded infusion of Aeromonas hydrophila over 4 h . Injury/hemorrhage was produced by a 30 min, 30% total blood volume hemorrhage followed by a 30 min shock period and then reinfusion of shed blood . Nociceptive afferent nerve stimulation was applied to the brachial plexi to mimic the cardiovascular responses to tissue injury . There was no increase in eicosanoid or TNF levels in the injury/hemorrhage model . In sepsis there was an early peak in TNF (at 60 min) followed by peaks in LTB4 and LTC4D4E4 at 180 min . Both TXB2 and 6-keto-PGF1 alpha showed large increases at the end of the study but there was no evidence that they had reached a peak . These results suggest that the very early inflammatory response in bacteremic shock and injury/hemorrhagic shock may be quite different . This may have implications for any therapies aimed at reducing the incidence of multiple organ failure after either of these physiological insults.

Int J Syst Bacteriol, 1997 Oct, 47(4), 1157 - 64
Inclusion of Aeromonas DNA hybridization group 11 in Aeromonas encheleia and extended descriptions of the species Aeromonas eucrenophila and A . encheleia; Huys G et al.; The recently reported chemotaxonomic and genotypic description of two well-separated subgroups (I and II) in Aeromonas eucrenophila and their affiliation to Aeromonas encheleia and the unnamed Aeromonas DNA hybridization group (HG) 11 (G . Huys, M . Altwegg, M.-L . Hanninen, M . Vancanneyt, L . Vauterin, R . Coopman, U . Torck, J . Luthy-Hottenstein, P . Janssen, and K . Kersters, Syst . Appl . Microbiol . 19:616-623, 1996) has questioned the original species descriptions of A . eucrenophila and A . encheleia . In order to elucidate the unclear taxonomic status of these taxa in the genus Aeromonas, we have further investigated a collection of 14 reference strains and 14 related isolates encompassing the taxa A . eucrenophila subgroups I and II, A . encheleia, and HG11 by DNA-DNA hybridization (on 17 of the 28 strains) and phenotypic characterization (on all 28 strains) . Genotypically, the investigated strains could be grouped into two DNA hybridization groups that exhibited between-group homologies ranging from 42 to 52% . The members of DNA homology group I (DNA binding, 76 to 100%) were strains of A . eucrenophila subgroup I, including the type strain LMG 3774, and two A . eucrenophila-like isolates, leading to the conclusion that these strains should be considered true representatives of the species A . eucrenophila . The strains of A . eucrenophila subgroup II, HG11, and A . encheleia, on the other hand, were closely joined in DNA homology group II (DNA binding, 74 to 105%) together with two presumptive A . encheleia isolates . The fact that strain LMG 16330T of A . encheleia was the only type strain residing in DNA homology group II implies that HG11 and A . eucrenophila subgroup II should be classified in the species A . encheleia . Except for the somewhat aberrant phenotypic positions of HG11 strains LMG 13075 and LMG 13076, the establishment of DNA homology groups I and II was supported by the delineation of phena 1 and 2 (level of correlation, 90%), respectively, as revealed by numerical analysis of 136 phenotypic test results . These data indicate that A . eucrenophila and A . encheleia are phenotypically highly related but can be easily separated by testing the production of acid from D-cellobiose and lactose and the assimilation of D-cellobiose . Extended descriptions of both species are given.

Infect Immun, 1997 Oct, 65(10), 4299 - 308
Hyperproduction, purification, and mechanism of action of the cytotoxic enterotoxin produced by Aeromonas hydrophila; Ferguson MR et al.; A gene encoding the cytotoxic enterotoxin (Act) from Aeromonas hydrophila was hyperexpressed with the pET, pTRX, and pGEX vector systems . Maximum toxin yield was obtained with the pTRX vector . Approximately 40 to 60% of Act was in a soluble form with the pTRX and pET vector systems . The toxin protein was purified to homogeneity by a combination of ammonium sulfate precipitation and fast protein liquid chromatography-based column chromatographies, including hydrophobic, anion-exchange, sizing, and hydroxylapatite chromatographies . Purified mature toxin migrated as a 52-kDa polypeptide on a sodium dodecyl sulfate (SDS)polyacrylamide gel that reacted with Act-specific antibodies in immunoblots . The minimal amount of toxin needed to cause fluid secretion in rat ileal loops was 200 ng, and the 50% lethal dose for mice was 27.5 ng when injected intravenously . Binding of the toxin to erythrocytes was temperature dependent, with no binding occurring at 4 degrees C . However, at 37 degrees C the toxin bound to erythrocytes within 1 to 2 min . It was determined that the mechanism of action of the toxin involved the formation of pores in erythrocyte membranes, and the diameter of the pores was estimated to be 1.14 to 2.8 nm, as determined by the use of saccharides of different sizes and by electron microscopy . Calcium chloride prevented lysis of erythrocytes by the toxin; however, it did not affect the binding and pore-forming capabilities of the toxin . A dose-dependent reduction in hemoglobin release from erythrocytes was observed when Act was preincubated with cholesterol, but not with myristylated cholesterol . With 14C-labeled cholesterol and gel filtration, the binding of cholesterol to Act was demonstrated . None of the other phospholipids and glycolipids tested reduced the hemolytic activity of Act . The toxin also appeared to undergo aggregation when preincubated with cholesterol, as determined by SDS-polyacrylamide gel electorphoresis . As a result of this aggregation, Act's capacity to form pores in the erythrocyte membrane was inhibited.

Indian J Exp Biol, 1997 Feb, 35(2), 144 - 7
Enterotoxicity, haemolytic activity and antibiotic susceptibility of Aeromonas eucrenophila strains isolated from water and infected fish; Singh DV et al.; Strains of A . eucrenophila isolated from fresh water (2 strains) and infected fish (4 strains) were tested for haemolytic activity and enterotoxicity and any correlation between them . Also, the resistance patterns of A . eucrenophila were tested especially in relation to ampicillin . None of the A . eucrenophila strains caused fluid accumulation in the initial tests, however, they did so only after one to four sequential passages through the gut of a susceptible host . All the strains of A . eucrenophila showed beta-haemolytic activities . Production of beta-haemolysin could be correlated with enterotoxicity . Since all the strains of A . eucrenophila were resistant to ampicillin, media containing this antibiotic may be used for their isolation from diverse sources.

EMBO J, 1997 Aug 1, 16(15), 4760 - 9
Crystal structure at 1.2 A resolution and active site mapping of Escherichia coli peptidyl-tRNA hydrolase; Schmitt E et al.; Peptidyl-tRNA hydrolase activity from Escherichia coli ensures the recycling of peptidyl-tRNAs produced through abortion of translation . This activity, which is essential for cell viability, is carried out by a monomeric protein of 193 residues . The structure of crystalline peptidyl-tRNA hydrolase could be solved at 1.2 A resolution . It indicates a single alpha/beta globular domain built around a twisted mixed beta-sheet, similar to the central core of an aminopeptidase from Aeromonas proteolytica . This similarity allowed the characterization by site-directed mutagenesis of several residues of the active site of peptidyl-tRNA hydrolase . These residues, strictly conserved among the known peptidyl-tRNA hydrolase sequences, delineate a channel which, in the crystal, is occupied by the C-end of a neighbouring peptidyl-tRNA hydrolase molecule . Hence, several main chain atoms of three residues belonging to one peptidyl-tRNA hydrolase polypeptide establish contacts inside the active site of another peptidyl-tRNA hydrolase molecule . Such an interaction is assumed to represent the formation of a complex between the enzyme and one product of the catalysed reaction.

J Antimicrob Chemother, 1997 Aug, 40(2), 171 - 8
Distribution and expression of beta-lactamase genes among Aeromonas spp; Walsh TR et al.; Clinical and environmental isolates of Aeromonas spp . (20 Aeromonas caviae, 33 Aeromonas veronii and 21 Aeromonas hydrophila) were examined for their ability to yield mutants derepressed for beta-lactamase production and for the distribution of the three chromosomally encoded beta-lactamase genes, ampS and cepS from A . veronii bv . sobria and cphA from A . hydrophila . Of these isolates, 100% and 96% of the isolates from A . hydrophila and A . caviae, respectively, yielded beta-lactamase derepressed mutants but only 38% of A . veronii isolates yielded the resistant phenotype at 37 degrees C . However, when tested at 30 degrees C, all isolates gave rise to the derepressed mutants, indicating a temperature effect on the control mechanism . All mutants had significantly higher beta-lactamase activity against ampicillin, oxacillin, cephaloridine and imipenem . Hybridization studies with cloned aeromonas beta-lactamase genes indicated that the cephalosporinase gene, cepS, is almost ubiquitous for the three species tested . The cphA gene cross-hybridized with all isolates of A . veronii and A . hydrophila but not to A . caviae isolates . In contrast, hybridization studies using ampS revealed that only 25% of A . caviae, 45% of A . veronii and 38% of A . hydrophila tested carried the ampS gene or one closely homologous to it . Nonetheless, strains that failed to hybridize with ampS showed two serine beta-lactamases when analysed by isoelectric focusing.

FEMS Microbiol Lett, 1997 Sep 1, 154(1), 1 - 7
The synthesis, secretion and role in virulence of the paracrystalline surface protein layers of Aeromonas salmonicida and A . hydrophila; Noonan B et al.; The S-layers of the Aeromonas spp . studied to date are composed of identical protein subunits which are translocated across the cytoplasmic membrane, periplasm and outer membrane to the cell surface, where they are assembled and tethered to the cell via an interaction with the O-polysaccharide side chains of the lipopolysaccharide . Aeromonas S-layers have the ability to bind a number of host factors such as fibronectin, laminin and vitronectin as well as providing resistance to serum killing and protease digestion . Aeromonas mutants unable to produce an S-layer are altered in their ability to cause disease . In the case of Aeromonas salmonicida, the loss of ability to produce an S-layer effectively abolishes virulence . However, in the case of A . hydrophila, the reduction in virulence caused by the loss of the S-layer is less significant.

J Bacteriol, 1997 Sep, 179(17), 5271 - 81
Quorum sensing in Aeromonas hydrophila and Aeromonas salmonicida: identification of the LuxRI homologs AhyRI and AsaRI and their cognate N-acylhomoserine lactone signal molecules; Swift S et al.; Spent culture supernatants from both Aeromonas hydrophila and Aeromonas salmonicida activate a range of biosensors responsive to N-acylhomoserine lactones (AHLs) . The genes for a quorum sensing signal generator and a response regulator were cloned from each Aeromonas species and termed ahyRI and asaRI, respectively . Protein sequence homology analysis places the gene products within the growing family of LuxRI homologs . ahyR and asaR are transcribed divergently from ahyI and asaI, respectively, and in both Aeromonas species, the genes downstream have been identified by DNA sequence and PCR analysis . Downstream of both ahyI and asaI is a gene with close homology to iciA, an inhibitor of chromosome replication in Escherichia coli, a finding which implies that in Aeromonas, cell division may be linked to quorum sensing . The major signal molecule synthesized via both AhyI and AsaI was purified from spent culture supernatants and identified as N-(butanoyl)-L-homoserine lactone (BHL) by thin-layer chromatography, high-pressure liquid chromatography analysis, and mass spectrometry . In addition, a second, minor AHL, N-hexanoyl-L-homoserine lactone, was identified . Transcriptional reporter studies with ahyI::luxCDABE fusions indicate that AhyR and BHL are both required for ahyI transcription . For A . salmonicida, although the addition of exogenous BHL gives only a small stimulation of the production of serine protease with comparison to the control culture, the incorporation of a longer-chain AHL, N-(3-oxodecanoyl)-L-homoserine lactone, reduced the final level (by approximately 50%) and delayed the appearance (from an A650 of 0.9 in the control to an A650 of 1.2 in the test) of protease in the culture supernatant . These data add A . hydrophila and A . salmonicida to the growing family of gram-negative bacteria now known to control gene expression through quorum sensing.

Biochemistry, 1997 Aug 12, 36(32), 9837 - 46
Spectroscopically distinct cobalt(II) sites in heterodimetallic forms of the aminopeptidase from Aeromonas proteolytica: characterization of substrate binding; Bennett B et al.; The Co(II)Zn(II)- and Zn(II)Co(II)-substituted derivatives of the aminopeptidase from Aeromonas proteolytica (AAP) were probed by EPR spectroscopy . EPR spectra of the high-spin S = 3/2 Co(II) ions in {CoZn(AAP)} and {ZnCo(AAP)} indicated that each metal binding site provides a spectroscopically distinct signature . For {CoZn(AAP)}, subtraction of EPR spectra recorded at pH 7.5 and 10 revealed that two species were present and that the relative contributions to each of the experimental spectra were pH-dependent . The first EPR species, predominant at lower pH values, was simulated as a relatively featureless axial signal with geff values of 2.20, 3.92, and 5.23 which correspond to an Ms = |+/-1/2> ground state transition with a greal of 2.29 and an E/D of 0.1 . The second species, predominant at high pH, was simulated with geff values of 1.80, 2.75, and 6.88 and exhibited a characteristic eight-line 59Co hyperfine pattern with an Az(59Co) of 7.0 mT . These parameters correspond to an Ms = |+/-1/2> ground state transition with a greal of 2.54; however, the signal exhibited marked rhombicity (E/D = 0.32) indicative of an asymmetric tetrahedral or five-coordinate Co(II) ion . Summation of these two species provided an excellent simulation of the observed {CoZn(AAP)} EPR spectrum . The EPR spectrum of {ZnCo(AAP)} also contained two species, at least one of which also exhibited 59Co hyperfine features . However, this signal exhibited little pH dependence, and individual species could not be isolated . The addition of the competitive inhibitor 1-butaneboronic acid (BuBA) to {CoZn(AAP)} resulted in a distinct change in the EPR spectrum; however, addition of BuBA to {ZnCo(AAP)} left the EPR spectrum completely unperturbed . These data indicate that BuBA binds only to the first metal binding site in AAP and does not interact with the second site . On the basis of the X-ray crystallographic data for the transition state analog-inhibited complexes of AAP and the aminopeptidase from bovine lens, BuBA was reclassified as a substrate analog inhibitor rather than a transition state analog inhibitor as previously suggested {Baker, J . O., & Prescott, J . M . (1983) Biochemistry 22, 5322-5331} . From difference spectroscopy and from the simulation of the {CoZn(AAP)} EPR spectrum, a third signal appearing upon BuBA binding was isolated . This signal was simulated with geff values of 2.08, 3 . 15, and 6.15 which correspond to an Ms = |+/-1/2> ground state transition with a greal of 2.41 and an E/D of 0.22 . This simulation also invoked an eight-line unresolved 59Co hyperfine pattern with an Az(59Co) value of 4.0 mT . Summation of the these three species provided an excellent simulation of the observed {CoZn(AAP)} + BuBA EPR spectrum at both pH values . This work establishes that substrate binds only to the first metal binding site in AAP and thus substantiates the first step in catalysis in the recently proposed mechanism of action for AAP {Bennett, B., & Holz, R . C . (1997) J . Am . Chem . Soc . 119, 1923-1933; Chen, G., et al . (1997) Biochemistry 36, 4278-4286}.

Anal Biochem, 1997 Jul 15, 250(1), 29 - 34
Continuous spectrophotometric assay of peptide deformylase; Wei Y et al.; A continuous assay for peptide deformylase has been developed using a formylated dipeptide, formyl-Met-Leu-p-nitroanilide, as substrate . Removal of the formyl group by a peptide deformylase renders the dipeptide product, which contains a free NH2 terminus, a substrate for an aminopeptidase from Aeromonas proteolytica . Sequential hydrolysis of the dipeptide by the aminopeptidase releases a p-nitroaniline, which is monitored spectrophotometrically at 405 nm . This assay was applied to determine the pH optimum and the catalytic activity of a peptide deformylase from Escherichia coli . The E . coli enzyme is most active near neutral pH (pH 7.0) and displays Michaelis-Menten kinetics toward the formylated dipeptide, with K(M) = 20.3 +/- 1.3 microM, k(cat) = 38 +/- 2 s(-1), and k(cat)/K(M) = 1.9 x 10(6) M(-1) s(-1) . It also exhibits an acylase activity, capable of deacylating N-acetyl-Met-Leu-p-nitroanilide and N-trifluoroacetyl-Met-Leu-p-nitroanilide, albeit at drastically reduced rates . These results demonstrate that the current assay is a convenient, rapid, and sensitive method for kinetic studies of peptide deformylase . The strategy employed in this work should also be generally applicable to the characterization of other acylases.

Biosci Biotechnol Biochem, 1997 Jul, 61(7), 1102 - 8
Purification and properties of an aminopeptidase from a protamine-degrading marine bacterium; Obata H et al.; A protamine-degrading marine bacterium was isolated from marine soil and identified as Aeromonas salmonicida subsp . based on its taxonomical characteristics . An alanine-specific aminopeptidase, called aminopeptidase K, from an extract of the strain was purified and characterized . The aminopeptidase K was purified about 80-fold by fractionation with ammonium sulfate and column chromatography on QA-52 cellulose, Phenyl Superose and Superose 12 . The purified enzyme is composed of 6 subunits of 86 kDa with a molecular mass of 520 kDa according to gel filtration and SDS-PAGE . The N-terminal sequence of the enzyme was H.Gly-Gln-Gln-Pro-Gln-Ile-Lys-Try-Tyr-His-Asp-Tyr-Asp-Ala-Pro-Asp-Tyr-Ty r- Ile-Thr- . It is inhibited by monoiodoacetate, N-ethylmaleimide, and puromycin . The Michaelis constant (K(m)) and the maximal rate of hydrolysis (Vmax) were, respectively, 0.28 mM and 49.4 mumol/min/mg for the L-Ala-beta-naphthylamide substrate . The optimum pH and optimum temperature were 6.5 and 45 degrees C, respectively . The purified enzyme was highly specific to L-Ala-beta-naphthylamide.

Ann Clin Lab Sci, 1997 Jul-Aug, 27(4), 254 - 9
Pathogenic analysis of Aeromonas hydrophila septicemia; Chang CY et al.; Aeromonas hydrophila has emerged as a potential pathogen in the immunocompromised host . Various aeromonal infections, including septicemia, have also been reported in apparently healthy individuals . For years, researchers have disagreed over the epidemiologic roles of aeromonads in gastroenteritis . Isolation rates of aeromonads by stool culture among patients with gastroenteritis are not consistently high . Carriers of this bacterium also exist . The septicemic course is, however, often fulminant and fatal, and may lack an obvious focus . Pathogenic mechanisms are complex and largely unresolved . The objective of this study is to report the necropsy findings from a uremic patient who presented with typical aeromonal septicemia of obscure origin asking if such investigation could give insight into some of the questions mentioned previously . Western blot immunostaining for aerolysin (beta-hemolysin of aeromonads) was used to evaluate whether or not such a virulence factor is involved in the process of septic dissemination . The autopsy showed that the skin and liver contained microabscesses . The upper gastrointestinal mucosae and spleen contain patchy putrefactive lesions with adjacent focal hemorrhage . Perimortem blood cultures grew Aeromonas hydrophila . A conventional Western blot analysis of the culture supernatant failed to show aerolysin . A control Aeromonas sobia American Type Culture Collection (ATCC) strain produces readily detectable aerolysin . It is concluded that this isolate may be aerolysin-deficient or one secreting low levels of aerolysin; these would require more sensitive methods of detection . The primary focus of infection might be the upper gastrointestinal tract . Other virulence factors including the bacterial proteases and/or phospholipases might be responsible for the pathogenesis of septic dissemination.

J Clin Microbiol, 1997 Jul, 35(7), 1671 - 4
Identification of Aeromonas clinical isolates by restriction fragment length polymorphism of PCR-amplified 16S rRNA genes; Borrell N et al.; Identification of Aeromonas species, emergent pathogens for humans, has long been controversial due to their phenotypic and genomic heterogeneities . Computer analysis of the published 16S rRNA gene sequences revealed that restriction fragment length polymorphism of the PCR-amplified 16S rRNA gene is a good and rapid way of assessing the identities of all known species of Aeromonas . The method was evaluated with the reference strains of all species (or DNA homology groups) and 76 clinical isolates of diverse origin . Most results from the two approaches were in agreement, but some discrepancies were discerned . Advantages over previous phenotypic and genetic methods are discussed.

FEMS Microbiol Lett, 1997 Jun 15, 151(2), 245 - 8
Purification and characterization of L-allo-threonine aldolase from Aeromonas jandaei DK-39; Kataoka M et al.; L-allo-Threonine aldolase (L-allo-threonine acetaldehyde-lyase), which exhibited specificity for L-allo-threonine but not for L-threonine, was purified from a cell-free extract of Aeromonas jandaei DK-39 . The purified enzyme catalyzed the aldol cleavage reaction of L-allo-threonine (K(m) = 1.45 mM, Vmax = 45.2 mumol min-1 mg-1) . The activity of the enzyme was inhibited by carbonyl reagents, which suggests that pyridoxal-5'-phosphate participates in the enzymatic reaction . The enzyme does not act on either L-serine or L-threonine, and thus it can be distinguished from serine hydroxy-methyltransferase (L-serine:tetrahydrofolate 5,10-hydroxy-methyltransferase, EC 2.1.2.1) or L-threonine aldolase (EC 4.1.2.5).

FEMS Microbiol Lett, 1997 Jun 15, 151(2), 213 - 7
The role of flagella and motility in the adherence and invasion to fish cell lines by Aeromonas hydrophila serogroup O:34 strains; Merino S et al.; We compared the ability of Aeromonas hydrophila wild-type strains of serogroup O:34, non-motile Tn5 aflagellar mutants and the same mutants harboring a recombinant cosmid DNA from a library of A . hydrophila AH-3 (O:34, wild-type) that allows these mutants to make flagella and to be motile, to adhere and invade two fish cell lines . We found that motility is essential in these strains for adhesion, and also that possession of flagella is essential for the ability to invade the fish cell lines . We cannot rule out that flagella may be an adhesin, or that motility may also be involved in A . hydrophila serogroup O:34 bacterial invasion of both fish cell lines.

Zentralbl Veterinarmed B, 1997 Jun, 44(4), 245 - 52
Molecular and phenotypic features of aeromonads isolated from snails (Helix aspersa) affected with a new summer disease; Kodjo A et al.; Forty-four aeromonads were isolated during the summer of 1994 from snails (Helix aspersa) affected or not by a newly described disease . Snta 1 rRNA gene restriction patterns (ribotyping) and nine selected conventional phenotypic tests were performed to retrospectively determine relationships among these isolates regarding the disease . Results from ribotyping were found highly discriminant in strain differentiation and suggest the possible existence of a group of Aeromonas associated with the disease . Biochemical and molecular characterizations indicated that most of these disease-associated aeromonads could belong to the phenospecies A . hydrophila . Phenospecies of aeromonads from healthy snails were distinct from those isolated from diseased snails and could be identified as A . caviae or remained undetermined . To the authors' knowledge, this is the first report of a probable pathogenic aeromonad found in snails, extending the host-pathogen spectrum of Aeromonas.

Zentralbl Veterinarmed B, 1997 Jun, 44(4), 221 - 33
Computer aided assignment of motile Aeromonas strains to genospecies level by standard biochemical tests; Brunner B et al.; A procedure is given for differentiation of motile Aeromonas spp . Based on nine to 12 biochemical properties it allows an assignment of isolated Aeromonas strains first to phenotypes and, in the second step, to hybridization groups (HGs) 1-13 as well as to the genotypically defined species Aer . allosaccharophila and Aer . encheleia . The computer aided classification is carried out according to the principles of numerical taxonomy . Using this differentiation scheme 23 Aeromonas strains, which were isolated from food, and two reference strains were speciated . A total of 16 strains were assigned to Aer . hydrophila, six strains to Aer . caviae and one strain to Aer . sobria . Of the 16 Aer . hydrophile strains, 11 were attached to HG 1, one to HG 2 and four could not be classified clearly as HG 3 or HG 1 . All six Aer . caviae isolated were assigned to HG 5 and the Aer . sobria strain was ranked among HG 8 . The reference strains were assigned to the same genotypes by this method than by DNA-DNA hybridization assays.

Lett Appl Microbiol, 1997 Jun, 24(6), 479 - 82
Antibiotic resistance and plasmid profile of Aeromonas hydrophila isolates from cultured fish, Telapia (Telapia mossambica); Son R et al.; Strains of Aeromonas hydrophila isolates from skin lesions of the common freshwater fish, Telapia mossambica, were screened for the presence of plasmid DNA by agarose gel electrophoresis and tested for susceptibility to 10 antimicrobial agents . Of the 21 fish isolates examined, all were resistant to ampicillin and sensitive to gentamycin . Most isolates were resistant to streptomycin (57%), tetracycline (48%) and erythromycin (43%) . While seven of 21 isolates harboured plasmids, with sizes ranging from 3 to 63.4 kilobase pair (kb), it was only possible to associate the presence of a plasmid with antibiotic resistance (ampicillin and tetracycline) in strain AH11 . Both the plasmid and the associated antimicrobial resistance could be transferred to an Escherichia coli recipient by single-step conjugation at a frequency of 4.3 x 10(-3) transconjugants per donor cell.

J Bacteriol, 1997 Jun, 179(11), 3555 - 60
L-allo-threonine aldolase from Aeromonas jandaei DK-39: gene cloning, nucleotide sequencing, and identification of the pyridoxal 5'-phosphate-binding lysine residue by site-directed mutagenesis; Liu JQ et al.; We have isolated the gene encoding L-allo-threonine aldolase (L-allo-TA) from Aeromonas jandaei DK-39, a pyridoxal 5'-phosphate (PLP)-dependent enzyme that stereospecifically catalyzes the interconversion of L-allo-threonine and glycine . The gene contains an open reading frame consisting of 1,014 nucleotides corresponding to 338 amino acid residues . The protein molecular weight was estimated to be 36,294, which is in good agreement with the subunit molecular weight of the enzyme determined by polyacrylamide gel electrophoresis . The enzyme was overexpressed in recombinant Escherichia coli cells and purified to homogeneity by one hydrophobic column chromatography step . The predicted amino acid sequence showed no significant similarity to those of the currently known PLP-dependent enzymes but displayed 40 and 41% identity with those of the hypothetical GLY1 protein of Saccharomyces cerevisiae and the GLY1-like protein of Caenorhabditis elegans, respectively . Accordingly, L-allo-TA might represent a new type of PLP-dependent enzyme . To determine the PLP-binding site of the enzyme, all of the three conserved lysine residues of L-allo-TA were replaced by alanine by site-directed mutagenesis . The purified mutant enzymes, K51A and K224A, showed properties similar to those of the wild type, while the mutant enzyme K199A was catalytically inactive, with corresponding disappearance of the absorption maximum at 420 nm . Thus, Lys199 of L-allo-TA probably functions as an essential catalytic residue forming an internal Schiff base with PLP of the enzyme to catalyze the reversible aldol reaction.

J Bacteriol, 1997 Jun, 179(11), 3397 - 403
Cloning and characterization of two immunophilin-like genes, ilpA and fkpA, on a single 3.9-kilobase fragment of Aeromonas hydrophila genomic DNA; Wong CY et al.; Antiserum to Aeromonas hydrophila A6 cell envelopes was shown in a previous study (C . Y . F . Wong, G . Mayrhofer, M . W . Heuzenroeder, H . M . Atkinson, D . M . Quinn, and R . L . P . Flower, FEMS Immunol . Med . Microbiol . 15:233-241, 1996) to protect mice against lethal infection by this organism . In this study, colony blot analysis of an A . hydrophila genomic library using antiserum to A . hydrophila A6 cell envelopes revealed a cosmid clone expressing a 30-kDa protein which has not been described previously in aeromonads . The nucleotide sequence of a 3.9-kb fragment derived from this cosmid which expressed the 30-kDa protein revealed two potential open reading frames (ORFs) with homology to known immunophilin proteins . ORF1 encoded a 212-amino-acid protein (molecular mass, 22.4 kDa) with 56% identity to the immunophilin SlyD protein of Escherichia coli . ORF1 was subsequently designated ilpA (immunophilin-like protein) . ORF3 encoded a potential gene product of 268 amino acids with a typical signal sequence and a predicted molecular size of 28.7 kDa . The inferred amino acid sequence showed 46% identity with the sequence of the FkpA protein of E . coli and 40% identity with the sequence of the macrophage infectivity potentiator (Mip) protein of Legionella pneumophila . ORF3 was designated fkpA (FK506 binding protein) by analogy with the E . coli FkpA protein . Expression of the FkpA protein was confirmed by Western blot (immunoblot) analysis, which detected a 30-kDa protein, with antiserum to the Mip protein of Legionella longbeachae and a specific antiserum to anA . hydrophila 30-kDa membrane protein . PCR and Southern analysis showed that a DNA sequence encoding FkpA was found in all 178 aeromonads of diverse origins tested . A nonpolar insertion mutation in the fkpA gene did not attenuate virulence in a suckling mouse model nor did it affect the expression of hemolysins or DNase . This suggests that either the fkpA gene is not essential in the virulence of A . hydrophila under these conditions or there are other genes in A . hydrophila coding for proteins with similar functions.

J Biol Chem, 1997 May 2, 272(18), 12170 - 4
The glycosylphosphatidylinositol-anchored surface glycoprotein Thy-1 is a receptor for the channel-forming toxin aerolysin; Nelson KL et al.; Aerolysin is a channel-forming protein secreted by virulent Aeromonas spp . Some eucaryotic cells, including T-lymphocytes, are sensitive to very low concentrations of the toxin (<10(-9) M) . Here we show that aerolysin binds selectively and with high affinity to the glycosylphosphatidylinositol (GPI)-anchored surface protein Thy-1, which is found on T-lymphocyte populations as well as in brain . Less than 1 ng of purified Thy-1 could be detected by probing Western blots with the toxin . Mutant T-cell lines that lack the ability to add GPI anchors to Thy-1 and other surface proteins were much less sensitive to aerolysin, as were wild-type cells that were pretreated with phosphatidylinositol-specific phospholipase C to remove GPI-anchored proteins . Phosphatidylcholine/cholesterol liposomes containing purified Thy-1 in their membranes were much more sensitive to aerolysin than protein-free liposomes.

Vet Microbiol, 1997 May, 56(1-2), 147 - 58
Molecular and phenotypic methods for the characterization of atypical Aeromonas salmonicida; Hanninen ML et al.; Atypical Aeromonas salmonicida form a taxonomically diverse group among the psychrophilic A . salmonicida . Characteristics of 53 atypical A . salmonicida strains originating from Finland, Denmark, Norway and Sweden were studied using 60 phenotypic tests . Ribopattern analysis and plasmid profiles were used as genetic methods . The production of brown pigment on the furunculosis agar containing L-tyrosine divided the atypical oxidase-positive strains into two groups: pigment-producing (n = 35) and achromogenic (n = 16) . PstI differentiated all the atypical A . salmonicida from A . salmonicida subsp . salmonicida . Combined ribopatterns ClaI/PstI divided pigment producing atypical strains into four major groups B/B, G/G, G/T, F/F . Most of the achromogenic oxidase-positive strains belonged to two major groups H/H or U/U . Cluster analysis of ribopatterns and plasmid profile analysis also supported the division of atypical oxidase-positive A . salmonicida into pigment-producing and achromogenic groups . The oxidase-negative strains formed a distinct group which differed from oxidase-positive atypical A . salmonicida type biochemically and in terms of ribopatterns . Our results also support the use of ribopattern analysis as a valid method to study the epidemiology of infections caused by atypical A . salmonicida on fish farms.

J Comp Physiol {B}, 1997 May, 167(4), 256 - 63
Changes in selected aspects of immune function in the leopard frog, Rana pipiens, associated with exposure to cold; Maniero GD et al.; The effect of exposure to low temperatures (5 degrees C) on lymphocyte proliferation, leukocyte populations, and serum complement levels was examined in the northern leopard frog, Rana pipiens . Proliferation of T lymphocytes in response to phytohemagglutinin stimulation was significantly decreased in frogs kept for 2, 3, and 5 months at 5 degrees C compared to that of animals kept at 22 degrees C . A significant increase in the average percentage of neutrophils and a decrease in the mean percentage of eosinophils was observed in the blood of frogs held for 5 months in the cold compared to animals held at 22 degrees C for the same length of time . Mean serum complement activity after 1 month at 5 degrees C was significantly reduced in comparison to animals held at 22 degrees C and was not detectable after 5 months in the cold . Recovery of complement levels at room temperature (22 degrees C) was also examined after cold exposure . Complement levels were significantly higher than controls (at 22 degrees C) in frogs returned to 22 degrees C for 7 and 14 days after 5 months in the cold . After frogs were held at 5 degrees C for 1 month, serum complement levels increased significantly within 2 days after returning to 22 degrees C and continued to rise 5 and 9 days after warming . Injections with Aeromonas hydrophila following a 5-week exposure to 5 degrees C failed to cause death or observable symptoms of disease in frogs that were returned to 22 degrees C.

Microb Pathog, 1997 May, 22(5), 315 - 20
Complement resistance of capsulated strains of Aeromonas salmonicida; Merino S et al.; The complement resistance of Aeromonas salmonicida strains grown under conditions promoting capsule formation was investigated using well characterized strains and their isogenic mutants . Complement resistance was previously studied using the same strains growing under non-capsulating conditions . The serum resistant strains were found to activate complement, but rapidly degrade C3b preventing productive formation of the lytic complex C5b-9 . Isogenic lipopolysaccharide rough mutants grown under non-capsulating conditions were serum sensitive, binding a large amount of C3b and leading to productive formation of C5b-9 . When grown under conditions promoting capsule formation, these mutants were partially resistant to complement because less C3b is bound to them and also partially degraded, with a concomitant reduction in lytic C5b-9.

J Biotechnol, 1997 Apr 25, 54(2), 113 - 20
Purification and characterization of lipase from Aeromonas sobria LP004; Lotrakul P et al.; Lipase from Aeromonas sobria LP004, isolated from raw milk, was purified and characterized . The lipase was purified 10.29 fold to a homogeneous state by ultrafiltration and column chromatography on phenyl sepharose . The molecular weight of the lipase determined by SDS-PAGE was 97 kDa . Purified A . sobria LP004 lipase exhibited the maximum activity at pH 6.0 and 45 degrees C and was stable under alkaline conditions (pH 6.5-10.0) and at temperatures lower than 40 degrees C . This lipase could be classified as a 1,3-position specific enzyme and its catalytic activity was calcium dependent . PMSF, a serine enzyme inhibitor and 2-mercaptoethanol, a reducing agent, did not affect the enzyme activity.

J Biol Chem, 1997 Apr 25, 272(17), 11109 - 13
Studies on the energetics of proaerolysin secretion across the outer membrane of Aeromonas species . Evidence for a requirement for both the protonmotive force and ATP; Letellier L et al.; Aeromonas spp . secrete the channel-forming protein proaerolysin across their inner and outer membranes in separate steps using the general secretion pathway . Here we show that treating A . hydrophila or A . salmonicida with the protonophore carbonyl cyanide m-chorophenyl hydrazone blocks the second step in transport, secretion across the outer membrane from the periplasm, under conditions where the ATP levels in the cell are no different than the levels in control, secreting cells . A threshold for DeltaPsi was observed in the region of 120 mV, below which secretion by both species was inhibited . Treatment of cells with arsenate, which lowered ATP levels but did not affect DeltaPsi, also reduced secretion from the periplasm, an indication that there is an ATP requirement for this step independent of the requirement for DeltaPsi . Secretion across the outer membrane was also arrested by increasing the osmotic pressure of the medium, even though cellular ATP levels and DeltaPsi were not affected . This may be due to disruption of some necessary association between the inner and outer membranes.

Eur J Biochem, 1997 Apr 15, 245(2), 289 - 93
The GLY1 gene of Saccharomyces cerevisiae encodes a low-specific L-threonine aldolase that catalyzes cleavage of L-allo-threonine and L-threonine to glycine--expression of the gene in Escherichia coli and purification and characterization of the enzyme; Liu JQ et al.; The GLY1 gene of Saccharomyces cerevisiae is required for the biosynthesis of glycine for cell growth {McNeil, J . B., McIntosh, E . V., Taylor, B . V., Zhang, F-R., Tang, S . & Bognar, A . L . (1994) J . Biol . Chem . 269, 9155-9165}, but its gene product has not been identified . We have found that the GLY1 protein is similar in primary structure to L-allo-threonine aldolase of Aeromonas jandiae DK-39, which stereospecifically catalyzes the interconversion of L-allo-threonine and glycine . The GLY1 gene was amplified by PCR, with a designed ribosome-binding site, cloned into pUC118, and expressed in Escherichia coli cells . The enzyme was purified to homogeneity, as judged by polyacrylamide gel electrophoresis . The enzyme has a molecular mass of about 170 kDa and consists of four subunits identical in molecular mass . The enzyme contains 2 mol pyridoxal 5'-phosphate/4 mol of subunit as a cofactor, and its absorption spectrum exhibits maxima at 280 nm and 420 nm . The enzyme catalyzes the cleavage of not only L-allo-threonine to glycine but also L-threonine . We have termed the enzyme a low-specific L-threonine aldolase to distinguish it from L-allo-threonine aldolase.

FEMS Microbiol Lett, 1997 Apr 15, 149(2), 157 - 63
In vivo production of A-protein, lipopolysaccharide, iron-regulated outer membrane proteins and 70-kDa serine protease by Aeromonas salmonicida subsp . salmonicida; Ellis AE et al.; Using specific immunostaining of Western blots, the in vivo expression of several putative virulence factors of Aeromonas salmonicida subsp . salmonicida was demonstrated in infected muscle tissue of Atlantic salmon and rainbow trout . Three virulent isolates of A . salmonicida were used . One isolate was chosen because in vitro it was apparently a non-producer of the 70-kDa serine protease . Infected furuncle tissue was centrifuged and samples of the pellet and supernatant probed for evidence that the components of interest were bacterial cell-associated or secreted . The A-protein was detected in pelleted furuncle material but not in the supernatant . Lipopolysaccharide, both high and low molecular mass, was present in the pellet but only high molecular mass lipopolysaccharide was detected in the furuncle supernatant . Iron-regulated outer membrane proteins were detected in the furuncle pellet . The 70-kDa serine protease was detected in the furuncle supernatant of both protease-producing strains . However, whilst the protease-deficient isolate was demonstrated to produce low levels of the 70-kDa protease when grown in vitro under iron restricted conditions, none could be detected in vivo.

Biochemistry, 1997 Apr 8, 36(14), 4278 - 86
Mechanistic studies on the aminopeptidase from Aeromonas proteolytica: a two-metal ion mechanism for peptide hydrolysis; Chen G et al.; The aminopeptidase from Aeromonas proteolytica (AAP) is uncompetitively inhibited by fluoride ion at pH 8.0 with an inhibition constant (Ki) of 30 mM . Thus, fluoride inactivates AAP only after substrate binding, and only a single fluoride ion binds to AAP . On the other hand, chloride ion does not inhibit AAP up to concentrations of 2 M at pH 8.0 . The pH dependence of fluoride inhibition of AAP was measured over the pH range 6.0-9.5 . Between pH values of 6.0 and 9.0, fluoride ion acts as a pure uncompetitive inhibitor of AAP, and the Ki increases from 1.2 to 370 mM . From a plot of pKi vs pH, a pKa value of 7.0 +/- 0.3 was extracted which corresponds to a single deprotonation process . At pH values higher than 9.0, the fluoride inhibition pattern changes to competitive . This change in inhibition pattern was attributed to a change in ionic strength or perhaps pH of the solution since fluoride ion was also found to become a competitive inhibitor of AAP at pH 8.0 in the presence of 2 M NaCl . These data, taken together with previous kinetic studies of mono- and dinuclear hydrolases with fluoride ion, suggest that a Zn(II)-bound water/hydroxide exists at the dimetal active site of AAP with a pKa of 7.0 and that this water/hydroxide acts as the active site nucleophile . The hydrolysis of L-leucine-p-nitroanilide was measured spectrophotometrically in triplicate between 25 and 85 degrees C at eight substrate concentrations ranging from 5 to 800 microM . From these data, Km values were derived at each temperature studied and were found to increase exponentially with increasing temperature . Moreover, the calculated Vmax values were also found to increase over this temperature range, mimicking the Km values . An Arrhenius plot was constructed from k(cat) values and was found to be linear over the temperature range 25-85 degrees C, indicating that the rate-limiting step in AAP peptide hydrolysis is product formation and does not change as a function of temperature . From the slope of the line, the activation energy (Ea) was calculated to be 36.5 kJ/mol . The enthalpy and entropy of activation at 25 degrees C calculated over the temperature range 298-358 K were found to be 34.0 kJ/mol and -94.2 J/(mol x K), respectively . The free energy of activation at 25 degrees C was found to be 62.1 kJ/mol . Combination of the available X-ray crystallographic data with the present kinetic and thermodynamic results, as well as the previously reported kinetic and spectroscopic data, has allowed a detailed catalytic mechanism for AAP to be proposed.

FEMS Immunol Med Microbiol, 1997 Apr, 17(4), 243 - 50
Enteropathogenicity of Aeromonas jandaei and A . trota; Singh DV et al.; An experimental study of five isolates of Aeromonas jandaei and 12 of A . trota was carried out to examine if they produced an enterotoxic substance, and if so, to characterise that factor and to see if it caused any mucosal damage . Only two of the A . trota strains caused fluid accumulation in the initial rabbit ileal loop (RIL) tests . The remaining strains did so only after one to five sequential passages through RILs and once they caused a secretory response they showed a gradual enhancement of fluid outpouring after each subsequent passage . Inocula of approximately 1 x 10(5) viable cells and 0.25 ml of culture filtrate caused fluid accumulations comparable to those of toxigenic V . cholerae 569B . The enterotoxic factors of both organisms were inactivated when held at 56 degrees C for 20 min or 65 degrees C for 10 min and showed biological activity over a wide range of pH . The only histopathological change observed in the ileal loop was depletion of mucus from the goblet cells . These data thus indicate that strains of A . jandaei and A . trota may produce a heat-labile and pH-stable diarrhoeagenic substance that causes little or no damage to the intestinal mucosa, like that of other known heat-labile enterotoxins.

FEMS Immunol Med Microbiol, 1997 Apr, 17(4), 217 - 23
Plasmids and Aeromonas virulence; Brown RL et al.; Most putative virulence determinants of Aeromonas species are chromosomally encoded . However, several recent reports have indicated that some may be carried on or regulated by plasmids . Therefore, we examined the plasmid carriage rate of a total of 140 clinical and environmental Aeromonas isolates . Plasmid carriage was compared with the ability of an isolate to produce toxins and adhere to HEp-2 cells . Overall, plasmid incidence in Aeromonas species was low (23/140, 16%) and independent of the source of the isolate . Plasmids were, however, more common in environmental isolates of A . veronii biovar sobria than in clinical isolates of this species (P < 0.05) . We could find no evidence to support the recent literature findings that plasmids may have a role in Aeromonas virulence.

Lett Appl Microbiol, 1997 Apr, 24(4), 233 - 9
Rapid and sensitive method for the detection of Aeromonas caviae and Aeromonas trota by polymerase chain reaction; Khan AA et al.; A 16S rDNA-based polymerase chain reaction (PCR) method was developed for the detection of Aeromonas caviae and Aeromonas trota . These two species were identified from other Aeromonas spp . and closely related species by primers set (AER1 and AER2) . The amplified product was 316 bp . The identity of the amplified product was confirmed by DNA-DNA hybridization . Two sets of primers (AER8 and AER9) were used for specific identification of Aer . caviae . Amplifying the 260 bp fragment of 16S rRNA gene region and digesting it with AluI restriction enzyme, yielded 180- and 80-bp fragments . For PCR assay, template DNA was released by mixing equal volumes of homogenized seeded crab meat with Aer . caviae and Chelex 100 (6%) incubated for 10 min at 56 degrees C followed by addition of an equal volume of 0.1% Triton-X-100 and boiled for 10 min . The detection limit was between 50 and 100 cells g-1 of crab meat . This method is very rapid and obviates the need for DNA isolation from complex food matrices and is specific for detecting two Aeromonas species.

Infect Immun, 1997 Apr, 65(4), 1245 - 50
Influence of osmolarity on lipopolysaccharides and virulence of Aeromonas hydrophila serotype O:34 strains grown at 37 degrees C; Aguilar A et al.; Growth of Aeromonas hydrophila serotype O:34 strains at 37 degrees C at low and high osmolarity resulted in changes in the lipopolysaccharide (LPS) and virulence of the strains tested . We previously described the effect of growth temperature on LPS and virulence of these strains (S . Merino et al., Infect . Immun . 60:4343-4349, 1992) . The effect of osmolarity can be observed when the cells grow at 37 degrees C but not when they grow at 20 degrees C . Purified LPS from cells cultivated at 37 degrees C and high osmolarity was smooth, while the LPS extracted from the cells cultivated at low osmolarity was rough . Furthermore, the strains were more virulent for fish and mice when they were grown at high osmolarity than when they were grown at low osmolarity and also showed increased extracellular activities when they were grown at high osmolarity . Finally, cells grown at high osmolarity showed better adhesion to HEp-2 cells than the same cells grown at low osmolarity, and furthermore the cells grown at high osmolarity were resistant to the bactericidal activity of nonimmune serum, while the same cells grown at low osmolarity were sensitive.

Shock, 1997 Apr, 7(4), 282 - 7
Pathophysiologic plasma levels of leukotriene C4 in relation to the hemodynamic dysfunction and mediator release of graded bacteremia; Zeltsman D et al.; This study was undertaken to identify those events of bacteremic shock that pathophysiologic levels of leukotriene C4 (LTC4) alone were sufficient to cause . Sixteen adult swine were studied for 4 h in three groups: ANES (n = 6) received anesthesia only; Septic (n = 6) received Aeromonas hydrophila, 10(9)/mL, intravenously, increased incrementally from .2 to 4.0 mL/kg/h; LTC4 (n = 4) received LTC4 infused intravenously, at rates that approximated LTC4 levels of Septic animals . Measurements included mean arterial pressure and arterial PO2, mmHg, pulmonary and systemic (SVRI) vascular resistance indexes, cardiac index (CI), oxygen extraction ratio, hematocrit; thromboxane B2 (TxB2), prostaglandin 6 keto F1 alpha (6 keto), leukotrienes B4 and C4D4E4, and tumor necrosis factor were measured in pg/mL by ELISA . Statistical analysis was performed by ANOVA and general linear model) . Mean arterial pressure increased from 100 +/- 5 to 141 +/- 9 in the LTC4 group, but decreased in the Septic group from 90 +/- 7 at baseline to 62 +/- 6 at 3 h . In the LTC4 group, SVRI did not differ from ANES, and pulmonary vascular resistance, PO2, and CI did not change from baseline . In the LTC4 group, TxB2 and 6 keto levels decreased from 149 +/- 26 to 87 +/- 18 and 58 +/- 10 to 44 +/- 12, respectively; in the Septic group, TxB2 increased 140-fold and 6 keto increased 60-fold . Pathophysiologic LTC4 is not sufficient alone to cause the derangements in CI and SVRI, and tissue metabolism induced by graded bacteremia . Significantly increased systemic blood pressure suggests that endogenous pathophysiologic LTC4 may be involved . LTC4 does not increase plasma eicosanoids and tumor necrosis factor, but may down-regulate prostaglandin and leukotriene release.

Structure, 1997 Mar 15, 5(3), 337 - 47
Crystal structure of carboxypeptidase G2, a bacterial enzyme with applications in cancer therapy; Rowsell S et al.; BACKGROUND: Carboxypeptidase G enzymes hydrolyze the C-terminal glutamate moiety from folic acid and its analogues, such as methotrexate . The enzyme studied here, carboxypeptidase G2 (CPG2), is a dimeric zinc-dependent exopeptidase produced by Pseudomonas sp . strain RS-16 . CPG2 has applications in cancer therapy: following its administration as an immunoconjugate, in which CPG2 is linked to an antibody to a tumour-specific antigen, it can enzymatically convert subsequently administered inactive prodrugs to cytotoxic drugs selectively at the tumour site . CPG2 has no significant amino acid sequence homology with proteins of known structure . Hence, structure determination of CPG2 was undertaken to identify active-site residues, which may in turn provide ideas for protein and/or substrate modification with a view to improving its therapeutic usefulness . RESULTS: We have determined the crystal structure of CPG2 at 2.5 A resolution using multiple isomorphous replacement methods and non-crystallographic symmetry averaging . Each subunit of the molecular dimer consists of a larger catalytic domain containing two zinc ions at the active site, and a separate smaller domain that forms the dimer interface . The two active sites in the dimer are more than 60 A apart and are presumed to be independent; each contains a symmetric distribution of carboxylate and histidine ligands around two zinc ions which are 3.3 A apart . This distance is bridged by two shared zinc ligands, an aspartic acid residue and a hydroxyl ion . CONCLUSIONS: We find that the CPG2 catalytic domain has structural homology with other zinc-dependent exopeptidases, both those with a single zinc ion and those with a pair of zinc ions in the active site . The closest structural homology is with the aminopeptidase from Aeromonas proteolytica, where the similarity includes superposable zinc ligands but does not extend to the rest of the active-site residues, consistent with the different substrate specificities . The mechanism of peptide cleavage is likely to be very similar in these two enzymes and may involve the bridging hydroxyl ion ligand acting as a primary nucleophile.

Intern Med, 1997 Mar, 36(3), 171 - 4
Aeromonas bacteremia in patients with hematologic diseases; Funada H et al.; Over a 23-year period, 17 patients with hematologic diseases developed Aeromonas bacteremia while in our hematology ward . Male predominance (14 patients, 82%) was seen, with a predilection for the elderly . Hematologic malignancies, especially acute leukemia, accounted for 15 (88%) of all patients . Cancer chemotherapy and neutropenia (15 patients each) were the most common preceding host conditions . Aeromonas bacteremia generally occurred in the second half of the year (July-December), with no exposure to water or fish . Seven recent isolates comprised Aeromonas sobria (five isolates) and Aeromonas hydrophila (two isolates) . Twelve patients (71%) showed a clinical picture ranging from mild gastroenteritis to severe enterocolitis . Anorectal and hepatobiliary infections were also noted in a few patients . The overall mortality rate was 35% . Ten (77%) of the 13 patients who were treated with aminoglycoside plus cephalosporin or carbapenem survived in association with marrow recovery.

Microbiology, 1997 Mar, 143 ( Pt 3), 803 - 12
Molecular analysis and expression of the extracellular lipase of Aeromonas hydrophila MCC-2; Chuang YC et al.; The structural gene encoding the extracellular lipase of Aeromonas hydrophila MCC-2 was cloned and found to be expressed in Escherichia coli using its own promoter . When the cloned gene (lip) was expressed in E . coli minicells, an 80 kDa protein was identified . Subcellular fractionation of E . coli carrying the lip gene indicated that the Lip protein was mainly associated with the membrane fraction . Nucleotide sequence analysis revealed that the gene is 2253 bp long, coding for a 79-9 kDa protein with an estimated pl of 10.36 . The deduced protein contains two putative signal peptide cleavage sites: one is a typical signal peptidase cleavage site and the other bears a strong resemblance to known lipoprotein leader sequences . Radioactivity from {3H}palmitate was incorporated into the Lip protein when expressed in E . coli . The deduced protein contains a sequence of VHFLGHSLGA which is very well conserved among lipases . It shows 67% and 65% overall identity to the amino acid sequences of lipase from A . hydrophila strains H3 and JMP636, respectively, but shows little homology to those of other lipases . The Lip protein was purified to homogeneity from both A . hydrophila and recombinant E . coli . In hydrolysis of p-nitrophenyl esters and triacylglycerols, using purified enzyme, the optimum chain lengths for the acyl moiety on the substrate were C10 to C12 for ester hydrolysis and C8 to C10 for triacylglycerol hydrolysis.

J Bacteriol, 1997 Mar, 179(6), 2006 - 13
Expression of the AsbA1, OXA-12, and AsbM1 beta-lactamases in Aeromonas jandaei AER 14 is coordinated by a two-component regulon; Alksne LE et al.; Aeromonas jandaei AER 14 (formerly Aeromonas sobria AER 14) expresses three inducible beta-lactamases, AsbA1, OXA-12 (AsbB1), and AsbM1 . Mutant strains that constitutively overexpress all three enzyme simultaneously, suggesting that they share a common regulatory pathway, have been isolated . Detectable expression of the cloned genes of AsbA1 and OXA-12 in some Escherichia coli K-12 laboratory strains is achieved only in the presence of a blp mutation . These mutations map to the cre operon at 0 min, which encodes a classical two-component regulatory system of unknown function . Two regulatory elements from A . jandaei which permit high-level constitutive expression of OXA-12 in E . coli were cloned . Both loci encode proteins with characteristics of response regulator proteins of two-component regulatory systems . One of these loci, designated blrA, bestowed constitutive expression of all three beta-lactamases in A . jandaei AER 14 when present on a multicopy plasmid, confirming its role in the regulatory pathway of beta-lactamase production in this organism.

J Mol Biol, 1997 Feb 7, 265(5), 620 - 36
Streptomyces griseus aminopeptidase: X-ray crystallographic structure at 1.75 A resolution; Greenblatt HM et al.; The X-ray crystal structure of the enzyme Streptomyces griseus aminopeptidase (SGAP) has been determined in its double zinc form to 1.75 A resolution, in its apo-enzyme from (zinc removed) to 2.1 A resolution, and as a mercury replaced derivative to 2.1 A resolution . The structure solution was achieved by single isomorphous replacement with phasing from anomalous scattering (SIRAS), followed by density modification with histogram matching . The protein consists of a central beta-sheet made up of eight parallel and antiparallel strands, surrounded by helices on either side . The active site is located at the carbonyl ends of two middle strands of the beta-sheet region . Two sections of the chain that could not be traced were Glu196 to Arg202, which borders the active site, and the final seven C-terminal residues starting with Gly278 . The active site contains two zinc cations, each with similar ligands, at a distance of 3.6 A from each other . An unknown molecule appears to be bound to both zinc ions in the active site at partial occupancy and has been modelled as a phosphate ion . A calcium binding site has also been identified, consistent with the observations that calcium modulates the activity of the enzyme, and increases its heat stability . The mechanism by which the calcium cation modulates enzyme activity is not apparent, since the location of the calcium binding site is approximately 25 A distant from the active site zinc ions . Comparison of the structure of SGAP to other known aminopeptidases shows that the enzyme is most similar to Aeromonas proteolytica aminopeptidase (AAP) . Both enzymes share a similar topology, although the overall sequence identity is very low (24% in aligned regions) . The coordination of the two active site zinc cations in SGAP resembles that of AAP . These two microbial enzymes differ from bovine lens leucine aminopeptidase (LAP) in both overall structure and in coordination of the two zinc ions.

J Clin Microbiol, 1997 Feb, 35(2), 369 - 73
Characterization of Aeromonas spp . isolated from humans with diarrhea, from healthy controls, and from surface water in Bangladesh; Kuhn I et al.; Aeromonas isolates from patients with diarrhea in Bangladesh (n = 69), from healthy controls (n = 11), and from surface water (n = 40) were analyzed with respect to their hybridization groups (HGs) by the aid of fatty acid methyl ester (FAME) characterization and DNA fingerprinting by AFLP, biochemical phenotypes (Phe-nePlate {PhP} types), and the production of hemolysin and cytotoxin . The aim of the investigation was to find out whether certain strains carrying virulence factors predominated among patient isolates . According to FAME and/or AFLP analysis, most human isolates were allocated to DNA HGs 4 (Aeromonas caviae) and 1 (A . hydrophila) . Most environmental strains were allocated to HG8 (A . veronii biogroup sobria) and HG4 (A . caviae), and only one was of HG1 . According to PhP typing, the diversity among patient isolates was lower than that among other strains, and two dominating PhP types (types BD-1 and BD-2) were identified in 29 and 30% of the patient isolates, respectively . PhP type BD-1 was also common among the environmental isolates, whereas PhP type BD-2 was only identified in two of the other isolates . Twenty-five of 26 isolates belonging to HG1 were of the same PhP type (BD-2), whereas isolates of other common HGs were more diverse according to their PhP types . Hemolytic and cytotoxin-producing strains occurred more frequently among the environmental isolates than among patient isolates . However, the hemolytic and cytotoxic activities among human isolates was strongly correlated to the HG1/BD-2 type, which, in addition, showed high cytotoxin titers (median values, 1/512 compared to 1/128 for cytotoxin-positive isolates belonging to other types) . Thus, the HG1/BD-2 type may represent a pathogenic A . hydrophila type that is able to produce diarrhea in humans.

Dev Biol Stand, 1997, 90, 371 - 9
Vaccinated fish welfare: protection versus side-effects; Midtlyng PJ; Active immunisation of fish involves a number of potentially harmful procedures like handling, anaesthesia or injection of more or less toxic substances . Adjuvanted vaccines may cause inflammation, granuloma and pigmentation at the site of injection . Intraperitoneal administration of oil-adjuvanted vaccines to Atlantic salmon pre-smolts has occasionally resulted in impaired growth and reduced carcass quality . The consequences of such vaccination for fish welfare may therefore be questioned . With respect to furunculosis caused by Aeromonas salmonicida, scientific data suggest, however, that only oil-adjuvanted vaccines are protective throughout the production cycle of farmed salmon . Data are presented to show that salmonids are highly at risk to epizootics if left unprotected against this or other endemic diseases . A panel of parameters partly adopted from experimental animal medicine is proposed to assess the impact of vaccine side-effects in farmed fish . In intensive salmon aquaculture systems, reduced disease risks are thought to justify the observed level of side-effects following current vaccination practices . For future fish vaccines, reduction of side-effects without compromising long-term protective immunity constitutes a challenging goal.

Dev Biol Stand, 1997, 90, 135 - 41
Immunization with bacterial antigens: infections with motile aeromonads; Karunasagar I et al.; Motile aeromonads are a heterogeneous group of organisms which are involved in a number of disease syndromes of warm water fish . They are commonly associated with bacterial haemorrhagic septicaemia, infectious dropsy, red mouth disease, ulcerative conditions etc . A variety of factors has been considered to be associated with virulence including haemolysins, proteases, surface array protein, acetylcholinesterase etc . We have studied the immune response of Indian major carps to antigens of motile aeromonads . The Indian major carp, Labeo rohita, showed immunological memory and secondary response on booster administration . The extent of protection showed good correlation with titres of agglutinating antibody . When polyvalent vaccine was used, the fish showed antibody titres against all the component strains . However, the level of antibody was less compared to immunization by monovalent vaccines . Cross-reacting antibodies induced by monovalent vaccines showed varying degrees of protection.

Scand J Infect Dis, 1997, 29(1), 91 - 2
Fatal myofascial necrosis due to imipenem-resistant Aeromonas hydrophila; Gonzalez-Barca E et al.; We report the case of a fatal myofascial necrosis caused by an imipenem-resistant Aeromonas hydrophila in a patient with a history of aplastic anemia . He presented with fever and left thigh tenderness . The CT scan was consistent with cellulitis and, after cultures were obtained, empirical treatment with imipenem and amikacin was started . Two days later, necrotic bullae appeared on his thigh, and cultures showed Aeromonas hydrophila which was imipenem-resistant . Although surgical debridement was performed and ciprofloxacin was initiated, the patient died.

Rev Esp Enferm Dig, 1997 Jan, 89(1), 48 - 50
{Severe acute gastroenteritis due to Aeromonas in a patient colectomized for Crohn's disease}; de Sola Earle C et al.; We report a case of severe acute diarrhoea produced by Aeromonas sobria, a specimen with controversial human pathogenicity . A 26-year-old man with Crohn's disease previously colectomized was admitted with a cholera-like clinical presentation and renal failure . Aeromonas sp . can be isolated in both children and adults and in healthy people, A . hydrophila being most often detected . Severe infections due to other Aeromonas sp., usually A . sobria and A . caviae, have been rarely described . Most patients have underlying illnesses such as chronic liver disease or neoplasms . In our patient colectomy played a key role.

Mol Gen Mikrobiol Virusol, 1997, (1), 22 - 5
{Isolation and characteristics of plasmids from Aeromonas}; Kul'ba AM et al.; Fourteen out of fifty-two examined strains of Aeromonas contain plasmids . One of them determines the resistance to tetracycline, streptomycin, and chloramphenicol . The pAs30 plasmid, 53 t . n . p . in size, is capable of conjugative transfer to bacteria of different genera, which permits us to consider it a broad host range plasmid . Using 12 restriction endonucleases, the physical map of the plasmid was plotted, on which the genes responsible for transporting functions and streptomycin resistance were tentatively located.

Can J Microbiol, 1997 Jan, 43(1), 9 - 16
A 4-year study of the diversity and persistence of coliforms and Aeromonas in the water of a Swedish drinking water well; Kuhn I et al.; Coliforms and Aeromonas, isolated over a sampling period of 4 years from a Swedish drinking water well, were analysed for their phenotypical diversity and for their ability to persist in the well water . From each of the 40 water samples collected from the well, 32 bacterial isolates were subjected to typing by the PhenePlate (PhP) biochemical fingerprinting system . Strains able to persist in the well water were further characterized using the API 20E system, gas-liquid chromatographic cellular fatty acid analysis, and the DNA fingerprinting technique AFLP . Using the PhP system, a total of 170 different phenotypes were identified among 1143 studied isolates . Most phenotypes were only represented by a few isolates and (or) were restricted to one or two sampling occasions . However, one particular phenotype (RV-C01), identified as Aeromonas hydrophila using the API 20E system and fatty acid analysis, reoccurred in 28 samples distributed over the whole study period and often dominated the bacterial population in the well water . AFLP analysis revealed that the RV-C01 isolates displayed basically identical fingerprints . Our results thus suggest that a genetically stable Aeromonas clone resided in the well water over the whole 4-year study, whereas other bacterial strains studied were only transient inhabitants of the well.

Int J Food Microbiol, 1997 Jan, 34(1), 17 - 26
Aeromonas species in fish, fish-eggs, shrimp and freshwater; Hanninen ML et al.; Aeromonas spp . are common contaminants of fish and seafood . They also are ubiquitous in the water environment . Aeromonas spp . were identified in 27 (93%) of 29 fish, in 17 (100%) fish-egg, in two (16%) of 12 shrimp samples and in 23 (100%) freshwater samples . In total, 117 Aeromonas strains were isolated from 69 positive samples, several samples having had two or three Aeromonas species . Included in this were also 26 mesophilic Aeromonas strains isolated in association with the study on fish diseases . The distribution of the species into 13 known hybridization groups (HGs) were studied by phenotypic and molecular methods . Ribopattern analysis of SmaI digested DNA was used for the identification of HGs . The predominant HG in fish, fish-eggs and freshwater samples was A . hydrophila HG 3 because 63% (22/37), 28% (16/57) or 80% (16/20) of the strains, respectively, were in HG 3 . A . hydrophila HG 2 was also common in fresh fish samples but was not identified in fish-egg samples . HG 7 was common in fish samples studied for fish diseases and in freshwater samples . Strains which were not allotted to any HGs were common (19 of 143 strains) . A . hydrophila HG 1, A . caviae HG 4, A . veronii subspecies sobria or subspecies veronii HG 8/10 known to be associated with human diarrhea were uncommon in all samples . The three strains isolated from frozen shrimp during two suspected food-borne outbreaks were A . hydrophila HG 2 and HG 3.

Biosci Biotechnol Biochem, 1997 Jan, 61(1), 174 - 6
Isolation and characterization of chitinase from a flake-chitin degrading marine bacterium, Aeromonas hydrophila H-2330; Hiraga K et al.; A flake-chitin degrading marine bacterium was isolated and identified as Aeromonas hydrophila . This strain secreted five chitinases and an beta-N-acetylglucosaminidase . The main chitinase (Chi-A) was purified and characterized . The optimum pH of Chi-A was 5-8, and the activity was inhibited by Hg2+ and Fe3+ . Chi-A was different from chitinases of other Aeromonas species with respect to molecular weight (62,000) and insensitivity to monoiodoacetate . The amino-terminal amino acid sequence showed extensive similarity with chitinases from Gram-negative bacteria.

J Immunol, 1997 Jan 1, 158(1), 384 - 92
Acute phase proteins in salmonids: evolutionary analyses and acute phase response; Jensen LE et al.; Inflammation induces dramatic changes in the biosynthetic profile of the liver, leading to increased serum concentrations of positive acute phase (AP) proteins and decreased concentrations of negative AP proteins . Serum amyloid A (SAA) and the pentraxins C-reactive protein (CRP) and serum amyloid P component (SAP) are major AP proteins: their serum levels can rise by 1000-fold, indicating that they play a critical role in defense and/or the restoration of homeostasis . We have cloned SAA and a SAP-like pentraxin from salmonid fish species . The salmonid SAA shares approximately 70% amino acid identity with mammalian AP SAA . When salmonids are challenged with an AP stimulus, i.e., Aeromonas salmonicida, SAA responds dramatically as a major AP reactant . The salmonid pentraxin shows approximately 40% amino acid identity to both mammalian SAP and CRP . Evolutionary analysis suggests the presence of only a single such protein in teleosts and lower animal species . Surprisingly, the salmonid pentraxin behaves as a negative AP reactant, reminiscent of the SAP-like Syrian hamster female protein, in that hepatic mRNA concentrations decline to 50% of prestimulus levels . This study reinforces the hypothesis that SAA induction is an essential and universal feature of the vertebrate AP response and that it represents part of an ancient host defense system . Conversely, the species-dependent heterogeneity of pentraxin expression during the vertebrate AP response supports the possibility that its most important ancestral (and perhaps present) function is not related to its AP behavior.

Indian J Biochem Biophys, 1996 Dec, 33(6), 527 - 30
Metabolism of proteins and glycoproteins in tumour bearing mice treated with Aeromonas L-asparaginase; Benny PJ et al.; L-asparaginase, isolated in our laboratory, from Aeromonas had been found to be antileukaemic . In the present study, changes in the levels of proteins and glycoproteins in leukaemic mice and under treatment with Aeromonas L-asparaginase have been compared . Levels of protein bound hexose, fucose and sialic acid which were increased during leukaemia attained normal levels when treated with L-asparaginase . The increased blood urea level declined significantly during enzyme therapy . Effects of L-asparaginase are compared with 'Leunase', a commercially available drug used in the treatment of leukaemia.

J Diarrhoeal Dis Res, 1996 Dec, 14(4), 274 - 9
Production of haemolysin and enterotoxin by Aeromonas jandaei and Aeromonas trota strains after animal passage; Singh DV et al.; Five Aeromonas jandaei and 12 Aeromonas trota isolates were tested for the production of haemolysin and enterotoxin, and the correlation between these two properties . The majority (10 isolates) of the strains produced beta-haemolysis . The titres of haemolytic activity for both species were 8-64 HU/mL . In the initial ileal loop test, only two (A . trota) of the 17 isolates produced enterotoxin . One each of these 2 A . trota strains was beta-haemolytic and non-haemolytic . The remaining isolates of A . trota and A . jandaei included alpha-, beta- and non-haemolytic strains, and failed to cause any fluid accumulation in the initial tests, but did so after one-to-five sequential passages through the rabbit ileal loops . Three alpha- and 4 non-haemolytic strains switched over to the production of beta-haemolysis when they showed the positive ileal loop reaction . However, on repeated subcultures or on storage in the laboratory, all of them reverted back to their original alpha- or non-haemolytic character and no longer produced enterotoxin.

Lett Appl Microbiol, 1996 Dec, 23(6), 445 - 7
Characterization of a stable L-form of the fish pathogen Aeromonas salmonicida; Gibb A et al.; A stable L-form of Aeromonas salmonicida, which resulted from induction with benzylpenicillin, contained more of an outer membrane protein, with an estimated molecular weight of 40 kDa but less of 47.9 and 38 kDa proteins, than did parental walled cells . In addition, from Western blots, two protein bands reacted strongly with a polyclonal antiserum . The antiserum did not react demonstrably with the band detected in the L-forms on the gels.

J Appl Bacteriol, 1996 Dec, 81(6), 585 - 93
Immunological analysis of extracellular products and cell surface components of motile Aeromonas isolated from fish; Santos Y et al.; The present work describes the characterization of antigens present in the extracellular products (ECP) and cell wall of strains of motile Aeromonas isolated from rainbow trout culture systems . The relationships among virulence for fish, O-serogroup and profile of LPS were also examined . The slide agglutination test showed that most of the virulent strains of motile Aeromonas (72%) were included in the serotypes O3, O6, O11 and O19 (Guinee and Jansen System) . However, there were also non-pathogenic strains within these groups . Electrophoretic analysis of lipopolysaccharides (LPS) and proteins from cell envelope and ECP showed heterogeneity not only among the different serogroups but also within the same serotype . Immunoblot assays of cell envelope components, and of LPS present in the ECP demonstrated a close relationship among Aeromonas strains from the same serotype, while strains from different serotypes were not immunologically related . Moreover, this assay showed that motile Aeromonas belonging to distinct serotypes produced extracellular proteins immunologically related . On the other hand, antigenic cross reactivity was observed between the LPS obtained from cell envelope and those obtained from the ECP . The present results point out the need to include strains representative of each of the serotypes which predominates in a particular area and their ECPs in the formation of vaccines against motile Aeromonas septicaemia.

Microb Pathog, 1996 Dec, 21(6), 447 - 61
The cell surface of Aeromonas salmonicida determines in vitro survival in cultured brook trout (Salvelinus fontinalis) peritoneal macrophages; Daly JG et al.; Aeromonas salmonicida strains phenotypically differing in their A-layer, lipopolysaccharide, and macrophage cytotoxicity were tested in vitro for survivability in brook trout (Salvelinus fontinalis) serum with or without antibodies, and in vivo following intraperitoneal injection . The ability of brook trout peritoneal macrophages to phagocytize and kill the different phenotypes was investigated in an in vitro assay . The virulent strain, A . salmonicida 80204, which has the full complement of known virulence factors, as well as the recently described macrophage cytotoxin, was resistant in vitro to both the bactericidal activity of normal and immune serum, and to brook trout peritoneal macrophages . A . salmonicida SS-70.1, which possesses the A-layer but lacks the cytotoxin, was resistant to the bactericidal activity of normal and immune serum but was avirulent and killed by macrophages . Phenotypes lacking the A-layer, regardless of whether or not they possessed the macrophage cytotoxin were avirulent, susceptible to normal and immune serum and the bactericidal activity of peritoneal macrophages . A . salmonicida virulence expression requires both the A-layer and the macrophage cytotoxin.

Infect Immun, 1996 Dec, 64(12), 5302 - 9
Mesophilic Aeromonas sp . serogroup O:11 resistance to complement-mediated killing; Merino S et al.; The complement activation by and resistance to complement-mediated killing of Aeromonas sp . strains from serogroup O:11 were investigated by using different wild-type strains (with an S-layer characteristic of this serogroup) and their isogenic mutants characterized for their surface components (S-layer and lipopolysaccharide {LPS}) . All of the Aeromonas sp . serogroup O:11 wild-type strains are unable to activate complement, which suggested that the S-layer completely covered the LPS molecules . We found that the classical complement pathway is involved in serum killing of susceptible Aeromonas sp . mutant strains of serogroup O11, while the alternative complement pathway seems not to be involved, and that the complement activation seems to be independent of antibody . The smooth mutant strains devoid of the S-layer (S-layer isogenic mutants) or isogenic LPS mutant strains with a complete or rather complete LPS core (also without the S-layer) are able to activate complement but are resistant to complement-mediated killing . The reasons for this resistance are that C3b is rapidly degraded, and therefore the lytic membrane attack complex (C5b-9) is not formed . Isogenic LPS rough mutants with an incomplete LPS core are serum sensitive because they bind more C3b than the resistant strains, the C3b is not completely degraded, and therefore the lytic complex (C5b-9) is formed.

J Clin Microbiol, 1996 Dec, 34(12), 3203 - 5
Characterization of cytotoxic, hemolytic Aeromonas caviae clinical isolates and their identification by determining presence of a unique hemolysin gene; Wang G et al.; Aeromonas caviae has recently been recognized as an important enteropathogen and its hemolysin is purported to be one of the virulence factors, In this study, a total of 80 clinical isolates of Aeromonas spp . were investigated by PCR with synthetic oligonucleotides targeting a cloned hemolysin-encoding sequence from an A . caviae isolate of clinical origin . Of the 35 clinical A . caviae isolates tested, only 6 contained the target sequence.

Philos Trans R Soc Lond B Biol Sci, 1996 Nov 29, 351(1347), 1539 - 57
Pathological and microbiological findings from incidents of unusual mortality of the common frog (Rana temporaria); Cunningham AA et al.; In 1992 we began an investigation into incidents of unusual and mass mortalities of the common frog (Rana temporaria) in Britain which were being reported unsolicited to us in increasing numbers by members of the public . Investigations conducted at ten sites of unusual mortality resulted in two main disease syndromes being found: one characterized by skin ulceration and one characterized by systemic haemorrhages . However, frogs also were found with lesions common to both of these syndromes and microscopic skin lesions common to both syndromes were seen . The bacterium Aeromonas hydrophila, which has been described previously as causing similar lesions, was isolated significantly more frequently from haemorrhagic frogs than from those with skin ulceration only . However, as many of the latter were euthanased, this may have been due to differences in post mortem bacterial invasion . An iridovirus-like particle has been identified on electron microscopical examination of skin lesions from frogs with each syndrome and iridovirus-like inclusions have been detected in the livers of frogs with systemic haemorrhages . Also, an adenovirus-like particle has been cultured from one haemorrhagic frog . A poxvirus-like particle described previously from diseased frogs has now been found also in control animals and has been identified as a melanosome . Both the prevalence of the iridovirus-like particle and its association with lesions indicate that it may be implicated in the aetiology of the disease syndromes observed . Specifically, we hypothesize that primary iridovirus infection, with or without secondary infection with opportunistic pathogens such as A . hydrophila, may cause natural outbreaks of 'red-leg', a disease considered previously to be due to bacterial infection only.

J Emerg Med, 1996 Nov-Dec, 14(6), 737 - 41
Near-drowning-associated Aeromonas pneumonia; Ender PT et al.; Aeromonas is increasingly recognized as a human pathogen that causes a variety of different infections . Aeromonas has rarely been reported as a cause of respiratory infection, and it has been described in near-drowning-associated pneumonia . This article reviews a case of Aeromonas sobria pneumonia associated with a near drowning and considers the clinical and epidemiological characteristics of 10 previously reported cases . Nearly all of the cases involved young healthy men, a rapid development of pneumonia and sepsis after a brief stable period postimmersion, and bilateral infiltrates on chest radiography . A very high rate of positive blood cultures and mortality was also noted . The epidemiological and clinical data in this review may be helpful to the clinician caring for near-drowning victims . Although prophylactic antibiotics are not recommended for near-drowning victims, broad-spectrum antibiotics should be rapidly instituted with any evidence of infection.

Mol Microbiol, 1996 Nov, 22(4), 595 - 604
A TonB-like protein and a novel membrane protein containing an ATP-binding cassette function together in exotoxin secretion; Howard SP et al.; Protein secretion by many Gram-negative bacteria occurs via the type II pathway involving translocation across the cytoplasmic and outer membranes in separate steps . The mechanism by which metabolic energy is supplied to the translocation across the outer membrane is unknown . Here we show that two Aeromonas hydrophila inner membrane proteins, ExeA and ExeB, are required for this process . ExeB bears sequence as well as topological similarity to TonB, a protein which opens gated ports for the inward translocation of ligands across the outer membrane . ExeA is a novel membrane protein which contains a consensus ATP-binding site . Mutations in this site dramatically decreased the rate of secretion of the toxin aerolysin from the cell . ExeB was stable when overproduced in the presence of ExeA, but was degraded when synthesized in its absence, indicating that the two proteins form a complex . These results suggest that ExeA and ExeB may act together to transduce metabolic energy to the opening of a secretion port in the outer membrane.

Microb Pathog, 1996 Nov, 21(5), 357 - 77
Molecular and biochemical characterization of a heat-labile cytotonic enterotoxin from Aeromonas hydrophila; Chopra AK et al.; We report herein the DNA sequence analysis of the heat-labile cytotonic enterotoxin gene (alt) from Aeromonas hydrophila and the biological function of the purified hyperproduced toxin (Alt) . One large open-reading frame (ORF), comprised of 1104 bp, was detected at positions 804 to 1907 bp on a 4.0-kb Sa/l DNA fragment from Aeromonas . This ORF encodes for a protein having 368 amino acids (aa) with a computed molecular weight of 38 kDa . The aa sequence of the first 15 NH2-terminal residues of the mature native Alt from A . hydrophila matched with the DNA-derived aa sequence of the alt gene expressed in E . coli starting at position 19, which was leucine . The first 18aa residues of the Alt represented a putative signal sequence with alanine at its carboxy terminus . A BLAST search of the entire database showed 45-51% identity of the Alt, starting at position 158 with the carboxy half of the phospholipase C (PLC) and lipase from A . hydrophila; however, the purified Alt had no lipase/PLC activity . The alt gene was hyperexpressed using gene fusion expression vector systems, and the recombinant Alt exhibited a size of 35-40 kDa . The pure recombinant Alt elongated Chinese hamster ovary cells and elicited fluid secretion in rats ligated intestinal loops, indicating its enterotoxicity . Immunization of mice with recombinant Alt resulted in a reduced fluid secretory response when challenged with Aeromonas . The biological activity of the recombinant Alt in E . coli was about 10-fold less, compared to native Alt from Aeromonas, indicating differential processing of the toxin . The antibodies to native Alt neutralized the biological activity of the recombinant toxin, and these antibodies reacted with the same specificity to the native and recombinant Alt in immunoblots . The role of cyclic adenosine monophosphate and prostaglandins in causing a fluid secretory response by Alt also was demonstrated.

Gene, 1996 Oct 10, 175(1-2), 133 - 6
Cloning, characterization and expression of the recA gene of Aeromonas salmonicida; Umelo E et al.; The Aeromonas salmonicida A449 recA gene has been cloned, sequenced and expressed in vitro . The predicted amino acid sequence of A . salmonicida RecA was determined and, when compared to other RecA, was found to possess a number of domains identical to those characterized in Escherichia coli RecA . The A . salmonicida recA was mobilized into an E . coli recA mutant strain and was shown to allow increased survival in the presence of the chemical mutagen MMS and after ultraviolet (UV) irradiation . The A . salmonicida recA also possesses a potential regulatory SOS box in the DNA 5' of the gene . The rate of A . salmonicida-mediated recombination in E . coli was increased by exposure to UV light, which suggests that SOS induction in A . salmonicida parallels that of E . coli.

Gene, 1996 Oct 10, 175(1-2), 127 - 31
An Aeromonas salmonicida gene required for the establishment of infection in rainbow trout (Oncorhynchus mykiss); Noonan B et al.; The asoB gene of Aeromonas salmonicida is located approximately 9 kb downstream of the structural gene (vapA) for the surface layer (A-layer) . The nucleotide sequence of asoB was determined and found to encode a putative polytopic cytoplasmic membrane protein which exhibited homology to a number of bacterial transport proteins . Allele exchange mutagenesis of asoB resulted in a mutant (A449-D) which was avirulent when administered by bath immersion . However, when administered by intraperitoneal injection, A449-D is as lethal as wild type . Characterization of the phenotype of A449-D showed that there were pleiotropic effects on VapA secretion, haemolysis and outer membrane protein composition . Mobilization of cloned asoB on a broad-host-range plasmid into A449-D resulted in the complementation of VapA translocation, haemolytic activity and virulence.

FEMS Immunol Med Microbiol, 1996 Oct, 15(4), 233 - 41
Measurement of virulence of aeromonads using a suckling mouse model of infection; Wong CY et al.; Virulent and avirulent strains of Aeromonas spp . were identified and virulence quantified using an animal model . Virulence was measured by determining a 50% lethal dose (LD50) 43 h after oral administration of live bacteria . The LD50 of virulent Aeromonas isolates ranged from log10 7.53 (mean) organisms to log10 8.88 (mean) . Some isolates were avirulent in this model . Detection of cytotoxic activity in culture supernatants correlated with virulence (Fisher exact test, P = 0.0029) . There was no correlation between LD50 and the source of the isolate, beta-haemolysis or lipopolysaccharide (LPS) banding profile on SDS-PAGE . In this animal model, virulence was multifactorial in that: (i) bacterial multiplication in the gut was associated with fatal infection; (ii) the increase in bacterial numbers in the gut of mice administered a lethal dose of bacteria was accompanied by accumulation of fluid; and (iii) there was evidence of extraintestinal spread of infection . Protection of suckling mice by rabbit antiserum to Aeromonas cell envelopes was observed.

Carbohydr Res, 1996 Sep 23, 291, 165 - 74
Structural studies of the O-antigenic polysaccharide from an Aeromonas caviae strain; Linnerborg M et al.; The structure of the O-antigenic polysaccharide from a strain of Aeromonas caviae, isolated from the stools of a patient with diarrhoea, has been investigated . Sugar analysis, methylation analyses, and a uronic acid degradation together with NMR spectroscopy were the principal methods used . The sequence of the sugar residues could be determined by NOESY and HMBC experiments . It is concluded that the polysaccharide is composed of pentasaccharide repeating units with the following structure: {sequence: see text}

J Antimicrob Chemother, 1996 Sep, 38(3), 435 - 41
Expression of Aeromonas caviae bla genes in Escherichia coli; Sayeed S et al.; An isolate of Aeromonas caviae 035 carried a 55.5 kb self-transferable plasmid . Transfer of the plasmid to Escherichia coli K12 resulted in the expression of a TEM-like beta-lactamase that was not expressed in parental A . caviae . The bla gene sequence was detectable by DNA hybridization and PCR amplification of the plasmid when extracted from parental A . caviae or from E . coli K12 transconjugants . Sequence analysis of the bla genes revealed in each case an 858 bp open reading frame, differing from the TEM-1 sequence by five nucleotide substitutions . Only one of these resulted in amino acid substitution (at position 162 serine-->arginine) . The sequence most closely resembles that of TEM-12.

Shock, 1996 Sep, 6(3), 206 - 12
The cardiopulmonary, eicosanoid, and tissue microanatomic effects of fluconazole during graded bacteremia; Salartash K et al.; Imidazole compounds have been shown to be beneficial in systemic sepsis and inflammation . The purpose of this study was to delineate the effects of fluconazole on systemic hemodynamics and on microanatomy of the heart, lung, liver, and kidney parenchyma of swine during graded bacteremia . Eighteen adult swine were studied in three groups: 1), anesthesia control; 2), septic control (Aeromonas hydrophila, 10(9)/mL, infused i.v . for 4 h); 3) fluconazole (fluconazole, 30 mg/kg i.v., followed by A . hydrophila infusion) . After 4 h of graded bacteremia, autopsy was performed . Compared with the septic control group, cardiac index, oxygen delivery, and oxygen consumption were reduced significantly after fluconazole pretreatment, and mixed venous hemoglobin oxygen saturation (SVO2) and oxygen extraction were increased . Plasma thromboxane A2 and leukotriene levels were not affected by fluconazole . Computerized digital image analysis of the liver, heart, and kidney specimens revealed no statistically significant differences between the septic control group and fluconazole-pretreated animals . In the lung specimens, preinfusion of fluconazole decreased alveolar wall thickness in septic swine (anesthesia control group: 8.15 x 10(-3) +/- 1.3 x 10(-3)mm versus septic control group: 9.9 x 10(-3) +/- 1.3 x 10(-4) versus fluconazole group: 6.8 x 10(-3) +/- 1.6 x 10(-3); p < or = .05) . Fluconazole pretreatment before graded bacteremia has no beneficial effect on cardiopulmonary performance or septic tissue edema of the heart, kidney, or liver . Tissue oxygen metabolism might be down-regulated by fluconazole . However, preinfusion of fluconazole appears to normalize the sepsis-induced increase in pulmonary alveolar wall thickness . The net significance of these changes on clinical outcome is not clear from these data.

FEMS Microbiol Lett, 1996 Sep 1, 142(2-3), 185 - 9
The role of the capsular polysaccharide of Aeromonas salmonicida in the adherence and invasion of fish cell lines; Merino S et al.; The ability of several Aeromonas salmonicida strains grown under different conditions (capsulated and non-capsulated) to adhere to and invade two fish cell lines was compared . The level of adherence was slightly higher when the strains were grown under conditions promoting capsule formation than when the same strains were grown under conditions which did not promote capsule formation . However, the most significant difference among the wild-type strains grown under conditions promoting capsule formation was the ability to invade fish cell lines, which was significantly higher than when the same strains were grown under conditions which did not promote capsule formation . From these results we conclude that the capsular polysaccharide, in these strains, is an important factor for intracellular invasion.

J Appl Bacteriol, 1996 Sep, 81(3), 309 - 18
Survival of cells and DNA of Aeromonas salmonicida released into aquatic microcosms; Deere D et al.; The survival of the bacterial fish pathogen Aeromonas salmonicida, and persistence of its DNA, were monitored in aquatic microcosms using selective culture and most probable number PCR . Bacterial cells and naked DNA were released into natural non-sterile microcosms consisting of lake sediment overlayered with lake water . Two different types of surface sediment were used . One was sandy in character, taken from the shoreline whilst the other was a littoral loamy surface mud . Inoculated cells and naked DNA became undetectable from water overlayers within 4 weeks of release . Colony counts of Aer . salmonicida declined below detectable limits after 4 weeks in loamy sediment or 7 weeks in sandy sediment; however, naked DNA and DNA from released cells remained detectable for more than 13 weeks.

Appl Environ Microbiol, 1996 Sep, 62(9), 3544 - 7
Differential media for quantitative recovery of waterborne Aeromonas hydrophila; Handfield M et al.; Because of the ubiquity of Aeromonas spp., their prevalence in drinking water, and the increasing number of reports on Aeromonas sp.-related infections, a standard method for routine and quantitative recovery had to be defined . On the basis of a survey of 10 media for recovery analysis and subsequent differentiation assays in mixed cultures, we conclude that ampicillin-dextrin agar performed the best for the recovery of Aeromonas spp . in drinking water and the differentiation by simple criteria of that genus from other common waterborne bacteria.

Appl Environ Microbiol, 1996 Sep, 62(9), 3459 - 61
Aeromonas hydrophila isolated from food and drinking water: hemagglutination, hemolysis, and cytotoxicity for a human intestinal cell line (HT-29); Handfield M et al.; Aeromonas hydrophila isolated from food and drinking water was tested for pathogenicity by studying its hemolysis, hemagglutination, and cytotoxicity . Hemolysis, tested on erythrocytes from six different species, was more frequently seen with water isolates (64%) than with food isolates (48%) . Hemagglutination was more frequently encountered with food isolates (92%) than with water isolates (73%) . Cytotoxicity, evaluated on seven cell lines, was frequently observed with food isolates (92%) and with water isolates (73%) . Heat treatment (56 degrees C for 10 min) of culture supernatant fluids inhibited the toxicity of some but not all toxin-producing isolates . Our results suggest that the human intestinal cell line HT-29 could be a useful complement for testing A . hydrophila exotoxins and for studying the enteropathogenicity of this species for humans.

Infect Immun, 1996 Sep, 64(9), 3863 - 9
A live (delta aroA) Aeromonas salmonicida vaccine for furunculosis preferentially stimulates T-cell responses relative to B-cell responses in rainbow trout (Oncorhynchus mykiss); Marsden MJ et al.; We have previously described (L . M . Vaughan, P . R . Smith, and T . J . Foster, Infect . Immun . 61:2172-2181, 1993) the construction of a kanamycin-resistant aromatic-dependent mutant of Aeromonas salmonicida, the causative agent of furunculosis, and its use as a live vaccine . Here we describe the construction of an unmarked aroA deletion mutant and examine the nature and magnitude of immune responses in rainbow trout (Oncorhynchus mykiss) to this vaccine strain . Good proliferative and antibody responses were elicited by using a range of vaccine doses from 2 x 10(6) to 2 x 10(9) live bacteria per fish, and a clear vaccine dose effect was apparent . A significant positive effect of using live bacteria to prime for lymphocyte proliferation and antibody production was apparent . However, the problem of directly comparing the vaccine doses of live and killed bacterial preparations is discussed, since some replication of live bacteria in vivo is expected . Most importantly, the live vaccine preferentially stimulated enhanced T-cell responsiveness, as evidenced by significantly greater increases in T-cell proliferation than in B-cell proliferation, compared with responses by the respective cell populations from fish given a killed vaccine . The manner in which live vaccines elicit strong cell-mediated immune responses and the relevance to fish vaccine design are discussed.

Int J Food Microbiol, 1996 Aug, 31(1-3), 121 - 31
Incidence and toxigenicity of Aeromonas hydrophila in seafood; Tsai GJ et al.; Three selective media, Oxoid Aeromonas agar (OA), blood ampicillin agar (BA) and starch ampicillin agar (SA) were used to evaluate the presence of Aeromonas hydrophila in 66 samples of oyster, shrimp, fish and surimi products . Oyster had the highest incidence, with 50% positive, whilst no A . hydrophila was found in the surimi . Of the three selective media, BA displayed the highest recovery rate of A . hydrophila from seafood . Forty-eight isolates from this survey were tested for their capability to produce hemolysin and cytotoxin . Hemolysin was produced by 79.2% of the isolates and cytotoxin was produced by 91.7% of the isolates in brain heart infusion broth . One of the toxin-producing isolates from oyster, strain 8-169, was further tested for growth and toxin production in oyster, shrimp and fish at various temperatures . This particular isolate grew best and had highest toxin production in oyster . Hemolysin and cytotoxin were produced earlier at 28 degrees C than at 37 degrees C, and titers of hemolysin were also higher at 28 degrees C . At 5 degrees C, it was able to grow and produce hemolysin in oyster.

J Trauma, 1996 Aug, 41(2), 291 - 6; discussion 296-7
Platelet activating factor mediates cardiopulmonary dysfunction during graded bacteremic shock; Woolley DS et al.; OBJECTIVE: To determine whether or not platelet activating factor (PAF) is a necessary mediator of cardiovascular dysfunction during graded bacteremia, and to identify PAF interactions with eicosanoids and tumor necrosis factor-alpha (TNF-alpha) . METHODS: Seventeen anesthetized, hemodynamically monitored adult swine were studied for 4 hours in three groups . Group 1 (ANES, n = 5) were anesthesia controls; group 2 (septic control, SC, n = 6) received intravenous Aeromonas hydrophila (109/mL) at rates incrementally increased from 0.2 to 4.0 mL/ kg/h; group 3 (WEB, n = 6) received the PAF receptor antagonist WEB 2086, 3.0 mg/kg intravenously, then A . hydrophila . Cardiopulmonary parameters and plasma thromboxane B2 (TXB2), prostaglandin 6-keto F1 alpha (PGI2), leukotriene B4 (LTB4), leukotrienes C4D4E4 (LTC4D4E4), and TNF-alpha were measured hourly . Statistical analysis was carried out using two-way analysis of variance (ANOVA) for repeated measurements, Dunnett's t test, and Student's t test, where appropriate . Statistical significance was determined at the 95% confidence interval . Values are presented as the mean +/- SEM . RESULTS: Pulmonary arterial pressure, pulmonary capillary wedge pressure, central venous pressure heart rate, VO2 and O2ER decreased significantly after WEB 2086 infusion, compared with SC, and mean arterial pressure, systemic vascular resistance index, stroke volume index, and left ventricular stroke work index increased . Arterial pH decreased significantly in SC animals, but was maintained at normal levels during bacteremia in the WEB group . Differences between WEB and SC for cardiac index, pulmonary vascular resistance index, right ventricular stroke work index, PaO2, SaO2, and PcO2, were not significant . The addition of WEB 2086 significantly decreased plasma levels of TXB2, PGI2, LTB4, and TNF-alpha compared with the SC group . LTC4D4E4 was decreased in WEB compared with SC animals, in which LTC4D4E4 increased during graded bacteremia . CONCLUSIONS: PAF is necessary to the development of systemic vasodilation and hypotension, pulmonary hypertension, decreased stroke volume, metabolic acidosis, and increased oxygen uptake during graded bacteremia . PAF-induced eicosanoid and cytokine release may be involved.

Curr Microbiol, 1996 Aug, 33(2), 104 - 8
Characterization of Aeromonas hydrophila strains of clinical, animal, and environmental origin expressing the O:34 antigen; Khashe S et al.; A collection of Aeromonas strains of different origins were characterized for isolates expressing the O:34 somatic antigen . Of over 200 strains tested, approximately 14% belonged to serogroup O:34 with >85% of these strains identified as A . hydrophila regardless of source . A subset of 14 A . hydrophila O:34 strains were further analyzed for a number of structural and pathogenic features . Most O:34 strains expressed similar whole-cell protein profiles with regards to minor bands, but major band differences were noted in outer membrane proteins (OMPs) migrating between the 31K and 58K region . OMP profiles could be subdivided into three distinct patterns . All O:34 strains expressed a heterogeneous O polysaccharide side chain profile in their lipopolysaccharide (LPS), although some variation in the electrophoretic migration of lower and higher molecular weight LPS bands was noted . Polyclonal antisera raised against a 45-K OMP-associated protein of one O:34 strain (AH-195) reacted in immunoblot assays with a major 43 to 46-K OMP in 11 of 14 (79%) O:34 strains tested . Most O:34 strains (69%) were found to be pathogenic in mice with LD-50 values (i.p.) of <1.0 x 10(7) CFU; pathogenicity appeared to correlate best with elevated protease activity . The collective results suggest significant differences in both structural and pathogenic properties between some members of the O:34 group originating from human and nonhuman (fish, water) sources.

Microb Drug Resist, 1996 Summer, 2(2), 253 - 6
Overproduction and purification of the Aeromonas hydrophila CphA metallo-beta-lactamase expressed in Escherichia coli; Hernandez Villadares M et al.; The Aeromonas hydrophila CphA metallo-beta-lactamase was overexpressed in a soluble secreted form in Escherichia coli using a T7 RNA polymerase-based expression system, and a simple protocol based on a single cation-exchange chromatographic step was developed, which is suitable for rapid purification of the overexpressed enzyme from E . coli lysates . A yield of up to 30 micrograms of purified enzyme per milliliter of culture was obtained . The purified enzyme preparation showed properties identical to those previously reported in the literature.

Microb Drug Resist, 1996 Summer, 2(2), 245 - 52
The Aeromonas metallo-beta-lactamases: genetics, enzymology, and contribution to drug resistance; Rossolini GM et al.; Aeromonads are environmental microorganisms that can be responsible for both human and animal infections . Individual Aeromonas strains can produce up to three different, inducible, chromosomally encoded beta-lactamases, including a group 1 molecular class C cephalosporinase, a group 2d molecular class D penicillinase, and a group 3 molecular class B metallo-beta-lactamase, which contribute to beta-lactam resistance in members of this genus . Among these enzymes, the metallo-beta-lactamases are clinically relevant because of their ability to hydrolyze carbapenem antibiotics, and also represent a relevant investigational model for studying molecular class B beta-lactamases because of their unique enzymological behavior . An overview on the distribution, genetics, and enzymology of these enzymes is reported, and the contribution of these enzymes to microbial drug resistance is also discussed.

Microb Pathog, 1996 Jul, 21(1), 23 - 34
Characterization of a type IV bundle-forming pilus (SFP) from a gastroenteritis-associated strain of Aeromonas veronii biovar sobria; Kirov SM et al.; The colonization mechanisms of enteropathogenic Aeromonas strains are poorly characterized, but recent studies indicate that some filamentous structures are intestinal adhesins . This study describes the purification and characterization of a long, flexible pilus from a gastroenteritis-associated strain of Aeromonas veronii biovar sobria . SDS-PAGE analysis (various conditions) of pili preparations yielded a pilin protein band of approximately 21 kDa . Its N-terminal amino acid sequence was unambiguous and homologous with those of type IV pilins . Immunogold electron microscopy with rabbit antisera produced against this pilin protein (SFP) decorated single pili and rope-like bundles of pili on the bacterial surface . These were seen more frequently on strains grown at 22 degrees C compared with 37 degrees C and in liquid rather than on solid medium . SFP was not detected on any of 104 strains of Aeromonas (different species and sources) from our culture collection, although morphologically similar structures were seen on a number of these strains . This finding and differences among other published amino acid sequences show that Aeromonas type IV pili are antigenically diverse . Bundle-forming type IV 'class B' pili are important in the virulence of other enteropathogenic bacteria . The N-terminal amino acid sequence of the Aeromonas SFP, however, showed closer homology to the type IV 'class A' pilins . Studies are in progress to investigate the role of SFP in Aeromonas virulence.

Biosci Biotechnol Biochem, 1996 Jul, 60(7), 1195 - 7
Expression of the chitinase III gene of Aeromonas sp . no . 10S-24 in Escherichia coli; Ueda M et al.; The chitinase III gene of Aeromonas sp . No . 10S-24 was expressed in Escherichia coli . Production of chitinase III by E . coli was 3-fold higher than that of chitinases in the culture supernatant of Aeromonas sp . The enzyme from E . coli was purified and characterized . The molecular weight of the chitinase III from E . coli was estimated by SDS-polyacrylamide gel electrophoresis (SDS-PAGE) to be 55,000 . This agreed with the calculated molecular weight of the mature chitinase III (54,111) . However, it was different from that of the enzyme from Aeromonas sp . It showed that the chitinase III from Aeromonas sp . had an additional sugar chain, causing the higher molecular weight . Chitinase III from E . coli had almost the same enzymatic properties as chitinase III from Aeromonas sp., but the specific activity of the chitinase III from E . coli is slightly higher than that of the native chitinase III . Both enzymes hydrolyzed chitosan (80% deacetylated) well.

FEMS Microbiol Rev, 1996 Jul, 18(4), 319 - 44
Bacterial aminopeptidases: properties and functions; Gonzales T et al.; Aminopeptidases are exopeptidases that selectively release N-terminal amino acid residues from polypeptides and proteins . Bacteria display several aminopeptidasic activities which may be localised in the cytoplasm, on membranes, associated with the cell envelope or secreted into the extracellular media . Studies on the bacterial aminopeptide system have been carried out over the past three decades and are significant in fundamental and biotechnological domains . At present, about one hundred bacterial aminopeptidases have been purified and biochemically studied . About forty genes encoding aminopeptidases have also been cloned and characterised . Recently, the three-dimensional structure of two aminopeptidases, the methionine aminopeptidase from Escherichia coli and the leucine aminopeptidase from Aeromonas proteolytica, have been elucidated by crystallographic studies . Most of the quoted studies demonstrate that bacterial aminopeptidases generally show Michaelis-Menten kinetics and can be placed into either of two categories based on their substrate specificity: broad or narrow . These enzymes can also be classified by another criterium based on their catalytic mechanism: metallo-, cysteine- and serine-aminopeptidases, the former type being predominant in bacteria . Aminopeptidases play a role in several important physiological processes . It is noteworthy that some of them take part in the catabolism of exogenously supplied peptides and are necessary for the final steps of protein turnover . In addition, they are involved in some specific functions, such as the cleavage of N-terminal methionine from newly synthesised peptide chains (methionine aminopeptidases), the stabilisation of multicopy ColE1 based plasmids (aminopeptidase A) and the pyroglutamyl aminopeptidase (Pcp) present in many bacteria and responsible for the cleavage of the N-terminal pyroglutamate.

J Bacteriol, 1996 Jul, 178(13), 3926 - 33
Cloning, sequencing, and characterization of the nucH gene encoding an extracellular nuclease from Aeromonas hydrophila JMP636; Dodd HN et al.; An Escherichia coli clone expressing activity on DNase agar was obtained by cloning chromosomal DNA of Aeromonas hydrophila JMP636 into plasmid pUC19 . Examination (of the clone's nuclease activity on a sodium dodecyl sulfate (SDS)-polyacrylamide gel containing DNA as a substrate revealed an activity band at approximately 100 kDa . Subsequently, subcloning localized the gene, designated nucH, to a 3.6-kb DNA fragment (pJP9521) . Southern blotting of the nucH gene against chromosomal DNA of JMP636 confirmed that it had originated from this strain and demonstrated that it was present in a single copy, although additional faint bands were also detected . Analysis of the subclone using in vivo transcription and translation revealed only a single polypeptide of approximately 110 kDa . Sequencing of pJP9521 predicted an open reading frame of 3,213 bp encoding a protein of 1,070 amino acids and having a molecular mass of 114 kDa . Comparison of the deduced nucleotide sequence and the NucH predicted protein sequence with relevant databases indicated that no known homologs have previously been identified . A signal sequence was predicted from these data, and cellular fractionation of a nucH clone in E . coli indicated that the protein was able to be processed to the periplasm . An activity similar in size was detected in an extracellular protein sample of JMP636, while inactivation of the nucH gene resulted in loss of this activity band . By native SDS-polyacrylamide gel electrophoresis, NucH substrate specificity, cofactor requirements, and sensitivity to denaturing agents were assessed.

Jpn J Med Sci Biol, 1996 Jun, 49(3), 95 - 102
Acid sensitivity as affected by physico-chemical stresses in Aeromonas hydrophila; Parvis A et al.; This work focuses mainly on the effect of NaCl along with other mono and divalent anions and cations at pH 4 on survival and virulence properties of Aeromonas hydrophila . To find the optimum stress condition, effects of several other physical factors on NaCl induction were also assayed . A . hydrophila collected from International Center for Diarrheal Disease Research, Bangladesh (ICDDR,B) was found to be more sensitive to pH 4.0 when grown in media containing 200 mM or more salt . Induction of acid sensitivity was rapidly gained in NaCl-supplemented broth at 37 C . There was only slight sensitization after 5 min, but a marked effect was observed within 30 min . Uninduced A . hydrophila gave an average of 40% survival after exposure to pH 4.0 for 5 min . However, NaCl-induced cells of this organism reduced the survival to a great extent having an average of 0.06% . Either increase in salt concentration (100 mM through 400 mM) or decrease (50 mM) resulted in decrease in percent survival when exposed to gradually increased concentrations of salt . The most effective dose for induction was 400 mM NaCl salt . NaCl-induction was found to be more pronounced in log-phase organisms . All other monovalent and divalent anions and cations tested were almost as effective as NaCl except KCl.

An Esp Pediatr, 1996 Jun, 44(6), 548 - 52
{Gastroenteritis due to Aeromonas in pediatrics}; Gomez Campdera J et al.; OBJECTIVE: In recent years the incidence of gastroenteritis due to Aeromonas spp has increased significantly . The purpose of this study was to investigate the etiology and clinical manifestations of this disease . PATIENTS AND METHODS: In the period between 1986 and 1992, we found Aeromonas spp in seventy patients (88 samples) between 0 and 16 years of age . We were able to analyze 53 of these samples . RESULTS: Of all of the patients, 66% were males and 58.5% were younger than two years old . We found a pattern in the disease with 83% of the cases occurring in summer and autumn . The infection was polymicrobial in 43% of the patients . The clinical manifestations most often found were fever (71%), vomiting (62.5%) and abdominal pain (9.4%) . Diarrhea was watery in 71.7% and 64% of the cases lasted less than a week . The number of stools was 5 to 10 per day in 58% of the patients . Forty patients (75.5%) required hospitalization, with the stay being longer than 10 days in 25% . There were 30% of the patients that required antibiotic therapy, mostly due to concomitant infections and not due to the diarrheic episodes, with all of them having a satisfactory evolution.

Zentralbl Bakteriol, 1996 Jun, 284(1), 32 - 46
A biochemical protocol for the differentiation of current genomospecies of Aeromonas; Oakey HJ et al.; A data file consisting of 40 biochemical and physiological tests for the differentiation of aeromonads was constructed based upon existing published data from various geographical locations and laboratories . The data file covers all the current genomospecies (or hybridisation groups) of Aeromonas and is therefore applicable to bacteriologists from a wide variety of fields . The protocol derived from the data file was adapted for use with a semi-interactive computer identification program . This program was challenged with the type strains of all the currently recognised genomospecies and each genomospecies was correctly identified, with only one strain (ATCC 7966, HG1) having an identification probability of less than 90% . The program was also tested with environmental and clinical isolates and again identifications were achieved with high probabilities . This protocol is designed for use on presumptive isolates of Aeromonas spp . and can be carried out in routine laboratories not equipped to perform the complex DNA hybridisation techniques which are currently used for the differentiation of genomospecies of Aeromonas.

Microb Pathog, 1996 Jun, 20(6), 325 - 33
The role of the O-antigen lipopolysaccharide on the colonization in vivo of the germfree chicken gut by Aeromonas hydrophila serogroup O:34; Merino S et al.; We compared the ability of different Aeromonas hydrophila strains from serogroup O:34 grown at different temperatures to colonize in vivo the germfree chicken gut . We found a good colonization when the strains were grown at 20 degrees C but not when they were grown at 37 degrees C . We previously described that these strains were able to form the O-antigen lipopolysaccharide (LPS) when they grow at low temperature but not at high temperature . We also obtained by transposon mutagenesis mutants only devoid of the O-antigen LPS (rfb mutants), and showed that they were unable to colonize the germfree chicken gut . All these results prompted us to conclude that the O-antigen LPS, in these strains, is a main factor for colonization in this animal model system.

Appl Environ Microbiol, 1996 Jun, 62(6), 1885 - 8
Differential susceptibility of aeromonads and coliforms to cefsulodin; Alonso JL et al.; Cefsulodin was evaluated as a potential selective agent for aeromonads . Resistance of Aeromonas and coliform isolates was determined by using a standard disk diffusion technique . A total of 119 Aeromonas and 78 coliform strains were isolated . For 102 of 130 {corrected} Aeromonas isolates (environmental and reference strains), the MIC of cefsulodin was < 8 micrograms/ml . Results of MIC tests by the agar dilution method showed that a concentration of cefsulodin of 10 micrograms/ml or less inhibited the growth of 96% of isolates . In comparison, for 81 of 94 coliform isolates (environmental and reference strains), the MIC of cefsulodin was > 32 micrograms/ml . Because cefsulodin suppresses growth of Aeromonas and other oxidase-positive organisms, total coliform (TC) and Escherichia coli counts on Chromocult Coliform agar (CC agar) without cefsulodin and on CC agar with 10 mg of cefsulodin per liter (CC-CFS) were compared . Variance analysis of data from 14 sewage-polluted irrigation water specimens did not demonstrate any statistically significant difference in the enumeration of E . coli with CC and CC-CFS media . On average, the CC agar recovered 2.46 times as many TCs as CC-CFS . However, Aeromonas colonies made up an average of 58.6% of the TC counts on CC agar . Because no Aeromonas spp . were recovered on CC-CFS, background interference was eliminated and the counts that were obtained reflected more accurately the number of TCs . Results of this study suggest that cefsulodin may be a useful selective agent against Aeromonas spp . which should be included in coliform chromogenic media when high levels of accompanying flora are expected.

FEMS Microbiol Lett, 1996 Jun 1, 139(2-3), 97 - 101
The O:34-antigen lipopolysaccharide as an adhesin in Aeromonas hydrophila; Merino S et al.; We compared the ability of different Aeromonas hydrophila strains from serogroup O:34 grown at different temperatures to adhere to Hep-2 cells . We found a high level of adhesion when the strains were grown at 20 degrees C but not when they were grown at 37 degrees C . We previously described that these strains were able to form the O-antigen lipopolysaccharide when they grow at low temperature but not at high temperature . We also obtained by transposon mutagenesis mutants only devoid of the O-antigen lipopolysaccharide (rfb mutants), and they showed significantly lower levels of adhesion to Hep-2 cells than the smooth strains . All these results prompted us to conclude that the O-antigen LPS, in these strains, is an important adhesin.

J Med Microbiol, 1996 Jun, 44(6), 434 - 7
Biochemical characterisation, enteropathogenicity and antimicrobial resistance plasmids of clinical and environmental Aeromonas isolates; Chaudhury A et al.; One hundred and eight strains of Aeromonas from clinical and environmental samples were speciated . Seven species were identified, the most prevalent of which was A . hydrophila . Experimental studies in an animal model with 36 representative strains of different species revealed that all strains could cause significant fluid accumulation in rabbit ileal loops . Of 107 strains showing single or multiple antimicrobial resistance, the highest incidence of resistance was shown for beta-lactam antibiotics other than cefotaxime . Transferable resistance plasmids, encoding resistance to ampicillin, cephalexin, cefoxitin, erythromycin and furazolidone, either alone or in combination, were detected in 35 strains . A further proportion of strains could be cured of one or more resistance markers, including resistance to nalidixic acid, and this was accompanied by the loss of plasmid DNA . The plasmids ranged in size between 85.6 and > 1 50 kb.

Curr Microbiol, 1996 May, 32(5), 239 - 45
Diarrheal and environmental isolates of Aeromonas spp . produce a toxin similar to Shiga-like toxin 1; Haque QM et al.; Diarrheal and environmental isolates of 39 strains of Aeromonas spp . were studied for detection of virulence factors . Although these 39 strains did not produce either heat-labile or heat-stable enterotoxins, culture filtrates of 31 strains produced cytopathic effects on Vero cells . Among these, culture filtrates of three strains of Aeromonas hydrophila and one strain of Aeromonas caviae could be neutralized by Escherichia coli O157:H7 Shiga-like toxin 1 antiserum . A single band of plasmid DNA of 2.14 kbp was isolated from these strains of Aeromonas spp . and E . coli O157:H7, which could be amplified by the polymerase chain reaction (PCR), employing oligonucleotide primers from the Shiga-like toxin 1 (SLT1) gene of E . coli O157:H7 . E . coli HB 101 cells when transformed with the same plasmid showed cytopathic effects on Vero cells, which indicates that the SLT 1 homolog gene(s) of Aeromonas spp . is plasmid encoded . These results suggest that Aeromonas spp . may also produce Shiga-like toxin 1, or at least a cytotoxin with some homology with the Shiga-like toxin 1 of E . coli O157:H7.

Vet Immunol Immunopathol, 1996 May, 51(1-2), 189 - 200
Multiple regulation of carp (Cyprinus carpio L.) macrophages and neutrophilic granulocytes by serum factors: influence of infection with atypical Aeromonas salmonicida; Verburg-van Kemenade BM et al.; Normal carp serum contains inhibitory and stimulatory factors for macrophage and neutrophilic granulocyte respiratory burst activity . As stimulatory factors were only effective in combination with phorbol myristate actetate (PMA) activation, it is concluded that they are probably linked to protein kinase C activation . Both the stimulatory and inhibitory factors are heat stable . Macrophage- and neutrophilic granulocyte-enriched cell fractions from the pronephros of carp had high respiratory burst- and high bactericidal in vitro responses to virulent atypical Aeromonas salmonicida bacteria . Serum factors were inhibitory for the A . salmonicida induced respiratory burst activity . No change in inhibitory or stimulatory serum factors could be observed during a 12-day challenge experiment with A . salmonicida, or during a rechallenge of survivors from a previous sub-lethal infection . The sensitivity of macrophages and neutrophilic granulocytes to stimulation of respiratory burst activity by PMA was not significantly altered . Culture supernatants from PHA pre-treated lymphocytes stimulated the respiratory burst activity of macrophages and neutrophilic granulocytes suggesting that serum factors may partially be lymphocyte derived.

Intern Med, 1996 May, 35(5), 410 - 2
Fulminant pneumonia and sepsis due to Aeromonas hydrophila in an alcohol abuser; Takano Y et al.; A 69-year-old alcoholic man with pneumonia and sepsis due to Aeromonas hydrophila is presented . He died of suffocation by a copious amount of hemoptysis six hours after his first symptoms of abdominal pain, diarrhea and dyspnea . Aeromonas hydrophila was isolated from blood and bronchial secretion . A fulminant form of pneumonia could develop in patients with predisposing underlying conditions such as alcoholism with chronic hepatitis and diabetes mellitus . Aeromonas hydrophila pneumonia may be characterized by hemoptysis and rapid clinical deterioration with a high mortality rate.

Eur J Clin Microbiol Infect Dis, 1996 May, 15(5), 420 - 2
Prevention of suicide phenomenon in aeromonads; Guimaraes MS et al.; Clinical isolates of Aeromonas (13 Aeromonas caviae), 8 Aeromonas hydrophila, 3 Aeromonas spp., and 2 Aeromonas media recovered from diarrheal feces of children were submitted to the suicide phenomenon test and investigated at intervals of 24 h for up to 120 h . The same isolates were also stimulated by repeated passages in broth for ten days before the test . After the bacterial stimulus, a decreases in the number of aeromonads with suicidal capacity was observed . The suicide phenomenon was expressed after 72 h of incubation in only some isolates . The results show that the suicide phenomenon can be prevented by stimulation of bacterial metabolism.

Antimicrob Agents Chemother, 1996 May, 40(5), 1260 - 2
Increasing antibiotic resistance in clinical isolates of Aeromonas strains in Taiwan; Ko WC et al.; A total of 234 clinical isolates of Aeromonas, primarily A . hydrophila, were collected for the present study . Most were isolates from blood . By the agar dilution method, more than 90% of the Aeromonas strains were found to be susceptible to moxalactam, ceftazidime, cefepime, aztreonam, imipenem, amikacin, and fluoroquinolones, but they were more resistant to tetracycline, trimethoprim-sulfamethoxazole, some extended-spectrum cephalosporins, and aminoglycosides than strains from the United States and Australia.

Am J Kidney Dis, 1996 May, 27(5), 733 - 5
Fatal Aeromonas hydrophila bacteremia in a hemodialysis patient treated with deferoxamine; Lin SH et al.; A 49-year-old woman undergoing long-term hemodialysis and treated with deferoxamine (DFO) 1.5 g twice weekly for aluminum bone disease developed fever and bilateral calf pain caused by myonecrosis with gas gangrene . She had a rapidly fatal outcome . The cultures of blood and aspirates from both calf muscles demonstrated Aeromonas hydrophila . No obvious entry point could be traced . The in vitro growth of the patient's strain was found to be stimulated by the deferoxamine-iron complex in an iron-deprived medium . It is suggested that high-dose DFO therapy in this patient was responsible for promoting a bacterial infection by this microorganism.

FEBS Lett, 1996 Apr 22, 384(3), 269 - 72
Characterisation of the heptameric pore-forming complex of the Aeromonas toxin aerolysin using MALDI-TOF mass spectrometry; Moniatte M et al.; Aerolysin, a virulence factor secreted by Aeromonas hydrophila, is representative of a group of beta-sheet toxins that must form stable homooligomers in order to be able to insert into biological membranes and generate channels . Electron microscopy and image analysis of two-dimensional membrane crystals had previously revealed a structure with 7-fold symmetry suggesting that aerolysin forms heptameric oligomers {Wilmsen et al . (1992) EMBO J . 11, 2457-2463} . However, this unusual molecularity of the channel remained to be confirmed by an independent method since low-resolution electron crystallography had led to artefactual data for other pore-forming toxins . In this study, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) was used to measure the mass of the aerolysin oligomer preparation . A mass of 333 850 Da was measured, fitting very well with a heptameric complex (expected mass: 332 300 Da) . These results confirm the earlier evidence that the aerolysin oligomer is a heptamer and also show that MALDI-TOF mass spectrometry could be a valuable tool to study non-covalent association of proteins.

Eur J Biochem, 1996 Apr 15, 237(2), 393 - 8
The structure of the Aeromonas proteolytica aminopeptidase complexed with a hydroxamate inhibitor . Involvement in catalysis of Glu151 and two zinc ions of the co-catalytic unit; Chevrier B et al.; The structure of the complex of Aeromonas proteolytica aminopeptidase, a two-zinc exopeptidase, with the inhibitor p-iodo-D-phenylalanine hydroxamate has been determined by X-ray crystallography . Refinement of the structure, which includes 220 water molecules, using data at 0.80-0.23-nm resolution resulted in a crystallographic residual R value of 16% . The hydroxamate group adopts a planar conformation whereby the two oxygen atoms interact with the zinc ions . The N-hydroxyl group of the inhibitor is located between the two zinc ions, a position which is close to that occupied by a water molecule in the native structure . The carbonyl oxygen of the inhibitor binds to Zn1, which becomes pentacoordinated while Zn2 remains tetracoordinated, in contrast to the native protein where both zinc ions were shown to be tetracoordinated and structurally equivalent . Interactions of the carboxylate oxygens of Glu151 with the hydroxamate group play an important role in the stabilization of the complex.

Wei Sheng Wu Xue Bao, 1996 Apr, 36(2), 144 - 50
{Purification and characterization of S-layer protein from Aeromonas hydrophila}; Yan Y et al.; The regular surface protein array (S-layer) present on Aeromonas hydrophila J-1 was composed of a single species of protein of apparent molecular weight 51500 . This protein was extracted from whole cells by treatment with 0.2 mol/L glycine hydrocholoide (pH4.0) . The protein was purified by Sephadex G-200 gel filtration chromatography and an ion exchange chromatography on DEAE-cellulose . Amino acid composition analysis showed that the protein contained 36.8% hydrophobic amino acids . But the protein did not confer hydrophobicity to the cell surface when present as an intact S-layer by salt aggregation test . ELISA and immunoblotting with two different polyclonal antisera against surface exposed-(PM) and non-surface-exposed epitopes (PR) of the protein revealed that the sensitivity of PM was higher than that of PR . Antigenic diversity of the S-layer proteins from 20 bacterial samples was analysed by ELISA with PM and PF1 (polyclonal antiserum against Aeromonas hydrophila TF7 S-layer protein) . The S-layer proteins were distinguishable from the extracellular toxin of the homogeneous strains in antigenic and biochemical characterization and the S-layer proteins were one of the main protective antigens.

FEMS Microbiol Lett, 1996 Apr 1, 137(2-3), 193 - 200
Biochemical characterization of the carbapenem-hydrolyzing beta-lactamase AsbM1 from Aeromonas sobria AER 14M: a member of a novel subgroup of metallo-beta-lactamases; Yang Y et al.; AsbM1, a carbapenem-hydrolyzing beta-lactamase produced by Aeromonas sobria AER 14M, was purified chromatographically, with anion exchange chromatography performed in the absence of Zn2+ . The molecular mass of AsbM1 was approximately 34,000; the isoelectric point was 9.1 . AsbM1 had high hydrolytic specificity for carbapenems but low hydrolysis rates for penicillins and cephalosporins . AsbM1 was resistant to the commercially available beta-lactamase inhibitors but was inhibited by pCMB and the chelators EDTA and o-phenanthroline . Zinc, an activator for many metallo-beta-lactamases, inhibited AsbM1 with an IC50 of 8 microM . Analysis of the N-terminal sequence (27 amino acids) showed 26% similarity to the CphA metallo-beta-lactamase . Because of the high specificity for carbapenems and the sensitivity to inhibition by Zn2+, AsbM1 should be included in a new subgroup of metallo-beta-lactamases.

Int J Syst Bacteriol, 1996 Apr, 46(2), 572 - 80
High-resolution genotypic analysis of the genus Aeromonas by AFLP fingerprinting; Huys G et al.; We investigated the ability of a recently developed genomic fingerprinting technique, named AFLP, to differentiate the 14 currently defined DNA hybridization groups (HGs) in the genus Aeromonas . We also determined the taxonomic positions of the phenospecies Aeromonas allosaccharophila, Aeromonas encheleia, Aeromonas enteropelogenes, and Aeromonas ichthiosmia, which have not been assigned to HGs yet . A total of 98 Aeromonas type and reference strains were included in this study . For the AFLP analysis, the total genomic DNA of each strain was digested with restriction endonucleases ApaI and TaqI . Subsequently, restriction fragments were selectively amplified under high-stringency PCR conditions . The amplification products were electrophoretically separated on a polyacrylamide gel and visualized by autoradiography . Following high-resolution densitometric scanning of the resulting band patterns, AFLP data were further processed for a computer-assisted comparison . A numerical analysis of the digitized fingerprints revealed 13 AFLP clusters which, in general, clearly supported the current Aeromonas taxonomy derived from DNA homology data . In addition, our results indicated that there is significant genotypic heterogeneity in Aeromonas eucrenophila (HG6), which may lead to a further subdivision of this species . A . allosaccharophila and A . encheleia did not represent a separate AFLP cluster but were found to be genotypically related to HG8/10 and HG6, respectively . In addition, the results of the AFLP analysis also confirmed the phylogenetic findings that A . enteropelogenes and A . ichthiosmia are in fact identical to Aeromonas trota (HG13) and Aeromonas veronii (HG8/10), respectively . The results of this study clearly show that the AFLP technique is a valuable new high-resolution genotypic tool for classification of Aeromonas species and also emphasize that this powerful DNA fingerprinting method is important for bacterial taxonomy in general.

Appl Environ Microbiol, 1996 Apr, 62(4), 1167 - 70
Identification of Aeromonas hydrophila hybridization group 1 by PCR assays; Cascon A et al.; Synthetic oligonucleotide primers of 24 and 23 bases were used in a PCR assay to amplify a sequence of the lip gene, which encodes a thermostable extracellular lipase of Aeromonas hydrophila . A DNA fragment of approximately 760 bp was amplified from both sources, i.e., lysed A . hydrophila cells and isolated DNA . The amplified sequence was detected in ethidium bromide-stained agarose gels or by Southern blot analysis with an internal HindIII-BamHI 356-bp fragment as a hybridization probe . With A . hydrophila cells, the sensitivity of the PCR assay was < 10 CFU, and with the isolated target, the lower detection limit was 0.89 pg of DNA . Primer specificity for A . hydrophila was determined by the PCR assay with cells of 50 strains of bacteria, including most of the 14 currently recognized DNA hybridization groups of Aeromonas spp . as well as other human and environmental Aeromonas isolates . Detection of A . hydrophila by PCR amplification of DNA has great potential for rapid identification of this bacterium because it has proved to be highly specific.

J Appl Bacteriol, 1996 Apr, 80(4), 402 - 10
Differentiation of Aeromonas genomospecies using random amplified polymorphic DNA polymerase chain reaction (RAPD-PCR); Oakey HJ et al.; Random amplified polymorphic DNA polymerase chain reaction (RAPD-PCR) was used to investigate the differentiation of the genus Aeromonas at the genomospecies level . Of 20 primers evaluated, six produced profiles which contained multiple bands capable of differentiating the genomospecies . These six primers were also used in RAPD-PCR analyses of clinical and environmental isolates of the different genomospecies . In most cases, each strain gave a unique fingerprint, illustrating genetic heterogeneity at the genomospecies level . However, some homogeneity in fragment sizes was seen among strains within a genomospecies which was not apparent in strains from different genomospecies . This study therefore complements and supports the current classification of Aeromonas into genomospecies . These results also show that RAPD-PCR has the potential to differentiate between the genomospecies of Aeromonas.

J Bacteriol, 1996 Apr, 178(7), 2060 - 4
Identification of the catalytic triad of the lipase/acyltransferase from Aeromonas hydrophila; Brumlik MJ et al.; Aeromonas hydrophila secretes a lipolytic enzyme that has several properties in common with the mammalian enzyme lecithin-cholesterol acyltransferase . We have recently shown that it is a member of a newly described group of proteins that contain five similar blocks of sequence arranged in the same order in their primary structures (C . Upton and J . T . Buckley, Trends Biochem . Sci . 233:178-179, 1995) . Assuming that, like other lipases, these enzymes have a Ser-Asp-His catalytic triad, we used these blocks to predict which aspartic acid and histidine would be at the active site of the Aeromonas enzyme . Targeted residues were replaced with other amino acids by site-directed mutagenesis, and the effects on secretion and activity were assessed . Changing His-291 to asparagine completely abolished enzyme activity, although secretion by the bacteria was not affected . Only very small amounts of the D116N mutant appeared in the culture supernatant, likely because it is sensitive to periplasmic proteases it encounters en route . Assays of crude preparations containing this variant showed no detectable enzyme activity . We conclude that, together with Ser-16, which we have identified previously, Asp-116 and His-291 compose the catalytic triad of the enzyme.

FEMS Microbiol Lett, 1996 Mar 15, 137(1), 37 - 44
Study of the intergenic exeF-exeG region and its application as a simple preliminary test for Aeromonas spp; Karlyshev AV et al.; The exeF-exeG intergenic regions from different hybridization groups (HG) of Aeromonas were studied by PCR amplification using a single pair of primers . Six main classes of PCR products were identified according to size: 360 bp, 320 bp, 280 bp, 230-240 bp, 220 bp and 160 bp . Direct sequencing of the PCR products indicated that the shorter intergenic regions had probably originated from deletion of DNA segments between direct repeats . Correlation of certain PCR products with Aeromonas caviae (HG4), A . caviae (HG5), A . veronii (HG8) and A . salmonicida (HG3) was revealed . The PCR reaction was also shown to be generally specific for Aeromonas spp . Thus, the usefulness of this rapid, single colony-based PCR test for both identification and preliminary differentiation of Aeromonas spp . is demonstrated.

J Antimicrob Chemother, 1996 Mar, 37(3), 423 - 31
Enzyme kinetics and biochemical analysis of ImiS, the metallo-beta-lactamase from Aeromonas sobria 163a; Walsh TR et al.; The metallo-beta-lactamase from Aeromonas sobria 163a, ImiS, was isolated in a two stage purification procedure using protein affinity columns . Enzyme kinetics show that ImiS hydrolyses the carbapenems but displays poor activity against other beta-lactams . ImiS possesses the narrowest spectrum of activity of the Group 3 enzymes that have been analysed . Sequencing of the 40 N-terminal amino acids show this region to be identical to that of the CphA metallo-beta-lactamase from Aeromonas hydrophila (Massidda, Rossolini & Satta, 1991) . Light scattering analysis indicates that ImiS is functionally active as a monomer.

Vet Immunol Immunopathol, 1996 Mar, 50(1-2), 157 - 66
The effect of temperature and water quality on antibody response to Aeromonas salmonicida in sunshine bass (Morone chrysops x Morone saxatilis); Hrubec TC et al.; The kinetics of the antibody response to Aeromonas salmonicida were determined in sunshine bass (hybrid striped bass: female Morone chrysops X male Morone saxatilis) acclimated to 10, 18, 24, 29 degrees C, and to 0.15 mg 1(-1) un-ionized ammonia and 200 mg 1(-1) nitrate levels . Temperature and water quality factors affected the immune response of sunshine bass . Temperatures of 10 degrees C and 18 degrees C decreased the magnitude and delayed the time of the antibody response to A . salmonicida . The antibody response was not affected at 29 degrees C, which is above the optimal temperature for sunshine bass . Elevated un-ionized ammonia concentrations of 0.15 mg 1(-1) also did not affect the antibody response . Elevated nitrate levels of 200 mg 1(-1), however, decreased the antibody response to the same extent as 18 degrees C water.

Southeast Asian J Trop Med Public Health, 1996 Mar, 27(1), 132 - 8
Characterization of Aeromonas hydrophila: a comparative study of strains isolated from diarrheal feces and the environment; Haque QM et al.; Thirty-five strains of Aeromonas hydrophila isolated from feces of diarrheal patients and from the environments were collected from Thailand and Japan . The physiological, biochemical, and serological characteristics, antibiotic resistance patterns and cell surface-related properties were compared . The diarrheal and environmental isolates of A hydrophila were found to be remarkably consistent in general culture and biochemical characteristics, with the exception of the reaction to D-arabinose in which the diarrheal strains were positive and environmental strains were negative . The plasmid patterns and cell surface-related properties of the environmental and diarrheal isolates were different . All strains produced Vero cell cytotoxin, hemolysin and lecithinase at 37 degrees, 30 degrees and 15 degrees C . In contrast, 83% of the environmental strains produced these virulence factors even at 4 degrees C . All strains indicated almost uniform susceptibility to the 16 antibiotics tested . Variations were found in the plasmid profile, toxin production in relation to the differences of temperature and cell surface-related properties of the strains . These variations between the clinical and environmental isolates could have potential as epidemiological markers for the sources of strains.

J Appl Bacteriol, 1996 Mar, 80(3), 277 - 82
Pulsed-field gel electrophoresis as an epidemiological tool for clonal identification of Aeromonas hydrophila; Talon D et al.; Pulsed-field gel electrophoresis (PFGE) was used to characterize Aeromonas hydrophila strains isolated from a cluster of hospital-acquired infections that occurred over approximately 1 month in a French hospital . Five isolates from patients and 10 isolates from the water supply were characterized by biotyping and antibiotic susceptibility patterns and compared with 10 epidemiologically unrelated strains isolated from patients and rivers, by PFGE of digests of chromosomal DNA . Five environmental and four clinical isolates belonged to the same biotype and antibiotic susceptibility pattern type . The endonucleases XbaI, SpeI and SwaI gave satisfactory profiles whereas DraI did not . The profiles were stable, reproducible and discriminatory . The 10 epidemiologically unrelated strains exhibited 10 different patterns after digestion with XbaI, the least expensive, suitable endonuclease . PFGE is a rapid and discriminatory technique for the typing of Aeromonas hydrophila where a common origin of infection is suspected.

J Diarrhoeal Dis Res, 1996 Mar, 14(1), 27 - 32
Colonization of streptomycin-treated mice by Aeromonas species; Sanderson K et al.; Streptomycin-treated adult mice were investigated as a possible model for studying the enteropathogenicity of Aeromonas species . C57BL mice pre-treated with streptomycin (5.0 g/L drinking water, 48 hours) received a single intragastric dose (10(10) bacteria /10.5 mL) of one of six well-characterized, toxin-producing, human diarrhoeal isolates of A . veronii biovar sobria (n = 3) or A . hydrophila (n = 3) . Their faeces were examined for Aeromonas for 10 days post-challenge . All strains colonized the antibiotic-treated mice . Colonization did not occur in mice which did not receive streptomycin . Strains of A . hydrophila were recovered in greater numbers than strains of A . veronii biovar sobria, and colonized ( > or = 10(3) cfu/g of faeces) a greater proportion of mice at day 10 . Strains of the latter species, however, were more adherent in cell line assays used as models of intestinal adhesion . A . hydrophila strains localized in the large intestine and appeared not to be cell associated . This study, therefore, points to species-related differences in intestinal colonization mechanisms . The streptomycin-treated adult mouse model may prove useful for further investigation of some of these mechanisms . Diarrhoeal symptoms were, however, not produced in this model.

Biophys J, 1996 Feb, 70(2), 723 - 32
Optical single-channel analysis of the aerolysin pore in erythrocyte membranes; Tschodrich-Rotter M et al.; Scanning microphotolysis (Scamp), a recently developed photobleaching technique, was used to analyze the transport of two small organic anions and one inorganic cation through single pores formed in human erythrocyte membranes by the channel-forming toxin aerolysin secreted by Aeromonas species . The transport rate constants of erythrocyte ghosts carrying a single aerolysin pore were determined to be (1.83 +/- 0.43) x 10(-3) s-1 for Lucifer yellow, (0.33 +/- 0.10) x 10(-3) s-1 for carboxyfluorescein, and (8.20 +/- 2.30) x 10(-3) s-1 for Ca2+ . The radius of the aerolysin pore was derived from the rate constants to be 19-23 A, taking steric hindrance and viscous drag into account . The size of the Ca2+ rate constant implies that at physiological extracellular Ca2+ concentrations (> 1 mM) the intracellular Ca2+ concentration would be elevated to the critical level of > 1 microM in much less than a second after formation of a single aerolysin pore in the plasma membrane . Thus changes in the levels of Ca2+ or other critical intracellular components may be more likely to cause cell death than osmotic imbalance.

Burns, 1996 Feb, 22(1), 48 - 52
Aeromonas bacteraemia in burn patients; Barillo DJ et al.; Human aeromonas infection is uncommon and is usually associated with immunosuppression, chronic disease or trauma in an aquatic setting . Burn injury may induce a state of immunosuppression, making the thermally injured patient a suitable host for aeromonas infection . We reviewed the experience of one burn centre with this pathogen . Retrospective examination of blood culture results from 8151 patients admitted between 1959 and 1994 disclosed eight patients with clinically relevant Aeromonas hydrophilia bacteraemia . Five were burned outside the USA . Aquatic exposure was known or suspected in only three cases . Five of the eight patients died . Aeromonas infection in burn patients is rare but may occur in the absence of aquatic exposure.

Immunopharmacol Immunotoxicol, 1996 Feb, 18(1), 129 - 44
Immunotoxic effects of copper and cadmium in the sea bass Dicentrarchus labrax; Bennani N et al.; Two phagocytes-mediated activities of the sea bass Dicentrarchus labrax were examined after exposure to sublethal concentrations of copper and cadmium: (a) phagocytosis (measured by phagocytotic index), and (b) the production of reactive oxygen intermediates (luminol-dependent chemiluminescence) in response to bacteria Aeromonas salmonicida . In vivo exposure for 48 h to each metal separately by intraperitoneal injection did not affect the quantity of phagocytes of pronephros and their viability but inhibited, in dose-dependent manner, phagocytosis and chemiluminescence of these cells . The half-inhibition value was 250 micrograms kg-1 for copper and 1 mg kg-1 for cadmium . In vitro exposure to copper for 30 min had the same immunomodulatory effect on macrophage chemiluminescence as that observed in vivo, whereas treatment with cadmium under the same conditions had a dose-dependent effect opposite to that observed in vivo . Assessment of these two macrophage-mediated functions could therefore be used as early bioindicators of the marine pollution.

J Clin Pathol, 1996 Feb, 49(2), 173 - 5
Gastroenteritis caused by Aeromonas trota in a child; Reina J et al.; A case of acute diarrhoea caused by Aeromonas trota (formerly HG 13 group) in a Spanish child is reported . The strain was isolated in the faeces using the CIN agar (cefsulodin-irgasan-novobiocin) culture media . The strain was initially identified as A sobria by the commercial GNI card and API 20E biochemical systems . The strain was, however, VogesProskauer and sucrose negative, so complementary tests of cellobiose fermentation and gluconate oxidation were performed . These tests, together with the strain susceptibility to ampicillin (MIC 1 microgram/ml) and carbenicillin (MIC < 16 micrograms/ml) led to the final identification of A trota . The microbiological characteristics of this new species and the principal tests required for its identification are presented . The isolation, for the first time, of A trota in the Mediterranean area confirms the suspected worldwide distribution of this species.

Folia Microbiol (Praha), 1996, 41(6), 505 - 9
Application of a colorimetric DNA-DNA hybridization method for identification of Aeromonas genomic species, isolated from diarrheal stools; Kaznowski A; The colorimetric DNA-DNA hybridization method for the identification of 18 strains of Aeromonas spp . isolated from human stools was used . Bacterial isolates were also examined by phenotypic characteristics . On the basis of biochemical tests 13 strains were included in phenogroup A . caviae and 5 strains in A . sobria . Identification to the species level was obtained by colorimetric hybridization method . DNA-DNA similarity values showed that isolates of A . caviae group belong to hybridization group (HG) 4 whereas isolates of A . sobria belong to HG 8/10 . DNA relatedness results obtained by the colorimetric method showed good agreement with values detected by the spectrophotometric method . The background in the colorimetric method is lower than in the spectrophotometric one . Results of this study indicate the usefulness of the colorimetric DNA-DNA hybridization in microplates method for the identification of Aeromonas genomic species, isolated from human diarrheal stools.

Vet Res, 1996, 27(6), 553 - 60
Water quality parameters associated with Aeromonas spp-affected hatcheries; Ortega C et al.; This study investigates the role of water quality parameters as possible risk or protection factors in Aeromonas spp-affected rainbow trout hatcheries in northeastern Spain . The results revealed an association between oxygen concentration, ammonia concentration and total dissolved solids (TDS) with the prevalence of Aeromonas spp cases on the affected fish farms . The oxygen and ammonia concentrations acted as risk factors when their values were lower than 7.06 mg/L or higher than 0.05 mg/L, respectively, generating odds ratio (OR) values of 2.0 and 2.3 . TDS levels, however, acted as a protective factor (OR = 0.39), from an epidemiological point of view but not statistically, when the values were outside the normal range, 199-261 mg/L . On a multivariate level, fish farms exposed to all the associated factors at the same time, had a risk of being affected by Aeromonas spp that was 1.74 times higher than farms with normal quality parameters; the risk increased when TDS had a normal value and it decreased when oxygen and/or ammonia concentrations had normal values.

Mol Microbiol, 1996 Jan, 19(2), 205 - 12
Aerolysin--the ins and outs of a model channel-forming toxin; Parker MW et al.; Aerolysin is one of a large group of bacterial proteins that can kill target cells by forming discrete channels in their plasma membranes . The toxin has many properties in common with the porins of the Gram-negative bacterial outer membrane, including an extensive amount of beta-structure, a high proportion of hydrophilic amino acid side-chains and no hydrophobic stretches in the primary structure . It also oligomerizes to produce an insertion-competent state . Aerolysin is secreted as a dimer by members of the Aeromonas family . It binds to a high-affinity receptor on the target cell that has recently been shown to be a glycosylphosphatidylinositol-anchored glycoprotein . Binding is followed by heptamerization to form a structure that we propose contains a beta-barrel which can insert into the membrane and produce a channel.

Acta Vet Scand, 1996, 37(2), 139 - 46
Atypical Aeromonas salmonicida isolated from diseased turbot (Scophtalmus maximus L.); Larsen JL et al.; Atypical Aeromonas salmonicida were isolated from 3 outbreaks of disease among farmed turbot (Scophthalmus maximus L.) in 3 different farms, 1 from Norway (N1) and 2 from Denmark (DK1 and DK2) . In all 3 cases, the incidence of disease and mortality was high and the main characteristic pathological finding was skin ulcers and septicaemia . The isolated bacteria were subjected to a thorough phenotypic and genotypic examination and comparison in the laboratory . All 3 isolates belonged to A . salmonicida but displayed some very different biochemical properties . However, the 2 Danish strains, DK1 and DK2 had identical ribotypes but different from that of N1, whereas the plasmid profiles of DK1 and N1 were identical but different from that of DK2 . These observations emphasize the need for an improvement of our understanding of the taxonomy and epidemiology of atypical A . salmonicida.

Z Lebensm Unters Forsch, 1996 Jan, 202(1), 60 - 2
Combined effect of gamma-irradiation and conventional cooking on Aeromonas hydrophila in meatball; Ozbas ZY et al.; Irradiation combined with a conventional cooking procedure was applied to meatball and the effects on bacterial load and inoculated Aeromonas hydrophila were determined . Meatball samples were irradiated by using a 60Co source at the dose levels of 0, 0.30, 0.75, 1.50, 2.50 kGy and cold stored at 4 +/- 1 degrees C for 7 days . Bacterial load and the count of A . hydrophila decreased when the irradiation dose level increased . A minimum inhibition effect was found at the dose of 0.30 kGy . Irradiation in combination with a conventional cooking procedure was found to be more effective in reducing A . hydrophila and the bacterial load in meatball . This study indicated that a dose of 0.75 kGy was sufficient to destroy approximately 10(4) cfu/g of A . hydrophila in meatball.

J Appl Bacteriol, 1996 Jan, 80(1), 37 - 44
Characterization of atypical Aeromonas salmonicida isolates by ribotyping and plasmid profiling; Pedersen K et al.; A total of 38 strains of atypical Aeromonas salmonicida, three oxidase-negative but otherwise typical Aer . salmonicida, three typical Aer . salmonicida, and two reference strains, isolated from several countries and fish species were examined with respect to rRNA gene restriction patterns (ribotypes) and plasmid profiles . Most epidemiologically unrelated strains had different ribotypes, whereas isolates from the same outbreak were identical . All strains, except one, carried one or more large plasmids (> 55 kbp) and all strains, except two, additionally carried one or more smaller plasmids . Many strains isolated from the same outbreak showed different plasmid profiles although some plasmids were identical . The results suggest the existence of several atypical Aer . salmonicida . It also seems that ribotypes are stable properties for these bacteria while the plasmids are more labile.

Int J Food Microbiol, 1996 Jan, 28(3), 379 - 92
Survival and growth of Aeromonas hydrophila on modified atmosphere packaged normal and high pH lamb; Doherty A et al.; The growth of A . hydrophila on normal pH (5.5-5.8) and high pH ( > 6.0) lamb stored under modified atmospheres was examined . Lamb pieces and mince, inoculated with A . hydrophila were packaged in air, vacuum pack, 80% O2/20% CO2, 50% CO2/50% N2, or 100% CO2 and stored at 5 or 0 degrees C for up to 42 days . Samples were examined for the survival and/or growth of A . hydrophila by enrichment in alkaline peptone water and/or direct plating on starch ampicillin agar . The pH of each sample was estimated . On lamb pieces and mince of normal pH, A . hydrophila numbers decreased during storage at 5 and 0 degrees C under all the packaging conditions . The organism was not detected after 21 days storage . In contrast, A . hydrophila numbers were maintained or increased on high pH lamb under most storage regimes . Storage at 5 degrees C allowed significant increases in A . hydrophila numbers on high pH lamb under all the atmospheres, except 100% CO2 . In lamb held at 5 degrees C under 100% CO2 for up to 42 days, A . hydrophila was recovered from most samples, although cell numbers decreased during storage . After storage at 0 degrees C, A . hydrophila was recovered from high pH packs stored under all atmospheres . Significant increases in cell numbers were only observed in minced lamb of high pH stored under air or vacuum . The pH values of lamb pieces and mince held at 5 or 0 degrees C under any of the packaging atmospheres did not change in a uniform manner during storage.

J Antimicrob Chemother, 1996 Jan, 37(1), 33 - 44
The 'hidden' carbapenemase of Aeromonas hydrophila; Hayes MV et al.; It has been presumed that there are just two beta-lactamases in the motile Aeromonas species, a carbapenemase and a cephalosporinase, based on the premise that all beta-lactamases can be detected by hydrolysis of the chromogenic cephalosporin, nitrocefin . However, when it was recently found that a non-motile species of Aeromonas that causes furunculosis in salmon, contained three beta-lactamases, one of which was a carbapenemase which could not be detected with nitrocefin, it was hypothesised that genetic exchange could occur between fish pathogens and human pathogens resulting in the transfer of the carbapenemase-encoding gene . This could have a potentially serious impact on intensive therapy units where carbapenems are employed . The purpose of this study was to determine whether the human pathogen Aeromonas hydrophila demonstrated the same beta-lactamase profile . After anion and cation exchange chromatography had been employed to separate the beta-lactamases of a clinical strain of A . hydrophila, three different beta-lactamases were found, one of which is a carbapenemase which does not hydrolyse nitrocefin . It is, therefore, probable that many strains of Aeromonas spp . contain a similar array of beta-lactamases which include a carbapenemase that cannot be detected with nitrocefin . Similar carbapenemases may well remain hidden in other species of bacteria unless appropriate techniques to detect the enzymes are employed.

Microbios, 1996, 85(343), 105 - 15
Growth and exotoxin production at low temperatures by Aeromonas strains in meat slurries; Majeed KN; The ability of enterotoxigenic strains of Aeromonas hydrophila and Aeromonas sobria to produce exotoxins (haemolysin and enterotoxin) and exoenzymes (protease and lipase), as well as their growth in meat slurries stored at low temperatures (5 and 12 degrees C) was investigated . The results showed that Aeromonas grew well in meat slurries stored at low temperatures in the presence of background flora . Exotoxins and exoenzymes were not detected in filtrates from meat slurries inoculated with enterotoxigenic Aeromonas strains after 5 and 8 days incubation at both incubation temperatures . The significance of the competitive growth of aeromonads in foods at refrigeration temperatures is discussed.

Wei Sheng Wu Xue Bao, 1995 Dec, 35(6), 460 - 4
{Serogroups, virulence and hemolytic activity of Aeromon as hydrophila which caused fish bacterial septicaemia}; Qian D et al.; A new infected disease called bacterial septicaemia occurred in cyprinid fish throughout China during 1989-1992 . A . hydrophila was known as the most important pathogen of this harmful disease . Thirty-three strains of A . hydrophila, most isolated from moribund fishes, were serogrouped by tube-agglutination with rabbit antisera . Most of the isolates could be grouped into two serotypes, TPS-30 and PBJS-76 . These two groups could be found not only in Zhejiang province but in other province in south China . It can be concluded that the two serogroups were the main Aeromonas groups caused this fish disease . These isolates were virulent to Carassius auratus, with LD50 values of 10(4) to 10(6) . The hemolytic activity ranged from titers of 1/8 to 1/16 . No relationship were observed with the hemolytic activity and virulence.

Epidemiol Infect, 1995 Dec, 115(3), 465 - 73
Adhesion of Aeromonas sp . to cell lines used as models for intestinal adhesion; Kirov SM et al.; Adhesion to HEp-2 cells has been shown to correlate with enteropathogenicity for Aeromonas species . Such adhesion is thought to reflect the ability of strains to adhere to human intestinal enterocytes, although HEp-2 cells are not of intestinal origin . In this study strains of Aeromonas veronii biotype sobria isolated from various sources were investigated in parallel assays for their ability to adhere to HEp-2 cells and to an intestinal cell line (Caco-2) . Quantitative assays showed identical adhesion values were obtained with both cell lines . Adhesion was best when bacteria were grown at 22 degrees C compared with 37 degrees C and 7 degrees C . Some environmental isolates showed greater adhesion when grown at 7 degrees C than when grown at 37 degrees C . Filamentous structures on these strains are also optimally expressed under the above conditions (reported elsewhere) . Mechanical shearing or trypsin treatment to remove surface structures from several adhesive strains grown at 22 degrees C decreased adhesion to cell lines by 50-80% providing further indirect evidence that filamentous adhesins may play a role in cell adhesion for this Aeromonas species.

S D J Med, 1995 Dec, 48(12), 405 - 7
Treatment of Aeromonas hydrophila infection in a deep tissue wound; Archer BJ et al.; We report the case of a young woman who sustained a knee laceration in an automobile accident and was subsequently exposed to water . Although properly cleansed and closed, her wound became infected and she was initially treated with a single-dose parenteral cephalosporin . The infection progressed and cultures indicated a polymicrobial infection which included Aeromonas hydrophila . Significant tissue damage ensued and a lengthy hospitalization was required . Aeromonas, although rarely a cause of infection in otherwise healthy individuals, should be suspected in wounds exposed to fresh water.

Am J Gastroenterol, 1995 Dec, 90(12), 2234 - 5
Aeromonas sobria infection with severe muscle degeneration in a patient with alcoholic liver cirrhosis; Kohashi T et al.; A 56-yr-old male who had been followed for alcoholic liver disease was admitted for abdominal pain and a high fever . Gastrointestinal endoscopy revealed bleeding esophageal varices that were treated by endoscopic sclerotherapy . Blood culture on admission was positive for Aeromonas sobria . Then skin bullas and ulcers and severe muscle degeneration developed . The patient died despite extensive treatment with antibiotics . A . sobria infection in patients with liver cirrhosis is rare.

Vet Immunol Immunopathol, 1995 Nov, 49(1-2), 127 - 42
Study of the humoral response of Atlantic salmon (Salmo salar L.), naturally infected with Aeromonas salmonicida ssp . achromogenes; Magnadottir B et al.; The humoral antibody response of healthy Atlantic salmon and of two groups of salmon, naturally infected with Aeromonas salmonicida ssp . achromogenes, was examined in some detail . One diseased group was chronically infected and the other recently infected . It was found that the humoral response of these two infected groups was quite different . The chronically infected fish showed poor specific response to the causative agent whereas the recently infected salmon produced strong specific antibody response . The chronically infected fish showed evidence of increased unspecific response including an elevated level of natural antibodies . The specific humoral response of the recently infected fish was primarily directed against two cell-associated antigens of the A . salmonicida ssp . achromogenes bacterium, the A-layer protein and the o-polysaccharide component of LPS . In the chronically infected fish the humoral response was primarily directed against the A-layer protein.

Biosci Biotechnol Biochem, 1995 Nov, 59(11), 2162 - 4
Purification and some properties of six chitinases from Aeromonas sp . no . 10S-24; Ueda M et al.; Six chitinases were purified from a culture supernatant of Aeromonas sp . no . 10S-24 by ammonium sulfate precipitation, DEAE-Sephadex A-50, Butyl-Toyopearl 650M, and chromatofocusing . These enzymes were most active at pH 3.5-4.5 and the optimum temperature were 50 degrees C . The molecular weights of the enzymes were 89,000 to 120,000 from SDS-polyacrylamide gel electrophoresis . N-Terminal amino acid sequences of the enzymes were similar to that of chitinase I.

Can J Microbiol, 1995 Oct, 41(10), 941 - 5
Capsulated cells of Aeromonas salmonicida grown in vitro have different functional properties than capsulated cells grown in vivo; Garduno RA et al.; When grown in vivo in the peritoneal cavity of rainbow trout, Aeromonas salmonicida produces a clearly defined capsule with virulence-related functions . Aeromonas salmonicida grown in vitro in a glucose-rich medium (GRM) has also been reported to reproduce capsular material . Because in vitro mimicry of in vivo induced traits is highly desirable in vaccine design, the extent to which growth in GRM mimicked in vivo growth was examined . Antibodies specific to in vivo grown cells partially labeled the surface of GRM-grown cells, as well as two distinct proteins (81,700 and 41,000 Mr) in immunoblots of mutants with S-layer or lipopolysaccharide defects . GRM-grown strains showed an increased sensitivity to trout serum in contradistinction to the complete serum resistance of in vivo grown cells; as well, GRM-grown cells were more adherent to trout macrophages . Thus in spite of possessing some surface antigens normally expressed in vivo, cells grown on solid GRM did not possess all functional properties of in vivo grown cells.

Mol Cell Probes, 1995 Oct, 9(5), 311 - 3
Class D and E tetracycline resistance determinants in gram-negative bacteria from catfish ponds; DePaola A et al.; DNA probes were used to examine tetracycline-resistant Gram-negative bacteria (281 strains representing eight species) from catfish ponds . The isolates, which did not previously hybridize with the Tet A, B and C determinants, were examined for the presence of tetracycline-resistance Tet D and Tet E determinants . The distribution of the Tet D determinant ranged from 0 to 83%, depending on the bacterial species . Tet E was found only in 69% of Aeromonas hydrophila isolates . Eighteen per cent failed to hybridize with any of the five Tet determinants.

Enferm Infecc Microbiol Clin, 1995 Oct, 13(8), 469 - 72
{Soft-tissue infection caused by Aeromonas hydrophila}; Ramos JM et al.; BACKGROUND: Two cases of soft tissue infection by Aeromonas hydrophila are presented with review of the literature . PATIENTS AND METHODS: Two cases of soft tissue infection by Aeromonas hydrophila diagnosed from 1992-1993 are reported . RESULTS: Most soft tissue infection produced by Aeromonas organisms are caused by Aeromonas hydrophila . These infections predominantly affect the lower limbs of middle-aged males with previous history of injury favoring infection . The most common clinical presentation is cellulitis with a good prognosis if bacteremia is not produced . Antibiotics, such as mainly third generation cephalosporins, imipenem, aztreonam, cotrimoxazole, tetracycline, chloramphenicol, quinolones and aminoglucosides (except streptomycin) are usually very active in vitro against these organisms . Surgery is often necessary to cure the process . CONCLUSIONS: Cellulitis by Aeromonas hydrophila is a very infrequent entity in Spain and is usually associated to previous injury and probable contamination by environmental bacteria.

Appl Environ Microbiol, 1995 Oct, 61(10), 3586 - 91
Recombinant infectious hematopoietic necrosis virus and viral hemorrhagic septicemia virus glycoprotein epitopes expressed in Aeromonas salmonicida induce protective immunity in rainbow trout (Oncorhynchus mykiss); Noonan B et al.; Fragments of the glycoprotein genes of viral hemorrhagic septicemia virus (VHSV) and infectious hematopoietic necrosis virus (IHNV) were cloned into a bacterial broad-host-range expression vector under the control of the plac promoter . Western blot (immunoblot) analysis with monoclonal antibodies specific to the glycoproteins demonstrated the inducible expression of the fusion proteins in Escherichia coli . Aeromonas salmonicida is the causative agent of furunculosis in salmonid fish . It was confirmed that an avirulent strain of A . salmonicida, A440, which contains a deletion in the structural gene for the paracrystalline surface protein array, will provide protective immunity against furunculosis when used as a live attenuated vaccine . The plasmid-encoded viral epitopes were then mobilized into A440 for use as a shuttle system for the expression of fragments of the glycoprotein genes of IHNV and VHSV . Vaccination of rainbow trout with A440 containing the viral epitopes resulted in the development of protective immunity against both VHSV and IHNV . This indicates that the use of cloned fragments of the glycoproteins and the use of A . salmonicida as a shuttle system constitute a feasible approach to fish vaccine development.

Pathol Biol (Paris), 1995 Sep, 43(7), 622 - 7
Improved glutaminate-starch-penicillin agar for the isolation and enumeration of Aeromonas hydrophila from seawater by membrane filtration; Papapetropoulou M et al.; Glutaminate-starch-penicillin agar (GSP) in its original formula was found unsatisfactory for the detection and the enumeration of Aeromonas hydrophila from seawater by membrane filtration . It was also the case when GSP agar was adjusted to pH 8 or when ampicillin (10 mg/L) was incorporated to the original formula . The elevation of pH to 8 together with the addition of 10 mg/L ampicillin gave to the medium a high selectivity and permitted the detection of A . hydrophila from seawater . The numbers of A . hydrophila were monitored at 11 beaches along the coastline of Patras and the distribution of Aeromonas was not found homogenous . Low numbers of A . hydrophila were isolated from most samples tested, whereas high concentrations of A . hydrophila were isolated specifically from samples that were collected near sewage and fresh water inputs.

J Diarrhoeal Dis Res, 1995 Sep, 13(3), 183 - 6
Abundance of Aeromonas spp . in river and lake waters in and around Dhaka, Bangladesh; Parveen S et al.; Aeromonas spp . are widely distributed in the aquatic environment . In Bangladesh, seasonal distribution of these organisms in aquatic environment was studied during July 1986-August 1987 . Water, sediment, plant, and plankton samples were collected monthly from the Dhanmondi lake and the Buriganga river during the study period . Aeromonas spp . were isolated from all samples throughout the year . The seasonal peak of Aeromonas spp . was observed in warmer months (April-May) in the surface waters . In the sediment, the highest peak was observed in March and August . In most plants, the highest peak was observed during the winter months (December-February) . In the plankton samples of the Dhanmondi lake and the Buriganga river, the highest counts were obtained in July and February respectively . In both the sampling sites, plants were observed to contain more Aeromonas than did the water and sediment samples . The prevalence of Aeromonas spp . throughout the year in aquatic environment suggests the autochthonous nature of these organisms and that there is an association of Aeromonas with the aquatic environment.

J Diarrhoeal Dis Res, 1995 Sep, 13(3), 172 - 5
Relationship between enterotoxicity and multiple drug resistance in Aeromonas spp; Singh DV et al.; One hundred forty-seven isolates of Aeromonas spp., including 54 from diarrhoeal patients and 93 from the environmental sources, were examined for drug sensitivity and enterotoxin production . One hundred and fifteen (78%) isolates that included all A . hydrophila, 60% of A . sobria and 89% of A . caviae showed resistance to one or more antibiotic(s) . Most (65%) of the resistant isolates caused fluid accumulation in rabbit ileal loops, of these 57% were A . hydrophila, 69% of A . sobria and 65% A . caviae, whereas only a few drug-sensitive isolates did so . Multiple drug-resistant isolates caused comparatively more fluid accumulation than the drug-sensitive isolates . Furthermore, significant difference of ileal fluid accumulation was observed with the increase in the number of resistance markers . This study suggests that there is some association between multiple drug resistance and enterotoxicity of Aeromonas strains, regardless of their source of isolation and species.

J Am Podiatr Med Assoc, 1995 Sep, 85(9), 505 - 8
Motile Aeromonas as agent of infections of the foot; Wakabongo M; Motile Aeromonas infections of the foot are caused mostly by post-traumatic incidence, occurring mostly during summer months . Serious complications such as osteomyelitis and amputation can result if the infections go untreated or are inadequately treated . The role of each species of motile Aeromonas in pathogenesis and response to antimicrobial agents is not well understood because of taxonomic uncertainty . As a group, motile Aeromonas respond well to aminoglycosides, second-generation and third-generation cephalosporins, quinolones, and some beta-lactam antibiotics.

J Hosp Infect, 1995 Sep, 31(1), 55 - 60
Non-enteritic aeromonas infections in hospitalized patients; Murphy OM et al.; Aeromonas species were isolated from specimens other than faeces from 59 hospital inpatients over a 15 year period . Of the isolates, 79.7% were regarded as clinically significant, with skin and soft tissues and blood cultures as the commonest sites of infection . Of the isolates, 52.5% were hospital-acquired, and 55.9% of patients had serious underlying disease . Community-acquired infections in previously healthy individuals accounted for only 13.6% of isolates . However unlike many other opportunistic infections, aeromonas infection was not closely associated with prior antibiotic therapy, nor was there a significant increase in the frequency of infection over the study period.

FEMS Microbiol Lett, 1995 Aug 1, 130(2-3), 165 - 9
Evaluation of the suitability of bis-(1,3-dibutylbarbituric acid) trimethine oxonol, (diBA-C4(3)-), for the flow cytometric assessment of bacterial viability; Deere D et al.; The usefulness of oxonol (bis-(1,3-dibutylbarbituric acid)trimethine oxonol) as a generally applicable indicator of bacterial viability was investigated using untreated and killed cultures of a variety of bacterial genera . Killing methods involved either heat or bactericidal antibiotics . For all strains tested, the fluorescent dye showed significantly more intense staining of killed than untreated cells . The sensitivity of Aeromonas salmonicida to gentamicin was assessed using oxonol . Although the bacterium was shown to be sensitive to the antibiotic, there was a delay between the time cells lost culturability, as judged by numbers of colony forming units, and that for which a dead cell population could be detected by flow cytometry.

J Appl Bacteriol, 1995 Aug, 79(2), 181 - 5
RAPD analysis of Aeromonas salmonicida and Aeromonas hydrophila; Miyata M et al.; The randomly amplified polymorphic DNA (RAPD) technique was used to analyse the genetic differentiation of 13 strains of Aeromonas salmonicida subsp . salmonicida, and seven strains of Aer . hydrophila . Reproducible profiles of genomic DNA fingerprints were generated by polymerase chain reaction (PCR) using a single randomly designed primer . The RAPD profiles of all the non-motile aeromonads, Aer . salmonicida subsp . salmonicida were identical . However, profiles of the motile aeromonads, Aer . hydrophila differed between isolates . These findings reveal genomic homogeneity in Aer . salmonicida subsp . salmonicida and genetic variety in Aer . hydrophila strains.

Int J Syst Bacteriol, 1995 Jul, 45(3), 462 - 6
Aeromonas encheleia sp . nov., isolated from European eels; Esteve C et al.; Four strains isolated from European eels in Valencia, Spain, were found to constitute a DNA relatedness group which is 0 to 50% related to the 13 species and DNA group 11 of the genus Aeromonas . Phenotypically, these strains have all of the properties that define the genus Aeromonas . However, they differ from the previously described Aeromonas species by three or more properties . The strains are positive for motility, growth at 37 degrees C, indole production, and arginine dihydrolase activity . They exhibit negative reactions in tests for growth at 42 degrees C and in thiosulfate-citrate-bile salts-sucrose medium (Oxoid), Simmons citrate tests, and tests for lysine and ornithine decarboxylase activities . They produce acid from salicin but not from L-arabinose, D-cellobiose, or lactose . All four strains hydrolyze esculin and arbutin but not elastin . They use L-serine as a sole carbon and energy source but cannot utilize L-arabinose, L-arginine, D-gluconate, or L-glutamine . The strains are resistant to ampicillin . The guanine-plus-cytosine content of the DNA is 59.4 to 60.8 mol% . The name Aeromonas encheleia sp . nov . is proposed for these strains; strain S181 (= CECT 4342) is the type strain . This new species is generally not pathogenic for eels or mice.

Microb Pathog, 1995 Jul, 19(1), 1 - 9
Purification and characterization of a CHO cell-elongating toxin produced by Aeromonas hydrophila; McCardell BA et al.; A Chinese hamster ovary (CHO) cell-elongating toxin produced by Aeromonas hydrophila was purified from cell-free supernatant fluids by ammonium sulfate precipitation and fast protein liquid chromatography . The purified toxin had an isolelectric point (pl) of 3.7 and a molecular weight of 70,000 in a single band on isoelectric focusing (IEF) gels and SDS-PAGE gels, respectively . The N-terminal sequence, amino acids 1-20, and the amino acid content were determined from Western blots of the 70 kDa band . No homology with any known microbial toxin was found . CHO cell activity was not neutralized by antiserum to cholera toxin (anti-CT), and the toxin did not react with anti-CT on Western blots . The toxin did not increase cyclic AMP, cyclic GMP, or prostaglandin E2 levels in CHO cells . No cytotoxic activity was observed . Intragastric administration of purified toxin (5 x 10(4) and 5 x 10(8) CHO cell units) induced intestinal fluid accumulation in infant mice . These results suggest that this toxin may be a novel cytotonic toxin distinct from previously described toxins produced by A . hydrophila or A . sobria.

Biochem Mol Biol Int, 1995 Jul, 36(4), 827 - 33
Metal content and conformation of the metalloprotease from the marine sponge Spheciospongia vesparia; Arreguin R et al.; We have recently purified a protease from the marine sponge Spheciospongia vesparia . It consists of a single nonglycosylated polypeptide chain with a molecular weight of 29 600 and has one free thiol group . Metal analysis revealed the presence of zinc at 2.02 +/- 0.05 g-atoms per mole of protein, as measured by atomic absorption spectroscopy . The circular dichroism spectrum in the far UV region (183-259 nm) indicates that the sponge protease contains appreciable amounts of beta sheet . This enzyme resembles very much an aminopeptidase from Aeromonas proteolytica concerning activity and some physiochemical characteristics.

Curr Microbiol, 1995 Jul, 31(1), 28 - 33
A lipase of Aeromonas hydrophila showing nonhemolytic phospholipase C activity; Ingham AB et al.; Extracellular lipase activity detected on tributyrin agar has been identified in a cosmid clone, JM3084, constructed from the chromosome of Aeromonas hydrophila and vector pHC79 . This lipase, named apl-1, also exhibits nonhemolytic phospholipase C activity on lecithin and p-nitrophenylphosphorylcholine . Subcloning of the cosmid JMP3084 with partial Sau3a1 digestion localized the lipase gene to a 3.4-kb DNA fragment . Southern blot analysis shows the gene apl-1 to exist in single copy on the A . hydrophila chromosome . Expression of apl-1 in the pT7 system identified a single protein of molecular weight 70 kDa . Nucleotide sequencing of apl-1 has identified an open reading frame of 2055 bases predicting a protein of 73 kDa . The presence of an amino terminal signal sequence of 18 amino acids accounts for this molecular weight disparity . Further analysis of the lipase amino acid sequence revealed the presence of a classical serine active lipase site (Gly-X-Ser-X-Gly) located between residues 561 and 570 . The A . hydrophila chromosomal copy of apl-1 has been inactivated by use of the mutagenesis vector pJP5603, resulting in the complete removal of phospholipase C activity and lowered levels of lipase activity detected on tributyrin agar.

J Appl Bacteriol, 1995 Jul, 79(1), 12 - 21
Phenotypic and molecular characteristics of Aeromonas salmonicida subsp . salmonicida isolated in southern and northern Finland; Hanninen ML et al.; Aeromonas salmonicida subsp . salmonicida causes outbreaks of furunculosis in salmonid fish . Furunculosis was first detected in Finland in 1986 on fish farms located on the Finnish coast of the Bothnian Bay . Molecular methods, SDS-PAGE, ribotyping, randomly amplified polymorphic DNA (RAPD) and plasmid profile analysis as well as phenotypic characteristics (biochemical characteristics, maximum growth temperature, pigment and elastase production) were used both for typing the strains and to study the possible routes of transmission of the organism to Finland and the spread of infection within Finland from 1986 to 1993 . Ribopattern analysis of chromosomal DNA digested with SmaI, BglI, PstI and ClaI of 28 Finnish strains and eight foreign strains (Denmark, Sweden, Norway or Canada) showed that all Finnish strains and the Swedish strain originating from the Swedish coast of the Bothnian Bay had identical ribopatterns . All other foreign strains had distinct, unique ribotypes except for the second Swedish strain studied, the ribotype of which was identical with that of one Danish strain . RAPD typing, based on the results of two arbitrary primers, yielded 15 types for the Finnish strains . Except for both Danish strains, which had the RAPD type which was identical with that of one Finnish strain, the foreign strains had RAPD patterns differing from those of the Finnish strains . Plasmid profile typing and RAPD profile typing did not correlate . Ribotyping with four different enzymes proved to be the most sensitive method for studying genetically homogeneous Aer . salmonicida subsp . salmonicida . Ribopattern analysis showed that the infection which first started in 1984/1985 on the Swedish coast of the Bothnian Bay may have been transmitted to Finland where the first outbreaks occurred in 1986 . The strains infecting Finnish fish farms were very homogeneous, with most differences seen, for example, in maximum growth temperature, plasmid profiles and the RAPD profiles of the strains.

Immunology, 1995 Jul, 85(3), 389 - 93
Immunoregulatory activities of eicosanoids in the rainbow trout (Oncorhynchus mykiss); Knight J et al.; Eicosanoids such as prostaglandins (PG), leukotrienes (LT) and lipoxins (LX) have been shown to be potent immunoregulatory molecules in mammals . To determine if they have similar roles in 'lower' animals, rainbow trout (Oncorhynchus mykiss) were immunized with either sheep erythrocytes or Aeromonas salmonicida in the presence or absence of the stable analogue of PGE2, 16,16-dimethyl-PGE2, and the number of plaque-forming cells (PFC) or specific antibody levels determined . The higher dose of 16,16-dimethyl-PGE2 (200 micrograms/kg body weight) caused a significant reduction in both PFC number and antibody titre compared with the control . The effect of PGE2, PGE3, 16,16-dimethyl-PGE2, LTB4, LTB5, LXA4, 12-HETE and 12-HEPE on PFC generation following the in vitro challenge of trout splenocytes with sheep erythrocytes was also determined . All of the prostaglandins tested showed a dose-dependent inhibition of PFC after 11 days in culture, while of the remaining eicosanoids only LXA4 had any effect on PFC number, with a dose-dependent stimulatory effect . The cyclo-oxygenase inhibitor, indomethacin, also caused a stimulation in the number of PFC generated, with a maximal effect at c . 25 microM, while the lipooxygenase inhibitors, esculetin and nordihydroguaiaretic acid (5-100 microM), had no significant effect on PFC generation at all concentrations tested . The present results show that, as in mammals, prostaglandins and the cyclo-oxygenase pathway are also important in the regulation of the piscine humoral immune response . Of the lipoxygenase products tested, however, only LXA4 had any significant effect on PFC generation, suggesting that these compounds have only a limited role to play in immune regulation in this organism . Overall this work shows that eicosanoids have a long evolutionary history in immunoregulation, probably dating back at least to the appearance of bony fish some 400 million years ago.

Mol Microbiol, 1995 Jul, 17(2), 379 - 86
The leucine zipper of Aeromonas salmonicida AbcA is required for the transcriptional activation of the P2 promoter of the surface-layer structural gene, vapA, in Escherichia coli; Noonan B et al.; The Aeromonas salmonicida AbcA protein is involved in the synthesis of the O-polysaccharide side-chains on the lipopolysaccharide and is also capable of enhancing the expression of the structural gene for the A-layer, vapA, when cloned into Escherichia coli . The P2 promoter of the vapA gene of A . salmonicida was cloned into a promoter probe vector and expression in E . coli was monitored . The expression of P2::lacZ was shown to be increased when abcA was provided in trans . AbcA contains an N-terminal ATP-binding domain as well as a C-terminal leucine zipper domain . Site-directed mutagenesis has been used to show that the ATP-binding domain is required for the synthesis of the O-polysaccharide side-chains, but not for the enhancement of vapA expression . Conversely, the leucine zipper is needed for the increase in vapA expression, but not for O-polysaccharide side-chain synthesis . This indicates that AbcA is a bifunctional protein that can influence the synthesis of the two principle antigenic components of the A . salmonicida cell surface.

Antimicrob Agents Chemother, 1995 Jul, 39(7), 1629 - 31
The renal membrane dipeptidase (dehydropeptidase I) inhibitor, cilastatin, inhibits the bacterial metallo-beta-lactamase enzyme CphA; Keynan S et al.; The Aeromonas hydrophila AE036 chromosome contains a cphA gene encoding a metallo-beta-lactamase which is highly active against carbapenem antibiotics such as imipenem . Here we show that the cphA gene product shares inhibitory similarities with a mammalian zinc peptidase, membrane dipeptidase (MDP; dehydropeptidase I) . Both enzymes are able to hydrolyze imipenem and are inhibited by cilastatin . The active site similarities of these enzymes are not reflected in any significant primary sequence similarity.

Proc Natl Acad Sci U S A, 1995 Jun 6, 92(12), 5754 - 8
Endogenous mutagenesis by an insertion sequence element identifies Aeromonas salmonicida AbcA as an ATP-binding cassette transport protein required for biogenesis of smooth lipopolysaccharide; Chu S et al.; Analysis of an Aeromonas salmonicida A layer-deficient/O polysaccharide-deficient mutant carrying a Tn5 insertion in the structural gene for A protein (vapA) showed that the abcA gene immediately downstream of vapA had been interrupted by the endogenous insertion sequence element ISAS1 . Immunoelectron microscopy showed that O polysaccharides did not accumulate at the inner membrane-cytoplasm interface of this mutant . abcA encodes an unusual protein; it carries both an amino-terminal ATP-binding cassette (ABC) domain showing high sequence similarity to ABC proteins implicated in the transport of certain capsular and O polysaccharides and a carboxyl-terminal potential DNA-binding domain, which distinguishes AbcA from other polysaccharide transport proteins in structural and evolutionary terms . The smooth lipopolysaccharide phenotype was restored by complementation with abcA but not by abcA carrying site-directed mutations in the sequence encoding the ATP-binding site of the protein . The genetic organization of the A . salmonicida ABC polysaccharide system differs from other bacteria . abcA also differs in apparently being required for both O-polysaccharide synthesis and in energizing the transport of O polysaccharides to the cell surface.

Ugeskr Laeger, 1995 May 29, 157(22), 3204 - 5
{Fulminant myonecrosis and sepsis caused by Aeromonas hydrophila}; Madsen CF et al.; A case of fatal bilateral lower extremity myonecrosis in a nonimmunocompromized man with septicaemia caused by Aeromonas hydrophila is described . Immediate surgical revision combined with treatment with new cephalosporins should be considered in the treatment of severe soft tissue infections, especially when the patient is known to have a trauma with waterborne contamination or is immunocompromised.

Gene, 1995 May 26, 158(1), 77 - 82
Cloning and study of the genetic organization of the exe gene cluster of Aeromonas salmonicida; Karlyshev AV et al.; The Aeromonas salmonicida (As) exe gene cluster, an additional member of the pul-related operon family required for general signal-sequence-dependent secretion of proteins from Gram- bacteria, was cloned in the broad-host-range cosmid pLAFR3 . Twelve genes, exeC-N, were identified by partial nucleotide (nt) sequence analyses (exeE-N) or determination of the complete sequence (exeC and exeD) . The organisation of the exeC-N genes is similar to that of several other operons of this family . These genes are arranged contiguously and are apparently transcribed in the same direction . On alignment of As and A . hydrophila exe sequences a 73-bp 'silent' deletion was identified close to the end of the As exeF gene . No gene encoding prepilin peptidase (the PulO homolog) was detected in this region . The exeN gene is evidently the last gene of this operon; it is followed by an ORF encoding a putative transcription regulator.

Arch Microbiol, 1995 May, 163(5), 366 - 72
Cell-surface properties of the food- and water-borne pathogen Aeromonas hydrophila when stored in buffered saline solutions; Ascencio F et al.; Aeromonas hydrophila, a ubiquitous inhabitant of aquatic environments, commonly expresses several cell-surface properties that may contribute to virulence . Since many aquatic microorganisms in hostile environments can withstand starvation conditions for long periods, we examined the effect of storage under nutrient-poor conditions on the expression of cell-surface properties of this pathogen . Phenotypes studied were: (1) cell-surface hydrophobicity and charge, and (2) the ability to bind connective-tissue proteins and lactoferrin . Our results suggest that the response of A . hydrophila to nutrient-poor conditions is regimen specific . Generally, A . hydrophila cells became more hydrophobic and significantly increased their ability to bind the iron-binding glycoprotein lactoferrin when the bacterium was stored under nutrient-poor conditions; however, under these conditions, the cells seemed to lose their ability to bind connective-tissue proteins.

J Bacteriol, 1995 May, 177(10), 2684 - 94
Physical and functional S-layer reconstitution in Aeromonas salmonicida; Garduno RA et al.; The various functions attributed to the S-layer of Aeromonas salmonicida have been previously identified by their conspicuous absence in S-layer-defective mutants . As a different approach to establish the multifunctional nature of this S-layer, we established methods for reconstitution of the S-layer of A . salmonicida . Then we investigated the functional competence of the reconstituted S-layer . S-layers were reconstituted in different systems: on inert membranes or immobilized lipopolysaccharide (LPS) from purified S-layer protein (A-protein) or on viable cells from either A-protein or preassembled S-layer sheets . In the absence of divalent cations and LPS, purified A-protein in solution spontaneously assembled into tetrameric oligomers and, upon concentration by ultrafiltration, into macroscopic, semicrystalline sheets formed by oligomers loosely organized in a tetragonal arrangement . In the presence of Ca2+, purified A-protein assembled into normal tetragonal arrays of interlocked subunits . A-protein bound with high affinity (Kd, 1.55 x 10(-7) M) and specificity to high-molecular-weight LPS from A . salmonicida but not to the LPSs of several other bacterial species . In vivo, A-protein could be reconstituted only on A . salmonicida cells which contained LPS, and Ca2+ affected both a regular tetragonal organization of the reattached A-protein and an enhanced reattachment of the A-protein to the cell surface . The reconstitution of preformed S-layer sheets (produced by an S-layer-secreting mutant) to an S-layer-negative mutant occurred consistently and efficiently when the two mutant strains were cocultured on calcium-replete solid media . Reattached A-protein (exposed on the surface of S-layer-negative mutants) was able to bind porphyrins and an S-layer-specific phage but largely lacked regular organization, as judged by its inability to bind immunoglobulins . Reattached S-layer sheets were regularly organized and imparted the properties of porphyrin binding, hydrophobicity, autoaggregation, adherence to and invasion of fish macrophages and epithelial cells, and resistance to macrophage cytotoxicity . However, cells with reconstituted S-layers were still sensitive to complement and insensitive to the antibiotics streptonigrin and chloramphenicol, indicating incomplete functional reconstitution.

Appl Environ Microbiol, 1995 May, 61(5), 2010 - 2
Surface phenotypic characteristics and virulence of Spanish isolates of Aeromonas salmonicida after passage through fish; Fernandez AI et al.; Eleven strains of Aeromonas salmonicida were passaged twice by intraperitoneal injection through rainbow trout and reisolated from the kidney of moribund fish . The surface characteristics and virulence of the strains changed following passage through fish . None of the in vitro tests used could effectively predict the in vivo virulence.

J Mol Biol, 1995 Apr 28, 248(2), 316 - 27
Molecular analysis of an A-protein secretion mutant of Aeromonas salmonicida reveals a surface layer-specific protein secretion pathway; Noonan B et al.; The Aeromonas salmonicida Tn5 mutant, A449-TM1, is unable to secrete the surface layer protein (A-protein) through the outer membrane . Immunogold labeling of thin sections of A449-TM1, with polyclonal antisera against the A-protein, showed the accumulation of large quantities of A-protein in an enlarged periplasm . The majority of the labeled A-protein could be seen at the poles of the cells . The ability of A449-TM1 to secrete other extracellular proteins such as hemolysin and protease was not impaired by the Tn5 insertion, which indicates that the mutation in A449-TM1 interferes with a secretion pathway specifically for the translocation of the A-protein through the outer membrane . The mutant, A449-TM1, was shown to be avirulent for fish . A cosmid clone from a gene library of A449-TM1, which contains the Tn5 insertion from the chromosome, was used to identify a 1.4 kb SaII/ClaI fragment from immediately adjacent to the Tn5 insertion . This fragment was used to identify and clone a 4 kb HindIII fragment from a chromosomal DNA digest from the wild-type strain, A449 . DNA sequence analysis of this clone identified an open reading frame (ORF) of 1656 bp . The deduced product of this ORF showed sequence similarity to a family of ATP-binding secretion proteins, but appeared to be phylogenetically distinct from these proteins, consistent with its participation in a secretory pathway specific for surface layer protein.

FEMS Microbiol Lett, 1995 Apr 15, 128(1), 69 - 73
The presence of capsular polysaccharide in mesophilic Aeromonas hydrophila serotypes O:11 and O:34; Martinez MJ et al.; Mesophilic Aeromonas hydrophila from serotypes O:11 and O:34 grown in a glucose-rich medium produce a capsule that can be seen under light and electron microscopy . The purified capsular polysaccharide has a composition qualitatively similar for strains O:11 and O:34, but quantitatively different . The capsular polysaccharides were immunogenic in rabbits, and did not cross-react with specific antibodies against either purified lipopolysaccharide from strains O:34 or O:11 or against the S-layer characteristic of strains from serotype O:11.

Gene, 1995 Apr 14, 156(1), 79 - 83
Amino-acid residues involved in biological functions of the cytolytic enterotoxin from Aeromonas hydrophila; Ferguson MR et al.; Some amino acid (aa) residues within the cytolytic enterotoxin (Act) of Aeromonas hydrophila essential for biological activity were identified . Act is a 52-kDa polypeptide, possessing hemolytic, cytotoxic and enterotoxic activities . By deletion analysis, generation of anti-peptide Ab, and site-directed mutagenesis we showed that two regions in Act (aa 245-274 and 361-405) were very important for biological functions . As shown by competitive inhibition assays, peptide 2 (aa 245-274) blocked cytotoxic activity of Act, and aa Tyr256, Trp270 and Gly274 were essential for cytotoxicity . Within peptide 3 (aa 361-405), Trp394 and Trp396 were important for biological activities . Mutations in other regions of the toxin (e.g., Gly169, Asp170, Gly171, Trp172, Asn177,178, Asp179 and His144,209,355) also decreased biological activity . The reactivity of these mutant toxins with Ab in immunoblots was not altered . Data reported in this study suggested the role of some aa residues in biological function(s) of Act.

J Wildl Dis, 1995 Apr, 31(2), 272 - 5
An alternative bacteriological medium for the isolation of Aeromonas spp; Jenkins JA et al.; Two solid bacteriologic media were compared for cultivating Aeromonas spp . from piscine sources: the Rimler-Shotts (RS) medium and a starch-glutamate-ampicillin-penicillin-based medium (SGAP-10C) used for the recovery of Aeromonas spp . from water samples . The selective and differential capacities of the media were assessed March through October 1992 by recovery rate and phenotype of 99 isolates representing 15 genera of bacteria . Recovery frequency of Aeromonas spp . (n = 62) was similar at 97% on RS and 95% on SGAP-10C . The SGAP-10C medium proved to be more specific than RS toward Aeromonas species (P < or = 0.005) . Use of SGAP-10C at 24 C for 48 hr offers a better choice for the laboratory recovery of Aeromonas spp . from clinical fish specimens.

Acta Paediatr Jpn, 1995 Apr, 37(2), 192 - 5
Hypercalcemia associated with Aeromonas hydrophila gastro-enteritis; Murakami T et al.; We describe a 4 year old girl with acute Aeromonas hydrophila gastro-enteritis who presented with a combination of hypercalcemia, metabolic alkalosis, and renal impairment . Serum parathyroid hormone was not elevated . Both milk-alkali syndrome and intoxication of vitamins A and D were ruled out . The hypercalcemia, metabolic alkalosis, and renal impairment were improved by fluid infusion and intravenous administration of furosemide . Gastro-enteritis also improved with oral administration of the antibiotic norfloxacin . The association of A . hydrophila gastro-enteritis with hypercalcemia has not been described previously.

J Appl Bacteriol, 1995 Apr, 78(4), 445 - 55
Diversity of Aeromonas sp . in Flemish drinking water production plants as determined by gas-liquid chromatographic analysis of cellular fatty acid methyl esters (FAMEs); Huys G et al.; Gas-liquid chromatography of cellular fatty acid methyl esters (FAMEs) was used to determine the phenotypic and genotypic diversity among 489 presumptive Aeromonas strains isolated from five Flemish drinking water production plants . FAME profiles were compared with the predetermined library profiles of a representative database, AER48C, which contains the mean FAME data of all 14 currently established hybridization groups (HGs) or genospecies within Aeromonas . Using AER48C, more than 93% (457 strains) of all presumptive aeromonads isolated on ampicillin-dextrin agar were unequivocally identified as belonging to this genus . Moreover, 85.5% and 73.5% of these strains could be assigned to a particular phenospecies or HG, respectively . Raw and treated surface water samples were dominated by members of the Aer . hydrophila complex (38.8%, comprising HGs 1-3), followed by the Aer . caviae complex (22.7%, comprising HGs 4-6) and the Aer . sobria complex (16.7%, comprising HGs 7-9) . HGs 3, 5A/B and 8 were the most prominent genospecies in this type of water . On the other hand, it was found that raw and treated phreatic groundwater samples displayed a much more limited species diversity since these were almost entirely dominated (95.8%) by strains belonging to HGs 2 and 3 of the Aer . hydrophila complex . In general, flocculation-decantation and sand filtration were not shown to influence the overall species distribution in any of the plants examined.

Int J Syst Bacteriol, 1995 Apr, 45(2), 390 - 1
DNA relatedness among Aeromonas allosaccharophila strains and DNA hybridization groups of the genus Aeromonas; Esteve C et al.; The genomic relatedness among three Aeromonas allosaccharophila strains, including the type strain, and other Aeromonas type and reference strains that were assigned to DNA hybridization groups was estimated by DNA-DNA hybridization (competition procedure using a membrane method) . All A . allosaccharophila strains were highly related (70 to 100%) to strains 289T (= CECT 4199T) and ATCC 35942 . Type strains of other validated Aeromonas species, reference strains of DNA groups 8 and 11, and the Aeromonas sp . strain ATCC 43946 (enteric group 501) were 0 to 41% related to A . allosaccharophila 289T and ATCC 35942 . The G+Cs content of A . allosaccharophila strains were in the range 55.9 to 57.3 mol% . The G+C content of the type strain of this species was 56.9 mol%, a value somewhat lower than that reported in the original description.

Occup Med (Lond), 1995 Apr, 45(2), 89 - 92
Salmon farming: occupational health in a new rural industry; Douglas JD; The medical hazards of salmon farming can be grouped into those related to marine safety, fish husbandry, fish-farm diving and disease treatments . The hostile water environment requires thermal protection and personal buoyancy aids as workers frequently fall in the water from boats or cages . Feedstuffs may generate respirable dust and attract rats, creating a risk of leptospirosis . Musculo-skeletal injuries are common from lifting nets . Fish-farm diving has particular risks which can be minimized . Organophosphorous pesticides are used to treat sea lice and employees require health surveillance . Fish immunization is required to reduce the incidence of Aeromonas salmonitica . Needlestick injuries when using oil-based vaccines are a serious hazard to employees . The occupational health problems of salmon farming are predictable and preventable with primary safety measures . This new industry is safer than land-based agriculture on current evidence.

Eur J Epidemiol, 1995 Apr, 11(2), 171 - 5
Aeromonads in acute diarrhoea and asymptomatic infections in Nigerian children; Utsalo SJ et al.; Stool samples of 616 asymptomatic and 296 diarrhoeic school children were compared for the recovery rate of Aeromonas spp . on ampicillin (10 micrograms/ml) sheep blood agar . Culture filtrates of isolates were tested for haemolysin production with 1% freshly washed rabbit erythrocytes . Stools of 9 (3.0%) diarrhoeic children yielded five strains of A . hydrophila and four of A . veronii (two each of biotypes sobria and veronii), compared to 12 (1.9%) (p > 0.01) asymptomatic children who harbored seven A . hydrophila and five A . caviae strains . Isolates from-diarrhoeic stools were exclusively from children < or = 5 years, while all infected asymptomatic children were > or = 6 years . Culture filtrates of all nine diarrhoeic strains were uniformly enterotoxigenic (intestinal weight ratio > 0.083) and produced haemolysin titres > 128 . These phenotypes where variable in carriage strains of A . hydrophila but were not detected in A . caviae . The recovery of A . hydrophila, and A . veronii biotypes from diarrhoeic stools of children < or = 5 years may suggest their involvement in diarrhoea causation in the absence of other diarrhoeagenic agents.

J Antimicrob Chemother, 1995 Apr, 35(4), 453 - 61
Aeromonas infections and their treatment; Jones BL et al.; With advances in the identification and molecular taxonomy of Aeromonas spp., these organisms, which are widely distributed in the environment, are increasingly being recognised as human pathogens . Clinical infections include gastroenteritis, skin and soft tissue infections and bacteraemia . Antibiotic resistance poses a potential problem in the antimicrobial therapy of infections cased by Aeromonas spp . While most strains are susceptible to chloramphenicol, ciprofloxacin, co-trimoxazole and the aminoglycosides, the activity of amoxycillin/clavulanate and the acylureidopenicillins is inconsistent . Addition of a beta-lactamase inhibitor does not significantly enhance the activity of the acylureidopenicillins . Aztreonam and the carbapenems, imipenem and meropenem remain highly active . Although resistance to the first and second generation cephalosporins is variable, more than 90% of Aeromonas spp . are susceptible to the third generation agents . Of potential significance is the identification of chromosomally-encoded inducible beta-lactamases, associated with resistance to extended spectrum penicillins, cephalosporins, monobactams and carbapenems, in clinical isolates of Aeromonas spp . Two distinct enzymes are produced: the A1 enzyme, a serine beta-lactamase behaving as a group 1 cephalosporinase, and the A2 enzyme, a metallo beta-lactamase which hydrolyses a wide range of beta-lactam agents including the carbapenems . The clinical relevance of these enzymes in Aeromonas spp . is unclear.

J Med Microbiol, 1995 Mar, 42(3), 171 - 4
Possible virulence factors involved in bacteraemia caused by Aeromonas hydrophila; Vadivelu J et al.; Eighteen strains of Aeromonas hydrophila from patients with bacteraemia were investigated for possible virulence factors . Cytotoxin and haemolysin were produced by all strains, whereas cholera toxin-like factor was produced by 33% of strains only . Enterotoxin production was not detected . Haemagglutination of guinea-pig, fowl and rabbit erythrocytes was demonstrated by 83%, 67% and 61% of strains, respectively . Fucose- and mannose-sensitive haemagglutinins were predominant . None of the strains agglutinated sheep erythrocytes . Extrachromosomal DNA was detected in 17 strains, 16 of which had a plasmid (3.6-5.1 MDa), the majority being between 4.6 and 5.1 MDa.

Eur J Clin Microbiol Infect Dis, 1995 Mar, 14(3), 237 - 40
Aeromonas hydrophila myonecrosis accompanying mucormycosis five years after bone marrow transplantation; Moses AE et al.; A 36-year-old man, five years after bone marrow transplantation for aplastic anemia, was admitted with myonecrosis of the forearm after he had immersed his hand in sewage water several days prior to his admission . Blood cultures and specimens taken from the necrotic tissue of the arm all grew Aeromonas hydrophila . Following extension of the infection, the patient underwent amputation of the arm but ultimately died of cerebral mucormycosis . The epidemiology of Aeromonas infections is discussed and the literature of Aeromonas myonecrosis is reviewed.

Gene, 1995 Feb 27, 154(1), 71 - 5
Cloning, sequence and regulation of expression of the lexA gene of Aeromonas hydrophila; Riera J et al.; The lexA gene of Aeromonas hydrophila (Ah) has been isolated by using a specific one-step cloning system . The Ah LexA repressor is able to block Escherichia coli (Ec) SOS gene expression and is likely to be cleaved by the activated RecA protein of this bacterial species after DNA damage . Ah lexA would encode a protein of 207 amino acids (aa), which is 75% identical to the LexA repressor of Ec . Two Ec-like SOS boxes have been located upstream from Ah lexA, the distance between them being 4 bp, whereas this same distance in Ec lexA is 5 bp . The structure and sequence of the DNA-binding domain of the LexA repressor of Ec, as well as the region at which its hydrolysis occurs, are highly conserved in Ah LexA . Moreover, a residue of the region implicated in the specific cleavage reaction, and which is present in all known RecA-cleavable repressors, is changed in the Ah LexA . Expression of Ah lexA is DNA-damage inducible in both the Ah and Ec genetic backgrounds to the same extent . In contrast, Ec lexA is poorly induced in DNA-injured Ah cells.

J Mol Biol, 1995 Feb 3, 245(5), 568 - 81
Tyrosine phosphorylation of the tetragonal paracrystalline array of Aeromonas hydrophila: molecular cloning and high-level expression of the S-layer protein gene; Thomas SR et al.; High virulence strains of the fish pathogenic bacterium Aeromonas hydrophila produce a tetragonally arranged paracrystalline surface protein array (S-layer) . The gene (ahsA) encoding the S-protein subunit of A . hydrophila TF7 was cloned into lambda EMBL 3, and sub-cloned into pUC 18 . Transformation into Escherichia coli led to stable high-level expression of full-size S-protein under the control of its native promoter . The DNA sequence revealed a 1406 base-pair open reading frame encoding a protein consisting of a 19 amino acid residue signal peptide, and a 448 residue 45,400 Da molecular mass mature protein with a predicted isoelectric point (pI) of 6.72 compared with the measured M(r) of 52,000 and pI of 4.6 . This suggested that the S-protein was post-translationally modified and in vivo cell labelling with {32P}orthophosphate, acid phosphatase digestion of S-protein, ascending thin-layer chromatography of partially acid hydrolysed S-protein and Western blot analysis with monoclonal anti-phosphotyrosine antibody showed that the S-protein of strain TF7 contained phosphotyrosine . S-proteins produced by the other strains of motile aeromonads tested also reacted with this anti-phosphotyrosine antibody . Cell fractionation studies employing plasmid-encoded ahsA showed that in A . hydrophila the S-protein subunits were secreted across the outer membrane by the native S-protein secretion pathway, while in E . coli and A . salmonicida the cloned A . hydrophila S-protein inserted into the outer membrane of the foreign host . These findings indicate that the process employed to translocate Aeromonas S-proteins across the outer membrane is highly specific.

J Antimicrob Chemother, 1995 Feb, 35(2), 271 - 9
A clinical isolate of Aeromonas sobria with three chromosomally mediated inducible beta-lactamases: a cephalosporinase, a penicillinase and a third enzyme, displaying carbapenemase activity; Walsh TR et al.; Hydrolytic profiles of Aeromonas sobria 163a, non-induced and induced, and of a derepressed mutant 163a-M, indicate that this strain has inducible beta-lactamases with activities against cephalosporins, penicillins and carbapenems . Three enzymes were identified and two of the beta-lactamase genes, ampS, encoding a penicillinase and cepS, encoding a cephalosporinase, were cloned into Escherichia coli, permitting analysis of the individual enzymes . Isoelectric focusing (IEF) analysis using inhibition profiles with EDTA and BRL 42715, confirmed AmpS (pI 7.9) and CepS (7.0) to be serine beta-lactamases . A third beta-lactamase displaying hydrolytic activity against the carbapenems was inhibited by EDTA . The carbapenemase had a pI of 9.3 and was detected on IEF gels by overlaying the gel with agarose containing imipenem and the chromogenic pH indicator, bromothymol blue . Co-inducibility and the recovery of a derepressed mutant in which all three enzymes were produced at high levels indicate that this isolate of A . sobria has three co-ordinately controlled beta-lactamase genes.

Antimicrob Agents Chemother, 1995 Feb, 39(2), 346 - 9
Distribution of cphA or related carbapenemase-encoding genes and production of carbapenemase activity in members of the genus Aeromonas; Rossolini GM et al.; The prevalence of the cphA gene or related carbapenemase-encoding genes was investigated in 114 Aeromonas strains belonging to the six species of major clinical interest . A species-related distribution of cphA-related sequences was observed . Similar sequences were found in A . hydrophila, A . veronii bv . sobria, A . veronii bv . veronii, and A . jandaei, but not in A . caviae, A . trota, or A . schubertii . However, a single A . caviae strain (of 62 tested) was found carrying cphA-related sequences, suggesting the possibility of the horizontal transfer of this gene to species which normally do not carry it . Production of carbapenemase activity was detectable in 83% of the hybridization-positive strains but in none of the hybridization-negative ones . When it was present, carbapenemase activity was always inhibitable by EDTA . Either carbapenemase-producing or not, Aeromonas strains appeared to be susceptible to imipenem when in vitro susceptibility testing was performed with inocula of conventional size (10(5) CFU), for which MICs were always < or = 1 microgram/ml . With a larger inoculum (10(8) CFU), the MICs for carbapenemase-negative strains always remained < or = 1 microgram/ml, while those for carbapenemase-producing strains were always > or = 4 micrograms/ml, being usually higher than the breakpoint for susceptibility . The present results indicate that the production of metallocarbapenemase activity, apparently encoded by cphA homologs, is widespread among some of the Aeromonas species of clinical interest (A . hydrophila, A . veronii bv . sobria, A . veronii bv . veronii, and A . jandaei) and that imipenem MICs for carbapenemase-producing strains are subjected to a relevant inoculum size effect.

J Appl Bacteriol, 1995 Feb, 78(2), 175 - 9
Differences in production of several extracellular virulence factors in clinical and food Aeromonas spp . strains; Pin C et al.; Production of several extracellular virulence factors (lipase, protease and haemolysin) was compared in 15 Aeromonas spp . isolated from faeces of patients with Aeromonas-associated gastroenteritis and 81 strains isolated from food . Strains from food did not show differences in production of these factors when compared with strains isolated from faeces . However, if strains were considered in relation to autoagglutination (AA) character, the AA+ differed from AA- strains in lipase and protease production . Supernatant fluids of AA+ food and human strains showed 2.5-fold more protease production than that observed in AA- strains . These two characteristics of certain Aeromonas strains could be related with the more virulent capacity.

Arch Inst Pasteur Tunis, 1995 Jan-Apr, 72(1-2), 13 - 5
Haemolytic activity of Aeromonas species isolated in Libya; Ghenghesh KS et al.; Twenty seven Aeromonas strains (5A . hydrophila, 8A . sobria and 14A . caviae) isolated from children with diarrhoea and 34 Aeromonas strains (9A . hydrophila, 7A . sobria an 18A . caviae) isolated from children without diarrhoea were tested from haemolysin production . The results obtained showed that haemolysin production using human, horse or sheep erythrocytes was significantly associated with A.hydrophila and A sobria but not with A.caviae, regardless of whether these strains were isolated from children with or without diarrhoea . Human or horse rather than sheep erythrocytes are recommended for use in the haemolysin assay.

Scand J Infect Dis . 1995;27(3):295.
Aeromonas hydrophila lung abscess in a previously healthy man; Hur T et al.; We present a case of multilocular lung abscess caused by Aeromonas hydrophila, found in both sputum and bronchial washing . No aspiration or other significantly contributory medical conditions were found . We believe this to be the first report of lung abscess caused by this organism in a previously healthy individual.

Comp Immunol Microbiol Infect Dis, 1995 Jan, 18(1), 69 - 72
Fatal disease mimicking leptospirosis in a dog, caused by Aeromonas hydrophila; Andre-Fontaine G et al.; A dog was treated for leptospirosis on clinical and epidemiological arguments . The amoxicillin treatment was not successful . Pure culture of Aeromonas hydrophila was then obtained from liver and kidney, indicating that the septicemia was due to this bacteria commonly found in waters.

Mol Microbiol, 1995 Jan, 15(1), 65 - 75
Molecular characterization of an Aeromonas salmonicida mutant with altered surface morphology and increased systemic virulence; Noonan B et al.; The asoA gene of Aeromonas salmonicida is located approximately 7 kb downstream of the A-layer structural gene, vapA . A 6 kb BamHI fragment containing asoA was cloned and marker-exchange mutagenesis using a kanamycin-resistance cassette was performed to generate an asoA mutation in the low-virulence strain A449L . When analysed by electron microscopy, the mutant A449L-MB exhibited an altered surface morphology . Strands and blebs of membranous material were observed protruding from the disorganized cell surface . This material was shown to contain lipopolysaccharide and A-layer subunit protein . The disorganization of the surface of A449L-MB had no apparent effect on virulence when the bacteria were administered to rainbow trout (Oncorhynchus mykiss) by bath immersion . However, when administered by intraperitoneal injection, the mutant A449L-MB was found to exhibit significantly increased virulence . The predicted amino acid sequence of AsoA shows homology to a number of polytopic membrane proteins involved in translocation across the cytoplasmic membrane.

J Med Microbiol, 1995 Jan, 42(1), 32 - 8
Temperature-dependent protein and lipopolysaccharide expression in clinical Aeromonas isolates; Tso MD et al.; Clinical isolates of Aeromonas were grown at eight different temperatures from 10 degrees C to 40 degrees C . Whole cell lysates were examined by SDS-PAGE and major temperature-dependent changes to both protein and lipopolysaccharide (LPS) profiles were identified . Cells grown at the higher temperatures (37 degrees C and 40 degrees C) produced abundantly a protein of c . 60 kDa which was not detected at the lower temperatures . Temperature-dependent expressions of other proteins were also noted but these were more variable among the isolates . An effect of temperature on expression of lipopolysaccharides was also noted in that some strains produced significantly less O-polysaccharides at the higher temperatures . After fractionation of cells, major differences in the expression of cell envelope and outer-membrane proteins between cells grown at low and high temperatures were noted although no unifying patterns could be discerned . Such growth temperature-induced changes in the cell envelope constituents have not been described previously for Aeromonas isolates from man.

J Med Microbiol, 1995 Jan, 42(1), 26 - 31
Association of Aeromonas spp . with travellers' diarrhoea in Finland; Hanninen ML et al.; The association of Aeromonas spp . with travellers' diarrhoea was studied among 978 Finnish tourists travelling to Morocco in winter (n = 398) and autumn (n = 580) in 1989 . Fifty-five isolates from diarrhoeal patients with (n = 16) or without (n = 39) a recent travelling history in a developing country were also included . In Morocco, Aeromonas spp . were isolated from 8.7% of patients with diarrhoea and from 1.4% of non-diarrhoeal tourists (p < 0.001) . Aeromonas spp . were found as the sole pathogen in 5.5% of patients (p < 0.001) . Diarrhoea with multiple pathogens, including Aeromonas spp., was found in 3.1% of patients . Species identification by phenotypic and genotypic methods indicated that A . veronii biotype sobria (hybridisation group HG 8/10) and A . caviae (HG 4) were the most common Aeromonas spp . associated with travellers' diarrhoea . A . hydrophila (HG 1) and A . caviae (HG 4) were common in patients acquiring diarrhoea in Finland . Ribotyping of strains within a species showed that all strains had different ribotypes although the tourists were infected during the same trip . This study suggested that only certain Aeromonas spp . were commonly found in travellers' diarrhoea . However, the causative role of those species is unclear.

Vet Res, 1995, 26(1), 57 - 62
Ecopathology in aquaculture: risk factors in infectious disease outbreak; Ortega C et al.; This paper describes a study of the risk factors associated with disease outbreaks in fish species of fish farms and rivers of north-east Spain . We focused our work on the isolation of fish pathogens (bacteria, virus), the water quality (physicochemical and microbiological quality) and management characteristics . We have observed 2 important viral diseases, infectious pancreatic necrosis and spring viraemia of carp, and 2 important bacterial ones, furunculosis (Aeromonas salmonicida) and bacterial kidney disease (BKD) (Renibacterium salmoninarum) . Our preliminary results show that there are some potential risk factors associated with the main diseases of fish, such as fish age, fish species, production system, season and water temperature, but their role depends on the disease.

Int J Food Microbiol, 1995 Jan, 24(3), 375 - 84
Comparison of seven selective media for the isolation of mesophilic Aeromonas species in fish and meat; Gobat PF et al.; Seven selective agar media and two enrichment broths were evaluated for their suitability for the isolation of mesophilic Aeromonas species from meat, fish, and shellfish samples . In a first trial, aeromonads were inoculated in fish and meat samples and reisolated using all selected media . For qualitative isolation, enrichment in alkaline peptone water (pH 8.7 +/- 0.1) at 28 degrees C and subsequent plating onto sheep blood agar supplemented with 30 mg/L ampicillin (ASBA 30) and bile salts-irgasan-brilliant green agar (BIBG) at 35 degrees C led to the best results . For quantitative assays, direct plating on the same agar media is recommended . In a second trial, 829 meat, fish, and shellfish samples were investigated with the same methods . The results show that BIBG is the most selective medium and that presumptive identification of aeromonads on ASBA 30 is very easy . Finally, we could confirm the opinion of other workers that optimal recovery of mesophilic Aeromonas spp . requires the use of more than one agar medium.

Dev Comp Immunol, 1995 Jan-Feb, 19(1), 43 - 57
Yeast beta-glucan stimulates respiratory burst activity of Atlantic salmon (Salmo salar L.) macrophages; Jorgensen JB et al.; Previous studies have shown that head kidney macrophages isolated from glucan injected rainbow trout (Oncorhychus mykiss) and Atlantic salmon (Salmo salar L.) have increased ability to kill Aeromonas salmonicida . The present work was aimed at investigating the in vitro effects of glucan on the respiratory burst and bactericidal potential of Atlantic salmon head kidney macrophages . Salmon macrophages were incubated for 1-7 days with various concentrations of yeast beta-glucan (MacroGard) and tested for respiratory burst activity by the reduction of nitroblue-tetrazolium (NBT) after exposure to phorbol myristate acetate (PMA) or opsonized zymosan . The macrophages showed a marked increase in respiratory burst activity 4 to 7 days after addition of glucan . Macrophages treated with 0.1-1 microgram mL-1 gave a maximum respiratory burst response, whereas 10 micrograms mL-1 had no effect and 50 micrograms mL-1 was inhibitory . The glucan also triggered respiratory burst activity directly, but this occurred only at relative high concentrations with a maximal effect at > or = 200 micrograms mL-1 . The validity of using the NBT-assay as a measure of respiratory burst activity was confirmed by using inhibitors of O2- production (superoxide dismutase, trifluoperazine and diphenylene iodonium) . Despite the stimulatory effect of glucan on the respiratory burst activity of salmon macrophages, these cells did not show increased bactericidal activity against the avirulent and virulent strain of A . salmonicida . Upregulation of burst activity alone is thus apparently not sufficient to enhance bactericidal activity against this pathogen by Atlantic salmon macrophages.

Eur J Clin Microbiol Infect Dis, 1995 Jan, 14(1), 51 - 3
Chronic diarrhea due to a single strain of Aeromonas caviae; Rautelin H et al.; Over a period of 17 months, Aeromonas caviae was cultured 15 times as the sole enteropathogen from the feces of a man who had developed chronic diarrhea after traveling to Turkey . Determination of rRNA gene restriction patterns confirmed that the seven isolates of Aeromonas caviae studied were identical (hybridization group {HG}4) . After therapy with ciprofloxacin for four weeks, the patient was culture negative for the original isolate, and six months later a novel strain of Aeromonas media with a different ribopattern (HG 5A) was isolated from the feces of the patient . The patient responded again, both clinically and bacteriologically, to a four-week course of ciprofloxacin and has remained asymptomatic since then.

J Basic Microbiol, 1995, 35(4), 241 - 7
Proteolytic activity of Aeromonas caviae; Karunakaran T et al.; Aeromonas strains produce a variety of virulence factors including proteases . Studies on the kinetics of growth of Aeromonas caviae NRRL B-966 and its proteases suggest that the proteolytic activities are produced throughout the growth phase, with peak level occurring at stationary phase . A . caviae synthesize both intracellular and extracellular proteases with the latter account for major portion of the total activity . Optimum pH for the A . caviae proteolytic activity is at 7.0 . A . caviae produces a thermoresistant protease, whose activity is dependent on Mg++ and Ca++ ions . Inhibition of proteolytic activity by phenyl methyl sulfonyl fluoride suggest the presence of a serine protease in A . caviae . Nitrogenous compounds enhance the proteolytic activity while carbohydrates tested in this study inhibit the activity.

J Biol Chem, 1994 Dec 2, 269(48), 30496 - 501
The C-terminal peptide produced upon proteolytic activation of the cytolytic toxin aerolysin is not involved in channel formation; van der Goot FG et al.; The channel-forming toxin aerolysin is secreted by Aeromonas hydrophila as a protoxin that can be activated by nicking with endoproteinase Lys-C after Lys-427 near the C terminus of the protein . The fate of the 43-amino acid peptide distal to the activation site was investigated . A cysteine was introduced into the C-terminal region by replacing Ile-445, and another replaced Gly-202, which is on the proximal side of the activation site . In a double mutant, the two new cysteines were close enough in the folded molecule to form an intrachain 202-445 disulfide bond . Tryptophan fluorescence measurements on wild type and the 2 single cysteine mutants indicated that activation results in exposure of at least 1 tryptophan residue, leading to the conclusion that the peptide moves with respect to the protein when it is produced . This was supported by the observation that upon activation there was a decrease in energy transfer between a tryptophan in the bulk of the protein and a probe attached to Cys-445 . The peptide could be separated from active toxin by several methods, indicating that it leaves the protein when it is produced, and that it plays no further role in the process of channel formation.

Anat Rec, 1994 Dec, 240(4), 589 - 97
Phagocytic defence mechanism in sea bass (Dicentrarchus labrax L.): an ultrastructural study; Esteban MA et al.; BACKGROUND: The ultrastructure of the phagocytic process in fish has not been established in spite of the significant morphofunctional differences detected in the fish immune system with respect to the basic immunological pattern in vertebrates . We report the ultrastructure of the bacterial phagocytic defence mechanism in sea bass (Dicentrarchus labrax L.) . METHODS: Head-kidney, blood, and peritoneal exudate leukocytes were challenged with Aeromonas salmonicida and Escherichia coli and processed for transmission electron microscopic study . RESULTS: Macrophages challenged with bacteria showed changes in the cell outline, in the chromatin pattern, and in the ultrastructural features of the cytoplasm as a consequence of an activation process . The phagocytic process consists of the following: 1) Bacteria-macrophage contact . One or more spot contacts between the bacterial wall and the phagocyte membrane are observed . 2) Bacteria engulfment . Slight depressions, membrane invaginations, or cytoplasmic processes are formed at the phagocyte surface . Macrophage processes occasionally surround the bacteria, overlapping and roaming parallel, or a single, long pseudopod encircles a bacterium several times . 3) Endocytic vesicle formation . Macrophages show one or more bacteria inside membrane-bound cytoplasmic vesicles . 4) Phagolysosome formation . Some dense granules (lysosomes) fuse with the endocytic vesicle . 5) Intracellular killing/digestion . Bacteria inside the endocytic vesicles are observed both virtually intact or damaged at different digestion stages . CONCLUSIONS: Sea bass macrophages possess the mechanisms necessary to both engulf and kill bacteria . Cellular and subcellular events in the morphology of phagocytosis and lysosomal dissolution of bacteria fit the general pattern described for mammals.

J Appl Bacteriol, 1994 Dec, 77(6), 722 - 6
Rapid identification of Aeromonas species using 16S rDNA targeted oligonucleotide primers: a molecular approach based on screening of environmental isolates; Dorsch M et al.; Published 16S rDNA sequencing data for Aeromonas species were analysed and the validity of signature sequences derived from our investigations of these sequences was examined by sequencing the corresponding 16S rDNA regions of 67 environmental isolates from sewage effluents and receiving waters around Sydney and one clinical isolate, all previously classified as Aeromonas species . Species-specific probes for Aer . hydrophila and Aer . veronii were designed and tested in PCR assays and clearly discriminated these species from the other Aeromonas isolates as identified by 16S rDNA sequences.

Infect Immun, 1994 Dec, 62(12), 5483 - 90
Aeromonas salmonicida resistance to complement-mediated killing; Merino S et al.; The resistance of Aeromonas salmonicida to complement-mediated killing was investigated by using different strains and their isogenic mutants that had been previously characterized for their surface components . We found that the classical complement pathway is involved in serum killing of susceptible A . salmonicida strains, while the alternative complement pathway seems not to be involved . All of the A . salmonicida strains are able to activate complement, but the smooth strains (with or without the A-layer) are resistant to complement-mediated killing . The reasons for this resistance are that C3b may be bound far from the cell membrane and that it is rapidly degraded; therefore, the lytic final complex C5b-9 (membrane attack complex) is not formed . Isogenic rough mutants are serum sensitive because they bind more C3b than the smooth strains, and if C3b is not completely degraded, then the lytic complex (C5b-9) is formed.

J Protein Chem, 1994 Nov, 13(8), 659 - 67
Homology between the seed cytolysin enterolobin and bacterial aerolysins; Sousa MV et al.; Enterolobin, a 55-kDa cytolytic, inflammatory, and insecticidal protein isolated from seeds of the Brazilian tree Enterolobium contortisiliquum (Leguminosae-Mimosoideae) has been further purified and partially sequenced by using both manual and automated methods . A computational search of enterolobin partial amino acid sequence against the PIR database revealed possible sequence similarities with aerolysins, cytolytic proteins from Aeromonas species . An alignment of enterolobin partial sequence to the amino acid sequences of A . hydrophila and A . sobria aerolysins showed several similar regions with many residue identities . The seed protein enterolobin and the bacterial aerolysins may be homologous proteins despite the distant phylogenetic relationship.

Microbiology, 1994 Oct, 140 ( Pt 10), 2899 - 905
The susceptibility of S-layer-positive and S-layer-negative Aeromonas strains to complement-mediated lysis; Janda JM et al.; Forty strains of Aeromonas hydrophila and Aeromonas veronii recovered from invasive and non-invasive infections were tested for their susceptibility to complement-mediated lysis by 65% pooled human serum (PHS) . Based upon the results of this assay, two major populations could be defined . The first group (n = 20) consisted of serogroup O:11 strains, all of which possessed a paracrystalline surface layer (S layer); all of these strains were refractory to the bactericidal activity of 65% PHS with the exception of A . hydrophila strain AH-121, which was composed of mixed subpopulations of serum-susceptible and serum-resistant clones . A second collection of isolates (n = 20), all of which were S-layer-negative, contained a subgroup of strains (n = 7) that were highly susceptible to complement-mediated lysis, showing a greater than 100-fold reduction of viable progeny within 30 min of exposure to 65% PHS . Serum-resistant strains from both groups could not be lysed by exposure of bacterial cells to polyclonal somatic or whole cell antisera or to 30 micrograms ml-1 of polymyxin B nonapeptide prior to challenge with 65% PHS . Analysis of selected serum-resistant and serum-susceptible strains from both groups showed that all isolates activated the complement pathway and most bound C3b to the cell surface, indicating that the inability of complement to lyse serum-resistant strains was related to a defect in the terminal portions of the complement pathway.(ABSTRACT TRUNCATED AT 250 WORDS)

Eur J Clin Microbiol Infect Dis, 1994 Oct, 13(10), 805 - 11
Three beta-lactamases isolated from Aeromonas salmonicida, including a carbapenemase not detectable by conventional methods; Hayes MV et al.; The beta-lactamases of seven strains of Aeromonas salmonicida subsp . achromogenes resistant to amoxicillin (MIC > 1024 mg/l) and responsible for furunculosis in farmed Atlantic salmon in Scotland were examined to establish the mechanisms of beta-lactam resistance . Separation of a cell-free extract on an isoelectric focusing gel stained with the chromogenic cephalosporin nitrocefin showed the presence of two beta-lactamases, one with a pI of 7.9 and the other with a pI of 6.0 . Hydrolysis assays of cell-free extracts of these strains demonstrated carbapenemase, penicillinase and cephalosporinase activity . However, when the beta-lactamases were separated by anion exchange chromatography, the carbapenemase activity could not be retrieved in either of the peak fractions containing the separated enzymes that had been visualised by nitrocefin . Consequently, a novel carbapenemase was discovered which cannot be detected with nitrocefin.

Int J Food Microbiol, 1994 Oct, 23(2), 221 - 5
Presence of Aeromonas hydrophila in slaughtered animals; Buncic S et al.; The fate of Aeromonas hydrophila after a bacteriaemia in four healthy pigs intravenously inoculated with 10(9) and 10(15) cells of the bacterium was investigated . In two pigs slaughtered 30 min after inoculation the bacteria were found in blood (8 x 10(2)/ml and 4.2 x 10(2)/ml), meat and fatty tissues (1-10/g), but not in liver, spleen and superficial inguinal lymph nodes . A . hydrophila was not found in blood, meat, fatty tissue, liver, spleen, kidneys and superficial inguinal lymph nodes of other two pigs slaughtered 5.5 h postinoculation, with exception of one superficial inguinal lymph node of one pig.

Antimicrob Agents Chemother, 1994 Oct, 38(10), 2460 - 4
gyrA mutations in quinolone-resistant isolates of the fish pathogen Aeromonas salmonicida; Oppegaard H et al.; gyrA mutations in quinolone-resistant isolates of Aeromonas salmonicida have been detected by using PCR to amplify the quinolone resistance-determining region of gyrA and subsequent cloning and sequencing of PCR products . Comparison of nucleotide and derived amino acid sequences of PCR products from quinolone-susceptible and -resistant bacteria revealed a serine 83-to-isoleucine substitution in the gyrase A protein of resistant isolates . One of the resistant isolates differed from the other by a two- to fourfold-higher MIC of the fluoroquinolone enrofloxacin and carried an additional alanine 67-to-glycine substitution, which may contribute to the higher level of resistance.

Nippon Eiseigaku Zasshi, 1994 Oct, 49(4), 782 - 90
{Relationship between bacteria decomposing organic substances and water pollution in river water}; Wada M; In order to clarify the relationship between water pollution and bacteria decomposing organic substances, 48 samples of river water were collected at twelve stations of the Chikuma-Sai river system . The bacteria decomposing organic substances were enumerated and identified by GM plates, which contained fewer organic substances than agar plates . Sixteen biological-physicochemical examinations of the river water were also performed . The results were as follows: temperature and dissolved oxygen in river water influenced the number of bacteria decomposing organic substances; proportions of bacteria decomposing degradable organic substances were higher in summer and spring than those in winter and autumn; the proportions of bacteria decomposing undegradable organic substances were higher in winter and autumn than those in other seasons . Organic substances were decomposed mainly by Aeromonas, a coliform group of facultatively anaerobic Gram-negative rods, and Pseudomonas, Gram-negative aerobic rods . Organic substances decomposed by facultatively anaerobic Gram-negative rods were much more degradable than those decomposed by Gram-negative aerobic rods . It seemed that the bacterial population of Aeromonas and the coliform group in river water increased with increases in the effluent of domestic and sewage abundant in degradable organic substances . Although Gram-positive rods were hardly isolated from river water, most of them decomposed undegradable organic substances . These results suggest that most bacteria decomposing organic substances are mainly distributed in river water and soil, and that modification of the river environment influences self-purification of rivers.

J Wildl Dis, 1994 Oct, 30(4), 577 - 80
Relationship between resistance of salmonids to furunculosis and recovery of Aeromonas salmonicida from external mucus; Cipriano RC et al.; Fish were sampled at the Ed Weed State Fish Hatchery (South Hero, Vermont, USA) in September 1992 . Aeromonas salmonicida was common, with concentrations as high as 10(5) to 10(7) colony-forming units per gram of mucus, and readily recovered from most mucus samples obtained from furunculosis-sensitive populations of brook trout (Salvelinus fontinalis), lake trout (Salvelinus namaycush), and Atlantic salmon (Salmo salar) . The pathogen was the predominant microorganism and accounted for greater than 85% of the total number of bacteria isolated from the mucus of these fish . By comparison, A . salmonicida was recovered only from two rainbow trout (Oncorhynchus mykiss), and bacterial frequencies did not exceed 10(3) colony-forming units per gram of mucus . The pathogen was not recovered from the mucus of steelhead (O . mykiss) or Rome brown trout (Salmo trutta) selectively bred for resistance to furunculosis, even though there was widespread contagion throughout the hatchery and fish were cultured on a common, unprotected water supply.

Appl Environ Microbiol, 1994 Oct, 60(10), 3874 - 7
Detection of Aeromonas salmonicida, causal agent of furunculosis in salmonid fish, from the tank effluent of hatchery-reared Atlantic salmon smolts; O'Brien D et al.; The fish pathogen, Aeromonas salmonicida, could be detected only by bacteriological culture from the kidney of dead or moribund fish in one tank in a hatchery rearing Atlantic salmon (Salmo salar L.) smolts . However, by using a DNA probe specific for this species, allied to a PCR assay, the pathogen could be detected in water, feces and effluent samples taken from this fish tank . Also, the presence of the pathogen was found in effluent samples from two fish tanks containing apparently healthy fish . Subsequently, the presence of pathogen in these tanks was confirmed by an increase in the daily mortality rate and by a plate culture from moribund fish.

Parasitology, 1994 Sep, 109 ( Pt 3), 299 - 310
Modulation of the bacterial clearance activity of haemocytes from the freshwater mollusc, Lymnaea stagnalis, by the avian schistosome, Trichobilharzia ocellata; Nunez PE et al.; The ability of haemocytes, from the haemolymph of the gastropod mollusc Lymnaea stagnalis, to recognize and eliminate the bacterium Aeromonas salmonicida was shown using an in vitro bacterial clearance assay . The assay employs a dye which is reduced by A . salmonicida in direct proportion to the number of viable bacteria resulting in a colour change which can be determined spectrophotometrically . Addition of cytochalasin B resulted in a marked decrease in bacterial clearance, implicating both intracellular and extracellular cytotoxicity of haemocytes . A comparison of haemocytes from uninfected snails and snails infected with the avian schistosome parasite Trichobilharzia ocellata showed that both juveniles and adults of L . stagnalis were susceptible to infection with T . ocellata . After exposure to the trematode for 1.5 h the haemocytes from these infected snails had an enhanced clearance capacity, whilst cells obtained from snails with 24-96 h infections showed decreased clearance of the bacteria, indicating suppression by the parasite . Haemocytes, as well as plasma, which was tested on haemocytes from uninfected snails, were used and hence a distinction was made between cell and humoral-associated effects . The results show that both cellular and humoral components of immunity were activated, then suppressed, following exposure to the parasite . Infection with T . ocellata seems to have a modulating effect on the bactericidal activity of the internal defence system of the snail host, L., stagnalis.

What Is MIC?, What Is Anthrax?, What Is Pcr?, What Is Genome?, What Is Cell Biology?, a, Microbiology, c, Bacteriology, r, Microbe, a, Bacteria, a, Bacterium, o, Escherichia coli, n, Escherichia coli, o, Clostridia, o, Neisseria, c, Minimum inhibiting concentration, s, S. cerevisiae, r, Clostridia, c, S. cerevisiae, e, Culture medium, s, Microbial, s, Rhodococci, o, Culture medium, a, Klebsiella, i, Acinetobacter, a, Penicillin, c, Escherichia coli, c, Candida albicans, o, Salmonella, e, Bactericidal, r, Antibiotics, i, Yeasts

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

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

Last modified: May 25, 2005