Aeromonades

Microbiologia, 1994 Sep, 10(3), 257 - 62
Incidence of motile Aeromonas spp . in foods; Pin C et al.; A total of 80 food samples were purchased from local retail consumer shops and examined for the presence of motile Aeromonas spp . Of the food categories tested, poultry had the highest incidence, with 100% positive . This was followed by lamb samples, with 60% positive . Raw milk and cheese samples had very low incidence (20%) . No motile Aeromonas spp . were found in pre-prepared salads . Shellfish, fish, pork and beef samples had incidences of 40% . Most of the strains isolated were Aeromonas hydrophila, and for most of the food categories, no Aeromonas caviae isolates were obtained.

Infect Immun, 1994 Sep, 62(9), 4054 - 8
Carbohydrate-reactive, pore-forming outer membrane proteins of Aeromonas hydrophila; Quinn DM et al.; Two outer membrane proteins of Aeromonas hydrophila A6, isolated in a one-step affinity chromatography process based on carbohydrate reactivity, were found to be pore-forming molecules in artificial planar bilayer membranes . These carbohydrate-reactive outer membrane proteins (CROMPs; M(r)s, 40,000 and 43,000) were subjected to amino acid analysis . The amino acid profiles for these two outer membrane proteins were almost identical . A partial protein sequence of a 14-amino-acid fragment of the 40,000-Da protein revealed homology with outer membrane porins of Escherichia coli and A . hydrophila . CROMPs were compared with carbohydrate-reactive porins also extracted from outer membranes of A . hydrophila A6 . These porins were isolated by using standard porin purification techniques (insolubility in 2% sodium dodecyl sulfate, solubility in 0.4 M NaCl, and Sephacryl S-200 gel filtration), and then Synsorb H type 2 affinity chromatography was done . The physical and functional properties of the carbohydrate-reactive porins and CROMPs were found to be identical . On the basis of pore-forming properties in planar lipid bilayers and channel inhibition with maltotriose solutions, a nonspecific, general diffusion porin and a LamB-like maltoporin were identified in both CROMP and carbohydrate-reactive porin preparations . To our knowledge, the use of carbohydrate reactivity to isolate channel-forming proteins from bacterial outer membranes has not been reported previously.

Vet Immunol Immunopathol, 1994 Aug, 42(2), 199 - 208
Antigen-induced release of macrophage activating factor from rainbow trout Oncorhynchus mykiss leucocytes; Marsden MJ et al.; The production of macrophage-activating factor (MAF) by rainbow trout, Oncorhynchus mykiss, head kidney leucocytes at varying times post-immunisation, with the fish bacterial pathogen, Aeromonas salmonicida, was investigated and correlated with head kidney lymphocyte proliferation and serum antibody production . MAF production was preceded by lymphocyte proliferation and both responses were highest using whole bacterial cells as the in vitro stimulant . MAF production and antibody production increased 2-3 weeks post-immunisation, and peaked 4-5 weeks post-immunisation . The relative importance of MAF activated phagocytes in the immunological armoury of disease-resistant, vaccinated fish requires further investigation.

Can J Microbiol, 1994 Aug, 40(8), 622 - 9
Physiological consequences of the S-layer of Aeromonas salmonicida in relation to growth, temperature, and outer membrane permeation; Garduno RA et al.; S-layers are paracrystalline protein multimers that cover the entire cell surface of many bacterial species . The presence of an S-layer in Aeromonas salmonicida (also known as A-layer) predisposed this bacterium to apparently unrelated physiological consequences: inhibition of growth at 30 degrees C, enhanced cell filamentation at 37 degrees C, and enhanced uptake of the hydrophobic antibiotics streptonigrin and chloramphenicol . Growth inhibition or enhanced filamentation was not observed when the native A-layer was missing or its arrangement altered, as in Ca(2+)-limited or Ca(2+)- and Mg(2+)-limited cells, in A-layer-negative (A-) cells with an artificially reconstituted A-layer, or in mutants unable to correctly assemble this layer . A-layer-positive cells (A+) were far more sensitive to the intracellularly acting antibiotics streptonigrin and chloramphenicol than were A- cells, and streptonigrin-resistant mutants were predominantly A- . Hemin, a compound known to specifically bind to the A-layer, alleviated streptonigrin toxicity to A+, but not A-, cells . As well, Ca(2+)- and Mg(2+)-limited cells, or mutants harboring A-layer defects had a reduced sensitivity to streptonigrin, and A- cells with reconstituted A-layers remained resistant to streptonigrin and chloramphenicol . Thus, the presence of a native A-layer arrangement on the cell surface, and not the mere presence of A-layer protein subunits, predisposed A . salmonicida toward the aforementioned physiological consequences . The A-layer is suggested to specifically effect these consequences, in particular the permeation of streptonigrin or chloramphenicol, by a specific interaction of A-layer subunits with the outer membrane.

J Clin Pathol, 1994 Jul, 47(7), 642 - 6
Assessment of a chemiluminescent universal probe for taxonomical and epidemiological investigations of Aeromonas sp isolates; Carey PE et al.; AIMS--To assess a chemiluminescent universal probe for taxonomical and epidemiological investigations of Aeromonas sp isolates . METHODS--Total DNA was extracted from 69 well characterised Aeromonas sp strains and digested with the restriction endonucleases Sma I or Pst I . Following electrophoresis, the resulting fragments were transferred to a nylon membrane where they were hybridised to a commercially available universal probe of 16S + 23S rRNA . The banding patterns (ribotypes) were made visible by enhanced chemiluminescence . RESULTS--Both restriction endonucleases produced heterogeneous ribotypes so that no allocation could be made to any of the control genospecies tested . For A hydrophila and A caviae, however, groups of strains (mostly from the same patient) could be identified by indistinguishable banding patterns . A relatively high proportion (36%) of A sobria strains were non-typable . CONCLUSIONS--Although this universal chemiluminescent probe is user friendly, it is unsuitable for taxonomical investigations of Aeromonas sp . It is useful in epidemiological studies of A hydrophila and A caviae, but is of less value for A sobria.

Microbiology, 1994 Jul, 140 ( Pt 7), 1731 - 6
Adaptive acid tolerance response (ATR) in Aeromonas hydrophila; Karem KL et al.; Aeromonas hydrophila, a gastrointestinal pathogen of humans, was shown to exhibit a significant adaptive acid tolerance response (ATR) capable of protecting cells from severe acid at a pH of 3.5 . The ATR was induced by exposure to a relatively mild pH level of 5.0 for 20 min . Adaptation required protein synthesis since treatment with chloramphenicol during adaptation to pH 5.0 prevented the development of acid tolerance . The adaptation to acid environment was found to be a non-transient phenomenon . Also, iron was not required for acid adaptation in A . hydrophila . Two-dimensional protein analyses revealed an increased production of 28 proteins and decreased synthesis of 10 following pH shifts from 7.2 to 5.0 . The mild pH treatment must act as a signal to A . hydrophila to adapt and survive in acid environments by producing 'protective' proteins . The adaptation and survival of this pathogen in low pH may provide valuable information about its ability to withstand acid environments in nature and in the human gastrointestinal tract.

Biometals, 1994 Jul, 7(3), 227 - 36
Diversity of siderophore genes encoding biosynthesis of 2,3-dihydroxybenzoic acid in Aeromonas spp; Massad G et al.; Most species of the genus Aeromonas produce the siderophore amonabactin, although two species produce enterobactin, the siderophore of many enteric bacteria . Both siderophores contain 2,3-dihydroxybenzoic acid (2,3-DHB) . Siderophore genes (designated aebC, -E, -B and -A, for aeromonad enterobactin biosynthesis) that complemented mutations in the enterobactin genes of the Escherichia coli 2,3-DHB operon, entCEBA(P15), were cloned from an enterobactin-producing isolate of the Aeromonas spp . Mapping of the aeromonad genes suggested a gene order of aebCEBA, identical to that of the E . coli 2,3-DHB operon . Gene probes for the aeromonad aebCE genes and for amoA (the entC-equivalent gene previously cloned from an amonabactin-producing Aeromonas spp.) did not cross-hybridize . Gene probes for the E . coli 2,3-DHB genes entCEBA did not hybridize with Aeromonas spp . DNA . Therefore, in the genus Aeromonas, 2,3-DHB synthesis is encoded by two distinct gene groups; one (amo) is present in the amonabactin-producers, while the other (aeb) occurs in the enterobactin-producers . Each of these systems differs from (but is functionally related to) the E . coli 2,3-DHB operon . These genes may have diverged from an ancestral group of 2,3-DHB genes.

Clin Infect Dis, 1994 Jul, 19(1), 77 - 83
Aeromonas species in septicemia: laboratory characteristics and clinical observations; Janda JM et al.; We retrospectively analyzed clinical and epidemiological data on and laboratory characteristics of 53 cases of aeromonas septicemia . Only four Aeromonas genomospecies (species defined by DNA relatedness) were associated with the 53 cases, with Aeromonas hydrophila (sensu stricto) predominating (47%) . Nearly 60% of all Aeromonas isolates from blood fell into one of four somatic groups: serogroups O:11, O:16, O:18, and O:34 . Unlike Aeromonas-associated gastroenteritis, septicemia did not peak in frequency during the warmer months but rather was most common in January through March, when approximately 40% of cases occurred . In vitro tests of the pathogenicity of 20 selected blood isolates of Aeromonas indicated that resistance to complement-mediated lysis, elevated levels of protease and hemolysin activity, and the ability to elaborate siderophores correlated with higher virulence . Species and serogroup designations also correlated with the degree of virulence . Susceptibility studies of 50 strains indicated that A . hydrophila was the most drug-resistant species and that Aeromonas veronii was the most susceptible . Susceptibility to first- and second-generation cephalosporins and carbenicillin was species-associated.

J Wildl Dis, 1994 Jul, 30(3), 447 - 9
Isolation of Aeromonas salmonicida from paddlefish, Polyodon spathula; Ford LA et al.; Aeromonas salmonicida was isolated from paddlefish (Polyodon spathula) mortalities collected during an epizootic of furunculosis at the Spring River State Hatchery, Arkansas (USA), in 1992 . Isolates of the bacterium were obtained from culture of gill and kidney tissue . This is the first epizootic of bacterial etiology to be reported in paddlefish.

J Appl Bacteriol, 1994 Jul, 77(1), 21 - 30
Characterization of Aeromonas salmonicida subsp . salmonicida: a comparative study of strains of different geographic origin; Dalsgaard I et al.; A total of 130 strains of the fish pathogen Aeromonas salmonicida isolated in Denmark, Norway, Scotland, Canada and the USA were examined . The strains originated from farmed salmonid fish . The biochemical, physiological and serological characteristics, antibiotic resistance patterns and cell surface-related properties were compared . Aeromonas salmonicida was found to be remarkably consistent in general cultural and biochemical characteristics . It is noteworthy that the strains were positive in the fermentation of L-arabinose and were negative in the fermentation of D-arabinose . All the strains were highly proteolytic . It was observed, however, that 5% of the strains did not digest calf and trout serum and the production of haemolysin and degradation of casein by the same strains were delayed compared with the other strains . Common to all of the rough strains were auto-aggregation and ability to bind the dyes Coomassie brilliant blue and Congo red and the majority of these strains were highly hydrophobic . The strains were tested for their susceptibility to 22 antibacterial agents . Antibiotic resistance profiles of Aer . salmonicida indicated that resistance to the quinolones and oxytetracycline was increasing and that multi-resistant strains were found in several countries . The variation found in antibiograms could have potential as epidemiological markers in certain geographic areas.

Can J Microbiol, 1994 Jun, 40(6), 503 - 7
Isolation and characterization of a Tn5-induced tolQ mutant of Escherichia coli; Madrid C et al.; Transposon mutagenesis was used to isolate an Escherichia coli mutant that released into the external medium a heterologous protein, the Aeromonas hydrophila aerolysin . Genetic mapping and phenotypic characterization of E . coli CM209 showed that Tn5 is inserted in the tolQ gene . This mutant strain released a significant amount of unprocessed (proaerolysin) protein into the external medium, together with other periplasmic proteins . Similar levels of the toxin were detected in the intracellular compartments of the parental and mutant strains . Whereas inactivation of the tolQ gene itself was responsible for some of the phenotypic properties of strain CM209, such as tolerance to group A colicins or to filamentous bacteriophages, the leaky phenotype was associated with a polar effect exerted by Tn5 on distal genes of the tolQRA cluster.

Vet Immunol Immunopathol, 1994 Jun, 41(3-4), 341 - 52
Genetic variation in the humoral immune response in Atlantic salmon (Salmo salar) against Aeromonas salmonicida A-layer; Stromsheim A et al.; Antibody responses to Aeromonas salmonicida A-layer were analysed in family material of Atlantic salmon (Salmo salar), consisting of 791 fish belonging to 34 full-sib groups within 12 paternal half-sib groups . The fish were immunized twice and blood samples were collected three times . Significant increase in antibody titre from first to second, and from second to third sampling, was observed . Genetic variation in antibody titres was observed at the three samplings with estimated heritabilities ranging from 0.16 to 0.20, and a significant heritability estimate was recorded in the antibody response after the second immunization (h2 = 0.16) . Moderate to high genetic (r = 0.5-0.72) and phenotypic (r = 0.29-0.57) correlations were found between the titre values at different samplings, and between selected titres and titre increases . Production parameters, such as mean slaughter weight and mean survival rate were obtained for fish which were reared commercially in the sea, and which belonged to the same full-sib groups as those analysed for A . salmonicida A-layer antibodies . No significant correlation between the mean antibody titre to A . salmonicida A-layer in this study and mean slaughter weight and survival rate in full-sib family material in the sea was observed.

Biochemistry, 1994 May 3, 33(17), 5011 - 20
Characterization of interfacial catalysis by Aeromonas hydrophila lipase/acyltransferase in the highly processive scooting mode; Jain MK et al.; A glycerophospholipid:cholesterol acyltransferase (GCAT) that also has lipase activity is secreted by the bacterium Aeromonas hydrophila . Hydrolysis of the sn-2-ester bond of 1,2-dimyristoyl-sn-glycero-3-phosphomethanol (DMPM) vesicles by this enzyme is shown to occur in a highly processive scooting mode in which the enzyme, substrate, and the products of hydrolysis remain bound to the vesicle interface . This conclusion is based on the following observations . (a) When there is an excess of vesicles over enzyme, the hydrolysis of the sn-2-acyl group ceases after only a fraction of the total available substrate is hydrolyzed . Addition of more enzyme, but not of more substrate, leads to a new round of hydrolysis . (b) The extent of hydrolysis of vesicles per enzyme increases with the size of the vesicles, and it corresponds to the total hydrolysis of the outer monolayer of one vesicle by one enzyme . (c) The enzyme bound to vesicles composed of reaction products or of the non-hydrolyzable phospholipid 1,2-ditetradecyl-sn-glycero-3-phosphomethanol (DTPM) is not able to undergo intervesicle exchange . Instead, intervesicle transfer of the substrate or the bound enzyme due to vesicle fusion promotes hydrolysis of all of the vesicles present in the reaction mixture . (d) Addition of DTPM vesicles to a reaction mixture containing DMPM substrate vesicles and the enzyme has no noticeable effect on the course of hydrolysis . Substrate specificity studies in the scooting mode on DMPM vesicles reveal that GCAT displays essentially no selectivity in the hydrolysis of phospholipids with different polar head groups . Treatment of GCAT with trypsin, which removes a small peptide, results in an enzyme that displays comparable catalytic activity but increased affinity for the interface . Alkyltrifluoromethyl ketones are shown to be tight-binding competitive inhibitors of GCAT . The scooting mode analysis, which has previously been shown to provide a simplified approach for analyzing the steady-state kinetics of interfacial catalysis by secreted phospholipase A2, is also useful for analyzing the interfacial kinetic behavior of lipases.

Vet Immunol Immunopathol, 1994 May, 41(1-2), 141 - 52
A beta-glucan inhibitable zymosan receptor on channel catfish neutrophils; Ainsworth AJ; In mice and humans zymosan binds to the complement receptor three/Mac-1 receptor; however, identification of this receptor in channel catfish (Ictalurus punctatus) has not been accomplished . Soluble fluorescein isothiocyanate (FITC) conjugated beta-glucan, a component of zymosan, was found to bind to channel catfish anterior kidney (AK) neutrophils but not to B-lymphocytes . Serum activated zymosan (SAZ)-mediated chemiluminescence responses of channel catfish AK neutrophils could be inhibited by beta-glucan but not by mannan, and inhibition of chemiluminescence responses by beta-glucan was dose dependent . Similarly, phagocytosis of FITC-SAZ could be inhibited by beta-glucan in a dose-dependent manner . Treatment of channel catfish AK neutrophils with various concentrations of trypsin resulted in inhibition of phagocytosis of FITC-SAZ but not of Aeromonas hydrophila indicating that A . hydrophila phagocytosis was mediated by a trypsin-resistant receptor . Deleting serum or using heat-inactivated serum in the mixtures for the chemiluminescence and FITC-SAZ phagocytosis assays resulted in baseline readings . These data indicate that the beta-glucan component of zymosan is responsible for zymosan phagocytosis . Furthermore, the recognition of zymosan by a specific receptor is evident based on trypsin sensitivity assays . Based on these results it is proposed that a complement receptor 3, Mac-1-like receptor, is present on channel catfish AK neutrophils.

Vet Immunol Immunopathol, 1994 May, 41(1-2), 125 - 39
Dietary intake of immunostimulants by rainbow trout affects non-specific immunity and protection against furunculosis; Siwicki AK et al.; Immunostimulant preparations Macrogard, Candida utilis, Saccharomyces cerevisiae, Evetsel, Chitosan, or FinnStim were mixed into semipurified diets and fed to groups of rainbow trout for 1 week . Fish were bled by non-lethal caudal puncture and blood samples assayed for changes in non-specific cellular immunity and humoral protein levels . In the immunostimulated fish, hematocrit levels and lymphocyte counts remained relatively stable; however, elevations were observed in oxidative radical release, myeloperoxidase activity, phagocytic indexes, and potential killing activities of phagocytic cells including neutrophils . Total plasma protein and total immunoglobulin levels were elevated by the dietary immunostimulants . A challenge with the virulent pathogen that causes furunculosis, Aeromonas salmonicida, showed that the immunostimulated groups of fish were more resistant to the disease, confirming the potential use of these substances in fish culture for the prevention of disease.

Epidemiol Mikrobiol Imunol, 1994 May, 43(2), 61 - 6
{Identification of aeromonads from water sources}; Sedlacek I et al.; A total of 102 Aeromonas strains isolated from water were identified by both commercial ENTEROtest 1 & 2 kits and by several conventional tests . 83 strains (81.4%) were identified to the species level according to a differentiation table . A . hydrophila (36 strains), A . caviae (26 strains) and A . sobria (10 strains) species were isolated most frequently . Strains identified as A . allosaccharophila, A . eucrenophila, A . jandaei, A . media and A . trota were very rare . The remaining 19 strains could not be identified . The ENTEROtest kit without additional tube test was insufficient for the identification of Aeromonas strains to the species level . The arginine dihydrolase test and hydrolysis of esculin from the ENTEROtest kit were found to be the least reliable tests.

Epidemiol Mikrobiol Imunol, 1994 May, 43(2), 55 - 60
{Biochemical identification of aeromonads}; Aldova E et al.; To assess the species of the genus Aeromonas in 178 strains isolated from human and animal materials and from the environment (water and hospital environment), examined along with 11 type strains of the best known species, a key was used the basis of which are in addition to biochemical tests defining the genus Aeromonas 12 tests: Voges-Proskauer, lysine decarboxylase, gas from glucose, haemolysis, gluconate oxidation, elastase, arabinose, mannose, saccharose, salicine, esculine hydrolysis, arbutine . Three tests--salicine, esculine hydrolysis, arbutine--differentiate A . hydrophila (2-3 positive) from A . sobria (0-1 positive).

FEMS Microbiol Lett, 1994 May 1, 118(1-2), 163 - 6
Effect of growth temperature on complement-mediated killing of mesophilic Aeromonas spp . serotype O:34; Merino S et al.; Mesophilic Aeromonas spp . strains (serotype O:34) showed sensitivity to complement-mediated killing when they were cultivated at 37 degrees C (serum-sensitive) but not when they were cultivated at 20 degrees C (serum-resistant) . These strains produced smooth lipopolysaccharide when they were grown at 20 degrees C and rough lipolysaccharide when cultivated at 37 degrees C . The reason for the resistance to complement-mediated killing could be that C3b is rapidly degraded (possibly because it is bound far from the cell membrane), consequently the lytic complex (C5b-9) is not formed.

J Appl Bacteriol, 1994 May, 76(5), 511 - 20
Characteristics of 'atypical', cytochrome oxidase-negative Aeromonas salmonicida isolated from ulcerated flounders (Platichthys flesus (L.)); Wiklund T et al.; 'Atypical', cytochrome oxidase-negative variants of the fish pathogen Aeromonas salmonicida, isolated from ulcerated flounder (Platichthys flesus), were studied using different methods . Two of the strains possessed a protein that corresponded to the A-layer protein of Aer . salmonicida . The strains reacted with antibodies against the A-layer and monoclonal antibodies against the O-antigen of typical Aer . salmonicida . These tests confirm that the isolates from flounder should be classified as Aer . salmonicida . Analysis of the fatty acids showed that the isolates were rather homogeneous but the values of the guanine plus cytosine content of the DNA of the bacteria varied too much for any conclusion to be drawn on their taxonomic location . The strains examined exhibited several biochemical characters that differed from those of the type strains of Aer . salmonicida subsp . salmonicida and Aer . salmonicida subsp . achromogenes . The results suggest that these 'atypical', cytochrome oxidase-negative variants may form a new subspecies of Aer . salmonicida.

Structure, 1994 Apr 15, 2(4), 283 - 91
Crystal structure of Aeromonas proteolytica aminopeptidase: a prototypical member of the co-catalytic zinc enzyme family; Chevrier B et al.; BACKGROUND: Aminopeptidases specifically cleave the amino-terminal residue from polypeptide chains and are involved in the metabolism of biologically active peptides . The family includes zinc-dependent enzymes possessing either one or two zinc ions per active site . Structural studies providing a detailed view of the metal environment may reveal whether the one-zinc and two-zinc enzymes constitute structurally and mechanistically distinct subclasses, and what role the metal ions play in the catalytic process . RESULTS: We have solved the crystal structure of the monomeric aminopeptidase from Aeromonas proteolytica at 1.8 A resolution . The protein is folded into a single alpha/beta globular domain . The active site contains two zinc ions (3.5 A apart) with shared ligands and symmetrical coordination spheres . We have compared it with the related bovine lens leucine aminopeptidase and the cobalt-containing Escherichia coli methionine aminopeptidase . CONCLUSIONS: The environment and coordination of the two zinc ions in A . proteolytica aminopeptidase strongly support the view that the two metal ions constitute a co-catalytic unit and play equivalent roles during catalysis . This conflicts with the conclusions drawn from the related bovine leucine aminopeptidase and early biochemical studies . In addition, the known specificity of the aminopeptidase for hydrophobic amino-terminal residues is reflected in the hydrophobicity of the active site cleft.

J Mol Biol, 1994 Apr 8, 237(4), 452 - 63
Mutagenesis of the paracrystalline surface protein array of Aeromonas salmonicida by endogenous insertion elements; Gustafson CE et al.; The tetragonal paracrystalline surface protein array (A-layer) of the fish pathogenic bacterium Aeromonas salmonicida is a virulence factor and bacteria which are unable to produce A-layer are attenuated in their ability to kill fish . Ten independent mutants of Aeromonas salmonicida which were unable to produce A-layer were isolated by growth at 30 degrees C . These mutants displayed either reduced synthesis of the A-layer subunit, synthesis of a truncated subunit, or complete loss of the ability to produce the subunit protein . Restriction mapping and analysis by polymerase chain reaction showed that the mutations had resulted from insertion of two different insertion sequence (IS) elements into different sites in the A-layer subunit gene (vapA) and its promoter . Sequence comparisons indicated that ISAS1 is unique among reported IS elements . It is 1223 bp long with imperfect terminal inverted repeats of 22 bp and insertion resulted in a duplicated 8 bp target sequence in vapA . ISAS1 expressed a 42,000 molecular weight (M(r)) protein in mini-cells . ISAS2 was 1084 bp long, expressed proteins of M(r) 38,000 and 39,000 in vitro, had imperfect 29 bp terminal inverted repeats and had duplicated a 3 bp target sequence . Sequence comparisons indicated that ISAS2 was also unique to A . salmonicida; however, the proteins encoded by ISAS2 showed strong homology to the putative transposases encoded by the IS30 family of IS elements . Southern analyses showed that both ISAS1 and ISAS2 were restricted to A . salmonicida strains A449 and A450 where they were present in low copy number . The ability of these two IS elements to mutate the ability of A . salmonicida to produce its paracrystalline surface array provides a novel method for the attenuation of virulence.

Epidemiol Infect, 1994 Apr, 112(2), 291 - 8
Characterisation of haemolytic activity from Aeromonas caviae; Karunakaran T et al.; Aeromonas caviae, an enteropathogen associated with gastroenteritis, displays several virulence characteristics . Studies on the kinetics of growth of A . caviae and expression of beta-haemolytic toxin revealed that A . caviae produced maximum haemolytic activity extracellularly during the stationary phase . Preliminary studies on the properties of A . caviae haemolysin suggested that divalent cations (Mg2+ and Ca2+) and thiol compounds, dithiothreitol and mercaptoethanol enhanced the haemolytic activity . Addition of L-cysteine, glutathione and EDTA reduced the haemolytic activity . The iron chelator, 2-2' bipyridyl, significantly inhibited the growth of A . caviae possibly by iron limitation, with parallel enhancement of haemolysin production compared to A . caviae grown in excess of iron . These results suggest that A . caviae produces only beta-haemolysin, which resembles the haemolysins reported for several other bacteria and the activity might be regulated by environmental factors especially iron.

J Clin Microbiol, 1994 Apr, 32(4), 1130 - 1
Aeromonas species exhibit aggregative adherence to HEp-2 cells; Neves MS et al.; Clinical and environmental isolates of Aeromonas species (five A . hydrophila isolates, three A . caviae isolates, and two A . sobria isolates) were tested for their adherence to HEp-2 cells . Clinical isolates of A . hydrophila and A . sobria exhibited aggregative adherence similar to that presented by enteroadherent-aggregative Escherichia coli . Bacterial aggregates adhered to cells with a typical "stacked-brick" appearance . In contrast, A . caviae strains showed a diffuse adherence pattern.

Appl Environ Microbiol, 1994 Apr, 60(4), 1379 - 82
Comparison of putative virulence factors in Aeromonas hydrophila strains isolated from the marine environment and human diarrheal cases in southern Italy; Krovacek K et al.; Aeromonas hydrophila strains isolated from the same geographical region (southern Italy) but from different sources (sea sediments and human diarrhea cases) were characterized for the production of potential virulence determinants, such as production of cytotoxins, cytotonic toxins, hemolysin, and dermonecrotic factors and their capacity to adhere to human intestinal 407 cells in vitro . The results showed that isolates from both the sources produced all or some of the virulence factors which may be involved in the pathogenesis of Aeromonas-associated infections . Our study indicates that further epidemiological studies are necessary to elucidate the public health significance of infections caused by Aeromonas spp.

FEMS Microbiol Lett, 1994 Mar 15, 117(1), 85 - 90
O-serogrouping and surface components of Aeromonas hydrophila and Aeromonas jandaei pathogenic for eels; Esteve C et al.; The relationship between virulence, O-serogroup, and some cell-surface features (self-pelleting {SP} and precipitation after boiling {PAB}, profile of lipopolysaccharides {LPSs} and outer membrane proteins {OMPs}) was investigated in strains of the pathogenic species Aeromonas hydrophila and A . jandaei isolated from eels . Virulent strains of A . hydrophila reacted mostly with O:19 antiserum, and those of A . jandaei reacted with O:4, O:11, O:15 and O:29 antisera (Guinee and Jansen system) . Regarding the PAB and LPS profiles two groups could be distinguished; (i) five PAB+ strains of serotype O:19 that possessed a homogeneous O polysaccharide side chain and (ii) thirteen PAB- strains antigenically diverse that either exhibited a heterogeneous side chain or were side chain deficient . A major 50 kDa protein was only found in the PAB+ strains, whereas major OMPs detected in PAB- strains ranged from 33 to 45 kDa irrespective of the species . Epizootic eel isolates of A . hydrophila belong to serotype O:19 and share cell-surface features with the Aeromonas highly virulent for other hosts . In contrast, epizootic A . jandaei isolates were antigenically diverse . These findings reinforce the importance of an O-serotype as an epidemiological marker in motile Aeromonas strains pathogenic for eels.

Changgeng Yi Xue Za Zhi, 1994 Mar, 17(1), 68 - 73
Long term survival of a patient with a regressed giant hepatocellular carcinoma after transcatheter hepatic artery embolization (TAE) complicated with liver abscess; Chuah SK et al.; A 62-year-old male patient with histologically proven hepatocellular carcinoma, received transcatheter hepatic artery embolization (TAE) therapy . Development of right pyothorax and liver abscess at the tumor region occurred 4 months later after TAE . Aeromonas hydrophila was isolated from the liver abscess . After repeated percutaneous drainage, the abscess cavity disappeared and the tumor became undetectable by ultrasonography . Nineteen months after the initial presentation, a second tumor at the dome of the right lobe liver was found . TAE was repeated . Bile stasis with stricture of left intrahepatic ducts were found by Tc-99m HIDA cholangiography and endoscopic retrograde cholangiography . The patient had a normal lifestyle until the third tumor appeared at the right lower liver 18 months after the second TAE . TAE was conducted a third time . A shunting between the hepatic artery and vein developed at the new tumor area 3 months later . The patient is surviving today which is five and a half years after the initial diagnosis . We believe that the liver abscess after TAE contributed to the complete regression of the giant tumor, in addition to the anti-tumor effect of the successful TAE.

J Reconstr Microsurg, 1994 Mar, 10(2), 83 - 5
Intestinal flora of the medicinal leech Hirudinaria manillensis; Bickel KD et al.; Medicinal leeches are widely used to treat venous congestion in microvascular surgery . Aeromonas hydrophila infection, following application of the leech species Hirudo medicinalis, is a recognized complication . Administration of antibiotics directed at Aeromonas has been successful in minimizing complications of infection from this organism . A different leech species, Hirudinaria manillensis, has recently been introduced for microsurgical use . A study of the enteric content of 30 of these leeches showed that Aeromonas hydrophila was isolated in only 20 percent of animals, while the majority of remaining positive cultures were single and mixed gram-negative rods . All organisms isolated were sensitive to current recommended coverage for Aeromonas hydrophila . This study suggests that the enteric flora of different leech species may be variable and should be carefully characterized, to direct appropriate prophylactic therapy prior to release of new species for clinical use.

J Med Microbiol, 1994 Mar, 40(3), 188 - 93
Cytotoxic and haemagglutinating activities of motile Aeromonas species; Majeed KN et al.; Cytotoxic and haemagglutinating properties were determined in 114 Aeromonas strains isolated from various sites in slaughtered lambs and from processed lamb meat . Cytotoxic activity on Vero cells was observed in 48 (42%) of the strains . It was more common in A . sobria and A . hydrophila isolates than with A . caviae isolates . Haemagglutination (HA) activity was found frequently in motile aeromonads irrespective of species; it was present in 50% of A . sobria strains, 51% of A . hydrophila strains and 48% of A . caviae strains . HA was inhibited by fucose, galactose and mannose at low concentration, and in most cases, two or three of these sugars were inhibitory . A significant association was found between certain HA-inhibition patterns and the production of cytotoxin by Aeromonas spp.

Prikl Biokhim Mikrobiol, 1994 Mar-Apr, 30(3), 454 - 7
{Activity of lysosomal proteinases in carb tissue in aeromonas infection}; Nemova NN et al.; The activity of major lysosomal proteinases (cathepsins B and D) increased in carp tissues infested with Aeromonas hydrophila . The value and character of changes in the activity of cathepsins depended on the degree of infestation and the physiological state of fishes (normally fed or starved).

Dev Comp Immunol, 1994 Mar-Apr, 18(2), 123 - 36
Immunoregulation in fish . I: Intramolecular-induced suppression of antibody responses to haptenated protein antigens studied in Atlantic salmon (Salmo salar L); Killie JE et al.; We report here evidence for intramolecular-induced suppression of the in vivo antibody response in fish, using a panel of T-dependent hapten-carrier antigens . Atlantic salmon were immunized intraperitoneally with protein antigens (Limulus polyphemus hemocyanin, chicken gamma globulin, and Aeromonas salmonicida A-layer protein) given in their native form or haptenated with either 4-hydroxy-3-iodo-5-nitrophenyl-acetic acid (NIP), 2,4,6-trinitrophenyl-acetic acid (TNP), or fluorescein-5-iso-thiocyanate (FITC) . The salmon immune system responds to these hapten-carrier antigens by eliciting high anti-hapten titers whereas the antibody titers against protein determinants were suppressed 87-99%, determined by ELISA . NIP also induced suppression of the anti-FITC response when NIP and FITC were intramolecularly conjugated to Limulus polyphemus hemocyanin (LPH) . The suppression was found to be independent of haptenation ratios and time after immunization . The possibility that haptenation interferes with or blocks the protein determinants is not likely because antisera raised against native LPH recognize LPH-specific epitopes even on heavily NIP-substituted LPH . Although the mechanism behind intramolecular-induced suppression is poorly understood, even in mammals, this study demonstrates that intramolecular-induced suppression may be one means by which antibody responses in fish are regulated . The possible impact of antigen-induced suppression on immune responses against vaccine antigens in fish is discussed.

Clin Diagn Lab Immunol, 1994 Mar, 1(2), 182 - 5
Serum antibody responses of divers to waterborne pathogens; Losonsky GA et al.; To assess the significance of exposure of divers to waterborne pathogens, specific immunoglobulin G serum antibody responses to Pseudomonas and Aeromonas isolates recovered from dive sites from the respiratory tracts of nine experienced divers and seven diving trainees working in the Chesapeake Bay area over a 6- to 18-month period were measured . A significant increase in the frequency of isolation of these organisms from respiratory surfaces both groups of divers after each dive was noted, with the divers' ears being the predominant recovery site (48%; P < 10(-8), chi-square) . The acute serum responses of the majority of experienced divers (83%) showed evidence of preexisting antibody to these potential pathogens, whereas the acute serum response of only 32% of naive divers showed such evidence (P < 10(-8), chi-square) . Six months into their training, the rate of seroresponse of the trainees to organisms recovered after their first dives increased to 61% (P = 0.003, chi-square), suggesting that repeated exposure in necessary for generation of a specific systemic immunologic response . The rate of acquisition of a new seroresponse to recovered organisms was approximately 12% per dive for both groups of divers, suggesting that there is continuous exposure to, and infection with, new strains present in the water during dives . These data suggest that, in cases in which systemic antibody is important for protection, there are various levels of susceptibility to waterborne potential pathogens in both experienced and inexperienced divers.

Toxicology, 1994 Feb 28, 87(1-3), 19 - 28
The cytolytic toxin aerolysin: from the soluble form to the transmembrane channel; van der Goot FG et al.; Aerolysin is a cytolytic toxin which forms channels in the plasma membranes of eucaryotic cells . The protein is secreted by Aeromonas hydrophila as an inactive protoxin . Its stability and water solubility are conferred by its ability to dimerize . Maturation of the protein occurs through proteolytic removal of a C-terminal peptide outside the secreting cell . Although the aerolysin which is so produced is still a dimer, it then has the ability to oligomerize . The oligomer is the active form of the toxin, capable of forming the transmembrane channels that disrupt cells . We review here the present knowledge about the structure of aerolysin in relation to the various steps in channel formation.

Gene, 1994 Feb 11, 139(1), 87 - 91
Cloning and expression of putative cytotonic enterotoxin-encoding genes from Aeromonas hydrophila; Chopra AK et al.; A genomic library from a diarrheal isolate, SSU, of Aeromonas hydrophila was constructed in a cosmid vector, pHC79, and in bacteriophage lambda EMBL3 . Cell lysates from various Escherichia coli clones containing the recombinant cosmid were examined for their ability to elongate Chinese hamster ovary (CHO) cells, which is a typical enterotoxic response . Based on restriction analysis, a 4.0-kb SalI DNA fragment from one of the clones that exhibited enterotoxic activity was subcloned into a bacteriophage T7 RNA polymerase/promoter hyperexpression system . The cell lysate from this E . coli {pSL24} clone caused CHO cells to elongate and revealed the presence of a major 35-kDa polypeptide by {35S}methionine labeling and sodium dodecyl sulfate (SDS)-polyacrylamide-gel electrophoresis (PAGE) . The toxin was biologically heat labile, losing all activity within 20 min at 56 degrees C . In addition, another enterotoxin-producing clone, E . coli{pSBS32}, was isolated from cosmid and lambda bacteriophage libraries . We localized this heat-stable (56 degrees C/20 min) enterotoxin to a 4.8-kb SalI-BamHI fragment . Both enterotoxins caused elevation of cyclic adenosine monophosphate (cAMP) in CHO cells . The DNA fragments encoding these enterotoxins did not hybridize with each other . However, a 4.8-kb SalI-BamHI DNA fragment encoding a heat-stable enterotoxin hybridized to a 3.5-kb BamHI DNA fragment of a plasmid, pHPC100, that contained a cytotonic enterotoxin-encoding gene isolated from A . trota . Our data suggest Aeromonas species produce different structural types of cytotonic enterotoxins that are functionally similar.

Antimicrob Agents Chemother, 1994 Feb, 38(2), 353 - 5
beta-Lactam resistance of motile Aeromonas isolates from clinical and environmental sources; Morita K et al.; The MICs of various beta-lactams for 182 isolates of Aeromonas species, i.e., A . hydrophila (n = 101), A . sobria (n = 69), and A . caviae (n = 12), from clinical and environmental sources were determined by an agar dilution technique . All strains were resistant to ampicillin and susceptible to aztreonam . A . sobria and A . caviae demonstrated lower resistance rates than A . hydrophila . Penicillin-hydrolyzing beta-lactamases were detected in all strains.

J Biol Chem, 1994 Jan 21, 269(3), 2146 - 50
Influence of active site and tyrosine modification on the secretion and activity of the Aeromonas hydrophila lipase/acyltransferase; Robertson DL et al.; Aeromonas sp . secrete a lipase/acyltransferase that shares several properties with the mammalian plasma enzyme lecithin:cholesterol acyltransferase . Reaction of the enzyme with tetranitromethane led to modification of 2 tyrosines and a nearly 80% decline in enzyme activity . Replacing Tyr230 with Phe altered the activity of the enzyme in the same way as did treatment with tetranitromethane . Unlike the wild type enzyme, which preferentially hydrolyzes the 2-position acyl chain of phosphatidylcholine, the Y230F mutant enzyme did not discriminate between the 1- and 2-positions of the phospholipid . Tyr230 may be necessary to correctly position phospholipid substrates at the active site . Several amino acids around the active site Ser16 of the lipase were also changed . Replacing Ser18 with Gly, bringing the enzyme's sequence into line with the "lipase consensus sequence," resulted in reduced secretion of the protein and complete loss of activity . Changing this serine to Val led to an inactive protein that was not secreted at all . Substituting Phe13 in the hydrophobic region of the consensus sequence with Ser also prevented secretion, although the mutant protein appeared to be active . The Aeromonas lipase may represent a distinct group of lipolytic enzymes which have a novel active site structure.

Nature, 1994 Jan 20, 367(6460), 292 - 5
Structure of the Aeromonas toxin proaerolysin in its water-soluble and membrane-channel states; Parker MW et al.; Aerolysin is chiefly responsible for the pathogenicity of Aeromonas hydrophila, a bacterium associated with diarrhoeal diseases and deep wound infections . Like many other microbial toxins, the protein changes in a multistep process from a completely water-soluble form to produce a transmembrane channel that destroys sensitive cells by breaking their permeability barriers . Here we describe the structure of proaerolysin determined by X-ray crystallography at 2.8 A resolution . The protoxin (M(r) 52,000) adopts a novel protein fold . Images of an aerolysin oligomer derived from electron microscopy have assisted in constructing a model of the membrane channel and have led to the proposal of a scheme to account for insertion of the protein into lipid bilayers to form ion channels.

J Med Microbiol, 1994 Jan, 40(1), 55 - 61
Adhesion to and invasion of human colon carcinoma Caco-2 cells by Aeromonas strains; Nishikawa Y et al.; The enteropathogenicity of Aeromonas strains that showed mannose-resistant adhesion to INT407 cells was evaluated by infecting Caco-2 cells and observing them by light and electronmicroscopy . Five of six strains adhered in large numbers to Caco-2 cells in the presence of mannose and caused cytopathic effects . Two strains of Aeromonas spp . seemed to invade Caco-2 cells, as membrane-bound bacteria were seen within the cytoplasm of these cells; however, staining by acridine orange-crystal violet appeared to show intracellular fluorescent bacteria in three strains . Fimbriae did not appear to play an important role in adhesion because fimbrial structures were not seen by transmission electronmicroscopy . Adhesion of four strains was inhibited by the addition of L-fucose . The strains were negative in the fluorescence actin staining test, which in enteropathogenic Escherichia coli strains correlates with the ability to attach and efface intestinal microvilli . The DNA of the Aeromonas strains did not hybridise with the E . coli eae and ipaB probes, associated with attaching and effacing ability and invasion, respectively . These results give support to the enteropathogenicity of adhesive strains of Aeromonas spp., although the mechanisms of adhesion, and possibly invasion, remain to be elucidated.

Microbios, 1994, 77(310), 47 - 55
Adherence pattern of non-pilated Aeromonas hydrophila strains to tissue cultures; Bartkova G et al.; Adherence of non-pilated Aeromonas hydrophila strains to HEp-2, HeLa, CHO and Vero tissue culture cells was studied . The strains were isolated from intestinal and extra-intestinal human infections and from the environment . The environmental isolates revealed a diffuse type of adherence to all types of cell lines while clinical isolates showed localized adherence (50%) . Strains revealing the diffuse type of adherence showed high levels of adhesion i.e . > 20 bacteria per cell . This activity correlated with hydrophobicity of the strains tested . Haemagglutination assay with human erythrocytes was negative, showing no association with plasmid profile, Congo red binding and adherence to tissue culture cells . Thus the experiments showed that in non-pilated strains, hydrophobicity may be the major factor responsible for adherence to epithelial cells.

Zentralbl Hyg Umweltmed, 1994 Jan, 195(2), 121 - 34
Assessment of some selective media for the recovery of Aeromonas hydrophila from surface waters; Bernagozzi M et al.; A comparison was made of three different growing media already proposed by some authors for the recovery of Aeromonas hydrophila in environmental water samples of various origins . The media tested were Rippey and Cabelli m Aeromonas agar, Rimler-Shotts agar and the Ryan Aeromonas Base Medium with the addition of ampicillin . The efficiency of the three media was evaluated on the basis of the following reference criteria: accuracy, selectivity and specificity . The results obtained, analyzed by calculating the Kendall concordance coefficients, demonstrated that m Aeromonas agar is the most suitable media for quantitative recovery of Aeromonas hydrophila from surface water samples even if a reduction in the total heterotrophic load of 3-logs was never obtained with this medium.

Antibiot Khimioter, 1994 Jan, 39(1), 63 - 9
{Aeromonads and their sensitivity to antibacterial drugs (review of the foreign literature 1985-1992)}; Kardashova EV et al.; The review is concerned with the modern studies on the taxonomy of aeromonades and their role in the development of infectious complications of various localization, including intestinal infections . A special attention is paid to antibiotic resistance of aeromonades isolated from pathological materials and the modern notions of the factors of aeromonade pathogenicity.

Clin Infect Dis, 1994 Jan, 18(1), 32 - 7
Aeromonas peritonitis; Munoz P et al.; Five new cases of peritonitis caused by Aeromonas species are reported, and 29 others described in the literature are reviewed . Males predominated (71%), and the mean age was 56.9 years . Acquisition was nosocomial in 20% of the cases . All patients except one (3%) had significant underlying diseases; 73% had chronic hepatic disease, 15% had chronic renal failure (treated with chronic ambulatory peritoneal dialysis {CAPD}), and 9% had an intestinal perforation . Symptoms were similar to those of peritonitis caused by other pathogens, with the exception of diarrhea, which occurred in 25% of cases . Blood cultures were positive in 74% of the cases . The species isolated were Aeromonas hydrophila (27), Aeromonas sobria (5), and Aeromonas caviae (2) . The overall case-fatality rate was 57% . Three strains were resistant to cotrimoxazole . Aeromonas species should be taken into account as a cause of peritonitis in patients with cirrhosis or who are undergoing CAPD.

J Basic Microbiol, 1994, 34(4), 245 - 52
Factors influencing beta-galactosidase activity of Aeromonas caviae; Karunakaran T et al.; Aeromonas caviae, often reported to be associated with diarrhoeal patients, elaborates several virulence factors as well as catabolic enzymes such as xylanase and beta-galactosidase . Studies on the kinetics of growth of A . caviae and synthesis of beta-galactosidase suggested that the activity was cell associated and reached a peak during the late logarithmic phase of growth . The optimum pH for beta-galactosidase activity was 7.0 and required Ca2+ and glutathione for enhancement of its activity; IPTG also slightly improved the activity . Aerobic cultivation of A . caviae in LB containing glucose, fructose, maltose and sucrose completely inhibited the activity possibly due to acetic acid production . Addition of 100 mM cAMP to the media containing glucose (0.25%, w/v) restored the relative activity by 8.8%; however, the final pH of the media remained acidic . Aerobic growth of A . caviae with other carbon sources did not affect beta-galactosidase activity, probably as there was no acid production and thereby the final pH of the media unaltered . Arabinose, xylose and galactose induced the A . caviae beta-galactosidase activity by several folds and lactose moderately enhanced its activity.

Folia Microbiol (Praha), 1994, 39(4), 331 - 6
Virulence factors in clinical and food isolates of Aeromonas species; Pin C et al.; Virulence factors were compared in 15 Aeromonas spp . isolated from faeces of patients with Aeromonas-associated gastroenteritis and in 81 strains isolated from food . Strains from food did not show differences in the distribution of virulence factors when compared with strains isolated from faeces . However, 88.8% of Aeromonas strains isolated from food were capable of producing possible virulence factors . Characterization of 28 autoagglutinating (AA+) Aeromonas spp . indicated that the human strains differed from the food strains in hemagglutinating and hemolytic capacities . These results suggest that autoagglutination associated with hemagglutinating and hemolytic capacities in food strains may be a helpful indicator of potential pathogenicity.

J Biomol NMR, 1994 Jan, 4(1), 97 - 116
Assessing glycosidic linkage flexibility: conformational analysis of the repeating trisaccharide unit of Aeromonas salmonicida; Peters T et al.; A detailed conformational analysis was performed for the synthetic branched trisaccharide beta-D-ManNAc-(1-->4)-{alpha-D-Glc-(1-->3)}-L-Rha 1 which represents the repeating unit of the O-antigenic polysaccharide of Aeromonas salmonicida . The study was based on 26 experimental NOE curves from 1D transient NOE experiments, employing Gaussian-shaped inversion pulses at 600 MHz . Eight of the NOE curves were interglycosidic and thus useful for an analysis of glycosidic linkage orientations . Metropolis Monte Carlo (MMC) simulations and minimum-energy calculations with the program GEGOP were used to obtain theoretical NOE curves which were compared to the experimental ones . MMC simulations with different temperature parameters of 310, 600, 900 and 2000 K allowed identification of NOEs which are sensitive towards different conformation distributions--not only different conformations--at both glycosidic linkages in 1 . A comparison of trisaccharide 1 with the constituent disaccharides beta-D-ManNAc-(1-->4)-L-Rha 2 and alpha-D-Glc-(1-->3)-L-Rha 3 revealed effects of branching on glycosidic linkage flexibility . A quantitative evaluation was facilitated by the introduction of entropy-related flexibility parameters . Our study indicates a notable restriction of flexibility, especially at the (1-->3) linkage in 1 . Although overall flexibility in 1 is reduced as compared to the constituent disaccharides 2 and 3, it cannot be neglected altogether . In summary, combined transient NOE experiments and MMC simulations provide a simple approach to analyse glycosidic linkage flexibility.

Vet Rec, 1993 Dec 18-25, 133(25-26), 617 - 21
Amoxicillin concentrations in the serum of Atlantic salmon (Salmo salar L) during furunculosis therapy; Inglis V et al.; The effectiveness of the delivery of amoxicillin to Atlantic salmon, undergoing chemotherapy in natural outbreaks of furunculosis in sea-cages, was investigated by measuring the concentration of the drug in serum samples . Five groups of 50 sera from three outbreaks were collected two hours after oral treatment with doses of 80 or 120 mg/kg bodyweight . Amoxicillin was detected in 82, 82, 92, 100 and 90 per cent of the sera in the five groups (limit of detection 0.16 microgram/ml) . Many sera contained less than the minimum inhibitory concentration of amoxicillin for the causative agent Aeromonas salmonicida (0.3 microgram/ml), but a concentration more than double the minimum inhibitory concentration was achieved in 2, 2, 56, 32 and 44 per cent of the samples . There was wide variation in the serum concentrations between individuals in the same population and between populations receiving the same treatment; this variation was associated with population factors, the severity of infection and the accuracy of medicating the feed.

J Gen Microbiol, 1993 Dec, 139 ( Pt 12), 3215 - 23
Cloning and nucleotide sequence of an extracellular alpha-amylase gene from Aeromonas hydrophila MCC-1; Chang MC et al.; A gene encoding the extracellular alpha-amylase of Aeromonas hydrophila MCC-1 was cloned and expressed using its own promoter on the recombinant plasmid pCA101 . Subcellular fractionation of Escherichia coli JA221 carrying pCA101 revealed that approximately 60% of the amylase activity was localized in the periplasmic space . The extracellular amylase was purified to homogeneity, identified as an alpha-type and its amino-terminal sequence was determined . Nucleotide sequence analysis predicted a 443 amino acid ORF and 24 amino acids at the amino terminus of the sequence that are not found in the secreted protein . This 24 amino acid sequence has many of the characteristics common to known signal peptides . The predicted amino acid sequence has considerable similarity with mammalian, invertebrate and Streptomycete alpha-amylases . Most of the amino acid residues that are involved in catalytic activity, substrate binding and calcium binding in several alpha-amylases were also present in A . hydrophila alpha-amylase at the corresponding positions.

Clin Infect Dis, 1993 Dec, 17(6), 1058 - 60
Meningitis due to Aeromonas species: case report and review; Parras F et al.; In recent years, Aeromonas species has been reported to cause extraintestinal infections with a growing frequency . Meningitis due to Aeromonas species is, however, a rare entity . We report a case of aeromonas meningitis in a 54-year-old man with a history of chronic alcoholic liver disease who, after an episode of gastroenteritis, developed an acute clinical picture characteristic of meningitis with septic shock and ecthyma gangrenosum . Aeromonas veronii (biogroup sobria) was isolated from cultures of blood as well as from cultures of stool, peritoneal fluid, skin lesion, and CSF specimens (obtained by lumbar puncture) . Our review of seven additional cases of aeromonas meningitis in the world literature revealed that this condition is generally secondary to metastatic dissemination from primary bacteremia . Aeromonas meningitis, which may or may not be preceded by gastroenteritis, presents clinically as bacterial meningitis, although the presence of skin lesions may increase suspicion of the diagnosis . Third-generation cephalosporins are probably the therapy of choice for patients with aeromonas meningitis.

Int J Food Microbiol, 1993 Dec, 20(4), 179 - 98
The public health significance of Aeromonas spp . in foods; Kirov SM; There is now evidence that some strains of Aeromonas species are enteropathogens . Such strains possess virulence properties, such as the ability to produce enterotoxins, cytotoxins, haemolysins and/or the ability to invade epithelial cells . Strains with these properties are common contaminants of drinking water and a wide range of foods . Contact or consumption of contaminated water, especially in summer, is a major risk factor in Aeromonas-associated gastroenteritis . Aeromonas-contaminated foods may also be vehicles of infection . Given the properties of strains that have been described in foods it has been suggested that food-borne illness could result not only from colonization and in vivo expression of virulence factors, but possibly also by intoxication following ingestion of foods that have been stored for a period of time, even under refrigeration . This paper reviews what is known about Aeromonas spp . in foods, their expression of virulence determinants, particularly at refrigeration temperatures, and the questions remaining to be answered to evaluate the risk they pose, so that an appropriate public health response can be determined.

J Bacteriol, 1993 Dec, 175(24), 7968 - 75
Transcriptional analysis of the Aeromonas salmonicida S-layer protein gene vapA; Chu S et al.; The vapA gene of Aeromonas salmonicida encodes the subunit of the surface protein array known as A-layer . Nucleotide sequence analysis of the 374 bp of DNA immediately upstream of vapA revealed two potential promoter sequences and other possible regulatory sequences . Sequencing and polymerase chain reaction analysis showed that the region was conserved in wild-type A . salmonicida . Primer extension and Northern (RNA) blot analysis showed that vapA transcription in A . salmonicida was directed predominantly by a distal promoter, P1, resulting in a 1.7-kb unit-length mRNA with an untranslated 181-nucleotide leader sequence which contained two predicted low-free-energy stem-loop structures . Northern analysis of cells grown at 15 degrees C showed that vapA transcript production peaked during the mid-log phase of growth (A600 = 0.25) . At 15 degrees C, the half-life of the vapA mRNA was 22 min, while at 20 degrees C, the half-life was significantly shorter, 11 min . The amount of vapA transcript produced was reduced by growth in the presence of the DNA gyrase inhibitors nalidixic acid and novobiocin . Environmental factors such as growth temperature and atmospheric oxygen tension also affected the quantity of vapA mRNA . vapA transcript could not be detected in mutants which produced either low levels of full-length or truncated A protein or no detectable A protein.

Int J Food Microbiol, 1993 Nov 26, 20(3), 159 - 68
The growth and expression of virulence factors at refrigeration temperature by Aeromonas strains isolated from foods; Kirov SM et al.; A potentially significant subset (10%, 6/61) of Aeromonas strains isolated from food (milk, lamb, chicken, seafood), all A . veronii biotype sobria, were able to produce two or more exotoxins (haemolysin, enterotoxin, and cytotoxin) at 37 degrees C, and grow well at 43 degrees C . Although mesophilic organisms, they grew at 5 degrees C . In addition, they could adhere to HEp-2 cells when grown at 37 degrees C, or at 5 degrees C, and expressed flexible pili (possible colonization factors) in greater numbers at the lower temperature . These strains, as well as other exotoxin-producing strains (A . veronii biotype sobria and A . hydrophila) (33%, 20/61) lacking adhesive ability, were able to produce cytotoxins in broth cultures over a seven to 10-day period at 5 degrees C . One strain in particular, an A . hydrophila isolated from goats' milk, grew rapidly at low temperature . This psychrotrophic strain produced all three exotoxins within 3 days in broth cultures at 5 degrees C . The properties of the above strains suggest they could be of public health significance in food products that have an extended shelf-life at refrigeration temperature.

Infect Immun, 1993 Nov, 61(11), 4582 - 9
Novel antigens expressed by Aeromonas salmonicida grown in vivo; Thornton JC et al.; Virulent and avirulent Aeromonas salmonicida strains grown inside intraperitoneal implants in Rainbow trout (Oncorhynchus mykiss) were examined for unique antigen expression . Western blots (immunoblots), performed with immune rabbit serum raised against in vivo-grown cells, revealed several unique antigens . With the exception of lipopolysaccharide (LPS), these novel antigens were destroyed after proteinase K treatment . The majority of these antigens were not induced in vitro in response to either iron limitation or anaerobiosis . In addition, electron microscopy demonstrated the presence of a putative capsule on in vivo-grown cells . Purification and fractionation of this carbohydrate material from cells grown in carbon-rich synthetic media resulted in the isolation and separation of an antigenically distinct LPS not seen with cells grown in standard media . Antiserum raised against in vivo-grown cells recognized both this LPS and the typical LPS of A . salmonicida apparent in in vitro-grown cells . Antiserum raised against in vitro-grown cells recognized only the LPS expressed in vitro . Antiserum directed against in vivo-grown cells was approximately 10 times more sensitive than serum directed against in vitro-grown cells in detecting A . salmonicida in infected fish kidney tissue.

Can J Microbiol, 1993 Nov, 39(11), 1051 - 8
Fate of the fish pathogen Aeromonas salmonicida in the peritoneal cavity of rainbow trout; Garduno RA et al.; A model was developed to study the fate of the fish pathogen Aeromonas salmonicida in vivo, inside a specialized intraperitoneal chamber implanted in rainbow trout, Oncorhynchus mykiss . Although normally recalcitrant to lytic agents in vitro, owing to the presence of its regular surface array (S layer), A . salmonicida was rapidly killed in the peritoneal cavity by a host-derived, soluble lytic activity present in peritoneal fluid . Peritoneal fluid was also found to kill other bacteria and lyse various types of erythrocytes, but was particularly lytic to A . salmonicida . Intraperitoneal survival of injected (free) A . salmonicida cells was several orders of magnitude higher than survival of implanted (restrained) cells . Injected free cells could evade the lytic activity of peritoneal fluid because they readily spread, initiating lethal infections . One evasion strategy was envisioned to be the penetration of peritoneal and (or) tissue macrophages . In spite of the killing mechanisms of these phagocytic cells, A . salmonicida was still able to survive and even replicate inside head kidney macrophages, thereby supporting the notion of A . salmonicida as a facultatively intracellular pathogen . Intraperitoneal chambers in rainbow trout may constitute a valuable experimental tool for studying the in vivo fate of A . salmonicida, and perhaps of other fish pathogens as well.

Int J Food Microbiol, 1993 Nov, 20(2), 117 - 20
Distribution of mesophilic Aeromonas species in raw and ready-to-eat fish and meat products in Switzerland; Gobat PF et al.; A total of 829 poultry, meat, shellfish and fish products commonly consumed in Switzerland were qualitatively and quantitatively examined for the presence of mesophilic Aeromonas spp . Overall, aeromonads occurred in 24.1% of the samples . Raw food products were frequently contaminated (e.g . 94.1% in minced meat), with colony counts up to 6.0 x 10(6)/g . Some ready-to-eat products had a relatively high percentage of positive samples as well, such as cooked ham in slices (38.2%), mortadella (12.9%), smoked cooked sausage (15.6%), hot and cold smoked fish (10.9-14.3%) and gravad salmon (10.5%) . Colony counts, however, were somewhat lower (up to 1.7 x 10(3)/g) . The high contamination rate of cooked or hot smoked foods suggests recontamination after cooking or smoking, e.g., at the slicing and packaging stage . 61.2% of the identified strains were Aeromonas hydrophila, followed by 22.5% Aeromonas caviae and 16.3% Aeromonas sobria.

J Med Microbiol, 1993 Nov, 39(5), 325 - 33
Typing of Aeromonas spp . by numerical analysis of immunoblotted SDS-PAGE gels; Mulla R et al.; One hundred and three isolates of Aeromonas spp., collected from both environmental sources and patients, were examined by SDS-PAGE of whole cells followed by immunoblotting with polyclonal rabbit antiserum raised against whole cells of A . sobria . All isolates were typable, yielding 15-20 well separated bands . Reproducibility of the technique was good and discrimination excellent, yielding 30 types amongst 103 isolates . Immunoblot type was not related to biochemical phenotype . Attempts to correlate immunoblot type with serotype were unsuccessful because only 42% of the strains tested could be serotyped.

FEBS Lett, 1993 Nov 1, 333(3), 296 - 300
Physical and chemical characterization of the oligomerization state of the Aeromonas hydrophila lipase/acyltransferase; Ausio J et al.; Aeromonas glycerophospholipid:cholesterol acyl transferase undergoes a conformational transition upon activation by treatment with trypsin . Chemical cross-linking and sedimentation velocity analysis showed that the lipase dimerizes due to removal of a region near its C-terminus . The lipase monomer has a sedimentation coefficient s20.w = 2.83 S, whereas the dimer has s20.w = 3.65 +/- 0.22 S . Hydrodynamic analysis using these sedimentation values and the masses determined by mass spectrometry indicated that the monomers are aligned side-by-side in the dimer . An important change occurs in the apparent partial specific volume of the molecule upon activation.

J Mol Biol, 1993 Oct 20, 233(4), 753 - 65
Distribution of surface-exposed and non-accessible amino acid sequences among the two major structural domains of the S-layer protein of Aeromonas salmonicida; Doig P et al.; The tetragonally arranged crystalline surface protein array (A-layer) of the fish pathogenic bacterium Aeromonas salmonicida is a virulence factor . Circular dichroism studies in the presence or absence of 0.1% sodium dodecyl sulfate showed that the secondary structure of A-protein, and its 39,439 molecular weight amino-terminal trypsin-resistant peptide, were altered . In both cases alpha-helix was increased significantly at the expense of beta-structure when SDS was added . Western and dot immunoblotting, immuno-microscopy and enzyme-linked immunosorbent assay with monospecific polyclonal antiserum and eight monoclonal antibodies specific for epitopes exposed on the surface of native A-layer showed that the 481 residue A-protein subunit and the surface of A-layer were conserved antigenically . Mimeotope analysis of nonapeptides representing the sequence of A-protein allowed identification of 146 residues in presumed linear epitopes accessible on the surface of A-layer . Inaccessible or non-epitopic residues accounted for 70% of the protein . The majority of inaccessible residues were in the N-terminal 301 residues of A-protein . Dispersed among these were 65 surface-accessible residues in five linear epitope clusters illustrating the complex folding of this major structural domain of A-protein . The C-terminal 180 residues carried fewer linear epitopes but contained the major region of A-layers surface-accessible sequence, including four linear epitopes in predominantly hydrophobic sequence . Four A-layer surface-binding monoclonal antibodies also bound to this minor structural domain, although the epitopes of only two were identified by mimeotope analysis . The epitopes of six A-layer surface-binding monoclonals could not be identified, suggesting that A-layer may also contain conformation dependent surface epitopes.

Vet Rec, 1993 Oct 16, 133(16), 389 - 91
Assessment of the antimicrobial sensitivity of Aeromonas salmonicida isolates from farmed Atlantic salmon in Scotland; Grant AN et al.; Sixty-five isolates of Aeromonas salmonicida were assessed for antimicrobial sensitivity by disc diffusion tests and the results compared with the minimum inhibitory concentration for each isolate . The results demonstrated that disc diffusion, using a standard technique, may be used to categorize isolates as sensitive or resistant provided that the corresponding minimum inhibitory concentrations are known.

Microb Pathog, 1993 Oct, 15(4), 313 - 7
The role of a 40-megadalton plasmid in the adherence and hemolytic properties of Aeromonas hydrophila; Hanes DE et al.; A cured strain of Aeromonas hydrophila, MS-2PC, was examined for phenotypic changes in antibiotic resistance, adherence, and hemolysis . Parental strain MS-2 was resistant to ampicillin, novobiocin, and carbenicillin; MS-2PC, which lacked a 40-MDa plasmid, was also resistant to ampicillin but was sensitive to novobiocin and carbenicillin . The adherence of these isolates to CaCo-2 and HeLa cells was examined . MS-2PC demonstrated greater attachment to both cell lines than did strain MS-2 (p < 0.05) . MS-2PC also demonstrated greater hemolysis activity than did MS-2 (p < 0.01) . The 40-Mda plasmid was isolated and reintroduced into MS-2PC . The resulting transformant, 20T, regained resistance to carbenicillin and novobiocin . The attachment ability of 20T was equal to that of MS-2, and both strains demonstrated significantly lower attachment ability than that of MS-2PC (p < 0.01) . Strains MS-2 and 20T exhibited the same hemolysis pattern, which was markedly less than that of strain MS-2PC . These results indicate that the 40-Mda plasmid which codes for antibiotic resistance also controls other functions of A . hydrophila MS-2.

Comp Immunol Microbiol Infect Dis, 1993 Oct, 16(4), 267 - 72
Fatal septicaemia caused by Aeromonas hydrophila in a patient with cirrhosis; Krovacek K et al.; In this case report from Italy we describe a fatal infection caused by A . hydrophila in a 39 yr old cirrhotic patient . This pathogen was isolated as a pure single culture from the patient's blood sample . The patient died on the second day of hospitalization from overwhelming sepsis . The A . hydrophila isolate was tested for different potential virulence properties, such as invasiveness, adherence, exotoxins production, presence of fimbriae and for the patterns of resistance to a variety of antimicrobial agents . Although, the Aeromonas species are infrequently reported as a cause of human infections, the present case study confirms the capability of these pathogens to induce serious human infections.

New Microbiol, 1993 Oct, 16(4), 333 - 42
Characterization of mesophilic Aeromonas from clinical specimens by computerized analysis of SDS-PAGE protein profiles and by enzymatic activity; Arzese A et al.; Mesophilic Aeromonas (Aeromonas hydrophila, Aeromonas sobria, Aeromonas caviae) have recently been considered important aetiological agents of human diseases, mainly gastrointestinal infections . Although several findings have pointed out the significance of this group of microorganisms as enteric pathogens and suggested the presence of virulence factors, epidemiological and clinical studies are limited by the difficulty of correctly identifying mesophilic Aeromonas at the species level . SDS-PAGE of radiolabelled total protein profiles and bacterial enzymatic activities were used to type 31 clinical isolates (6 A . hydrophila, 7 A . sobria and 18 A . caviae) from patients with gastroenteritis and from healthy controls . Analysis of SDS-PAGE protein patterns, reinforced by the UPGMA-grouping system (AMBIS software) provided a good characterization of A . caviae strains as a homogeneous group of microorganisms, possessing significant differences from the other two species of mesophilic Aeromonas, in good agreement with biochemical and enzymatic tests . Data obtained in analyzing A . sobria protein profiles clearly showed two groups, with a correlation coefficient (CC) = 0.70, which in our experience is a doubtful value for assigning two strains to the same species . Strains biochemically identified as A . hydrophila showed a CC = 0.64, which is equally not acceptable for species assignment . Inter-species comparison highlighted this heterogeneity, showing two mixed subgroups, both containing strains that were assigned to A . sobria and A . hydrophila species on the basis of biochemical features.(ABSTRACT TRUNCATED AT 250 WORDS)

Int J Syst Bacteriol, 1993 Oct, 43(4), 855 - 6
Aeromonas enteropelogenes and Aeromonas ichthiosmia are identical to Aeromonas trota and Aeromonas veronii, respectively, as revealed by small-subunit rRNA sequence analysis; Collins MD et al.; The 16S rRNA gene sequences of the type strains of Aeromonas enteropelogenes and Aeromonas ichthiosmia were determined by polymerase chain reaction direct sequencing in order to clarify their interrelationships with other aeromonad species . On the basis of 16S rRNA gene sequence analysis, A . enteropelogenes and A . ichthiosmia were found to be identical to Aeromonas trota and Aeromonas veronii, respectively.

Antibiot Khimioter, 1993 Oct-Nov, 38(10-11), 20 - 2
{The comparative characteristics of the antibiotic sensitivity of psychrophilic and mesophilic aeromonads}; Shenderovich VA et al.; The general regularities of the antibiotic susceptibility of psychrophilic and mesophilic aeromonads were determined . The antibioticograms were in general similar . Still, there was observed a higher susceptibility of Aeromonas salmonicida to tetracycline, chloramphenicol and rifampicin, as well as a larger number of strains susceptible to semisynthetic broad spectrum penicillins (ampicillin and carbenicillin) and cephazoline . The susceptibility to aminoglycosides was lower.

FEMS Microbiol Lett, 1993 Sep 1, 112(2), 191 - 7
Molecular cloning and nucleotide sequence analysis of the maltose-inducible porin gene of Aeromonas salmonicida; Dodsworth SJ et al.; The gene for the Aeromonas salmonicida maltose-inducible porin (maltoporin) was cloned into phagemid pTZ18R in two restriction fragments, 0.6-kb PstI/KpnI and 1.7-kb SphI, of genomic DNA and their nucleotide sequences were determined . Open reading frames of 1329 and 1335 bp translated into sequences of 443 and 445 amino acids, with a 23 or 25 amino acid signal sequence and a 420 amino acid mature protein of molecular mass 46424 Da . Putative ribosome binding sites, AGGA and GGGAA, occurred 9 bp upstream of two possible ATG initiation codons . The A . salmonicida gene product showed a high degree of similarity with Escherichia coli LamB, and codon usage was very similar to that of another A . salmonicida outer membrane protein but markedly different from those of extracellular proteins.

Am J Clin Pathol, 1993 Sep, 100(3), 308 - 10
Failure of the Vitek AutoMicrobic system to detect beta-lactam resistance in Aeromonas species; Schadow KH et al.; The ability of the Vitek AutoMicrobic system (AMS; Vitek, Inc., Hazelwood, MO) and disk-diffusion method to detect beta-lactam resistance was assessed with 25 strains from four species of Aeromonas . A very major error was indicated when a strain was shown to be susceptible by the AMS or disk-diffusion method but resistant by the agar dilution method . The rates for very major errors for disk diffusion and the AMS were 0% and 43%, respectively . The beta-lactam agents and numbers of very major errors for the AMS were as follows: ticarcillin, 17; mezlocillin, 3; piperacillin, 4; cephalothin, 9; cefazolin, 3; cefoxitin, 1; cefotetan, 2; and cefuroxime, 1 . Thus, these data suggest that the AMS currently is not reliable for testing the resistance of Aeromonas to beta-lactam agents.

Infect Immun, 1993 Sep, 61(9), 3854 - 62
Aeromonas salmonicida grown in vivo; Garduno RA et al.; The virulent fish pathogen Aeromonas salmonicida was rapidly killed in vivo when restricted inside a diffusion chamber implanted intraperitoneally in rainbow trout . After a period of regrowth, the survivors had acquired resistance to host-mediated bacteriolysis, phagocytosis, and oxidative killing, properties which were subsequently lost by growth in vitro . Resistance to bacteriolysis and phagocytosis was associated with a newly acquired capsular layer revealed by acidic polysaccharide staining and electron microscopy . This capsular layer shielded the underlying, regular surface array (S-layer) from immunogold labeling with a primary antibody to the S-layer protein . Resistance to oxidative killing was mediated by a mechanism not associated with the presence of the capsular layer . An attenuated vaccine strain of A . salmonicida grown in vivo failed to express the capsular layer . Consequently, the in vivo-grown cells of this attenuated strain remained as sensitive to bacteriolysis, and as avidly adherent to macrophages, as the in vitro-grown cells . The importance of these new virulence determinants and their relation to the known virulence factors of A . salmonicida are discussed.

J Diarrhoeal Dis Res, 1993 Sep, 11(3), 157 - 60
Adherence of haemagglutinating and non-haemagglutinating clinical and environmental isolates of Aeromonas; Singh DV et al.; Twelve haemagglutinating and non-haemagglutinating isolates of Aeromonas spp., comprising 6 each of clinical and environmental origin, were examined for their ability to adhere to rabbit intestinal epithelium, for inhibition of adhesion with sugars, and for delineation of the portion of intestine, jejunum, or ileum that is most susceptible to adhesion . Although the environmental isolates of Aeromonas haemagglutinated human erythrocytes that were inhibited by D-mannose and/or L-fucose, the majority of the clinical isolates of Aeromonas adhered to rabbit intestinal epithelium in almost equal proportions regardless of their haemagglutination (HA) properties, species designation, and source of isolation . Adhesion of both haemagglutinating and non-haemagglutinating isolates of Aeromonas was inhibited by sugars; however, the ability of sugar inhibition to adhere was similar to that observed with HA . This study suggests that adhesion is probably mediated by a variety of pilus or non-pilus colonisation factors which may or may not be a haemagglutinin . The jejunum was found to be more susceptible to adhesion than the ileum . However, no appreciable difference was observed in the number of adhered bacteria to adjacent loops.

Immunology, 1993 Sep, 80(1), 68 - 72
Biological markers of macrophage activation: applications for fish phagocytes; Enane NA et al.; The immune defence mechanisms of fish seem to be related and similarly competent to those of mammals . Because of this, there is an increased interest in the immune responses of fish as models for higher vertebrates in immunological/immunotoxicological studies . Macrophages (M phi), phagocytic cells of the mammalian and teleost immune system which reside in tissues, represent a quiescent population of cells . However, upon stimulation, alterations in the physiology of these resident M phi occur which can be defined in terms of activation . This study was undertaken to determine whether biological markers used to assess mammalian M phi activation are applicable for use with fish M phi . Cells were recovered from the peritoneal cavity of non-injected and Aeromonas salmonicida-injected fish, and differences between resident and elicited M phi were evaluated with respect to protein content, phagocytic competence, enzyme activities and hydrogen peroxide production . Results demonstrate that biological markers used to assess mammalian M phi activation, with the exception of acid phosphatase activity, can be used to characterize the activation state of trout M phi, and that the activation process in both fish and mammals may occur by similar mechanism(s).

Zentralbl Mikrobiol, 1993 Sep, 148(6), 441 - 7
Aeromonas-associated gastroenteritis in Egypt; Ghanem EH et al.; Aeromonas spp . including A . hydrophila, A . sobria, and A . caviae, were recovered from the feces of 88% of diarrheic Egyptian children . In contrast, only 45% of nondiarrheic children contained Aeromonas spp . A probable source of Aeromonas spp . is from drinking water inasmuch as nine out of ten samples analysed from the district of Cairo in which the children resided tested positive for Aeromonas spp . Enterotoxigenicity of the isolates from various sources was tested . 33% of the diarrheic samples produced enterotoxin whereas 47% of the nondiarrheic and 56% of the tap water strains produced enterotoxin.

J Biol Chem, 1993 Aug 25, 268(24), 18272 - 9
Dimerization stabilizes the pore-forming toxin aerolysin in solution; van der Goot FG et al.; Aerolysin is a channel-forming protein secreted as a protoxin by Aeromonas hydrophila . Analytical centrifugation measurements showed that proaerolysin is a dimer in solution, and this was confirmed by chemical cross-linking with dimethyl suberimidate . Dissociation of proaerolysin with low concentrations of SDS resulted in the loss of tertiary structure, assessed by near ultraviolet circular dichroism . This was accompanied by an increase in the protein's ability to bind the hydrophobic dye 1-anilino-8-naphthalene sulfonate, as well as by increased sensitivity to proteolytic degradation . However, the monomer was not fully unfolded by the detergent, as the tryptophans remained in a hydrophobic environment, and the secondary structure measured by far ultraviolet circular dichroism did not seem to be affected . Aerolysin, the active form of the protein, was also shown to be a dimer, and its stability was found to be no different from the stability of the protoxin dimer . Substituting tryptophan 371 or tryptophan 373 with leucine greatly reduced the stability of dimeric proaerolysin . These substitutions are known to increase the protein's ability to oligomerize, supporting the conclusion that dimer dissociation is necessary for oligomerization to occur.

Appl Environ Microbiol, 1993 Aug, 59(8), 2437 - 41
Effects of nutrients on exopolysaccharide production and surface properties of Aeromonas salmonicida; Bonet R et al.; Extracellular polysaccharide (EPS) and capsular polysaccharide (CPS) production by Aeromonas salmonicida A450 and the influence of the capsule on cell surface properties were studied . A . salmonicida did not produce CPS or EPS when glucose, phosphate, magnesium chloride, or trace mineral components were absent from the medium . The addition of yeast extract improved capsule production . Neither EPS nor CPS formation depended on the C/N ratio, although it appeared to be influenced by the level of carbon and nitrogen in the culture . Both EPS and CPS production started at the end of the logarithmic growth phase . The amounts of EPS and CPS produced were not influenced by temperature changes between 15 and 20 degrees C and was maximal from pH 7 to 7.5 . Cell surface properties were strongly influenced by capsule production; high CPS production was associated with enhanced cell hydrophilicity and autoagglutination . The effect of CPS on cell surface properties was independent of the presence of the surface protein array (A-layer).

Appl Environ Microbiol, 1993 Aug, 59(8), 2411 - 7
Purification, gene cloning, amino acid sequence analysis, and expression of an extracellular lipase from an Aeromonas hydrophila human isolate; Anguita J et al.; A structural gene which codes for an extracellular lipase (EC 3.1.1.3) in Aeromonas hydrophila H3, which was isolated from a female hospitalized patient, was cloned in Escherichia coli by using pBR322 as a vector . Lipase purified from both A . hydrophila culture supernatant and the periplasmic fluids of E . coli containing the lip determinant in the original clone (plasmid pLA2) showed an M(r) of 67,000 on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, which agrees with the M(r) determined by Sephacryl S-200 chromatography . Regarding substrate specificity, the optimum chain lengths for the acyl moiety were C6 for ester hydrolysis and C6 and C8 for triacylglycerol hydrolysis . Sequence analysis showed a major open reading frame of 2,052 bp, which predicts a polypeptide with an M(r) of 71,804 . The polypeptide was found to contain an amino acid sequence (V-H-F-L-G-H-S-L-G-A) which is highly preserved among lipases.

J Med Microbiol, 1993 Aug, 39(2), 107 - 13
Characterisation of strains of Aeromonas spp . by phenotype and whole-cell protein fingerprint; Millership SE et al.; Sixty-eight isolates of Aeromonas spp . were examined biochemically and their cell proteins were analysed by silver-stained SDS-PAGE . Protein fingerprints did not correlate with phenotype . However, consideration of both phenotype and fingerprint showed clustering of epidemiologically related isolates . There was also evidence that similar strains could be found in infected people and water or other environmental samples.

J Infect Dis, 1993 Jul, 168(1), 215 - 8
Diarrhea associated with Aeromonas species in children in day care centers; de la Morena ML et al.; Outbreaks of diarrhea caused by enteropathogens have been reported in day care centers (DCC), but Aeromonas species have not been implicated . This study evaluated 381 children involved in 51 outbreaks in four DCC to determine the association of Aeromonas species with diarrhea and to characterize the isolates . The organism was identified in two outbreaks of diarrhea . In one, Aeromonas species were isolated from 6 (24%) of 25 children and in the other from 5 (21%) of 24 children . Seven other Aeromonas strains from children in DCC were studied . Fourteen (78%) of 18 were Aeromonas caviae and 15 were from children with diarrhea . Of the isolates, 75% did not have plasmids detected; all others had unique plasmid patterns . All strains had different DNA content . Twenty-two control isolates of Aeromonas from children with diarrhea in Mexico and Dallas had different chromosomal DNA patterns . Most Aeromonas infections were associated with symptoms . Chromosomal DNA patterns differentiated Aeromonas strains better than did plasmid DNA patterns . The outbreaks of diarrhea were unusual in that several different Aeromonas genospecies were involved in each outbreak.

Comp Biochem Physiol Comp Physiol, 1993 Jul, 105(3), 479 - 84
The effect of bacteria infection on mean selected body temperature in the common Agama, agama agama: a dose-response study; Ramos AB et al.; 1 . The fever response was studied in 43 common agamas using a self-pairing experiment in which animals received an intraperitoneal injection of sterile saline and an injection of one of six dosages of dead Aeromonas sobria (1 x 10(6), 1 x 10(7), 1 x 10(8), 1 x 10(9), 1 x 10(10), and 1 x 10(11) total organisms) . 2 . The results demonstrated a significant increase in Tb (1.6-3.1 degrees C) above the mean selected body temperature (MSBT) of the saline injection animals over a bacteria infection range of three orders of magnitude . At 1 x 10(8) organisms, an increase was observed on bacteria day 1 while at dosages of 1 x 10(9) and 1 x 10(10) an increase was observed on bacteria days 1 and 2 . 3 . At dosages of 1 x 10(6) and 1 x 10(7) there was no difference between saline MSBT and bacteria MSBT . 4 . At a dosage of 1 x 10(11), MSBTs on bacteria days 1 and 2 were below saline MSBT . 5 . The average duration of the fever response is related to the level of infection; however, the magnitude of the fever is relatively independent of the level of infection.

Int J Food Microbiol, 1993 Jun 1, 18(4), 339 - 42
Occurrence of Aeromonas spp . in samples of ground meat and chicken; Hanninen ML; Aeromonas spp . was commonly isolated from ground meat and chicken samples at the retail level . The dominant species in ground meat were A . hydrophila and A . caviae . In chicken, A . sobria was common while A . caviae was isolated infrequently . Although A . hydrophila was isolated from 75% of ground meat samples and 62% of chicken samples, DL-lactate-positive A . hydrophila (genospecies 1) was isolated from only 25 or 37% or respective samples . Sorbitol-positive A . hydrophila (genospecies 3) was common in both ground meat and chicken.

Antimicrob Agents Chemother, 1993 Jun, 37(6), 1324 - 8
High specificity of cphA-encoded metallo-beta-lactamase from Aeromonas hydrophila AE036 for carbapenems and its contribution to beta-lactam resistance; Segatore B et al.; The Aeromonas hydrophila AE036 chromosome contains a cphA gene encoding a metallo-beta-lactamase highly active against carbapenem antibiotics . This enzyme was induced in strain AE036 to the same extent by both benzylpenicillin and imipenem . When the cphA gene was inserted into plasmid pACYC184, used to transform Escherichia coli DH5 alpha, the MICs of imipenem, meropenem, and penem HRE664 for recombinant clone DH5 alpha(pAA20R), expressing the Aeromonas metallo-beta-lactamase, were significantly increased, but those of penicillins and cephalosporins were not . When the metallo-beta-lactamase purified from E . coli DH5 alpha(pAA20R) was assayed with several beta-lactam substrates, it hydrolyzed carbapenems but not penicillins or cephalosporins efficiently . These results demonstrate that this metallo-beta-lactamase possesses an unusual spectrum of activity compared with all the other class B enzymes identified so far, being active on penems and carbapenems only . This enzyme may thus contribute to the development of resistance to penems and carbapenems but not other beta-lactams.

J Bacteriol, 1993 May, 175(10), 3105 - 14
An Aeromonas salmonicida gene which influences a-protein expression in Escherichia coli encodes a protein containing an ATP-binding cassette and maps beside the surface array protein gene; Chu S et al.; A conserved Aeromonas salmonicida gene (abcA) affecting expression of the surface array protein gene (vapA) in Escherichia coli was identified . The 924-bp gene starts 205 bp after vapA and codes for a protein with a deduced molecular weight (M(r)) of 34,015 containing an N-terminal P-loop and significant homology to the ATP-binding cassette transport protein superfamily . AbcA was identified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) by using T7 polymerase expression and DNA-directed translation and was copurified with the sarkosyl-soluble cytoplasmic membrane fraction . The protein displayed aberrant migration during SDS-PAGE . A lacZ fusion containing 128 bp of upstream sequence and 387 bases in the 5' end of abcA was constructed, and the beta-galactosidase activity of the abcA-lacZ fusion gene was shown to be similar in E . coli and A . salmonicida . The 130,000-M(r) AbcA-LacZ fusion protein was purified, and by using an ATP affinity column, the 129 AbcA N-terminal P-loop-containing residues were shown to bind ATP.

Infect Immun, 1993 May, 61(5), 2172 - 81
An aromatic-dependent mutant of the fish pathogen Aeromonas salmonicida is attenuated in fish and is effective as a live vaccine against the salmonid disease furunculosis; Vaughan LM et al.; Aeromonas salmonicida is the etiological agent of furunculosis in salmonid fish . The disease is responsible for severe economic losses in intensively cultured salmon and trout . Bacterin vaccines provide inadequate protection against infection . We have constructed an aromatic-dependent mutant of A . salmonicida in order to investigate the possibility of an effective live-attenuated vaccine . The aroA gene of A . salmonicida was cloned in Escherichia coli, and the nucleotide sequence was determined . The codon usage pattern of aroA was found to be quite distinct from that of the vapA gene coding for the surface array protein layer (A layer) . The aroA gene was inactivated by inserting a fragment expressing kanamycin resistance within the coding sequence . The aroA::Kar mutation was introduced into the chromosome of virulent A . salmonicida 644Rb and 640V2 by allele replacement by using a suicide plasmid delivery system . The aroA mutation did not revert at a detectable frequency (< 10(-11) . The mutation resulted in attenuation when bacteria were injected intramuscularly into Atlantic salmon (Salmo salar L.) . Introduction of the wild-type aroA gene into the A . salmonicida mutants on a broad-host-range plasmid restored virulence . A . salmonicida mutant 644Rb aroA::Kar persisted in the kidney of brown trout (Salmo trutta L.) for 12 days at 10 degrees C . Vaccination of brown trout with 10(7) CFU of A . salmonicida 644Rb aroA by intraperitoneal injection resulted in a 253-fold increase in the 50% lethal dose (LD50) compared with unvaccinated controls challenged with a virulent clinical isolate 9 weeks later . A second vaccination after 6 weeks increased the LD50 by a further 16-fold.

Microb Pathog, 1993 May, 14(5), 411 - 5
Effects of the acetylcholinesterase toxin of Aeromonas hydrophila on the central nervous system of fish; Rodriguez LA et al.; The purified acetylcholinesterase (AcChE) toxin, crude extracellular products (ECP) or viable virulent Aeromonas hydrophila were injected intraperitoneally into rainbow trout in different sublethal and lethal doses . When fish showed signs of morbidity, brain tissue was excised and assayed for acetylcholinesterase activity . In all cases there was a large increase in AcChE activity (about 40-fold for purified AcChE-toxin) . This was shown to be due to an accumulation of the fish's own AcChE and not the bacterial toxin . Nevertheless, the latter was detected in brain homogenates from fish in all treatment groups using a rabbit antiserum to the purified toxin to probe Western blots of brain homogenates, demonstrating that the toxin does gain access to brain tissue and is produced during in vivo infection . The results strongly suggest that this toxin plays a central role in the pathogenesis of A . hydrophila infection.

Can J Microbiol, 1993 May, 39(5), 513 - 23
Cloning, expression, and sequence analysis of a cytolytic enterotoxin gene from Aeromonas hydrophila; Chopra AK et al.; The structural gene and regulatory element for a cytolytic enterotoxin of a diarrheal isolate, SSU, of Aeromonas hydrophila was cloned and its DNA sequence was determined . A complementary, mixed synthetic oligonucleotide based on the first 10 NH2-terminal amino acid residues of the Aeromonas cytolytic enterotoxin was used as a probe to screen a genomic library constructed in bacteriophage EMBL3 . Cell lysates of Escherichia coli (lambda CH4), containing the cytolytic enterotoxin gene, lysed rabbit red blood cells and destroyed Chinese hamster ovary cells, caused fluid secretion in rat ileal loops, and were lethal to mice when injected intravenously . All biological activities associated with the cytolytic enterotoxin were neutralized by rabbit homologous polyclonal antibodies . Sodium dodecyl sulfate polyacrylamide gel electrophoresis and subsequent Western blot analysis of the cell lysate of E . coli (lambda CH4) revealed a protein band of approximately 52 kDa, using antisera to the cytolytic enterotoxin or antibodies generated against a synthetic peptide to the toxin . DNA sequence analysis of a 2.8-kb SalI-BamHI fragment revealed the presence of one large open reading frame (1479 bp) that would encode a protein of 54.5 kDa, a precursor form of the cytolytic enterotoxin, with a 23 amino acid leader peptide . Despite a significant amount of homology at the DNA and amino acid levels between our cytolytic enterotoxin and two aerolysins of Aeromonas species, variation in the restriction maps of these three toxin genes was prominent . Likewise, considerable divergence in DNA sequence was observed upstream of the structural genes for the reported aerolysins and our cytolytic enterotoxin, suggesting that these structurally similar toxin molecules may be regulated differently . Finally, our data showed that the cytolytic enterotoxin from a diarrheal isolate, SSU, of A . hydrophila exhibited characteristics that were unique compared with those of the reported aerolysins.

Zhonghua Min Guo Wei Sheng Wu Ji Mian Yi Xue Za Zhi, 1993 May, 26(2), 78 - 85
Isolation and characterization of Aeromonas from seafoods in Taipei; Yaun SS et al.; A total of 124 fresh seafoods and 158 processed seafoods collected from the retail markets and supermarkets in Taipei were tested for the contamination with motile Aeromonas spp . Of the fresh seafoods analyzed, 88% displayed the presence of Aeromonas . The isolation rates of various samples were as follows: 100%, freshwater fish; 95%, seawater fish; 78%, fish fillets; 84%, shrimp and crab of the crustacea group; 83%, bivalve shellfish and 84%, non-bivalve shellfish of the mollusca group, and 100%, seaweed . Of the 158 processed seafoods, 11% were contaminated by Aeromonas . The isolation rates were as follows: 0%, canned, dried, or frozen fresh seafood; 18%, salted seafood; 30%, fish cake; 7% vacuum-packaged fish cakes; 14%, frozen seafood dumplings; 8%, cooked seafoods . One hundred and eighty-three Aeromonas strains isolated in this survey were characterized to species level and tested for their ability to produce beta-hemolysin . Ninety-eight percent (98%) of the A . hydrophila produced beta-hemolysin on 5% blood agar, 94% of the A . sobria and 33% of the A . caviae produced beta-hemolysin . Thus it is likely that fresh seafoods are potentially significant sources of the virulent Aeromonas species and may play an important role in the epidemiology of Aeromonas-associated gastroenteritis.

Antimicrob Agents Chemother, 1993 Apr, 37(4), 905 - 7
In vitro susceptibilities of tropical strains of Aeromonas species from Queensland, Australia, to 22 antimicrobial agents; Koehler JM et al.; Greater than 90% of 131 strains of Aeromonas species were susceptible to the aminoglycosides, ureidopenicillins, extended-spectrum cephalosporins, aztreonam, quinolones, tetracycline, and chloramphenicol, and all were uniformly resistant to ampicillin . Except for amoxicillin-clavulanate, sulfonamide, trimethoprim, and trimethoprim-sulfamethoxazole, there was good correlation between the results obtained by the agar dilution and disk diffusion techniques.

FEMS Microbiol Lett, 1993 Apr 1, 108(2), 151 - 5
Identification of Aeromonas schubertii and Aeromonas jandaei by using a polymerase chain reaction-probe test; Ash C et al.; Two oligonucleotide primers were used in a polymerase chain reaction-protocol to amplify a region (approx . 850 bp) of the 16S rRNA gene of Aeromonas schubertii and Aeromonas jandaei . Hybridization of the polymerase chain reaction products to specific internal probes provided a highly specific method for the identification of these two species.

Epidemiol Infect, 1993 Apr, 110(2), 279 - 87
Adherence to HEp-2 cells and enteropathogenic potential of Aeromonas spp; Grey PA et al.; Aeromonas strains (total = 60) of clinical, water and food origin were tested for adherence to HEp-2 cells . Environmental strains were selected (except for A . caviae) to include primarily those expressing other virulence-associated properties . Adhesion was markedly species-dependent (A . veronii biotype sobria, 15 of 26 {58%} . A caviae, 4 of 12 {33%} and A . hydrophila, 2 of 8 {11%}) . A . veronii biotype sobria were adhesive, irrespective of source (62 and 54% for clinical and environmental strains, respectively) . Adherent strains of this species were enterotoxin-positive and most (13 of 15) grew at 43 degrees C . A . caviae isolated from clinical specimens contained a higher proportion (75%) of adherent strains than environmental strains (13%) . Virulent subsets of A . veronii biotype sobria and A . caviae are adherent to HEp-2 cells . The HEp-2 assay is a useful model for investigating mechanisms of adherence and enteropathogenicity of virulent Aeromonas species.

Appl Environ Microbiol, 1993 Mar, 59(3), 874 - 80
Survival of nonculturable Aeromonas salmonicida in lake water; Morgan JA et al.; The survival of Aeromonas salmonicida subsp . salmonicida was investigated in sterile and untreated lake water . In sterile lake water (filtered and autoclaved), it was found that cells of A . salmonicida entered a nonculturable but viable condition . Viability was determined by flow cytometry with the dye rhodamine 123, which is taken up and maintained within cells with a membrane potential . For survival studies in untreated lake water, A . salmonicida was marked with the xylE gene by using the plasmid pLV1013 . Marked cells were detected by growth on tryptone soy agar and tryptone soy agar supplemented with kanamycin . Cells were also detected by polymerase chain reaction DNA amplification of the xylE gene and a chromosomal DNA fragment specific for A . salmonicida (pLV1013) . The results indicated that A . salmonicida entered a nonculturable condition in untreated lake water over a 21-day study . The viability of nonculturable cells could not be determined in mixed samples; however, the presence of nonculturable cells containing both chromosomal and plasmid DNA was confirmed.

Dev Comp Immunol, 1993 Mar-Apr, 17(2), 129 - 40
Activation of rainbow trout (Oncorhynchus mykiss) phagocytes by muramyl dipeptide; Kodama H et al.; Immunoenhancing activity of synthetic muramyl dipeptide (MDP) was investigated in relation to the activation of rainbow trout (Oncorhynchus mykiss) phagocytes and to nonspecific protection against challenge with the fish pathogen Aeromonas salmonicida . Head kidney phagocytes collected from MDP-injected fish showed significant chemotactic activity against zymosan-activated normal rainbow trout serum, and phagocytic activities against both A . salmonicida and plastic beads . The MDP-activated phagocytes also showed enhanced superoxide generation . When normal phagocytes were exposed to supernatants of phagocyte or peripheral blood lymphocyte cultures of MDP-injected fish, the cells showed significant chemotactic activity, indicating that the MDP-activated cells produced phagocyte-activating factor . Injection of MDP to fish provided protection against challenge with virulent A . salmonicida.

J Med Microbiol, 1993 Mar, 38(3), 227 - 34
Isolation and purification of Aeromonas sobria cytotonic enterotoxin and beta-haemolysin; Gosling PJ et al.; Aeromonas sp., grown in tryptone soya broth supplemented with yeast extract, 0.6%, pH 7.5, and incubated with agitation at 100 oscillations/min for 15 h at 37 degrees C produced optimal amounts of beta-haemolysin and cytotonic enterotoxin . More prolonged incubation resulted in the loss of enterotoxic activity and anion exchange chromatographic analysis indicated the presence of a moiety capable of breaking down the toxin . Anion exchange fast protein liquid chromatography resulted in a single peak of haemolytic activity and two peaks with enterotoxic activity . The cytotonic enterotoxin was purified from the fraction most active in the infant mouse assay; the second peak, which did not cross-react immunologically, may represent a second cytotonic enterotoxin . Neither peak was observed in the chromatographic fractions of filtrates from strains devoid of activity in the infant mouse assay . Purified enterotoxin, estimated to have a mol . wt of 15 kDa by SDS-PAGE, caused fluid accumulation in the infant mouse assay, was non-haemolytic to rabbit erythrocytes, caused an increase in cAMP activity in tissue culture cells and did not cross-react immunologically with components of cholera toxin or the whole toxin . Purified beta-haemolysin had an estimated mol . wt of 55 kDa, lysed rabbit erythrocytes and did not cause fluid accumulation in the infant mouse test.

J Diarrhoeal Dis Res, 1993 Mar, 11(1), 30 - 4
Detection of Aeromonas hydrophila serogroup 0:34 in faeces using an enzyme-linked immunosorbent assay; Merino S et al.; A microtitration plate, antibody capture, enzyme-linked immunosorbent assay was developed for detection of Aeromonas hydrophila serogroup 0:34 . The assay uses a detector antibody which shows no cross-reactions with Aeromonas strains not belonging to serogroup 0:34 or non-Aeromonas competing organisms . The detector antibody is mixed with the sample and incubated for 1 h; it is then microcentrifuged and the supernatant (unabsorbed antibody) titered on a microtiter plate coated with A . hydrophila cells from serogroup 0:34 . All A . hydrophila strains from serogroup 0:34 that we tested in this manner reacted strongly with the detector antibody . Also, by culturing and performing the immunoassay with the detector antibody we established and quantified the presence of A . hydrophila 0:34 on different samples.

J Hosp Infect, 1993 Mar, 23(3), 223 - 8
Bacteriological investigation of the occurrence and antibiotic sensitivities of the gut-flora of the potential southern African medicinal leech, Asiaticobdella buntonensis (Hirudinidae); Wilken GB et al.; The lack of availability of medicinal leeches is a major impediment to the widespread use of leech therapy for treatment of congested flaps and replants in southern Africa . An investigation into the suitability of an alternative leech, the indigenous southern African leech, Asiaticobdella buntonensis, was therefore started . The risk of hospital-acquired infection related to the use of leeches and the antibiotic sensitivities of bacteria isolated from the gastro-intestinal tract of wild-caught leeches were investigated . Eleven bacterial genera were isolated but Aeromonas were most frequently isolated, occurring in 82% of microbiological samples . All were sensitive to cefotaxime and amikacin . The gut-flora and their sensitivities to 19 antibiotics were similar to those reported for the traditional medicinal leech, Hirudo medicinalis . These results emphasize the need to anticipate unusual infections when prescribing prophylactic or curative antibiotics in the course of leech therapy.

Microbiologia, 1993 Feb, 9 Spec No, 49 - 56
{Incidence, behavior and control of Aeromonas hydrophila in meat and dairy products}; Garcia-Lopez ML et al.; This review deals with several aspects of Aeromonas hydrophila and other motile Aeromonas species associated with foodborne illness . Although it is mainly dedicated to the factors affecting growth and survival of this species in foods of animal origin, information on other topics is also provided . This paper includes sections on: Taxonomy, diseases caused by Aeromonas, virulence factors, reservoirs and prevalence in foods and water, factors affecting growth and survival, isolation and identification, and control measures.

Mol Microbiol, 1993 Feb, 7(4), 593 - 600
High-affinity binding of the basement membrane protein collagen type IV to the crystalline virulence surface protein array of Aeromonas salmonicida; Trust TJ et al.; The surface of the fish pathogen Aeromonas salmonicida is covered by a paracrystalline array (the A-layer) which is a virulence factor for the organism . Quantification of the ability of A . salmonicida cells to bind collagen types I and IV in a 125I-radiolabelled liquid-phase assay showed that A-layer-positive cells bound high levels of collagen type IV, but significantly lower levels of collagen type I . Collagen type IV binding was confirmed using non-radiolabelled enzyme-linked immunosorbent assays . 125I-Collagen type IV binding was rapid, specific, saturable, high affinity, and essentially irreversible by unlabelled collagen type IV . The A-layer was responsible for collagen type IV binding because binding was inactivated by selective removal of the A-layer at pH 2.2, and neither isogenic A-layer-deficient A . salmonicida mutants nor strains of Aeromonas hydrophila possessing a morphologically similar paracrystalline array bound this basement membrane protein.

Zentralbl Veterinarmed B, 1993 Feb, 40(1), 31 - 4
{The amine-forming ability of Aeromonas spp.}; Bergann T; Motile Aeromonas (A.) species are considered international more and more as potential food poisoning organisms . Their ability to produce biogenic amines, products of metabolism, which in case can cause a disease, was only searched insufficiently till now . 50 strains of the species A.hydrophila, A.sobria, A.caviae and the non-motile species A.salmonicida were included in the tests for amine producing potency . Qualitative investigations to the formation of histamine, tryptamine, and tyramine were ensued by the help of thin layer chromatography . Quantitative investigations were only done in respect of the production of tyramine, which had been proved qualitatively in several strains, while histamine and tryptamine were not produced . Concentrations of tyramine with foodhygienic relevance were found out partially.

J Appl Bacteriol, 1993 Feb, 74(2), 149 - 54
Detection of Aeromonas hydrophila in food with an enzyme-linked immunosorbent assay; Merino S et al.; A microtitration plate, antibody capture, enzyme-linked immunosorbent assay was developed for the detection of Aeromonas hydrophila serotype O: 11 (highly virulent strains) . The assay utilizes a detector antibody which shows no cross-reactions with Aeromonas strains other than serotype O: 11 or non-Aeromonas competing organisms . The detector antibody is mixed with the sample and incubated for 1 h, microcentrifuged and the supernatant fluid (unadsorbed antibody) titred in a microtitre plate coated with A . hydrophila cells from serotype O: 11 . All the A . hydrophila strains from serotype O: 11 tested reacted strongly with the detector antibody . Also by culturing and performing the immunoassay with the detector antibody we established and quantified the presence of A . hydrophila O: 11 in different foods.

J Appl Bacteriol, 1993 Feb, 74(2), 111 - 8
Influence of growth temperature on the production of extracellular virulence factors and pathogenicity of environmental and human strains of Aeromonas hydrophila; Mateos D et al.; The biochemical properties, virulence for mice and trout, and the extracellular virulence factors at 28 degrees and 37 degrees C of 11 environmental and nine human strains of Aeromonas hydrophila were compared . All the environmental isolates and four of the human group were virulent for trout at 3 x 10(7) cfu, but only human strains were able to cause death or lesions in mice by the intramuscular route . Extracellular virulence factors such as haemolysins, cytotoxins and proteases were also investigated in supernatant fluids of cultures grown at 28 degrees C and 37 degrees C . The production of haemolysins, caseinases, elastases and growth yields of environmental strains decreased sharply during cultivation at 37 degrees C but cytotoxins were produced to the same extent, or slightly less, than at 28 degrees C . The human strains differed from the environmental strains in response to growth temperatures: protease activity decreased at 37 degrees C, although growth yield was not affected, but more haemolysins and cytotoxins were produced by the virulent strains at this temperature than at 28 degrees C . Sodium caseinate SDS-PAGE of culture supernatant fluids of selected human strains revealed that temperature selectively inhibited the production of certain proteases.

J Gen Microbiol, 1993 Feb, 139 ( Pt 2), 245 - 9
A comparison of the amino acid sequence of the serine protease of the fish pathogen Aeromonas salmonicida subsp . salmonicida with those of other subtilisin-type enzymes relative to their substrate-binding sites; Coleman G et al.; The amino acid sequence of the so-called 70 kDa (actually 64 kDa) serine protease secreted by the Gram-negative fish pathogen Aeromonas salmonicida has been determined . It shows a high degree of homology with the complete sequence of other bacterial serine proteases which, with molecular masses of approximately 30 kDa, are less than half its size . This homology is particularly marked in regions adjacent to the catalytic triad Asp32, His64 and Ser221 of subtilisin BPN' . Significant features of the A . salmonicida enzyme, a new member of the group of cysteine-containing subtilisin-type serine proteases, are the presence of six cysteine residues in the mature enzyme, a 37 amino acid extension at the N-terminus and 215 amino acids at the C-terminus when compared with subtilisin BPN' . In addition to a number of smaller peptide insertions there is a non-aligned 32 amino acid sequence in a position corresponding to its introduction between Lys213 and Tyr214 of subtilisin BPN' . This sequence is highly hydrophilic, with Asp/Asn accounting for 10 of the 32 amino acids . Further, the possession of two Cys residues separated by 24 amino acids provides the capacity for stabilizing the peptide as an externalized loop.

Infect Immun, 1993 Feb, 61(2), 371 - 7
Isolation of carbohydrate-reactive outer membrane proteins of Aeromonas hydrophila; Quinn DM et al.; Outer membrane proteins of Aeromonas hydrophila A6 were isolated by affinity chromatography on the basis of their reactivity with trisaccharide structures analogous to the terminal trisaccharide of the H antigen of the human ABO(H) blood group system and were characterized by using antisera raised against the isolate . The outer membrane extract for affinity chromatography was prepared from pressure-disrupted outer membranes by differential centrifugation, followed by solubilization of outer membrane components in a nondenaturing, nonionic detergent . Carbohydrate-reactive outer membrane proteins (CROMPs) were then purified by affinity chromatography on two different affinity matrices composed of trisaccharides resembling the terminal trisaccharide of the H antigen, attached to inert silica beads . The relative efficiencies of H type 1 and 2 terminal trisaccharides as affinity adsorbents were established . Reactive proteins were eluted under alkaline conditions (pH 11.0) and in the presence of soluble H substance prepared from group O secretor saliva, but not by 60 mM alpha-L-fucose or under acid conditions (pH 3.0) . The eluate contained at least three components (M(r)s, 43,000, 40,000, and < 14,000), as detected by immunoblot analysis with a polyvalent, polyspecific rabbit antiserum to A . hydrophila A6 (serum 3/83) . A specific antiserum (serum 3/91) prepared in a rabbit by repeated immunizations with nitrocellulose containing the 43,000-Da band reacted with three bands (M(r)s, 43,000, 40,000, and < 14,000) in immunoblot analysis of solubilized outer membranes of A . hydrophila A6, suggesting that the 40,000- and < 14,000-Da elements are immunologically related to components of the 43,000-Da protein . Furthermore, pretreatment of A . hydrophila A6 with serum 3/91 reduced the strength of bacterial hemagglutination . The purified CROMPs did not agglutinate human group O erythrocytes . The reactivity of isolated CROMPs with a second CROMP-specific antibody (lipopolysaccharide-absorbed serum 3/83) was investigated . CROMPs, proteinase K-treated CROMPs, and bovine serum albumin were bound to latex beads and reacted with lipopolysaccharide-absorbed serum 3/83 . Antibodies eluted from CROMP-latex inhibited hemagglutination of human erythrocytes by A . hydrophila A6 to a titer of 4 . Antibody eluted from proteinase K-treated CROMP-latex beads showed hemagglutination inhibition activity only when undiluted . There was no hemagglutination inhibition antibody activity detectable in the eluate from bovine serum albumin-latex beads . These results show that antibodies which react with the isolated CROMPs also react with an H-antigen-reactive hemagglutinin of A . hydrophila A6 . The possibility that CROMPs act as an adhesin, or adhesins, and contribute to the virulence of this organism is discussed.

FEMS Microbiol Lett, 1993 Jan 15, 106(2), 129 - 33
Molecular characterization of DNA encoding 23S rRNA and 16S-23S rRNA intergenic spacer regions of Aeromonas hydrophila; East AK et al.; Amplification of the gene encoding 23S rRNA of Aeromonas hydrophila by polymerase chain reaction, with primers complementary to conserved regions of 16S and the 3'-end of 23S rRNA genes, resulted in a DNA fragment of approximately 3 kb . This fragment was cloned in Escherichia coli, and its nucleotide sequence determined . The region encoding 23S rRNA shows high homology with the published sequences of 23S rRNA from other members of the gamma division of Proteobacteria . The sequence of the intergenic spacer region, between the 16S and 23S rRNA genes, was determined in five clones . Three types of spacer were identified: two clones were identical and encoded tRNA(Ile) and tRNA(Ala) while the remaining three clones contained tRNA(Glu), only two had the same spacer sequences . This variation in sequence indicates that the different clones may be derived from different ribosomal RNA operons.

Clin Infect Dis, 1993 Jan, 16(1), 69 - 74
Aeromonas hydrophila infections of skin and soft tissue: report of 11 cases and review; Gold WL et al.; We report the clinical and microbiological characteristics of 11 cases of Aeromonas hydrophila infection of skin and soft tissue, and we review the English-language literature on such infections . Of our 11 patients, seven (64%) presented to the hospital between the months of May and September (inclusive) . Three patients (27%) had an underlying systemic illness, and two (18%) had nosocomially acquired infection . The nine patients with community-acquired infection had all experienced antecedent trauma, and seven (78%) of these nine reported recent exposure to freshwater . All patients had clinical evidence of soft-tissue inflammation, and nine (82%) had fever . Four wounds were characterized by a foul odor . The infection was polymicrobial in nine cases (82%) . Treatment included the administration of antibiotics in nine instances, but empirical antimicrobial therapy provided coverage against Aeromonas in only two cases . Ten patients required surgical management of their wounds . Posttraumatic wound infections with a history of freshwater exposure should alert the clinician to the possible presence of A . hydrophila . Prompt surgical evaluation of wounds in combination with appropriate antibiotic therapy is recommended for the management of these infections.

Comp Immunol Microbiol Infect Dis, 1993 Jan, 16(1), 51 - 4
Incidence of Aeromonas species in diarrhoeic stool in University College Hospital Ibadan, Nigeria; Ashiru JO et al.; Between February and July 1989, stool samples from 100 diarrhoeic patients were screened for Aeromonas species . For isolation, alkaline peptone water was used for enrichment and xylose desoxycholate citrate agar as differential and selective medium . Only one sample (1%) yielded Aeromonas hydrophila having come from a 2-month old baby . No other enteric pathogens were isolated from the positive stool sample, a strong indication that A . hydrophila was responsible for the diarrhoea in the baby . Of nine antimicrobial agents used the lone A . hydrophila isolate was resistant only to ampicillin.

J Med Microbiol, 1993 Jan, 38(1), 49 - 53
Haemagglutinating activity, serum sensitivity and enterotoxigenicity of Aeromonas spp; Singh DV et al.; Of 97 isolates of Aeromonas spp . that were examined for haemagglutination (HA) and enterotoxigenicity, 35 were from clinical and 62 from environmental sources; 66 of them were also screened for sensitivity to normal human serum (NHS) . HA was caused by 44 isolates (45%); it was unrelated to the source of the strain, but it was caused by a higher proportion of the isolates of A . hydrophila than of A . sobria or A . caviae . Of the haemagglutinating strains, 82% were enterotoxigenic, whereas most of the non-haemagglutinating strains were non-toxigenic when tested initially . All the latter became enterotoxin producers after serial passage through rabbit ileal loops, but without change in HA . Most (64%) of the isolates, including 68% of A . caviae (72% of clinical and 65% of environmental), were resistant to the bactericidal action of NHS . Most (92%) of the serum-sensitive strains were killed by activation of both the classical and alternate pathways of complement, the others only by the alternate pathway . Most (74%) of the serum-resistant strains caused fluid accumulation in the initial tests in ileal loops, regardless of species or source . Haemagglutinating and serum-resistant strains caused significantly more accumulation of fluid (p < 0.05) than non-haemagglutinating and serum-sensitive strains . This study shows partial correlation between HA or serum sensitivity and enterotoxigenicity, but the properties are probably not genetically linked.

Microbios, 1993, 74(298), 59 - 67
The effect of iron limitation on the growth of Aeromonas salmonicida; Neelam B et al.; The effects of the iron-chelating agents ethylenediamine dihydroxyphenylacetic acid (EDDA), 2,2'-dipyridyl (Dipy) and 8-hydroxyquinoline (8HQ) on the growth of Aeromonas salmonicida were examined . In these studies, EDDA caused a small decrease in growth, whereas Dipy and 8HQ reduced cell growth by 50 and 90%, respectively . The extracellular products contained a greater proportion of the major protease (70 kD) when cells were grown in the presence of the chelating agents . Analysis of the outer membrane proteins showed that the chelating agents caused a marked increase in the proportion of proteins in the 70-90 kD range . The effects of Dipy were compared for a number of strains of A . salmonicida.

Ann Biol Clin (Paris), 1993, 51(2), 91 - 100
{Mobile species of the genus Aeromonas: difficulties of identification and pathogenicity}; Ramboarina C et al.; Sixty-two Aeromonas strains (39 of clinical and 23 of environmental origin) were identified . The suicide phenomenon and autoagglutination were studied . Identification is based on esculin hydrolysis; fermentation of arabinose salicin, sucrose and mannitol; gas production from glucose, indole and beta hemolysis; Voges-Proskauer and decarboxylation reactions; and finally resistance to cephalothin (30 micrograms) and colistin (4 micrograms/ml) . Thirty-four per cent of A hydrophila, 33% A caviae, 28% A veronii subspecies sobria, 3% A jandaei, 2% A veronii subspecies veronii were accurately identified . Also, several new species were identified such as A trota, A enteropelogenes, A schubertii, A ichthiosmia, according to the more recently proposed taxa . This identification scheme could enhance our knowledge concerning virulence factors, pathogenicity and environmental distribution.

Roum Arch Microbiol Immunol, 1993 Jan-Mar, 52(1), 31 - 49
Studies on the hemagglutinant activity of some Aeromonas strains; Israil A et al.; 216 strains to Aeromonas genus (158 A . hydrophila, 33 A . salmonicida, 23 A . sobria, 1 A . caviae and 1 A . veronii strains) of different sources of isolation were studied concerning their hemagglutinating behaviour to 5 different erythrocyte species (human, bovine, chicken, African green monkey and guinea pig) in the presence/absence of mannose/fucose . The study aimed to establish the spectrum of their hemagglutinating activity and any possible correlation between the source of isolation, biochemical phenotype LDC VP and HA type/subtype . Different aspects of HA type/subtype and phenotype LDC VP of Aeromonas strains are discussed . Four Aeromonas hydrophila strains isolated from pig enteritis exhibited constantly FRHA to bovine erythrocytes suggesting a possible correlation between virulence and HA type of the respective strains.

Acta Orthop Belg, 1993, 59(4), 390 - 3
{Bone infections due to Aeromonas hydrophila--apropos of 2 case reports}; Pietu G et al.; The authors report on two cases of bone infection due to Aeromonas hydrophila: one case in a compound fracture and the other a late infection in an implant . They confirm the rapid onset of systemic infectious disease but not the magnitude of local manifestations . The use of modern antibiotics sensitive to Aeromonas proved effective in lowering the risk of dramatic local evolution which has been described.

Antonie Van Leeuwenhoek, 1993-94, 64(3-4), 315 - 23
Pyrolysis mass spectrometry characterisation and numerical taxonomy of Aeromonas spp; Magee JT et al.; Reference strains (2) and 29 isolates of Aeromonas spp . from clinical material and environmental specimens were characterised in traditional biochemical tests, and in pyrolysis mass spectrometry, which gives data reflecting whole-cell composition . Numerical taxonomic analyses of the data sets were compared with conventional identification at species level, and pathogenic potential, as inferred from the origin of the isolates . Clustering with conventional test reaction patterns showed, for each of the species represented, a clearly defined core group of 'typical' isolates, surrounded by a halo of aberrant strains . One further cluster comprised strains intermediate between A . caviae and A . hydrophila, and one strain was grossly atypical in both analyses . Clustering from pyrolysis data corresponded less well with species identification . Broadly, the biochemical division between core and halo strains was supported in pyrolysis for A . caviae and A . sobria, but the main group of A . hydrophila in pyrolysis comprised strains clustering in the core and halo groups of this species, and three strains intermediate between A . hydrophila and A . caviae in biochemical tests . Two further pyrolysis clusters comprised core and halo strains of A . hydrophila . However, pyrolysis clustering correlated well with inferred pathogenicity, showing four clusters of probable pathogens, six clusters of probable non-pathogens, and one two member cluster of doubtful status . Most strains that clustered in the species haloes, or in species-intermediate groups in biochemical tests, were non-human isolates, or were isolated in the absence of symptomatic infection . The correlation of inferred pathogenicity with biochemical clustering was poorer than that with pyrolysis clustering.

Rev Cubana Med Trop, 1993, 45(2), 136 - 8
{The identification of Aeromonas species isolated in Cuba}; Bravo Farinas L et al.; 100 Aeromonas strains, isolated from children under 5 years with acute diarrheal diseases from various health centers of the country, were studied from January to July, 1990 . Using the Janda-modified Popoff's and Veron's model, 63% of the strains were identified in species through primary tests, and 100% of the other 37% were identified in Aeromonas sobria, Aeromonas hydrophila, and Aeromonas caviae, using also supplementary tests.

Rev Cubana Med Trop, 1993, 45(2), 102 - 6
El fenómeno suicida en cepas de Aeromonas mesófilas aisladas de muestras clínicas {The suicide phenomenon in strains of mesophilic Aeromonas isolated from clinical specimens}; Guglielmetti P et al.; A study was carried out to determine the occurrence of the suicide phenomenon in Aeromonas spp strains, isolated from clinical samples, and to establish its relationship with the clinical manifestations of diarrheal diseases . 23 strains were studied: 10, of Aeromonas sobria; 7, of Aeromonas hydrophila; and 6, of Aeromonas caviae . All suicidal strains were isolated from patients with acute diarrheal disease . 3 out of 8, isolated from non-diarrheic feces, showed an intermediate phenotypic profile . Various growth patterns associated to the suicide phenomenon were reported.

J Biotechnol, 1993 Jan, 27(2), 159 - 72
Production of authentic human proapolipoprotein A-I in Escherichia coli: strategies for the removal of the amino-terminal methionine; Moguilevsky N et al.; Several methods were compared with respect to the production of authentic, N-terminal methionine-free proapolipoprotein A-I in engineered Escherichia coli bacteria . A first approach consisted of treating the purified methionylated recombinant protein with an amino-peptidase, purified from Aeromonas proteolytica . A second series of strategies was based on the construction of proapo A-I encoding cassettes carrying built-in recognition sites suitable for specific in vitro cleavage of the products with kallikrein and enterokinase, respectively . Along the same line, a fusion between ubiquitin and proapo A-I was produced in E . coli with the prospect to achieve post-purification cleavage with yeast ubiquitin hydrolase . Finally, proapo A-I was fused to the signal peptide of the bacterial outer membrane protein, OmpA, aiming at an in situ conversion to authentic proapo A-I during secretion to the bacterial periplasm . The data showed that, out of these five systems, the OmpA signal peptide system and, to a lesser extent, the one involving the fusion to ubiquitin were the most efficient in yielding authentic proapo A-I from engineered Escherichia coli.

J Clin Pathol, 1992 Dec, 45(12), 1079 - 83
Phenotypic methods for speciating clinical Aeromonas isolates; Wilcox MH et al.; AIMS: To establish the suitability of currently available phenotypic methods for speciation of clinical Aeromonas isolates in diagnostic microbiology laboratories . METHODS: Using 62 Aeromonas spp, three schemes based on biochemical reactions were compared: a series of conventional tests; a system based on the suicide phenomenon, comprising two tubes in total; and a commercially available test, API 20 NE, augmented with a plate assay for beta haemolysin production . The whole cell and outer membrane protein (OMP) profiles of strains were examined by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS PAGE), according to the results of the above schemes, to determine the intra-species homogeneity . RESULTS: Ninety per cent of strains were identified satisfactorily according to conventional criteria . For these strains, agreement was obtained using the suicide phenomenon and API schemes in 93% and 88% of cases, respectively . The three schemes concurred for 82% of strains . Whole cell protein profiles were unsuitable for comparing strains within a species . However, OMP patterns were similar for 89% of A caviae and 63% of A hydrophila . CONCLUSION: Phenospeciation of clinical Aeromonas isolates by the scheme based on the suicide phenomenon is simple to perform and accurate, and suitable for use in the diagnostic laboratory . OMP profiles are potentially useful for confirming the identity of A caviae and most A hydrophila, but not A sobria.

Appl Environ Microbiol, 1992 Dec, 58(12), 3816 - 25
Detection of Aeromonas salmonicida from fish by using polymerase chain reaction amplification of the virulence surface array protein gene; Gustafson CE et al.; A DNA-based assay was developed to detect Aeromonas salmonicida from infected fish by analyzing tissues, feces, and the tank water in which the infected fish were held . This analysis was done both by direct detection from samples and after a bacterial outgrowth step . Polymerase chain reaction (PCR) amplification of a 421-bp sequence from the 3' region of the surface array protein gene (vapA) of A . salmonicida provided a specific and sensitive method for the detection and identification of this important fish pathogen . The sensitivity of PCR detection of A . salmonicida directly from tissues was less than 10 CFU/mg . Furthermore, a detection level of 5 fg, equivalent to approximately 1 cell, was obtained by using purified chromosomal DNA as the template . This highly reproducible assay, which requires 45 min to complete, is therefore sensitive enough to be used as a noninvasive method for monitoring fish populations for the presence of carrier fish . Because the surface protein array (A-layer) is a virulence factor of A . salmonicida, PCR analysis with oligonucleotide primers directed at vapA can also be used to provide information on the potential virulence of a strain.

Bangladesh Med Res Counc Bull, 1992 Dec, 18(2), 61 - 7
Incidence of Aeromonas isolated from diarrhoeal children and study of some virulence factors in the isolates; Hossain MA et al.; Stool samples from 305 children with diarrhoea and equal number of age and sex matched non-diarrhoeal control children, less than 5 years of age, were examined during the period from Sept 1988 to April 1989 . Aeromonas spp . were isolated from 37 (12.1%) diarrhoeal and 05 (1.6%) control cases . Out of 37 diarrhoeal isolates 13 (35.1%) were A . hydrophila, 19 (51.1%) A . sobria and 05 (13.5%) A . caviae . All the isolated strains were tested for haem agglutination property and haemolysin production . Seventeen diarrhoeal and 05 control isolates were tested for cytotoxin production in He La cell line and enterotoxin production in rat ileal loop model and suckling mouse model . Chinese hamster ovary cell (CHO) assay and Gm-1 ELISA methods were also employed . Cytotoxin production was found in 82.5% of diarrhoeal and 40% of control isolates . Haemagglutination was found in 62.1% of Aeromonas isolated from diarrhoeal children and 20% from control children . Enterotoxin production was detected in 58.8% diarrhoeal and none of the control isolates by either of the methods . Of the virulence factors enterotoxin production was found to correlate well with enteropathogenicity but haemolysin, cytotoxin and haemagglutinin did not.

Microb Pathog, 1992 Dec, 13(6), 433 - 46
Nucleotide sequences and characterization of haemolysin genes from Aeromonas hydrophila and Aeromonas sobria; Hirono I et al.; Extracellular haemolysin is thought to be one of the important virulence factors in Aeromonas infection . Two extracellular haemolysin genes (AHH3 and AHH4) from Aeromonas hydrophila strain 28SA, one (AHH5) from A . hydrophila strain AH-1 and one (ASA1) from Aeromonas sobria strain 33 were cloned into cosmid and plasmid vector DNA in Escherichia coli . The nucleotide sequences of the open reading frames of AHH3 and AHH4 are both 1476 basepairs (bp), whereas AHH5 and ASA1 are 1455 and 1467 bp in length, respectively . The deduced amino acid sequences of AHH3, AHH4, AHH5 and the previously reported aerolysin from A . hydrophila showed a significant degree of sequence homology of over 90% each . The amino acid identity of the ASA1 haemolysin and those from A . hydrophila and Aeromonas trota aerolysins ranged from 58-68% . From DNA hybridization analysis using our cloned haemolysin genes as probes, we found that the AHH5 and ASA1 DNA probes hybridized with about 31 and 75% strains of motile Aeromonas species, respectively . The activity of haemolysins of cloned genes were different in medium agar containing various erythrocytes.

Wei Sheng Wu Xue Bao, 1992 Dec, 32(6), 432 - 8
{Purification and characterization of hec toxin produced by Aeromonas hydrophila}; Tu X et al.; An extracellular toxin produced by Aeromonas hydrophila from cultured crucian carp with septicemia was detected . The toxin was purified by ammonium sulfate precipitation, DEAE-cellulose chromatography and Sephadex G-100 gel filtration . The factor was a single polypeptide with a molecular weight of 52.5kd determined by SDS-PAGE . The heat-stable toxin possesses hemolytic, enterotoxic and cytolytic activities . The hemolytic activity on human erythrocytes was 3.81 x 10(3) HU/mg, CD50 for Vero cell was 0.26 microgram . The LD50 for crucian carp and mice was 4.44 micrograms and 3.58 micrograms respectively . The toxin was neutralized py homologous antibodies . The toxin shows unique characteristics as compared with other known bacterial toxins therefore the authors propose to name the toxin "hec" toxin.

J Diarrhoeal Dis Res, 1992 Dec, 10(4), 231 - 4
Biochemical characteristics and enterotoxicity of Aeromonas species isolated from man and environment; Singh DV et al.; A total of 147 isolates of Aeromonas spp., of which 54 were isolated from children and adults with diarrhoea, 44 from variety of water sources and 49 from environmental sources, were tested for enterotoxin production and its correlation with biochemical characters . Lysine was decarboxylated by 38% of A . hydrophila, 35% of A . sobria and 20% of A . caviae . Majority strains were unable to utilise citrate as the sole source of carbon except one of A . hydrophila, 8 of A . sobria and 6 of A . caviae . Beta-haemolysis was shown by 108 isolates that included 79% of A . hydrophila, 76% of A . sobria and 70% A . caviae . About 56% of Aeromonas strains including A . caviae caused fluid accumulation in the rabbit ileal loop in the initial tests and the remaining did so after 1-3 consecutive passages . Enterotoxin production did not correlate with the positive biochemical characters such as Voges-Prauskauer reaction, lysin decarboxylation, haemolysin production, citrate utilisation and failure to ferment arabinose either singly or in combination . This study indicates that enterotoxicity of Aeromonas may not be correlated with any of the biochemical characters either singly or in combination.

J Diarrhoeal Dis Res, 1992 Dec, 10(4), 213 - 6
Production of chitinase by enterotoxigenic Aeromonas species isolated from clinical and environmental sources; Singh DV et al.; Thirty-six isolates of Aeromonas, 13 from children and 23 from the environment were tested for production of chitinase in culture supernatants . Thirty-four isolates of the three species (91% clinical and 96% environmental) produced constitutive chitinase . The environmental isolates elaborated significantly more (p < 0.005) of the enzyme than those from the children . Four of the environmental isolates also produced inducible chitinase . All isolates of Aeromonas were enterotoxic, however, the isolates producing inducible chitinase showed significantly higher enterotoxic activity . This study indicates that there is correlation between production of enterotoxin and chitinase in Aeromonas species.

J Mol Biol, 1992 Nov 20, 228(2), 652 - 61
Roles of structural domains in the morphology and surface anchoring of the tetragonal paracrystalline array of Aeromonas hydrophila . Biochemical characterization of the major structural domain; Thomas S et al.; The tetragonally arranged S-layer of Aeromonas hydrophila contains two morphological domains . The mature S-layer protein of A . hydrophila has a subunit molecular weight of 52,000, and has been reported to contain two structural domains . Here a mutant has been isolated which produces an S-layer of subunit molecular weight 38,650 as determined by sedimentation analysis . This truncated S-protein was exported via the periplasm to the cell surface, but could not self-assemble into a tetragonal array or be anchored to the cell surface . Instead the truncated protein formed cup-like structures which were purified and characterized biochemically . Automated Edman degradation showed that the truncated protein comprised the amino-terminal structural domain of the S-protein . This domain had an increased hydrophobic amino acid content relative to the wild-type protein, and contained approximately 42% beta-sheet, 10% alpha-helix, and 19% beta-turn . Differences in alpha-helix and beta-turn contents between the wild-type and truncated proteins were observed when the effects of pH and SDS were examined, indicating that the carboxy terminus influences the effects of environmental change on the conformation of the S-protein . This lesser carboxy-terminal array also appears to be required for both correct array morphology, and array anchoring, while the greater amino-terminal domain appears to comprise the major morphological core of the surface array.

FEMS Microbiol Lett, 1992 Nov 15, 78(1), 65 - 71
The cloning and nucleotide sequence of the serine protease gene (aspA) of Aeromonas salmonicida ssp . salmonicida; Whitby PW et al.; The gene for Aeromonas salmonicida serine protease has been cloned into phagemid pTZ18R in two restriction fragments, 2.0-kb PstI and 2.3-kb KpnI, of genomic DNA . The nucleotide sequences of the two fragments have been determined, in both directions, after subcloning, by double-stranded sequencing of nested deletions . An open reading frame of 1863 bp translated into a sequence of 621 amino acids, a 24-amino acid signal peptide and a 597-amino acid mature enzyme of molecular mass 64,173 Da . The consensus sequence, NGTS, of a serine protease substrate primary binding site was identified and a putative ribosome-binding site GGAG occurred 6 bp upstream of the ATG initiation codon.

Enferm Infecc Microbiol Clin, 1992 Nov, 10(9), 536 - 8
{The suicide phenomenon and fermentative metabolic activity in strains of the Aeromonas group isolated from feces}; Reina J et al.; We study the "suicide" phenomena as well as metabolic pathways of mixed acids (methyl red test, MR) and butylene glycol (Voges-Proskauer, VP), in 107 strains belonging to mesophilic Aeromonas group, isolated from stools . The strains have been identified as A . hydrophila, 28 cases (26.1%), A . sobria 26 cases (24.3%) and A . caviae 53 cases (49.6%) . All A . caviae strains behave homogeneously as F+, RM+ and VP-, independently of temperature (30 or 37 degrees C) . A . hydrophila strains only showed their trend to "suicide" at 37 degrees C, being this behavior linked to RM test positivity . At 30 degrees C all strains were NS and RM-, keeping always positive the VP test (both temperatures) . In A . sobria we have recorded changes in their behavior related to the temperature of incubation . At 37 degrees C, 57.7% were NS, whereas at 30 degrees C, 69.2% showed the same phenotype . The metabolic activity had remained stable, therefore F+ strains were VP and RM+, and NS strains were VP+ and RM- . It seems that FS is a phenotypic behavior of this bacterial group species and temperature-dependent, and also is related to a fermentative metabolic activity modulation of each of them.

FEMS Microbiol Lett, 1992 Nov 1, 77(1-3), 285 - 9
Stimulation of neutrophil leukocyte chemotaxis by a cloned cytolytic enterotoxin of Aeromonas hydrophila; Jin GF et al.; A cytolytic enterotoxin produced by Aeromonas hydrophila, isolate SSU, has been cloned in our laboratory . This enterotoxin lysed rabbit red blood cells, destroyed Chinese hamster ovary cells, caused fluid secretion in rat ligated ileal loops, inhibited the phagocytic function of mouse phagocytes, and was lethal to mice when injected intravenously . In this study, the effect of this cytolytic enterotoxin on the chemotaxis of human leukocytes (cell line RPMI 1788) was examined . This toxin, at concentrations from 92.5 to 370 ng/ml, significantly stimulated the chemotactic activity of human leukocytes in a dose-dependent fashion . The stimulation of leukocyte chemotaxis elicited by cytolytic enterotoxin was abolished when the toxin was neutralized, heated, or exposed to low pH values . This stimulatory effect also was inhibited by various concentrations of pertussis toxin . These results demonstrated that cytolytic enterotoxin may stimulate increased chemotaxis of human leukocytes, and suggest that human leukocytes may possess cytolytic enterotoxin receptors which may be coupled to pertussis toxin-sensitive G-protein.

Dig Dis Sci, 1992 Nov, 37(11), 1697 - 703
Effect of Aeromonas hydrophila enterotoxins on function of mouse phagocytes; Jin GF et al.; Two enterotoxins produced by Aeromonas hydrophila isolate SSU have been characterized in this laboratory . One is a cholera toxin cross-reactive cytolytic enterotoxin (CTC toxin) and the other is a non-cholera toxin cross-reactive cytotonic enterotoxin (non-CTC toxin) . The two enterotoxins are capable of causing fluid accumulation in animal models; however, only the CTC toxin is lethal to mice and expresses hemolytic as well as cytotoxic activities . In this study, we have investigated the effects of these two toxins on mouse phagocytes . Four hours after intraperitoneal injection of a sublethal dose (460 micrograms/kg of body weight) of CTC toxin, the chemiluminescence (CL) response of phagocytes in mouse blood was depressed significantly when compared with that observed for controls (intraperitoneal injection of only Hanks' balance salt solution, non-CTC toxin or before treatment with CTC toxin) . When fresh whole blood was incubated with various concentrations (2.3, 11.5, 23, 230, 2300 ng/ml) of CTC toxin for 1.5 hr at 37 degrees C, the CL response of blood phagocytes was reduced strikingly in a dose-dependent fashion; however, non-CTC toxin did not inhibit the CL response . The inhibitory effect induced by CTC toxin of the phagocytic function not only was abolished completely, but phagocytosis was enhanced in the presence of interferon-gamma (IFN-gamma) . In addition, IFN-gamma alone induced the largest enhancement of the CL response in mouse phagocytes . These results demonstrated that CTC toxin inhibits the phagocytic ability of phagocytes either in vivo or in vitro and that IFN-gamma pretreatment can overcome this toxic effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Infect Immun, 1992 Nov, 60(11), 4612 - 20
Interaction of the fish pathogen Aeromonas salmonicida with rainbow trout macrophages; Garduno RA et al.; A procedure was developed to culture rainbow trout macrophages (M phi) on supported glass coverslips . Using this method and a variety of well-characterized Aeromonas salmonicida strains with normal or altered cell surfaces, we investigated the role of this unusual bacterial surface in the bacterium-M phi interaction . An intact crystalline protein array, the A-layer, mediated adherence of A . salmonicida cells to M phi even in the absence of opsonins . In contrast, unopsonized cells of an A-layer-negative (A-) mutant with a smooth lipopolysaccharide (LPS) layer were unable to interact with M phi . However, this ability was recovered when the A-layer was reconstituted onto the smooth LPS surface of these A- LPS+ cells . Two A . salmonicida mutants possessing the A-layer in different disorganized states had a reduced ability to interact with M phi . A+ cells grown under calcium limitation produced A-layers locked into an alternative conformation which mediated the highest levels of M phi association in the absence of opsonins or any other surface coating . Coating A+ cells with hemin greatly increased their levels of M phi association, and bacterial cells grown on trout blood agar plates also had a dramatic increase in their ability to interact with M phi . Only A+ A . salmonicida cells were highly cytotoxic to trout M phi, especially after being coated with hemin, presumably due to a more focused targeting of the bacterial cell onto the M phi surface and/or into the intracellular regions of the M phi.

J Struct Biol, 1992 Nov-Dec, 109(3), 184 - 95
Novel structural patterns in divalent cation-depleted surface layers of Aeromonas salmonicida; Garduno RA et al.; The fish pathogen Aeromonas salmonicida possesses a regular surface layer (or A-layer) which is an important virulence determinant . The A-protein, a single bilobed protein organized in a p4 lattice of M4C4 arrangement with two morphological domains, comprises this layer . The role of divalent cations in the A-layer structure was studied to better understand A-protein subunit interactions affecting structural flexibility and function . Divalent cation bridges were found to be involved in the integrity of the A-layer . Two novel A-layer patterns were formed as the result of growth under calcium limitation or by chelation of divalent cations with EDTA or EGTA, thereby constituting the first reported case of formation of distinct regular arrays upon divalent cation depletion . Furthermore, under these conditions A-protein was sometimes released as tetrameric units, rather than in monomeric form . The formation of the two novel patterns is best explained by a sequence of structural rearrangements, following disruption of only one of the two A-layer morphological units, that is, those held together by divalent cation bridges . The free tetrameric units represent four A-protein subunits clustered around the unaffected four-fold axis.

Vet Immunol Immunopathol, 1992 Nov, 34(3-4), 379 - 89
Immunostimulants added to injected Aeromonas salmonicida bacterin enhance the defense mechanisms and protection in rainbow trout (Oncorhynchus mykiss); Anderson DP et al.; Immunostimulants were given to rainbow trout for assaying effects on modulating non-specific defense mechanisms, specific immune response, and protection levels against pathogen challenge with Aeromonas salmonicida . Three drugs, levamisole (an approved veterinary drug in the USA), a quaternary ammonium compound (QAC), and a short-chain polypeptide (ISK) were found to affect the non-specific defense mechanism activities, which were measured by changes in circulatory neutrophil and phagocytic activity levels, and the specific immune response factors, which were measured by numbers of plaque-forming cells, and circulatory antibody levels . When given alone, the immunostimulants elevated the non-specific factors . When injected in combination with an A . salmonicida O-antigen bacterin, the non-specific factors were further elevated, and the specific response was raised over samples taken from fish given the bacterin without the immunostimulants . Challenge tests with the virulent pathogen, A . salmonicida, showed a 5-6 day delay in the onset of mortalities in the fish given the immunostimulants alone, and a 12-14 day delay when immunostimulants given were combined with the bacterin . In the groups given the QAC or ISK with the bacterin, there was a 20% and 40% survival rate, respectively.

Avian Dis, 1992 Oct-Dec, 36(4), 1110 - 1
Aeromonas hydrophila conjunctivitis in a pet parrot (Amazona versicolor); Garcia ME et al.; A bilateral conjunctivitis in a pet parrot (Amazona versicolor) is reported . Aeromonas hydrophila was isolated in pure culture from both eyes and considered of diagnostic significance . Biochemical characteristics and antimicrobial susceptibility of the strain were studied, as were the factors that could have contributed to the clinical conjunctivitis and the role of A . hydrophila as an opportunistic pathogen.

Zentralbl Veterinarmed B, 1992 Oct, 39(8), 585 - 94
Identification of a cyprinid fish, the tench Tinca tinca L., as a carrier of the bacterium Aeromonas salmonicida, causative agent of furunculosis in salmonids; Bernoth EM et al.; A typical, pigment-producing strain of Aeromonas salmonicida (A . sal.), the causative agent of furunculosis in salmonid fish species, was isolated from a cyprinid species, the tench Tinca tinca L . with papilloma-like skin alterations . Histopathology of the papilloma-like skin alterations in tench revealed "round holes", distinctly lined by thick layers of epithelial cells, but no bacteria . The organism was isolated from skin, gills and fins, but not internal organs . The isolate proved highly virulent for both juvenile tench and brown trout Salmo trutta L . in experimental infection, but it did not reproduce the clinical picture . The causative role of A . sal . for the surface lesions remains questionable . However, there is a perceived risk of the organism's transmission between tench and other susceptible species of fish, especially farmed trout.

J Med Microbiol, 1992 Oct, 37(4), 262 - 7
Production of haemolysis and its correlation with enterotoxicity in Aeromonas spp; Singh DV et al.; A total of 147 clinical and environmental isolates of Aeromonas that included 14 A . hydrophila, 60 A . sobria and 73 A . caviae strains was tested for haemolysin production and its correlation with enterotoxicity; 108 isolates produced beta-haemolysis . For A . hydrophila and A . sobria, titres of haemolysin were 16-128 HU/ml and for A . caviae, 16-64 HU/ml . In the ileal loop test, 82 (55.8%) strains of Aeromonas spp . produced enterotoxin . Of the beta-haemolytic strains, 72.7% of A . hydrophila, 58.6% of A . sobria and 68.6% of A . caviae isolates caused fluid accumulation in rabbit ileal loops . One strain each of alpha-haemolytic A . sobria and A . caviae, one of non-haemolytic A . sobria and nine of non-haemolytic A . caviae also caused a secretory response . The beta-haemolytic strains caused significantly more (p < 0.05) fluid accumulation than the alpha- and non-haemolytic isolates regardless of their species designation . The remaining 65 (44.2%) isolates belonging to the three species included alpha-, beta- and non-haemolytic strains: they failed to cause fluid accumulation in the initial experiments but did so after one to three consecutive passages through rabbit ileal loops . Two alpha- and 13 non-haemolytic strains switched to production of beta-haemolysis when they showed positive ileal loop reactions . However, on repeated subcultures or on storage in the laboratory, all of them reverted to their original haemolytic character and no longer produced enterotoxic activity.

Infect Immun, 1992 Oct, 60(10), 4373 - 82
S-layer-mediated association of Aeromonas salmonicida with murine macrophages; Garduno RA et al.; The interaction of Aeromonas salmonicida with the murine macrophage (M phi) cell line P388D1 was used as a convenient model to study the involvement of the bacterial crystalline surface array (or A-layer) in the association with M phi s . A-layer-positive (A+) cells readily associated with M phi s in phosphate-buffered saline, whereas A- mutants were unable to do so, even when the bacterium-M phi interaction was forced by centrifugation . M phi s selectively interacted with A+ cells when challenged with mixtures of A+ and excess A- cells . Electron microscopy indicated that in phosphate-buffered saline only A+ bacteria were readily internalized, although by a nonconventional mechanism, suggesting that efficient phagocytosis in the absence of opsonins was A-layer mediated . Latex beads coated with a partially assembled A-layer were more efficiently taken up than uncoated or A-protein-coated beads, indicating that an organized A-layer was essential for M phi uptake . The reduced ability of M phi s plated on a substratum coated with the A-layer to bind A+ bacteria also suggested that association was both A-layer and receptor mediated . In the presence of tissue culture medium, competent M phi s interacted efficiently with A- bacteria and internalized them through conventional phagocytosis . A+ cells were markedly cytotoxic to M phi s, whereas the A-protein or A-layer was not . A- cells were cytotoxic to a lesser extent, suggesting that cytotoxicity was targeted.

Infect Immun, 1992 Oct, 60(10), 4343 - 9
Effect of growth temperature on outer membrane components and virulence of Aeromonas hydrophila strains of serotype O:34; Merino S et al.; Growth of Aeromonas hydrophila strains from serotype O:34 at 20 and 37 degrees C in tryptic soy broth resulted in changes in the lipids, lipopolysaccharide (LPS), and virulence of the strains tested . Cells grown at 20 degrees C contained, relative to those cultured at 37 degrees C, increased levels of the phospholipid fatty acids hexadecanoate and octadecanoate and reduced levels of the corresponding saturated fatty acids . Furthermore, the lipid A fatty acids also showed thermoadaptation . In addition, LPS extracted from cells cultivated at 20 degrees C was smooth, while the LPS extracted from the same cells cultivated at 37 degrees C was rough . Finally, the strains were more virulent for fish and mice when they were grown at 20 degrees C than when they were grown at 37 degrees C and also showed increased different extracellular activities when they were grown at 20 degrees C.

Microb Pathog, 1992 Oct, 13(4), 325 - 34
Purification and characterization of Aeromonas sobria Ae24 pili: a possible new colonization factor; Hokama A et al.; Pili of Aeromonas sobria Ae24 were purified and characterized . The molecular mass of the pilin was estimated to be about 19 kDa by SDS-PAGE . The Ae24 pili were electrophoretically distinguishable from previously reported Aeromonas hydrophila Ae6 W pili and A . sobria Ae1 pili, although all three had indistinguishable morphology and shared a high degree of homology in the N-terminal amino acid sequences . Strain Ae24 and its purified pili adhered to rabbit intestine and agglutinated human and rabbit erythrocytes . Hemagglutination was inhibited by D-galactose and D-mannose, but not by L-fucose . Organisms pretreated with Fab fraction of the antipilus antibody failed to adhere to the intestine . Organisms did not adhere to intestine pretreated with the purified pili . These findings suggest that the pili are a colonization factor of A . sobria Ae24 for the rabbit intestine, and that the receptor is galactose- and mannose-containing structure.

Microb Releases, 1992 Oct, 1(2), 71 - 8
Non-culturable Aeromonas salmonicida in lake water; Morgan JA et al.; The survival of Aeromonas salmonicida subsp . salmonicida was investigated in lake water . During a 21-day study A . salmonicida became non-culturable in sterile lake water held at 10 degrees C . The incubation of replicate samples between 5 degrees C and 25 degrees C produced similar results . The recovery of colony-forming units of A . salmonicida from different lake water systems indicated that they survived longer in water that was naturally enriched (eutrophic) or enriched with tryptone soya broth . Flow cytometry, fluorescence light microscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) indicated that non-culturable cells were present . These cells could not be revived in dilutions of tryptone soya broth, whole dead fish or dissected fish tissue . Although viability could not be proven, it was shown that the morphological integrity found in viable cells was also maintained in non-culturable cells.

J Wildl Dis, 1992 Oct, 28(4), 515 - 20
Molecular and genetic characterization of cytochrome oxidase-negative Aeromonas salmonicida isolated from coho salmon (Oncorhynchus kisutch); Teska JD et al.; Cytochrome oxidase variants of the bacterial fish pathogen, Aeromonas salmonicida, were characterized for genetic and molecular homology with cytochrome oxidase-positive isolates that typically induce furunculosis in salmonids . Protein and lipopolysaccharide moieties of the cytochrome oxidase-negative variants were similar to their typical counterparts, based on sodium-dodecyl-sulfate polyacrylamide gel electrophoresis . Pathogenicity of aberrant isolates to brook trout (Salvelinus fontinalis) was similar to typical cytochrome oxidase-positive isolates . Colorimetric deoxyribonucleic acid (DNA) hybridization in 96-well microplates yielded homology values greater than 82.5% for typical aberrant A . salmonicida isolates when photobiotinylated DNA for reference A . salmonicida 3.101 was used as a probe . The only variation of these isolates from typical A . salmonicida was a negative cytochrome oxidase reaction.

Ann Plast Surg, 1992 Sep, 29(3), 245 - 9
Postprandial Aeromonas hydrophila cultures and antibiotic levels of enteric aspirates from medicinal leeches applied to patients receiving antibiotics; Lineaweaver WC et al.; Increasing use of medicinal leeches has been accompanied by increasing numbers of reports of Aeromonas hydrophila infections after leech application on or near damaged tissue . We examined the enteric contents of postprandial leeches after their application to patients receiving antibiotics . We found measurable levels of antibiotic in the leech enteric contents, and in leeches applied to patients receiving an antibiotic effective against Aeromonas hydrophila, there was a significant decrease in positive Aeromonas enteric cultures . Suppression of leech enteric bacteria by antibiotic administration to the patient may be an effective strategy to prevent invasive infection by Aeromonas hydrophila as well as bacterial colonization of devitalized tissue that could be the source of late infection . Clinical studies will be required to clarify whether suppression of leech enteric flora results in a decrease in infections associated with leech use.

Ann Plast Surg, 1992 Sep, 29(3), 238 - 44
Aeromonas hydrophila infections following use of medicinal leeches in replantation and flap surgery; Lineaweaver WC et al.; Aeromonas hydrophila infections are a recognized complication of postoperative leech application, and can occur with measurable frequency in populations of patients treated with leeches . We review 11 previously reported leech-related Aeromonas infections and analyze seven unreported cases . These infections range from minor wound complications to extensive tissue loss and sepsis . Often, these infections followed leech application to tissue with questionable arterial perfusion . Onset of clinical infection in these patients ranged from within 24 hours of leech application to 10 days or more after leech application . Late infections may represent bacterial invasion from colonized necrotic tissue . Based on these observations, we recommend that leech applications be restricted to tissue with arterial perfusion to minimize contamination of necrotic tissue . We also recommend that patients treated with leeches receive antibiotics effective against Aeromonas hydrophila before leech application . Patients treated with leeches and discharged with eschars or open wounds might benefit from oral antibiotic therapy until wound closure . These precautions may minimize or eliminate this complication of leech use.

Clin Infect Dis, 1992 Sep, 15(3), 449 - 52
Epidemiology of Aeromonas infections in California; King GE et al.; In May 1988, California became the first state to make aeromonas infection a reportable condition, thereby permitting the first population-based study of the epidemiology of infection caused by Aeromonas organisms . Case investigations were carried out on 219 of the 280 patients whose infections were reported during the first year of notification . The overall incidence rate for Aeromonas isolation was 10.6 cases per 1 million population . The gastrointestinal tract was the most commonly reported site from which Aeromonas was isolated (81%), with wounds being the next most common source (9%) . Five (2%) of the 219 patients died; all five had serious underlying medical conditions apart from aeromonas infection . No common-source enteric outbreaks were reported . The high rate of gastrointestinal symptoms and isolation of organisms from medically vulnerable patients and the fact that other bacterial enteric pathogens were rarely isolated from symptomatic patients support evidence from previous studies that Aeromonas is an enteric pathogen . The evidence from these case reports in California suggests that aeromonas infections are not an important public health problem and are largely nonpreventable . Thus, public health surveillance is not necessary and mandatory reporting has been discontinued.

FEMS Microbiol Immunol, 1992 Sep, 5(1-3), 13 - 7
The channel-forming toxin aerolysin; Buckley JT; Aeromonas sp . secrete a precursor of the cytolytic protein aerolysin into the culture medium, where it is activated by proteolytic removal of a C-terminal fragment . Activation can be achieved by a variety of mammalian proteases as well as by proteases released by the bacteria itself . Activated toxin binds with high affinity to the transmembrane protein glycophorin on the surface of eucaryotic cells . Binding is followed by oligomerization and the formation of transmembrane channels, leading to cell death . Using chemical modification and site-directed mutagenesis, we have identified regions of the molecule which are important in transfer across the outer membrane of the bacteria, and in proteolytic activation, binding, and oligomerization . A preliminary electron density map of proaerolysin crystals indicates that the protein is organized into three domains . Analysis of two-dimensional crystals of aerolysin suggests that the oligomeric form of the protein is heptameric.

Mol Microbiol, 1992 Sep, 6(18), 2725 - 32
Cloning and characterization of fxp, the flexible pilin gene of Aeromonas hydrophila; Ho AS et al.; The flexible pilus of Aeromonas hydrophila is a morphologically and biochemically unique organelle which binds eukaryotic cell surfaces and whose expression is induced by specific physiochemical conditions . fxp, the structural gene coding for the flexible pilus subunit, was localized on a 7.6kb plasmid of A . hydrophila strain AH26 . A putative Shine-Dalgarno sequence and -10 and -35 regions were identified, a signal peptide sequence delineated, and the coding sequence compared with other bacterial sequences and found to be unique . Plasmid and chromosomal DNA was prepared from 66 other Aeromonas strains and 12 strains from other bacterial genera and examined by Southern blot hybridization using a labelled fxp oligonucleotide and the 7.6kb plasmid as probes . No hybridizing sequences were identified except in the original strain, AH26 . It is proposed that fxp codes for a highly evolved organelle, possibly widely distributed in nature, but that it is carried on a genetic element that is rapidly lost from most strains upon in vitro cultivation and storage.

J Gen Microbiol, 1992 Sep, 138 ( Pt 9), 1913 - 9
Characterization of Aeromonas sobria TAP13 pili: a possible new colonization factor; Iwanaga M et al.; Pili of Aeromonas sobria TAP13 were purified and characterized . The molecular mass of the pilin was estimated to be about 23 kDa by SDS-PAGE . The TAP13 pili were immunologically different from A . sobria Ae1 pili and A . hydrophila Ae6 W pili as previously reported, nevertheless all three had indistinguishable morphology and shared a high degree of homology in their N-terminal amino acid sequences . Strain TAP13 and its purified pili did not agglutinate human, rabbit or sheep erythrocytes . However, they adhered to rabbit intestine . Organisms pretreated with the Fab fraction of an antipilus antibody failed to adhere to rabbit intestine, and organisms did not adhere to intestine pretreated with purified pili . These results suggest that the pili are a colonization factor of A . sobria TAP13 for the rabbit intestine.

Nippon Koshu Eisei Zasshi, 1992 Sep, 39(9), 707 - 13
{An outbreak of food poisoning suspected due to Aeromonas and characteristics of the isolated strains}; Tanaka K et al.; On June 7, 1990, food poisoning with main symptoms of abdominal pain and diarrhea occurred in Inuyama City, Aichi Prefecture . From results of bacteriological examination, three kinds of mesophilic Aeromonas spp . were detected from patients, leftover foods, well water, and cookers, one of which was A . hydrophila which was shown to produce haemolysin thought to be the cause of the food poisoning . On the other hand, A . sobria and A . caviae isolated from various materials did not produce haemolysin . The latter two strains of mesophilic Aeromonas spp . did not produce any other enterotoxins . Therefore, it appears that the well water containing A . hydrophila, A . sobria and A . caviae polluted the foods, which then had caused the food poisoning . Of nine strains of A . hydrophila, five do not dissolve sucrose, and these are typed as serogroup O:22 or O:23 . The other four strains dissolve sucrose, and these are typed as serogroup O:16 . According to the drug sensitivity test, all of these nine strains of A . hydrophila were resistant to Ampicillin, Erythromycin and Cephaloridine.

FEMS Microbiol Lett, 1992 Aug 15, 74(2-3), 127 - 31
Occurrence of a capsule in Aeromonas salmonicida; Garrote A et al.; Aeromonas salmonicida grown in a medium with excess glucose as carbon source produces both capsular and exocellular polysaccharides . The capsular polysaccharide is composed of glucose, mannose, rhamnose, N-acetylmannosamine and mannuronic acid in the molar ratios of approximately 5:3:0.75:2:1 . The extracellular polysaccharide is similarly constituted, but in the molar ratios of approximately 4.75:10.5:1.5:2:1 . The capsular and exocellular polysaccharides did not cross-react with monoclonal antibodies against the A-layer or the O-antigen lipopolysaccharide.

Diagn Microbiol Infect Dis, 1992 Aug, 15(6), 511 - 5
Rapid identification of motile Aeromonas; Wakabongo M et al.; The clinical relevance and taxonomy of motile Aeromonas species are areas of current controversy . Strains of motile Aeromonas isolates (n = 60) from various sources were identified to species level using the following tests (all incubated at 30 degrees and 37 degrees C): esculin hydrolysis; formation of gas from glucose; production of acetoin; production of acid from mannitol and arabinose; decarboxylation of lysine and ornithine, dihydrolation of arginine; and pyrazinamide hydrolysis in a semisolid medium . The tests' results were similar at incubation temperatures of 30 degrees and 37 degrees C . Of the strains, 59 (98%) of 60 were identified to species level by the full battery of tests: 25 as A . hydrophila, 18 as A . caviae, 14 as A . sobria, one as A . veronii, and one as A . schubertii . (The only A . veronii and A . schubertii isolates identified were ATCC strains) . All (25 of 25) strains of A . hydrophila and 17 (94%) of 18 of A . caviae hydrolyzed pyrazinamide in less than 24 hr, whereas all strains of A . sobria showed no pyrazinamidase activity . Absence of pyrazinamidase was, thus, a convenient phenotypic marker for A . sobria . Four additional tests (esculin hydrolysis, acetoin production, lysine decarboxylation, and gas production from glucose) identified within 24 hr all examples of the three common species of Aeromonas . Recently proposed species did not contribute to our ability to discriminate among stool, other clinical, and environmental isolates of Aeromonas spp.

Singapore Med J, 1992 Aug, 33(4), 375 - 7
Comparison of two assays for the detection of haemolysins of Aeromonas species; Vadivelu J et al.; The haemolysins produced by Aeromonas species were detected and compared by two assay methods--a modified blood agar plate assay and the rabbit erythrocyte haemolysin method . Both assays showed a high level of agreement (86%) . The titres of the rabbit erythrocyte haemolysin assay correlated with the haemolytic zone diameter of the ox blood agar assay . In addition the agar haemolysin assay had simple media requirements, was easy to perform and results were well defined.

Zentralbl Hyg Umweltmed, 1992 Aug, 193(2), 114 - 22
Comparative study of virulence and virulence factors of Aeromonas hydrophila strains isolated from water and sediments of a river; Mateos D et al.; Seventy-four strains of Aeromonas hydrophila isolated from water and sediments of the River Porma (Leon, N.W . Spain) were characterized biochemically and biologically . Fifty-seven strains (77.02%) were virulent for rainbow trout (Salmo gairdneri) by intramuscular challenge but showed differing degree of pathogenicity which could not be associated with the source . A lack of correlation between caseinase, haemolytic and cytotoxic activities of the strains and their isolation source was also observed . Only two surface characters, acriflavine 0.2% agglutination and non-agglutinating SP-/PAB-phenotypes, were significantly associated with water and sediment strains, respectively.

FEBS Lett, 1992 Jul 27, 307(1), 30 - 3
Crossing three membranes . Channel formation by aerolysin; Buckley JT; Aerolysin is a channel-forming toxin responsible for the pathogenicity of Aeromonas hydrophila . It crosses the inner and outer membranes of the bacteria in separate steps and is released as a 52-kDa inactive protoxin which is activated by proteolytic removal of approximately 40 amino acids from the C terminus . The toxin binds to the erythrocyte transmembrane protein glycophorin and oligomerizes before inserting into the membrane, producing a voltage gated, anion selective channel about 1 nm in diameter . Remarkably, proaerolysin appears to be dimeric, whereas the oligomer is a heptamer . Using chemical modification and site-directed mutagenesis, we have identified some of the regions of the molecule which appear to be involved in secretion and in channel formation.

Carbohydr Res, 1992 Jul 2, 231, 83 - 91
Structure of the core oligosaccharide in the lipopolysaccharide isolated from Aeromonas salmonicida ssp . salmonicida; Shaw DH et al.; The core oligosaccharide isolated from the lipopolysaccharide of Aeromonas salmonicida ssp . salmonicida has been investigated by methylation analysis, NMR spectroscopy (13C and 1H), oxidation with periodate and chromium trioxide, and Smith degradation . The following structure is proposed: {Formula: see text}

J Wildl Dis, 1992 Jul, 28(3), 453 - 6
The activity of ceftiofur sodium for Aeromonas spp . isolated from ornamental fish; Dixon BA et al.; Our objective was to determine the activity of ceftiofur sodium against Aeromonas hydrophila and A . sobria isolated from a variety of domestic and imported tropical fish . Twelve antimicrobial drugs were tested for effectiveness against these aeromonads using the Kirby-Bauer Disk Diffusion technique and minimum inhibitory concentration determinations . Ceftiofur sodium was highly effective in vitro against aeromonads isolated from ornamental fish . Of the 42 isolates of Aeromonas spp . tested, none were resistant to ceftiofur sodium; however, all isolates were resistant to ampicillin, and 71% were resistant to tetracycline.

Microb Pathog, 1992 Jul, 13(1), 17 - 24
Purification and characterisation of an extracellular metalloprotease, serine protease and haemolysin of Aeromonas hydrophila strain B32: all are lethal for fish; Rodriguez LA et al.; Three different lethal (for rainbow trout, Salmo gairdneri) extracellular toxins were purified by HPLC from the culture supernatants of Aeromonas hydrophila strain B32 which had been isolated from rainbow trout . A metalloprotease, MW 38 kDa, was stable at 56 degrees C for 10 min, had no cytotoxic activity and and LD50 of 150 ng/g fish . In narrow range isoelectric-focusing (IEF) the enzyme had 11 isomers with (pls) between 4.12 and 4.8 . A serine protease (22 kDa) was stable at 56 degrees C for 10 min, possessed cytotoxic activity and had an LD50 of 150 ng/g fish . In IEF, multiple isomers possessed pls between 4.5-5.2 . The haemolysin had alpha-haemolytic activity (68 kDa) multiple isomers in IEF with pl range 4.5-5.1 and an LD50 of 2 micrograms/g fish . It was stable after heating to 56 degrees C for 20 min, 60 degrees C for 10 min and possessed esterase activity on beta-naphthyl acetate . These latter properties suggest it may be a novel haemolysin distinct from alpha- and beta-haemolysin.

Int J Syst Bacteriol, 1992 Jul, 42(3), 384 - 9
rRNA gene restriction patterns as taxonomic tools for the genus Aeromonas; Martinetti Lucchini G et al.; In the genus Aeromonas there are at least 13 DNA hybridization groups, which are difficult to differentiate biochemically . We investigated the usefulness of rRNA gene restriction patterns for characterization and identification of the various groups . Genomic DNA was digested with restriction endonuclease SmaI, transferred to a nylon membrane, and hybridized with biotinylated plasmid pKK3535 containing the rrnB operon of Escherichia coli . The SmaI bands at 0.8 to 4 kb but not those at positions corresponding to sizes larger than 4 kb showed a good correlation with hybridization groups, allowing identification of strains to the level of genetic species . We demonstrated that the 567-bp fragment localized between positions 80 and 647 of the 16S ribosomal gene of E . coli was essential for hybridization to the low-molecular-weight fragments, whereas the remainder of the operon did not hybridize to these fragments . On the basis of these results, we concluded that the Aeromonas chromosome contains multiple rRNA operons which may be used for species identification.

Roum Arch Microbiol Immunol, 1992 Jul-Sep, 51(3), 147 - 56
Hemolytic properties of some Aeromonas strains; Nacescu N et al.; Considering the possible correlation between hemolytic and enterotoxigenic properties of Aeromonas strains mentioned in the literature, in the present work we studied the practical value of the hemolysis tests in the diagnosis of Aeromonas strains by using comparatively the hemolysis tube tests (with goat and sheep erythrocytes suspensions) as well as the technique on blood agar in aerobic conditions . There were studied comparatively 230 Aeromonas strains (different species: A . hydrophila, A . sobriae, A . caviae, A . veronii, A . salmonicida) isolated from different sources (meat products, fish of fresh waters, mussels, sea water, pipe water, diarrhoeal disease and animal faeces) . The comparison among the used tests for proving the hemolytic activity of Aeromonas strains showed that: 61.89% and 56.51% from the total number of Aeromonas strains were hemolytic in the tube tests with 1% goat and 1% sheep erythrocytes suspensions respectively after 48 hrs followed by 51.72% and 48.25% strains by the 5% goat and 5% sheep blood agar plates respectively in anaerobiosis and after 48 hrs incubation at 37 degrees C . The highest incidence of hemolysin presence was pointed out in motile Aeromonas strains (A . hydrophila--60.11% and A . sobria--56.52%) . Our results showing a high frequency of hemolytic activity among Aeromonas strains isolated especially in meat products are suggesting a possible correlation between the pathogenic potential and the hemolytic activity and are pleading for introduction of this test in the diagnosis of Aeromonas species.

Biochemistry, 1992 Jun 2, 31(21), 4974 - 80
Stereochemical and positional specificity of the lipase/acyltransferase produced by Aeromonas hydrophila; Robertson DL et al.; Aeromonas species secrete a glycerophospholipid-cholesterol acyltransferase (GCAT) which shares many properties with mammalian plasma lecithin-cholesterol acetyltransferase (LCAT) . We have studied the stereochemical and positional specificity of GCAT against a variety of lipid substrates using NMR spectroscopy as well as other assay methods . The results show that both the primary and secondary acyl ester bonds of L-phosphatidylcholine can be hydrolyzed but only the sn-2 fatty acid can be transferred to cholesterol . The enzyme has an absolute requirement for the L configuration at the sn-2 position of phosphatidylcholine . The secondary ester bond of D-phosphatidylcholine cannot be hydrolyzed, and this lipid is not a substrate for acyl transfer . In contrast to the phospholipases, but similar to LCAT, the enzyme does not interact stereochemically with the phosphorus of phosphatidylcholine . In fact, the phosphorus is not required for enzyme activity, as GCAT will also hydrolyze monolayers of diglyceride, although at much lower rates.

Thorax, 1992 Jun, 47(6), 482 - 3
Aeromonas hydrophila fulminant pneumonia in a fit young man; Goncalves JR et al.; A previously healthy 24 year old athletic man became ill suddenly with pneumonia the day after swimming in the sea . Despite intensive support measures in the intensive care unit he died three hours after admission and 21 hours after his first symptom . Necropsy showed bilateral haemorrhagic necrotising pneumonia . Aeromonas hydrophila was isolated from a blood culture taken at admission and from the lungs at necropsy . The infection may have come from contaminated sea water.

Int J Food Microbiol, 1992 Jun, 16(2), 131 - 9
Variation in growth kinetics and phenotype of Aeromonas spp . from clinical, meat processing and fleshfood sources; Hudson JA; Sixty-four strains of motile aeromonads (A . hydrophila, A . sobria and A . caviae), isolated from clinical meat processing and ready-to-eat fleshfood sources, and the A . hydrophila type strain were tested with respect to their growth kinetics at 4 degrees C and 37 degrees C, and the reported indicators of pathogenicity: autoagglutination and haemolysis (tested using a CAMP reaction) . Between the species, A . caviae grew the fastest at 37 degrees C and had the highest percentage of strains not able to grow at 4 degrees C (after 200 h incubation) . Within the species, food-derived strains of A . hydrophila were better adapted to growth at lower temperatures than those from clinical or meat processing sources . Clinical strains of A . hydrophila autoagglutinated more frequently than those from other sources, but not differences in CAMP reactions were noted . Aeromonas caviae and A . sobria isolates appeared to be homogeneous with respect to growth kinetics at the temperatures tested . A comparison of the growth kinetics of the A . hydrophila type strain and a food-derived A . hydrophila strain clearly reflected the latter's enhanced ability to grow at low temperatures.

J Gen Microbiol, 1992 Jun, 138 ( Pt 6), 1229 - 36
Immunochemical analysis and possible biological role of an Aeromonas hydrophila surface array protein in septicaemia; Kokka RP et al.; The biochemical, immunological, and biological properties of an S layer purified from an Aeromonas hydrophila strain (AH-342) involved in a case of bacteraemia were investigated . The S layer selectively removed from the cell surface was composed of a single acidic (pI 4.56) protein subunit (surface array protein, SAP) with a molecular mass of approximately 52 kDa . Amino acid analysis of this 52 kDa protein indicated a molecule composed of 498 amino acids with 46% hydrophobic residues . No cysteine residues were detected . The first 35 residues of the N-terminus were sequenced by Edman degradation; only 4-24% homology was noted between this sequence and those previously published for SAPs of Aeromonas salmonicida (A450) and a strain of A . hydrophila (TF7) originally isolated from a moribund fish . Polyclonal antibodies raised against AH-342 SAP were genospecific, reacting only against S layers produced by A . hydrophila strains and not those from Aeromonas veronii . Acute serum from the bacteraemic patient from whom AH-342 was isolated reacted strongly with the SAP of AH-342 in immunoblot studies . Purified SAP, when intraperitoneally co-inoculated with SAP- strains of A . hydrophila into Swiss-Webster mice, could reduce the 50% lethal dose by approximately 30-70 fold . The results suggest that the SAP of A . hydrophila strains may play an important role in systemic dissemination after invasion through the gastrointestinal mucosa.

Mol Microbiol, 1992 May, 6(10), 1351 - 61
The Aeromonas hydrophila exeE gene, required both for protein secretion and normal outer membrane biogenesis, is a member of a general secretion pathway; Jiang B et al.; The Aeromonas hydrophila Tn5-751 insertion mutant L1.97 is unable to secrete extracellular proteins, and is fragile because of defective assembly of its outer membrane . A KpnI 4.1 kb fragment, which complements this mutant when supplied with an exogenous promoter, was isolated and sequenced . It contains two complete genes, exeE and exeF, plus fragments of two others and may form part of an operon . The exeE and exeF open reading frames encode 501-residue M(r) 55,882 and 388-residue M(r) 43,431 proteins, respectively . These genes were expressed in vitro and their initiation codons verified by deletion analysis . Tn5-751 had inserted near the centre of the exeE gene in the L1.97 strain . Subclones of the KpnI 4.1 kb fragment which contained only the exeE gene fully complemented the mutation, indicating that its function is required both for extracellular secretion and outer membrane assembly . ExeE and ExeF are highly similar to other proteins which have been shown to be involved in extracellular secretion, suggesting that an additional export apparatus beyond that required for inner membrane translocation may be part of the physiology of many Gram-negative bacteria.

J Appl Bacteriol, 1992 May, 72(5), 435 - 44
Typing of Aeromonas strains from patients with diarrhoea and from drinking water; Havelaar AH et al.; Aeromonas strains (187) from human diarrhoeal stools and from drinking water (263) in The Netherlands were typed by three different methods . Biotyping alone was found to be of little value for epidemiological studies because 84% of all strains belonged to only 10 biotypes . Common biotypes could be further differentiated by serotyping . Gas-liquid chromatography of cell wall fatty acid methyl esters (FAME) was useful for species identification as well as for typing: 86% of all strains could be identified to the species level, and within this group 92% of all identifications corresponded with the biotype . Cluster analysis and principal component analysis of FAME profiles could be used for comparison of strains from different sources and gave the same general conclusions as bio- and serotyping . There was little overall similarity between Aeromonas strains from human (diarrhoeal) faeces and from drinking water, differences being most pronounced for Aeromonas caviae and least for A . sobria.

Clin Infect Dis, 1992 May, 14(5), 1061 - 8
Molecular studies on the aerolysin gene of Aeromonas species and discovery of a species-specific probe for Aeromonas trota species nova; Husslein V et al.; A large group of aeromonads and other enteric microorganisms were assayed for the presence of the aerolysin gene with use of DNA-DNA hybridization . Two DNA fragments corresponding to the regulatory region (aerC) and the structural gene (aerA) were used as probes for the detection of the aerolysin gene in these strains . Sequences corresponding to the aerolysin structural gene were widespread among Aeromonas isolates . In contrast, the aerC probe was much more selective, and sequences corresponding to the aerC region were detected in only a small subset of strains . Concurrent studies using numerical taxonomy and DNA hybridization with the aerC probe on a larger set of strains led to the identification of a distinct cluster of 14 presumed atypical Aeromonas sobria strains . These strains have recently been grouped into a new species designated Aeromonas trota . Hence, the DNA fragment aerC used in the study is a species-specific gene probe for A . trota . The ability of the aerC probe to detect strains belonging to a single species suggests that there is selection pressure to maintain the clonality of this species . These results have important implications with respect to the evolution of "pathogenic profiles" among these medically important bacteria.

J Clin Microbiol, 1992 May, 30(5), 1262 - 6
Identification of Aeromonas strains to the genospecies level in the clinical laboratory; Abbott SL et al.; One hundred thirty-three strains of Aeromonas (human, n = 102; animal, n = 16; environmental, n = 15) previously identified to the DNA group level by molecular methods were biochemically analyzed for 58 properties . On the basis of the use of between 9 and 16 selected tests, 132 of the 133 strains (99%) could be assigned to their correct hybridization group using this biochemical scheme . The results suggest a feasible approach for identifying aeromonads to genospecies level under appropriate conditions.

Infect Immun, 1992 May, 60(5), 2075 - 82
Structural and pathogenic properties of Aeromonas schubertii; Kokka RP et al.; We investigated the phenotypic, structural, and pathogenic properties of 11 Aeromonas schubertii strains recovered from extraintestinal sites . Most A . schubertii strains were autoagglutination positive, possessed a high surface charge but low hydrophobicity, and fell into one or two biogroups on the basis of carbon substrate utilization patterns . Fatty acid methyl ester analysis of A . schubertii revealed this species to contain a relatively high percentage of branched fatty acids (i-13:0, i-15:0, i-17:1, i-17:0) compared with A . hydrophila . Immunologic and biochemical analysis of the lipopolysaccharides of A . schubertii strains allowed for two groups to be distinguished, namely, (i) a collection of six strains belonging to serogroup O:11 that possessed a characteristic homogeneous O polysaccharide side chain profile by silver staining and immunoblotting techniques and (ii) a second antigenically diverse group (five strains) that either exhibited a heterogeneous side chain profile or were side chain deficient . A, schubertii O:11 strains were all found to contain a 55-kDa major protein associated with the outer membrane fraction which was glycine-hydrochloride extractable; non-O:11 strains did not harbor a similar protein molecule . Screening of A . schubertii strains for reputed virulence factors indicated (i) that slightly more than half of the isolates produce an apparent contact-dependent hemolysin that is not cell associated or released extracellularly, (ii) a potent cytotoxin active against HEp-2 cells that is devoid of hemolytic activity, and (iii) lack of enterotoxigeniclike activity as determined by suckling mouse assays . All A . schubertii strains were pathogenic for mice as determined by 50% lethal dose assays, although no single factor correlated with mouse pathogenicity.

Mayo Clin Proc, 1992 May, 67(5), 422 - 7
Musculoskeletal and soft tissue Aeromonas infection: an environmental disease; Voss LM et al.; During a 4-year period from November 1985 to November 1989, Aeromonas was isolated from wounds and soft tissues with clinical evidence of infection in 28 patients at our institution . Of the 28 patients, 23 (82%) had sustained an acute open or penetrating injury, more than half of which (13 of the 23) were water-related trauma . One patient had Aeromonas osteomyelitis . Five patients had no history of trauma, and three of these five had an underlying chronic disease . Treatment included debridement and antimicrobial agents . Susceptibility testing on 25 isolates from 23 patients showed uniform resistance to ampicillin and considerable resistance to cefazolin sodium (68%), but all isolates were sensitive to gentamicin sulfate, cefuroxime sodium, and the third-generation cephalosporins.

Kansenshogaku Zasshi, 1992 May, 66(5), 628 - 31
{Studies on motile-Aeromonas infection 3) . Phage typing of motile Aeromonas isolated from patients with diarrhea}; Fukuyama M et al.; Phage types were determined for 102 strains of motile Aeromonas isolated from patients with diarrhea at four metropolitan hospitals in Tokyo . The following results were obtained . 1) Of the 102 strains examined, 52 (51.0%) were divided into 28 phage types . This rate was considerably higher, compared to our previous results, namely, 21.7% for strains isolated from natural environments and 25% for those isolated from meats . By bacterial species, phage types could be determined for 33 (52.4%) of 63 strains of A . hydrophila, for 16 (45.7%) of 35 strains of A . sobria, 2 (50.0%) of 4 strains of A . caviae and 1 (100%) strain of Aeromonas spp . 2) Of the 52 strains for which the phage types could be determined, the greatest number (16 strains, 30.8%) were identified as belonging to Type I group . These are followed by 5 strains (9.6%) which were identified as Type I/III group and 2 strains (3.4%) each identified as Type I/II, I/II/V, IV, V and VI groups . The remaining 21 strains were identified as belonging to one of the other phage type groups . Thirty-five (67.3%) of the strains for which the phage types were identified, were found to belong either to Type I group or to combinations with Type I . This demonstrated that 34.0% of the isolates from patients with diarrhea were related to Type I.

J Biol Chem, 1992 Apr 25, 267(12), 8390 - 5
Isolation of the leucine aminopeptidase gene from Aeromonas proteolytica . Evidence for an enzyme precursor; Guenet C et al.; The leucine aminopeptidase of Aeromonas proteolytica (EC 3.4.11.10) is a monomeric metalloenzyme having the capacity to bind two Zn2+ atoms in the active site . Structural information of this relatively small aminopeptidase that could illuminate the catalytic mechanism of the metal ions is lacking; hence, we have obtained sequences from the purified enzyme, cloned the corresponding gene, and expressed the recombinant protein in Escherichia coli . The deduced primary amino acid sequence of this secreted protease suggests a potential signal peptide at the NH2 terminus . Expression of the recombinant and native proteins in E . coli and in extracts of culture media of A . proteolytica indicates that the aminopeptidase is secreted as an active and thermosensitive 43-kDa protein that is rapidly transformed to thermostable forms of 30 and 32 kDa . Comparison of the deduced amino acid sequence of the A . proteolytica leucine aminopeptidase with other Zn(2+)-binding metalloenzymes failed to show homologies to the consensus binding sequence His-Glu-X-X-His for the metal ion.

Enferm Infecc Microbiol Clin, 1992 Apr, 10(4), 224 - 6
{Usefulness of studies of susceptibility of ampicillin, carbenicillin, cefalotin and colistin as a presumptive identification system for the Aeromonas sp . group}; Reina J et al.; We have studied the restricted antibiotic susceptibility tests for 180 strains belonging to mesophilic Aeromonas sp . isolated from stools samples . Strains has been identified as follows: A . caviae (64.6%), A . hydrophila (17.7%) and A . sobria (17.7%) . Antibiotics tested were ampicillin (10 micrograms), carbenicillin (100 micrograms), cephalotin (30 micrograms) and colistin (10 micrograms), by means of agar diffusion tests (disk-plate) . We identified four different patterns of antibiotic susceptibility . The most frequent pattern (pattern #1) (77.8%) is characterized by susceptibility only to colistin, and was predominant among A . caviae strains (80%) . Pattern #2 (susceptibility to cephalotin and colistin) was found in 18.9% of strains, being predominant in A . sobria (88.2%) . We confirm the higher susceptibility of A . sobria sp . to cephalotin as well as the possibility that these different patterns might be used as screening method for species identification among mesophilic group of Aeromonas.

Vet Immunol Immunopathol, 1992 Apr, 32(1-2), 179 - 89
A comparison of total and specific immunoglobulin levels in healthy Atlantic salmon (Salmo salar L.) and in salmon naturally infected with Aeromonas salmonicida subsp . achromogenes; Magnadottir B et al.; Healthy Atlantic salmon and salmon with a history of chronic natural Aeromonas salmonicida subsp . achromogenes infection were compared with respect to total serum protein and the concentration and specificity of serum immunoglobulin . The immunoglobulin level was measured using competitive ELISA and the specific antibody activity against Aeromonas salmonicida subsp . achromogenes was measured using double sandwich ELISA . Significant elevation of serum protein and immunoglobulin concentration was observed in the infected salmon compared with the healthy fish . This was accompanied by weak anti-A . salmonicida activity in the infected fish which seemed to contribute to the raised immunoglobulin level to only a limited degree.

J Med Microbiol, 1992 Apr, 36(4), 269 - 72
Enterotoxicity of clinical and environmental isolates of Aeromonas spp; Singh DV et al.; Of 147 isolates of three species of Aeromonas, 54 were from clinical and 93 from environmental sources . When tested for enterotoxin production, most of the isolates (56%) caused accumulation of fluid in rabbit ileal loops (RILs) . Although large proportions of clinical and environmental isolates of A . caviae (55% and 65%, respectively) elicited such a response in RILs, isolates of A . hydrophila and A . sobria produced significantly more fluid (p less than 0.05) . Furthermore, the environmental strains of A . hydrophila and A . sobria produced more fluid than the clinical isolates (p less than 0.05) . The strains of Aeromonas spp . that caused little or no fluid accumulation in the initial experiments became enterotoxin producers after 1-3 passages through RILs, regardless of their source, and showed gradual enhancement of fluid outpouring after each passage . The present study suggests that all strains of these species of Aeromonas are potentially enterotoxigenic, whether from clinical or environmental sources.

Arch Biochem Biophys, 1992 Apr, 294(1), 91 - 7
Rapid purification of the Aeromonas proteolytica aminopeptidase: crystallization and preliminary X-ray data; Schalk C et al.; The heat-stable aminopeptidase from Aeromonas proteolytica has been purified using two new procedures, with the aim of preparing large single crystals for X-ray analysis . In a first procedure, we tried to avoid any drastic conditions capable of inducing microheterogeneities in the protein sample . The enzyme was purified through two chromatographic steps based on hydrophobic interactions and ion exchange . In a second procedure a heat treatment of the protein to a temperature of 70 degrees C over 5 to 8 h was performed . Both procedures led to an electrophoretically homogeneous and crystallizable aminopeptidase; however, unexpectedly, the crystals obtained through the first procedure contained, in addition to the native aminopeptidase, a cleaved form of the enzyme which has been characterized . Only the native protein was present when the second procedure was used . Large crystals obtained with the native protein form, having an approximate size of 0.4 x 0.4 x 0.6 mm, produced an X-ray diffraction pattern that exhibited the symmetry associated with the hexagonal space group P6(1)22 (or its enantiomorph P6(5)22) . The unit cell parameters were a = 109.1 A and c = 97.8 A . Assuming one molecule/asymmetric unit, a value of VM = 2.6 A3/Da and an approximate solvent content of 45% could be estimated . Measurable diffraction intensities were observed at a resolution of 2.5 A.

J Appl Bacteriol, 1992 Apr, 72(4), 341 - 51
Numerical classification and identification of Aeromonas genospecies; Kampfer P et al.; A total of 176 Aeromonas strains representing all currently characterized genospecies were tested for 329 biochemical characters . Overall similarities of all strains were determined by numerical taxonomic techniques, the UPGMA algorithm and the SSM and the SJ coefficients as measures of similarity . Sixteen clusters (two or more strains) and seven unclustered strains were recovered at the 93.5% similarity level (SSM) . Genospecies 1, 4, 5, 6, 7, 9, 12 and 13 were largely represented by single phena, whereas strains of genospecies 2 and 3 were found in closely-related phena . Strains belonging to genospecies 8 formed two distinct biotypes . Strains belonging to genospecies 11 formed a subcluster within a cluster representing different genospecies . In general, similar groupings were obtained with the Jaccard coefficient at a similarity level of 80.0% (SJ) with minor changes in the definition of clusters . The phenetic data showed good correlation with the taxa defined by DNA/DNA hybridization and those obtained by multilocus enzyme analysis . For all genospecies (independent from cluster assignment) 30 diagnostic characters were selected to construct a matrix for probabilistic identification . The correct identification rate of the matrix was 71.51% taking a Willcox probability greater than 0.99, and 83.7% taking a Willcox probability greater than 0.9 as identification threshold levels.

J Appl Bacteriol, 1992 Apr, 72(4), 322 - 6
Effect of culture age, pre-incubation at low temperature and pH on the thermal resistance of Aeromonas hydrophila; Condon S et al.; The thermal resistance of Aeromonas hydrophila strain NCTC 8049 was determined within the range 48 degrees-65 degrees C with a thermoresistometer TR-SC and McIlvaine buffer . The effects of culture age, pre-incubation at 7 degrees C and the pH of the heating menstruum were evaluated . The pattern of thermal death was dependent on culture age . Cells heated in the late logarithmic growth phase (15 h at 30 degrees C) were twice as resistant as those in the early stage (5 h at 30 degrees C), and the maximum D-value was obtained after 72 h incubation (5.5 total increase) . The age of the cells did not affect z-values significantly . The heat resistance of cells incubated for 48 h at 30 degrees C increased (twice) after holding at 7 degrees C for 72 h . Pre-incubation at low temperature of older cultures (72 h, 30 degrees C) did not influence their D-values . Maximum heat resistance was found at pH 6.0 and minimal at pH 4.0 . Decreasing the pH from 6.0 to 4.0 reduced D-values by a factor of 5 . Although the strain studied was heat-sensitive (D55 degrees C = 0.17 min; z = 5.11 degrees C), survivor curves of cultures older than 50 h showed a significant tailing . Organisms surviving in the tails were only slightly more resistant than were the original population.

FEMS Microbiol Lett, 1992 Mar 15, 70(3), 199 - 205
Aeromonas allosaccharophila sp . nov., a new mesophilic member of the genus Aeromonas; Martinez-Murcia AJ et al.; Phenotypic and genetic studies were performed on some atypical aeromonas strains of uncertain taxonomic position . 16S rRNA gene sequence analysis revealed that these strains represent a hitherto unknown genetic line within the genus Aeromonas, for which the name Aeromonas allosaccharophila sp . nov . is proposed . The type strain is CECT 4199.

J Diarrhoeal Dis Res, 1992 Mar, 10(1), 16 - 20
Haemolysin and enterotoxin production by Aeromonas caviae isolated from diarrhoeal patients, fish and environment; Singh DV et al.; Beta-haemolytic activity was shown by 46 (63%) of the 73 Aeromonas caviae strains isolated from diverse sources, such as diarrhoeal stools, fish ulcers and water in titres of 16-64 HU/ml . Only 2 strains showed alpha-haemolytic activity and the remaining 27% of them were nonhaemolytic . Live cells and culture filtrates of 60.3% of the A . caviae isolates caused accumulation of fluid in rabbit gut loops in the initial set of experiments . Of the 46 strains showing beta-haemolytic activity only 34 gave positive ileal loop reactions in the initial experiments . One of the 2 strains showed alpha-haemolytic activity and 9 of the 20 nonhaemolytic strains also caused fluid accumulation in the same set of experiments . Those strains that showed beta-haemolytic activity caused significantly more (p less than 0.01) fluid outpouring than the alpha- or nonhaemolytic isolates regardless of their sources of origin . Twenty-nine (39.7%) strains that showed alpha-, beta-, and nonhaemolytic activity and caused little or no fluid accumulation in initial experiments did so after 1-3 consecutive passages through rabbit gut . The nontoxic strain showing alpha- and non-haemolytic activity switched over to production of beta-haemolytic activity once their live cells gave positive loop reactions . However, on repeated subcultures or on preservation in the laboratory for 2-3 weeks, all of them reverted back to their original nontoxic haemolytic types, i.e . alpha- or nonhaemolytic activity.

Diagn Microbiol Infect Dis, 1992 Mar-Apr, 15(3), 201 - 6
Elastolytic activity among Aeromonas spp . Using a modified bilayer plate assay; Hasan JA et al.; A total of 166 isolates of Aeromonas, representing diverse geographical regions and originating from various sources, were evaluated for the ability to produce elastase by using a bilayer elastin agar medium (BEAM) plate assay . The degree of elastase activity of individual strains was roughly assessed by measuring the clear area beneath or peripheral to the colony and recorded as 1+, 2+, or 3+ . Of the 166 aeromonads tested, 53 (32%) were found to produce elastase, of which 26 (49%) were 3+, 21 (40%) were 2+, and 6 (11%) were 1+ . All but one A . hydrophila (n = 45) were observed to produce elastase (98%) . One of three A . schubertii strains as well as one isolate of Aeromonas group 501 were elastase positive . All 3+ elastolytic activity was associated with A . hydrophila only . Elastase activity was not detected even after prolonged incubation with A . veronii biogroup sobria (n = 26), A . caviae (n = 57), A . veronii biogroup veronii (n = 4), A . media (n = 1), and A . eucrenophila (n = 1) . In addition to its value as a reliable indicator of elastase production for eventual use in virulence assays, we have found that the detection of elastase using the BEAM plate serves as a very useful phenotypic marker for the major, clinically important Aeromonas spp.

Appl Environ Microbiol, 1992 Mar, 58(3), 1039 - 42
DNA probe for Aeromonas salmonicida; Hiney M et al.; A DNA fragment that is specific to Aeromonas salmonicida has been isolated from a genomic DNA library by differential hybridization . The specificity of this fragment as a DNA probe for A . salmonicida was shown by hybridization against reference strains and clinical isolates of A . salmonicida, related aeromonads, and species from several other bacterial genera . The sensitivity of detection by a polymerase chain reaction test, based on this fragment, was approximately two A . salmonicida cells.

J Clin Microbiol, 1992 Mar, 30(3), 619 - 22
Siderophore production and DNA hybridization groups of Aeromonas spp; Zywno SR et al.; A correlation between the genospecies (DNA-DNA hybridization group) and the type of siderophore produced by 118 isolates of the genus Aeromonas was established . Organisms in hybridization groups 1 through 5 (including 5A, 5B, and 5AB) and group 12 predominantly produced the siderophore amonabactin, while an enterobactinlike siderophore was prevalent in groups 8/10 and 9 . The siderophore produced by strains in group 6 may be an as-yet-unidentified nonphenolate, nonhydroxamate compound, and group 7 isolates synthesized no siderophores . Determination of the indigeneous siderophore (or the absence of one) produced by an isolate of the genus Aeromonas may assist in identification of the organism's genetic species and may suggest the presence of certain virulence properties.

Can J Microbiol, 1992 Mar, 38(3), 235 - 40
Characterization of an O-antigen bacteriophage from Aeromonas hydrophila; Merino S et al.; A unique bacteriophage of Aeromonas hydrophila serotype O:34 was isolated, purified, and characterized . The bacterial surface receptor was shown to be the O-antigen polysaccharide component of lipopolysaccharide specific to serotype O:34, which was chemically characterized . The high molecular weight lipopolysaccharide fraction (a fraction enriched in O antigen) was fully able to inactivate bacteriophage PM1 . Phage-resistant mutants of A . hydrophila O:34 were isolated and found to be specifically devoid of lipopolysaccharide O antigen . No other cell-surface molecules were involved in phage binding . The host range of bacteriophage PM1 was found to be very narrow, producing plaques only on A . hydrophila strains from serotype O:34.

Zentralbl Bakteriol, 1992 Feb, 276(3), 418 - 28
Virulence traits of Aeromonas strains in relation to species and source of isolation; Pal A et al.; The virulence traits of 39 well-defined clinical (29 strains) and environmental (10 strains) isolates of Aeromonas (16 A . hydrophila, 12 A . sobria and 11 A . caviae) were examined by a variety of assays to delineate differences, if any, in the enteropathogenic potential in relation to species and the source of isolation . The distribution of enterotoxin (ent), cytotoxin (cyt) and haemolysin (hae) producing strains of Aeromonas did not correlate to species and source of isolation . The extracellular virulence phenotype Ent+ Cyt+ Hae+ was the most common one among all the three species although unique phenotypes associated prominently with either A . hydrophila or A . sobria were also discernible . None of the cytotoxin or haemolysin producing strains hybridized with the vt1/vt2 or the tdh/trh gene probes, respectively, indicating that these two factors of Aeromonas were distinct . Haemagglutination of human O group erythrocytes was not related to the source of isolation or production of enterotoxin, cytotoxin or haemolysin but appeared to be related to species . The strains which did not exhibit cell-associated haemagglutination belonged to either A . hydrophila or A . caviae . Haemagglutination unaffected by fucose, mannose and galactose was the dominant inhibition pattern exhibited mainly by the clinical haemagglutinating strains of the three species . Only one clinical strain of A . caviae showed a diffuse pattern of adherence to HeLa cells . Expression of the 5 bacterial enzymes by strains of Aeromonas did not fall into a readily discernible pattern in relation to species or source of isolation . From this study, it is clear that the mechanism of the pathogenesis of Aeromonas is a multifactorial one.

J Gen Microbiol, 1992 Feb, 138 ( Pt 2), 261 - 7
Enterotoxic effects of Aeromonas sobria haemolysin in a rat jejunal perfusion system identified by specific neutralization with a monoclonal antibody; Millership SE et al.; Investigations into the pathogenesis of Aeromonas diarrhoea have demonstrated that several different cell-free products of motile aeromonads show enterotoxic activity in suckling mouse, rat, and rabbit assay systems . The relative contributions made by separate cytotoxic and cytotonic activities in the mixture produced by in vitro culture remains unresolved . Using a modified rat jejunal perfusion assay, we have studied the effects of A . sobria culture filtrates containing defined levels of haemolytic and cytotoxic activity and immunoreactivity for anti-cholera toxin . This material induced net water, potassium, and sodium loss with a rapid onset (less than 5 min) that was readily differentiated from the effects of purified cholera toxin (greater than 15 min) . In filtrates containing up to 128 haemolytic and cytotoxic units of activity, the enterotoxic activity was neutralized by an anti-haemolysin/cytotoxin monoclonal antibody . No specific histological changes could be found in preparations perfused with enterotoxic material for up to 65 min . These findings indicate that the cytotoxic/haemolytic component of A . sobria culture filtrate is the dominant enterotoxic activity.

Kansenshogaku Zasshi, 1992 Feb, 66(2), 127 - 34
{O serogroup and virulence factors of motile Aeromonas}; Watanabe N et al.; A total of 182 isolates of motile Aeromonas from patients with diarrhea and environmental sources was investigated for hemolytic activity to rabbit erythrocyte and cytotoxicity to HeLa 229 cell . Furthermore, the relation between O serogroup and virulence factors, which were lethal to mouse and autoagglutination, were investigated . There were many strains possessing both the hemolytic and cytotoxic activities in A . hydrophila from overseas traveller's diarrhea, suggesting that these activities were associated with intestinal pathogenecity . Although there was a clear correlation between hemolytic and cytotoxic activities in A . hydrophila from overseas traveller's diarrhea, the correlation was not found in A . hydrophila from domestic cases of diarrhea and A . sobria from overseas traveller's diarrhea . Especially, some A . hydrophila isolates from domestic case of diarrhea produced only hemolysin . These results indicated that there was a difference in specificity between the toxins accounted for hemolytic and cytotoxic activities, and more than two different toxins were developed . O serogroups 11, 34, 14, 16, and 35 in that order were the most frequent serogroups . About half of O11 and O34 strains possessed lethal activity to mouse . Autoagglutination phenomenon did not seem to be associated with the lethal activity . In O11 strains, high cytotoxic titer was more frequently found in lethal activity positive-strains than in the activity negative-strains, suggesting that cytotoxicity contributed preferentially to lethal activity to mouse . But such a correlation was not found in O34 strains, so other virulence factors than hemolysin and cytotoxin may be associated with the lethal activity.

FEMS Microbiol Lett, 1992 Feb 1, 70(1), 15 - 9
Mechanism of action of a cytotonic enterotoxin produced by Aeromonas hydrophila; Chopra AK et al.; In this study, we describe the mechanism of action of a cytotonic enterotoxin produced by two isolates of Aeromonas hydrophila . Isolates SSU and Ah65 are of different origin and both are capable of producing either a cytotoxic enterotoxin or aerolysin . A cytotonic enterotoxin produced by diarrheal isolate SSU, which was purified and characterized in our laboratory, elevated intracellular cAMP and PgE2 levels in cultured Chinese hamster ovary (CHO) cells . Likewise, enterotoxic activity expressed by a cytotonic enterotoxin was detected in the culture filtrate of a fish isolate (Ah65) after cytotoxic activity was neutralized with homologous aerolysin monoclonal antibodies . This cytotonic enterotoxin also elevated intracellular cAMP and PgE2 levels in CHO cells, suggesting a cholera toxin-like mechanism of action for Aeromonas cytotonic enterotoxins.

Vet Rec, 1992 Jan 18, 130(3), 45 - 8
Amoxycillin in the control of furunculosis in Atlantic salmon parr; Inglis V et al.; The efficacy of amoxycillin in the control of laboratory induced Aeromonas salmonicida infection in Atlantic salmon parr was investigated . When given in the diet at a dose rate of 80 mg per kg bodyweight it was effective against both a moderate and severe challenge (with mortality rates in untreated groups of 75 per cent and 45 per cent) . At 40 mg per kg it was effective against the moderate challenge only . The plasma levels in these regimens were 1.25 micrograms per ml and 0.3 to 0.6 micrograms per ml and the minimum inhibitory concentration of the challenge strain of A salmonicida was 0.6 micrograms per ml . The potential of the Charm radiobioassay system in detecting antibiotic residues in fish tissue was studied . The level of amoxycillin in muscle and bone from fish in mid-treatment at 80 mg per kg was 0.32 micrograms per ml . After a 12 day withdrawal period at 18 degrees C no residue was detected within the 0.005 micrograms per ml limit of this test.

J Biol Chem, 1992 Jan 5, 267(1), 43 - 9
Binding of laminin and fibronectin by the trypsin-resistant major structural domain of the crystalline virulence surface array protein of Aeromonas salmonicida; Doig P et al.; The surface of Aeromonas salmonicida is covered by a tetragonal paracrystalline array (A-layer) composed of a single protein (A-protein, Mr = 50,778) . This array is a virulence factor . Cells containing A-layer and isolated A-layer sheets specifically bound laminin and fibronectin with high affinity . Binding by cells was inactivated by selective removal of A-layer at pH 2.2, and neither isogenic A-layer-deficient A . salmonicida mutants nor tetragonal paracrystalline array producing Aeromonas hydrophila and Aeromonas sobria strains bound either matrix protein . Laminin binding was by a single class of high affinity interactions (cell Kd = 1.52 nM), whereas fibronectin bound via two classes of interactions, one being similar to that of laminin (cell Class 2 interaction Kd = 6.6 nM) . This interaction with both proteins was partly hydrophobic . The Class 1 fibronectin interaction was of lower affinity (cell Kd = 218 nM) and distinct . Purified A-protein inhibited binding of both matrix proteins to A-layer, and trypsin cleavage localized the matrix-protein binding region to the N-terminal major trypsin-resistant structural domain of A-protein . Monoclonal antibody inhibition studies showed that A-protein was folded such that Fabs of only one of two antibodies with epitopes mapping C-terminal to this trypsin-resistant peptide was capable of blocking binding.

Intensive Care Med, 1992, 18(3), 172 - 4
Aeromonas hydrophila: myofascial necrosis and sepsis; Vukmir RB; An alcoholic patient with ascites was admitted to the intensive care unit for gastrointestinal bleeding . He subsequently developed spontaneous myonecrosis of the extremities culminating in sepsis syndrome . This was a unique, non-traumatic presentation of Aeromonas hydrophila soft tissue injury.

Dev Comp Immunol, 1992 Jan-Feb, 16(1), 49 - 61
Toxicity of Aeromonas salmonicida cells to Atlantic salmon Salmo salar peritoneal macrophages; Olivier G et al.; Several strains of Aeromonas salmonicida were toxic to cultured peritoneal macrophages of Atlantic salmon, Salmo salar, in minimum doses of 5 x 10(6) CFU, whereas other strains were not . There was no correlation between cytotoxicity and in vivo virulence of the bacteria, the presence or absence of the two major surface components of A . salmonicida (namely, the A-layer and the O-polysaccharide chain of the LPS) nor, finally, with the ability of the strains to produce the following enzymes in vitro: protease, hemolysin, elastase and lecithinase . Toxicity was only observed with metabolically active bacteria and not with formalin- or heat-killed bacteria . The exact nature of the toxic factor remains unknown but is most likely associated with the surface of the bacteria . It is not extracellular since 24 and 48 h culture supernatants of the cytotoxic strains had no apparent effect on macrophages . The cytotoxic effect was found to be severe and rapid, it is likely a major virulence factor of A . salmonicida, but the exact role of such a potent toxin in the pathology of furunculosis has yet to be clarified.

J Med Assoc Thai, 1992 Jan, 75(1), 56 - 61
Case report with review of Aeromonas infection; Yenrudi S et al.; A 31-year-old woman with A . sobria infection and septicemia was reported . The patient was a known case of ANLL,M4 with incomplete remission following successive courses of chemotherapy . There were abscesses in the subcutaneous tissue of right knee and the liver at necropsy . Leukemic cell infiltration in various organs as well as the aforementioned organs were observed . Reported cases of Aeromonas infection with or without diarrhea were also reviewed . According to our knowledge the present case is the first reported case with A . sobria infection with liver abscess in Thailand.

Microbios, 1992, 69(280-281), 181 - 6
Susceptibility to antimicrobial agents and plasmid carrying in Aeromonas hydrophila isolated from two estuarine systems; Montoya R et al.; Susceptibility to various antimicrobial agents and the presence of plasmids was investigated in eleven strains of Aeromonas hydrophila isolated from samples of sea water and these strains isolated from Aulacomya ater . Transference of resistance to Escherichia coli was attempted by conjugation and transformation experiments . The strains showed multiple resistance toward beta-lactam antibiotics and susceptibility to other antimicrobial agents . Five strains harboured plasmids with molecular weights below 5.7 MD . It was not possible to relate the resistance of the strains with the presence of their plasmids.

Microbios, 1992, 70(282), 67 - 70
Occurrence of haemolysin producing Aeromonas species in the aquatic environment; Parveen S et al.; A total of 532 environmental isolates of motile aeromonads were evaluated for their ability to produce haemolysins . Of those isolates tested, 68 (12.5%) and 18 (3.4%) were found to be alpha and beta haemolytic, respectively . Aeromonas caviae was found to be alpha haemolytic (3.8%) for the first time . Isolates of Aeromonas which were either alpha or beta haemolytic on plate assay also produced detectable amounts of haemolysin in cell free broth assay.

Microbios, 1992, 71(287), 105 - 13
Electrophoretic mobility and immunoblot analysis of the outer membrane proteins of Aeromonas hydrophila, A . sobria and A . caviae; Maruvada R et al.; The outer membrane profiles of three species of the genus Aeromonas were examined by means of SDS-PAGE and immunoblotting to identify species-specific polypeptides and antigens which could presumably be applied to differentiate Aeromonas spp . at the species or subspecies level . Profiles on an 11% discontinuous SDS-PAGE showed common band sharing at the 52 kD position . Species-specific bands for the three strains could also be detected . Immunoblots using heterologous LPS-adsorbed polyclonal antisera revealed demarcated common and uncommon antigens within the three species . Outer membrane preparations were immunoblotted against whole cell polyclonal antisera . The previously documented host pathogenicity of A . sobria correlated well with the immunoblots which showed antigenicity, especially due to the LPS, when compared with the other two species.

Biometals, 1992 Spring, 5(1), 57 - 62
Novel heme-binding component in the serum of the channel catfish (Ictalurus punctatus); Massad G et al.; The serum of the channel catfish (Ictalurus punctatus) was examined for heme- and hemoglobin-binding proteins . Electrophoretic mobility retardation assays failed to detect a hemoglobin-binding material similar to mammalian haptoglobin; however, a heme-binding component (not previously described) was identified in catfish serum . The heme-binding component was purified by gel filtration chromatography; electrophoretic analyses suggested it to be composed of two polypeptide subunits of molecular masses about 115 and 98 kDa . This composition is inconsistent with hemopexin, the known heme-binding serum protein of mammals . Although it was not fully saturated with heme, the catfish component contained detectable heme in normal sera . When complexed by the binding material, heme was used as an iron source by isolates of the bacterial Gram-negative genus Aeromonas; the capacity of other bacteria to use the complex was not tested . The physiological function of the catfish heme-binding serum protein is presently not clear.

J Bacteriol, 1992 Jan, 174(1), 40 - 7
Antigenic diversity of the S-layer proteins from pathogenic strains of Aeromonas hydrophila and Aeromonas veronii biotype sobria; Kostrzynska M et al.; The antigenic relatedness of paracrystalline surface array proteins with subunit molecular weights of approximately 52,000 from isolates of Aeromonas hydrophila and Aeromonas veronii biotype sobria belonging to a single heat-stable serogroup was examined . Enzyme-linked immunosorbent assay and immunoblotting with two different polyclonal antisera against surface exposed and non-surface-exposed epitopes of the S-layer protein from A . hydrophila TF7 showed that the S-layer proteins of the mesophilic aeromonads were antigenically diverse . NH2-terminal amino acid sequence analysis of four antigenically different proteins showed that while the proteins were structurally related, they differed in primary sequence . Absorption experiments with heterologous live cells showed that cross-reactive epitopes were in non-surface-exposed regions of the S-layer proteins, while absorption with homologous live cells showed that the immunodominant epitopes of the S-layer protein of strain TF7 were strain specific and exposed on the surface of the native, tetragonal array produced by this strain . Proteolytic digestion of the TF7 S-layer protein with trypsin, chymotrypsin, or endoproteinase Glu-C produced an amino-terminal peptide of approximate Mr 38,000 which was refractile to further proteolytic cleavage under nondenaturing conditions . This peptide carried the immunodominant surface-exposed region of the protein, and chemical cleavage with cyanogen bromide further mapped the portion of these surface-exposed epitopes to a peptide of approximate Mr 26,000, part of which maps within the Mr 38,000 protease-resistant NH2-terminal peptide.

Rev Elev Med Vet Pays Trop, 1992, 45(3-4), 243 - 53
Studies on the infundibular cysts of the uterine tube in camel (Camelus dromedarius); Ali AM et al.; Two hundred eighteen genital tracts of slaughtered female camels were collected and examined . Infundibular cysts were observed in 35 tracts (16%); these were either unilateral (22 cases) or bilateral (13 cases) all containing fluids of different consistencies . The morphological and histological structures of the cysts were recorded . The bacteriological investigation and physicochemical analysis of cyst contents were carried out . Aeromonas hydrophila was isolated from 68.5% of cases . Rectal palpation and ultrasound technique were compared for the diagnosis of the cysts antemortem.

Microbios, 1992, 72(292-293), 215 - 20
Glucose repression of pigment production in atypical isolates of Aeromonas salmonicida responsible for goldfish ulcer disease; Altmann K et al.; The effect of glucose and other carbohydrates on the pigmentation of three atypical isolates of Aeromonas salmonicida indicated that the addition of D-glucose at a concentration of 0.1% (w/v) or more, inhibited pigment production and caused a reduction in the size of colonies . The addition of cAMP reversed the inhibitory effects of D-glucose on pigment production.

Appl Environ Microbiol, 1992 Jan, 58(1), 42 - 7
Characterization of lactoferrin binding by Aeromonas hydrophila; Ascencio F et al.; Various lactoferrin preparations (iron-saturated and iron-depleted human milk lactoferrins and bovine milk and colostrum lactoferrins) were bound by Aeromonas hydrophila . Binding was (i) reversible (65% of bound lactoferrin was displaced by unlabeled lactoferrin), (ii) specific (lactoferrin but not other iron-containing glycoproteins such as ferritin, transferrin, hemoglobin, and myoglobin inhibited binding), and (iii) significantly reduced by pepsin and neuraminidase treatment of the bacteria . The glycosidic domains of the lactoferrin molecule seem to be involved in binding since precursor monosaccharides of the lactoferrin oligosaccharides (mannose, fucose, and galactose) and glycoproteins which have homologous glycosidic moieties similar to those of the lactoferrin oligosaccharides (asialofetuin or fetuin) strongly inhibited lactoferrin binding . A . hydrophila also binds transferrin, ferritin, cytochrome c, hemin, and Congo red . However, binding of these iron-containing compounds seems to involve bacterial surface components different from those required for lactoferrin binding . Expression of lactoferrin binding by A . hydrophila was influenced by culture conditions . In addition, there was an inverse relationship between lactoferrin binding and siderophore production by the bacterium.

Ann Dermatol Venereol, 1992, 119(10), 749 - 52
{Leg cellulitis caused by Aeromonas hydrophila . Medical treatment}; Petit A et al.; A case of cellulitis of the leg caused by Aeromonas hydrophila in a cirrhotic patient is reported . The starting point of the infection could not be determined with certainty, but a direct local inoculation during foot-baths was suspected . Because of clinical signs suggestive of erysipelas, the disease was initially treated without success with penicillin G, which raises questions concerning the choice of the initial antibiotic therapy for cellulitis of the leg in immunocompromised patients, pending the bacteriological results . A purely medical treatment (adequate antibiotic therapy) resulted in complete cure of this patient, despite the fact that his lesions were necrotizing.

FEMS Microbiol Lett, 1991 Dec 15, 69(1), 29 - 33
The pathogenicity of Aeromonas strains relative to genospecies and phenospecies identification; Janda JM et al.; The relative pathogenicity of 80 Aeromonas strains typed by biochemical (phenospecies) and genetic (genospecies) methods was assessed by determining the 50% lethal dose for each isolate in Swiss-Webster mice by intraperitoneal injection . Overall, the maximum difference in virulence potential observed between the least and most pathogenic strains was a four log (10,000-fold) difference . Results according to phenospecies designation supported previous investigations indicating that both A . hydrophila and A . sobria are inherently more pathogenic for mice than A . caviae . According to genospecies designation, the relative virulence of individual groups in decreasing order was as follows: HG 9 (A . jandaei) greater than HG 1 (A . hydrophila) and HG 12 (A . schubertii) greater than HG 10 (A . veronii biotype veronii) greater than HG 8 (A . veronii biotype sobria) greater than HG 11 (unnamed) greater than HG 2 (unnamed) greater than HG 3 (A . salmonicida), HG 4 (A . caviae) and HG 6 (A . eucrenophila) greater than HG 5 (A . media) greater than HG 7 (A . sobria).

Antimicrob Agents Chemother, 1991 Dec, 35(12), 2634 - 5
In vitro susceptibility of the fish pathogen Aeromonas salmonicida to flumequine; Barnes AC et al.; The activity of the fluoroquinolone flumequine was investigated against the fish pathogen Aeromonas salmonicida and was compared with that of oxolinic acid . Flumequine was more active than oxolinic acid in terms of its MIC against oxolinic acid-resistant isolates of A . salmonicida and was as active as oxolinic acid against susceptible isolates . In contrast to oxolinic acid, flumequine was bactericidal, with only 1% of the bacteria surviving 6 h of exposure to the drug at concentrations slightly above the MIC . Mutation to resistance to flumequine was found to occur at a lower frequency than that to oxolinic acid . Hence, in vitro, flumequine appears to possess some advantages over oxolinic acid against this fish pathogen.

Nippon Eiseigaku Zasshi, 1991 Dec, 46(5), 1009 - 13
{A report on the hygienic status of sacred "temizu" water in shrines}; Yokoi K et al.; The quality of the sacred "temizu" water in shrines in Kyoto was surveyed . It was found that the sources of "temizu" were the municipal water supply or domestic wells and that the "temizu" was usually used for washing the hands and mouth, while in certain shrines it was drunk as well . Of 50 visitors responding to questions, 26 persons said that they drank "temizu" . In some shrines using the municipal water supply as "temizu", the free residual chlorine concentration was lower than that in the municipal water supply itself . Contamination of "temizu" by Escherichia coli or Aeromonas hydrophila was observed in some shrines.

J Clin Microbiol, 1991 Dec, 29(12), 2843 - 9
Aerokey II: a flexible key for identifying clinical Aeromonas species; Carnahan AM et al.; A small subset (n = 18) of highly discriminatory tests was derived from the feature frequency of 50 tests used in the study of 167 predominantly clinical Aeromonas strains . Seven of these eighteen tests were used to construct a flexible, dichotomous key, Aerokey II, for identifying clinical aerontonads: esculin hydrolysis, gas from glucose, acid from arabinose, indole production, acid from sucrose, Voges-Proskauer reaction, and resistance to cephalothin (30 micrograms) . This schema was initially evaluated in a single-blind trial of 60 well-characterized clinical Aeromonas hydrophila (n = 21), A . caviae (n = 19), and A . veronii bv . sobria (n = 20) strains from an independent laboratory . Of the 60 strains tested, 58 (97%) were accurately identified to the species level . Aerokey II was further evaluated with 18 additional American Type Culture Collection and reference strains representing the more recently proposed taxa A . veronii bv . veronii, A . schubertii, A . jandaei, and A . trota and accurately identified all of these strains.

Ecotoxicol Environ Saf, 1991 Dec, 22(3), 283 - 90
Cellular but not humoral antibacterial activity of earthworms is inhibited by Aroclor 1254; Roch P et al.; Earthworms, Eisenia fetida andrei and Lumbricus terrestris, exposed to Aroclor 1254, followed by infestation with Aeromonas hydrophila, elicited two types of responses . First, in E . fetida, there was no change in the LD50 nor in the in vitro antibacterial growth capacity of cell-free coelomic fluid . Thus, Aroclor exerts no influence on antibacterial proteins nor on the chloragogue cells responsible for their release . Second, in L . terrestris, both a high LD50 value and no antibacterial activity indicate that A . hydrophila was not pathogenic . The 10(4) times higher sensitivity of exposed L . terrestris suggests that Aroclor inhibits leukocyte activity since E . fetida eliminates nonpathogenic bacteria by a cellular mechanism.

J Med Microbiol, 1991 Nov, 35(5), 264 - 9
Plasmid associated virulence properties of environmental isolates of Aeromonas hydrophila; Borrego JJ et al.; The plasmid profiles, and their association with antimicrobial resistance, of 60 strains of Aeromonas hydrophila isolated from fish, shellfish and water were investigated . Only two strains were susceptible to all the antimicrobial agents tested; the highest incidences of resistance were to tetracycline (96.7%), prystanamycin (93.3%), ampicillin (91.7%) and cephalothin (91.7%) . Forty strains harboured one or more plasmids and the plasmid profile most frequently detected (15%) was the association of three small plasmids of 4.2, 3.2 and 2.8 Mda . Curing experiments indicated that the plasmid-free derivative strains simultaneously lost their resistance determinants to tobramycin, neomycin, gentamicin and kanamycin . More than 90% of the strains tested produced siderophores and displayed haemolytic activity . However, the relationship between these virulence characters and the presence of plasmids was different; in 74.5% of the strains there was siderophore production and plasmids were detectable, whereas only 60% of the strains simultaneously possessed plasmids and haemolytic activity.

Head Neck, 1991 Nov-Dec, 13(6), 528 - 30
Parapharyngeal soft-tissue infection with Aeromonas hydrophila; Wells RG et al.; Parapharyngeal soft tissue infections may be rapidly progressive and life-threatening . Prompt institution of appropriate antimicrobial therapy is of paramount importance . This report highlights the potential virulence of Aeromonas hydrophila in infection of the head and neck and the need to consider this organism in selected patients.

Mol Microbiol, 1991 Nov, 5(11), 2745 - 51
Site-directed mutagenesis at histidines of aerolysin from Aeromonas hydrophila: a lipid planar bilayer study; Wilmsen HU et al.; The role of histidine residues in the formation of channels by the cytolytic toxin aerolysin has been studied in planar lipid bilayers by substituting each of the six histidines in the native protein with asparagine . His341 or His186 mutants had the same channel-forming ability as native toxin, whereas the His332 and His121 mutants were less active . Mutations at His132 and His107, which interfere with the oligomerization of the toxin, drastically reduce pore formation . These findings support the conclusion that oligomerization of the toxin must precede channel formation, and that at least two of the six histidine residues are essential for this to occur . The aerolysin channel is a water-filled pore with an approximate diameter of 9.3 +/- 0.4 A.

J Wildl Dis, 1991 Oct, 27(4), 557 - 61
S-layer positive motile aeromonads isolated from channel catfish; Ford LA et al.; Motile aeromonads are ubiquitous aquatic bacteria that can cause motile aeromonad septicemia (MAS), a disease which affects channel catfish and can produce significant economic loss . Motile aeromonads isolated from commercially-raised channel catfish were screened for production of S-layer protein in order to evaluate its potential role in natural epizootics . The S-layer protein was produced by 14 of 24 (58%) isolates from epizootics evaluated in this study . Concomitant infections with other internal pathogens were detected in 10 of the 24 cases used in this study, and only one of those 10 isolates (10%) produced the S-layer protein . When Aeromonas sp . was the only internal pathogen diagnosed, 13 of 14 (93%) isolates produced the S-layer protein.

Clin Microbiol Rev, 1991 Oct, 4(4), 397 - 410
Recent advances in the study of the taxonomy, pathogenicity, and infectious syndromes associated with the genus Aeromonas; Janda JM; Over the past decade, the emergence of Aeromonas species as bona fide human pathogens and their probable role as etiologic agents of bacterial gastroenteritis have resulted in an explosion of scientific interest in the genus . Major accomplishments occurring in this field during that interval include a more refined taxonomy, identification of new cell-associated factors (surface layers, pili), and the molecular analysis of selected extracellular gene products that may play a critical role in pathogenesis (hemolysins, enterotoxins) . This review provides an updated overview of recent systematic, clinical, and pathophysiologic advances and defines key areas of medical and scientific interest in which major questions remain unanswered.

Infect Immun, 1991 Oct, 59(10), 3478 - 83
Purification and characterization of Aeromonas sobria pili, a possible colonization factor; Hokama A et al.; Pili of Aeromonas sobria Ae1 were purified and characterized . The molecular mass of the pilin was estimated to be about 23 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis . The Ae1 pili were electrophoretically and immunologically distinguishable from the W pili of A . hydrophila Ae6, although the two pili were morphologically indistinguishable . The N-terminal amino acid sequences of the two pilins were identical in the first 10 residues . Strain Ae1 and its purified pili adhered to human and rabbit intestines and agglutinated human and rabbit erythrocytes . Hemagglutination was inhibited by D-galactose and D-mannose, but not by L-fucose . Organisms pretreated with the Fab fraction of the antipilus antibody failed to adhere to the intestines . Organisms did not adhere to intestines pretreated with the purified pili . These findings suggest that the pili are a colonization factor of A . sobria Ae1.

FEMS Microbiol Lett, 1991 Sep 15, 67(1), 115 - 9
Specific binding of lactoferrin to Aeromonas hydrophila; Kishore AR et al.; The interaction of lactoferrin (Lf) with Aeromonas hydrophila (n = 28) was tested in a 125I-labeled protein-binding assay . The mean per cent binding values for human Lf (HLf) and bovine Lf (BLf) were 13.4 +/- 2.0 (SEM), and 17.5 +/- 2.7 (SEM), respectively . The Lf binding was characterized in type strain A . hydrophila subsp . hydrophila CCUG 14551 . The HLf and BLf binding reached a complete saturation within 2 h . Unlabeled HLf and BLf displaced 125I-HLf binding in a dose-dependent manner, and more effectively by the heterologous (1 microgram for 50% inhibition) than the homologous (10 micrograms for 50% inhibition) ligand . Apo- and holo-forms of HLf and BLf both inhibited more than 80%, while mucin caused approx . 50% inhibition of the HLf binding . Various other proteins (including transferrin) or carbohydrates did not block the binding . Two HLf-binding proteins with an estimated molecular masses of 40 kDa and 30 kDa were identified in a boiled-cell-envelope preparation, while the unboiled cell envelope demonstrated a short-ladder pattern at the top of the separating gel and a second band at approx . 60 kDa position . These data establish a specific interaction of Lf and the Lf-binding proteins seem to be porins in A . hydrophila.

Microb Pathog, 1991 Sep, 11(3), 189 - 97
Nucleotide sequence and expression of an extracellular hemolysin gene of Aeromonas hydrophila; Hirono I et al.; The extracellular hemolysin (AHH1) gene of Aeromonas hydrophila ATCC7966 was cloned into Charomid9-28 in Escherichia coli DH1, and its complete nucleotide sequence determined . Escherichia coli carrying this gene expressed an extracellular heat-labile hemolysin for rabbit red blood cells . The minimum size of the coding region of the 2.6 kilobase-pair BamHI-SphI fragment was subcloned into pUC118 and pUC119, selecting for hemolytic activity . The nucleotide sequence of this region contained a single open reading frame of 1734 base pairs, corresponding to a protein of 577 amino acid residues (63,658 daltons) . A consensus promoter sequence was present upstream of the AHH1 open reading frame . Maxicell analysis of {35S}methionine-labelled proteins in E . coli CSR603 carrying the AHH1 plasmid suggested that AHH1 gene codes for an approximately 60,000 dalton polypeptide . By colony DNA-DNA hybridization analysis, the AHH1 gene was detected in 43 of 62 hemolysin-producing strains of A . hydrophila (isolated from various sources and areas) and in all 43 hemolysin-producing strains of A . salmonicida (isolated from fish) . Three hemolysin-negative strains of A . hydrophila did not react with the AHH1 probe, whereas three non-hemolytic A . salmonicida strains hybridized with the probe.

J Biol Chem, 1991 Aug 15, 266(23), 15258 - 65
Structure of the tetragonal surface virulence array protein and gene of Aeromonas salmonicida; Chu S et al.; The paracrystalline surface protein array of the pathogenic bacterium Aeromonas salmonicida is a primary virulence factor with novel binding capabilities . The species-specific structural gene (vapA) for this array protein (A-protein) was cloned into lambda gt11 but was unstable when expressed in Escherichia coli, undergoing an 816-base pair deletion due to a 21-base pair direct repeat within the gene . However, the gene was stable in cosmid pLA2917 as long as expression was poor . A-protein was located in the cytoplasmic, inner membrane and periplasmic fractions in E . coli . The DNA sequence revealed a 1,506-base pair open reading frame encoding a protein consisting of a 21-amino acid signal peptide, and a 481-residue 50,778 molecular weight protein containing considerable secondary structure . When assembled into a paracrystalline protein array on Aeromonas the cell surface A-protein was totally refractile to cleavage by trypsin, but became trypsin sensitive when disassembled . Trypsin cleavage of the isolated protein provided evidence that both the NH2- and COOH-terminal regions form distinct structural domains, consistent with three-dimensional ultrastructural evidence . The NH2-terminal 274-residue domain remained refractile to trypsin activity . This segment connects by a trypsin and CNBr-sensitive 78-residue linker region to a COOH-terminal 129-residue fragment which could apparently refold into a partially trypsin-resistant structure after cleavage at residue 323.

J Biol Chem, 1991 Aug 5, 266(22), 14451 - 6
Site-directed mutagenesis of a single tryptophan near the middle of the channel-forming toxin aerolysin inhibits its transfer across the outer membrane of Aeromonas salmonicida; Wong KR et al.; The channel-forming protein aerolysin must cross both the inner and outer bacterial membranes during its secretion from Aeromonas hydrophila or from Aeromonas salmonicida containing the cloned structural gene . We examined the fate of three mutant proteins in which Trp-227, near the middle of the amino acid chain, was replaced with glycine, leucine, or phenylalanine by site-directed mutagenesis . All three proteins crossed the inner membrane and entered the periplasm in the same way as wild-type, and in each case the signal sequence was removed correctly . Little or none of the proaerolysin substituted with glycine or leucine was released into the culture supernatant . Instead, significant amounts became associated with the outer membrane . The Phe-227 protoxin was secreted by the bacteria but at a reduced rate . The leucine and phenylalanine mutant proteins were purified and compared with native proaerolysin . They were processed correctly to the mature forms by treatment with trypsin, and like native aerolysin, both were resistant to further proteolysis . In each case, processing was followed by the formation of oligomers similar to those produced by native toxin . The hemolytic activity of the processed Phe-227 mutant was one-quarter that of wild-type toxin whereas Leu-227 aerolysin had less than one-hundredth the wild-type activity . These results are further evidence that aerolysin is secreted in at least two steps . As well, they show that the last step, crossing the outer membrane, can be blocked by an apparently small change in the structure of the protein.

Microb Pathog, 1991 Aug, 11(2), 85 - 99
Surface-disorganized, attenuated mutants of Aeromonas salmonicida as furunculosis live vaccines; Thornton JC et al.; A slow-growing, aminoglycoside-resistant mutant and a rapidly-growing pseudo-revertant were isolated from Aeromonas salmonicida, the causative agent of salmonid furunculosis . These mutants continued to elicit a variety of classical virulence factors associated with A . salmonicida pathogenesis . They differed morphologically from the wild-type and from one another with respect to A-layer organization, membrane antagonist sensitivity and particularly to aerobic metabolism . Both mutants were drastically altered in the architecture of the 2D crystalline surface array (A-layer), although both were similar to wild-type with respect to cell surface composition . The slow-growing, antibiotic-resistant mutant differed significantly from the wild-type by the apparent loss of virtually all aerobic metabolism; the pseudo-revertant had partially recovered the ability to aerobically metabolize certain carbon sources . Both mutants were avirulent and incapable of tissue persistence . The rapidly-growing, antibiotic-sensitive pseudo-revertant, when administered either intraperitoneally or by immersion, effectively protected salmonid fish from challenge by a heterologous virulent stain suggesting its candidature as a live, attenuated furunculosis vaccine.

Microb Pathog, 1991 Aug, 11(2), 101 - 10
An extracellular acetylcholinesterase produced by Aeromonas hydrophila is a major lethal toxin for fish; Nieto TP et al.; A hitherto unrecognised lethal toxin from the extracellular products (ECP) of Aeromonas hydrophila is described . The pure toxin was 300 times more toxic than the crude ECP and is the most toxic substance so far described from this bacterium, with a minimum lethal dose of 0.05 micrograms g-1 fish . The toxin had high acetylcholinesterase activity and occurred in native ECP as a monomeric 15.5 kDa polypeptide . The purified toxin had five isoelectric focusing forms ranging from pl 4.45 to 4.70 . The ECP of each of six strains of A . hydrophila isolated from fish possessed acetylcholinesterase activity suggesting that the toxin is common in this species . The toxin was not a cytolysin and produced no gross pathology in injected fish . Its enzymic nature, low lethal dose, lack of tissue pathology and its apparent narcotic effect suggest that this toxin may act upon the central nervous system of the fish.

J Bacteriol, 1991 Aug, 173(16), 5121 - 8
Cloning, mutagenesis, and nucleotide sequence of a siderophore biosynthetic gene (amoA) from Aeromonas hydrophila; Barghouthi S et al.; Many isolates of the Aeromonas species produce amonabactin, a phenolate siderophore containing 2,3-dihydroxybenzoic acid (2,3-DHB) . An amonabactin biosynthetic gene (amoA) was identified (in a Sau3A1 gene library of Aeromonas hydrophila 495A2 chromosomal DNA) by its complementation of the requirement of Escherichia coli SAB11 for exogenous 2,3-DHB to support siderophore (enterobactin) synthesis . The gene amoA was subcloned as a SalI-HindIII 3.4-kb DNA fragment into pSUP202, and the complete nucleotide sequence of amoA was determined . A putative iron-regulatory sequence resembling the Fur repressor protein-binding site overlapped a possible promoter region . A translational reading frame, beginning with valine and encoding 396 amino acids, was open for 1,188 bp . The C-terminal portion of the deduced amino acid sequence showed 58% identity and 79% similarity with the E . coli EntC protein (isochorismate synthetase), the first enzyme in the E . coli 2,3-DHB biosynthetic pathway, suggesting that amoA probably encodes a step in 2,3-DHB biosynthesis and is the A . hydrophila equivalent of the E . coli entC gene . An isogenic amonabactin-negative mutant, A . hydrophila SB22, was isolated after marker exchange mutagenesis with Tn5-inactivated amoA (amoA::Tn5) . The mutant excreted neither 2,3-DHB nor amonabactin, was more sensitive than the wild-type to growth inhibition by iron restriction, and used amonabactin to overcome iron starvation.

Appl Environ Microbiol, 1991 Aug, 57(8), 2426 - 8
Cloning and expression of a chitinase gene from Aeromonas hydrophila in Escherichia coli; Chen JP et al.; An extracellular secreted chitinase gene from Aeromonas hydrophila was cloned in Escherichia coli, and the gene product was detected in the culture medium . Like the natural chitinase protein, the excreted chitinase had a molecular weight of approximately 85,000 and was subject to catabolite repression by glucose.

J Gen Microbiol, 1991 Jul, 137 ( Pt 7), 1583 - 90
The role of lipopolysaccharide in complement-killing of Aeromonas hydrophila strains of serotype O:34; Merino S et al.; The role of lipopolysaccharide (LPS) in the susceptibility of Aeromonas hydrophila strains of serotype O:34 to non-immune human serum was investigated using isogenic mutants (serum-sensitive), previously obtained on the basis of phage resistance, and characterized for their surface components . The classical complement pathway was found to be principally involved in the serum-killing of these sensitive strains . LPS preparations from serum-resistant or serum-sensitive strains, or purified core oligosaccharides (low-molecular-mass LPS) inactivated both bactericidal and complement activity of whole serum, while the O-antigen molecules (high-molecular-mass LPS) did not . The results indicate that LPS core oligosaccharide composition contributes to complement resistance of A . hydrophila strains from serotype O:34 with moderate virulence.

Kansenshogaku Zasshi, 1991 Jul, 65(7), 813 - 9
{Studies on motile-Aeromonas infection: 2) . Development of a bacteriophage typing system for motile Aeromonas}; Fukuyama M et al.; We succeeded in isolating Aeromonas-susceptible phages from river water and mud after a few years (1983-1985) of painstaking effort . For the first time in Japan, we investigated phagetypes of the bacterial strains isolated . The results obtained are summarized as follows: 1) Aeromonas-susceptible phages were isolated from 82 (40.1%) of 195 samples of river water and from 23 (25.6%) of 90 samples of river mud . By the cross-matching test of the phages isolated from the 105 samples, these were classified into 13 type groups (Groups I-XIII) . 2) When 594 Aeromonas strains isolated from river water, lake water, river mud and fresh-water fish were examined using the phage group patterns developed by us, 129 (21.7%) strains classified into these phagetypes . Phagetyping was possible for 11 (15.5%) of the 71 strains isolated from river and lake water, for 29 (35.4%) of the 82 strains from river mud and for 89 (20.2%) of the 441 strains from fresh-water fish . By bacterial species, phagetyping was possible for 53 (51.5%) of the 103 strains of A . hydrophila . 21 (7.2%) of the 292 strains of A . sobria, 13 (8.8%) of the 148 strains of A . caviae and 42 (82.4%) of the 51 strains of Aeromonas spp. . Especially the phages classified as Groups I, IV and VI amounted to the majority . Thus we succeeded in isolating Aeromonas-susceptible phages which could be classified into Groups I-XIII . The results suggested the possibility of utilizing this phagetyping for analysis of the ecological distribution of genus Aeromonas.

Int J Food Microbiol, 1991 Jul, 13(3), 217 - 24
Behavior of Aeromonas species at refrigeration temperatures; Beuchat LR; The ability of many strains of Aeromonas hydrophila and A . sobria to produce several types of virulence factors has been documented . The presence of Aeromonas in drinking water, as well as in river and saline waters and on various finfish and shellfish taken from them, has caused some concern relative to the role this bacterium plays as a causative agent of human gastroenteritis . The fairly common occurrence of Aeromonas on red meats, poultry and fresh produce and its ability to grow at 4 degrees C gives rise to further concern over public health risks which may be associated with consumption of these foods . A brief overview of the behavior of Aeromonas species at refrigeration temperatures is presented.

J Med Microbiol, 1991 Jun, 34(6), 363 - 7
Exotoxin profiles of clinical isolates of Aeromonas hydrophila; Vadivelu J et al.; Eighty-six clinical isolates of Aeromonas hydrophila were studied for their ability to produce four exotoxins: a haemolysin active against rabbit erythrocytes, cytotoxin and enterotoxin detectable with Vero cell cultures, and the cholera toxin-like factor detected by an enzyme-linked immunosorbent assay . At least one exotoxin was produced by 80% of enteric and 96% of non-enteric isolates . The exotoxin profiles of non-enteric isolates were more restricted than those of enteric isolates, with haemolysin and cytotoxin producers preponderant . Although haemolysin and cytotoxin were produced by isolates from all sources, the enterotoxin and cholera toxin-like factor were more common amongst enteric isolates . The production of haemolysin and cytotoxin were closely related but the association between the enterotoxin and the cholera toxin-like factor was not significant.

Enferm Infecc Microbiol Clin, 1991 Jun-Jul, 9(6), 329 - 34
{Aeromonas spp . isolated from human feces . Species and pathogenicity factors}; Acosta B et al.; The role of Aeromonas genus as a primary intestinal pathogen is still a matter of controversy . We have studied the isolation of Aeromonas spp . from human stools samples, looking for the production of pathogenic factors and its relationship with different species . From a total of 471 strains isolated, 241 were A . caviae, 127 A . sobria, 89 A . hydrophila and 14 non-typable strains . The pathogenic factors production was studied in a bacteria-free filtrate from a 18 hours trypticase-soy broth culture . Enterotoxin production was assessed by suckling-mice test, cytotoxin production by using Hela cells monolayer and hemolysin production by double dilution from the filtrate, plated in microdilution plates, against rabbit red-blood cells . Enterotoxin production test was positive for A . sobria, A . hydrophila and A . caviae in 81.1%, 62.9% and 7.0% of strains respectively . Cytotoxin production was also positive for these species in 96.6%, 76.4% and 4.1%, and hemolysin production was positive in 95.3%, 70.7% and 2.4% of the strains respectively.

J Gen Microbiol, 1991 Jun, 137 ( Pt 6), 1341 - 3
Atypical characteristics of the salmonid pathogen Aeromonas salmonicida; McIntosh D et al.; Incubation of Aeromonas salmonicida at supra-optimal temperatures, i.e . 30-37 degrees C, resulted in the expression of motility by polar flagella, and changes in sugar fermentation patterns, e.g . loss of acid production from mannitol, loss of the ability to degrade complex molecules (aesculin, DNA, elastin and gelatin), and an increase in antibiotic resistance (notably co-trimoxazole) . Motility was enhanced in cultures grown in brain heart infusion broth supplemented with 18% (w/v) Ficoll.

Int J Food Microbiol, 1991 Jun, 13(2), 165 - 75
Growth of and toxin production by Aeromonas hydrophila and Aeromonas sobria at low temperatures; Krovacek K et al.; The effects of different temperatures on the growth and toxin production of Aeromonas hydrophila and Aeromonas sobria were studied . The results showed that these Aeromonas species are not only able to grow at low temperatures (e.g . at 4 and 10 degrees C) but may also produce cytotoxin, hemolysin and enterotoxin under suitable growth conditions.

Appl Environ Microbiol, 1991 Jun, 57(6), 1777 - 82
Survival of Aeromonas salmonicida in lake water; Morgan JA et al.; The survival of Aeromonas salmonicida subsp . salmonicida in lake water was investigated by using a variety of techniques . They included acridine orange epifluorescence, respiration, cell culture, cell revival, flow cytometry, plasmid maintenance, and membrane fatty acid analysis . During a 21-day study, A . salmonicida became nonculturable in sterile lake water samples . Flow cytometry and direct microscopy indicated that cells were present . Although the nonculturable cells could not be revived, the recovery method did indicate that the presence of low numbers of culturable cells within samples could produce misleading results . Plasmid DNA, genomic DNA, and RNA were maintained in the nonculturable cells; in addition, changes in the fatty acid profiles were also detected . Although viability could not be proven, it was shown that the morphological integrity of nonculturable cells was maintained.

Experientia, 1991 May 15, 47(5), 437 - 9
Spectrum of Aeromonas and Plesiomonas infections in patients with cancer and AIDS; Rolston KV et al.; The spectrum of infection with Aeromonas and Plesiomonas included gastroenteritis, bacteremia, biliary tract infection, perirectal infection, and disseminated disease . Most patients (86%) with bacteremia were neutropenic (less than 500 PMN/mm3) . Colonization of stools and sputum also occurred . Therapy with aminoglycosides, beta-lactams, trimethoprim/sulfamethoxazole, and the newer quinolones was effective in patients with AIDS and cancer.

Experientia, 1991 May 15, 47(5), 434 - 6
Aeromonas caviae: ecologic adaptation in the intestinal tract of infants coupled to adherence and enterotoxin production as factors in enteropathogenicity; Namdari H et al.; Aeromonas caviae isolated from stools of diarrheic formula-fed infants and environmental sources produce acetic acid when grown in glucose broth, which is bactericidal (suicide phenomenon) . A . caviae grows anaerobically in a minimal medium or under permissive conditions such as the intestinal tract of formula-fed infants . These isolates adhered to HEp-2 cells and produced a cytotoxic and a cytotonic enterotoxin which underscore their enteropathogenicity.

Experientia, 1991 May 15, 47(5), 426 - 9
Re-examination of Rattus norvegicus as an animal model for Aeromonas-associated enteritis in man; Haberberger RL Jr et al.; We have developed an oral feeding model for Aeromonas hydrophila enteritis using Rattus norvegicus with clindamycin pretreatment . All animals in the clindamycin group developed a self-limited, loose stool by day four of feeding . Intestinal examination revealed evidence of enteritis . Moreover, antibiotic usage may be a predisposing risk factor to infection.

Experientia, 1991 May 15, 47(5), 424 - 6
Review of Aeromonas enterotoxins; Houston CW et al.; This report reviews the work of other investigators regarding Aeromonas toxins and describes work conducted in our laboratory relating to the biochemical characterization of a cytolytic factor with an antigenic moiety that cross-reacts with cholera toxin (referred to as CTC-cytolysin), as well as the purification and partial characterization of a non-CTC enterotoxin . These two toxins were produced by Aeromonas hydrophila, isolate SSU, and are capable of causing fluid accumulation in animal models.

Experientia, 1991 May 15, 47(5), 421 - 4
Application of the polymerase chain reaction (PCR) to detection of the aerolysin gene in whole cell cultures of beta-hemolytic Aeromonas hydrophila; Lior H et al.; Oligonucleotide primers were used in a polymerase chain reaction protocol to detect the aerolysin gene in Aeromonas hydrophila . Primers detected template DNA in hemolytic, cytotoxic and enterotoxic strains of A . hydrophila and no amplification was detected with hemolytic A . sobria, non-hemolytic A . hydrophila and A . caviae strains.

Experientia, 1991 May 15, 47(5), 420 - 1
Studies on aerolysin and a serine protease from Aeromonas trota sp . nov; Husslein V et al.; Hybridization of 257 mesophilic aeromonads revealed that the aerolysin gene is present in virtually all strains irrespective of origin of isolation . A probe comprising the promotor region was specific for a species now defined as Aeromonas trota sp . nov . Finally, isolation of a serine protease that is concomitantly expressed with aerolysin is described.

Experientia, 1991 May 15, 47(5), 418 - 9
Secretion and mechanism of action of the hole-forming toxin aerolysin; Buckley JT; Aeromonas hydrophila exports aerolysin as a protoxin which is activated by proteolysis after release . Aerolysin binds to the eucaryotic cell receptor glycophorin and oligomerizes, forming holes in the membrane . Important regions of the molecule have been identified by site-directed mutagenesis, and channel formation has been studied in planar lipid bilayers.

Experientia, 1991 May 15, 47(5), 414 - 6
New lectins and other putative adhesins in Aeromonas hydrophila; Ascencio F et al.; The ability of strains of Aeromonas hydrophila to bind 125I-labelled collagen types I and IV, fibronectin, laminin, lactoferrin, and immobilized mucins and orosomucoid on latex beads was found to be a property common to all the isolated strains . The binding was specific, was inhibited by homologous unlabelled glycoproteins, and was protease sensitive . The nature of the binding is discussed.

Experientia, 1991 May 15, 47(5), 412 - 4
Form and functions of the regular surface array (S-layer) of Aeromonas salmonicida; Kay WW et al.; The principal virulence factor of Aeromonas salmonicida is its S-layer (A-layer) which is comprised of tetragonally arrayed approximately 50,000 Mr protein subunits tethered to the cell surface via LPS . The detailed composition of its LPS is known, as is the primary sequence, and three-dimensional disposition of the A protein subunits . The A-layer physically protects the cell against bacteriophage, proteases, as well as immune and non-immune complement . The A-layer appears to be uniquely adapted towards binding biologically important molecules such as heme, and to various basement membrane proteins . In addition, the A-layer is required for macrophage infiltration and resistance . Specific mutants containing a disorganized A-layer are avirulent and provide significant protection to salmonids when applied by immersion.

Experientia, 1991 May 15, 47(5), 406 - 9
The taxonomy and nomenclature of the psychrotrophic aeromonads; Schubert RH; Following the introduction of the DNA hybridization technique several genotypes have been separated from the older phenotypically described Aeromonas species . Work has been undertaken on some arbutin-negative psychrotrophic Aeromonas strains . These were differentiated into three genotypically and phenotypically identifiable groups . One group (I) is genetically related to A . sobria (type 208) . The two other groups (II and J) can be separated genotypically and phenotypically from the A . sobria, A . veronii and A . hydrophila genotypes . Studies on ADH-negative anaerogenic surface water aeromonads showed them to be genotypically more distant from A . punctata type 239 than from type 545.

Experientia, 1991 May 15, 47(5), 402 - 3
Aeromonas update: new species and global distribution; Carnahan AM et al.; There are currently eight proposed or validated Aeromonas spp . of which five have been implicated in human disease: A . hydrophila, A . sobria, A . caviae, A . veronii, and A . schubertii . Recent studies have extended the geographic distribution and source of isolation of the newer species and resulted in the possibility of two new species, A . jandaei and A . trota, from diarrheal, wound, blood and environmental sources.

Experientia, 1991 May 15, 47(5), 416 - 8
Iron acquisition and virulence in the motile aeromonads: siderophore-dependent and -independent systems; Byers BR et al.; During an infection, a microbial pathogen must acquire all of its iron from the host . Aeromonas isolated producing the siderophore amonabactin obtain iron either from host Fe-transferrin (siderophore dependent) or from host heme-containing molecules (siderophore independent) . Isolates producing the siderophore enterobactin do not utilize Fe-transferrin in serum and probably rely exclusively on host heme iron.

Experientia, 1991 May 15, 47(5), 403 - 6
Methods for the identification of DNA hybridization groups in the genus Aeromonas; Altwegg M et al.; Among the 269 substrates tested in assimilation tests we found some that may help in the identification of DNA hybridization groups in the genus Aeromonas . In addition, isoenzyme analysis and ribotyping seem to be accurate although not routine procedures that allow discrimination between genetic species.

J Clin Microbiol, 1991 May, 29(5), 853 - 6
Aeromonas spp . and their association with human diarrheal disease; Deodhar LP et al.; Between January 1988 and December 1989 Aeromonas species were isolated from 45 (1.8%) of 2,480 patients with acute gastroenteritis . No other bacterial enteric pathogens were found in any of these 45 patients . Of the 45 Aeromonas isolates, 35 strains (77.8%) were Aeromonas hydrophila, 7 (15.5%) were Aeromonas sobria, and 3 (6.7%) were Aeromonas caviae . Most of the patients were under 5 years of age . No bacterial enteric pathogens, including Aeromonas species, were isolated from 512 age- and sex-matched control subjects . Examination of the Aeromonas isolates for exotoxin production (enterotoxin and hemolysin) indicated that all strains, irrespective of species, were enterotoxin positive (rabbit ileal loop model) and hemolysin positive (rabbit erythrocyte model) . These results suggest that Aeromonas species are potential enteric pathogens in our geographical region.

J Clin Microbiol, 1991 May, 29(5), 1056 - 7
Unusual case of Aeromonas hydrophila endocarditis; Ong KR et al.; We describe a case of Aeromonas hydrophila endocarditis in a 66-year-old man with myelodysplastic syndrome and non-A, non-B hepatitis, The infection resolved with antibiotic therapy, but the patient succumbed to complications of his underlying illness . This is the second case of Aeromonas endocarditis reported in the world literature.

Pediatr Nephrol, 1991 May, 5(3), 293 - 5
Haemolytic-uraemic syndrome associated with Aeromonas hydrophila enterocolitis; Bogdanovic R et al.; Haemolytic-uraemic syndrome (HUS) associated with Aeromonas hydrophila enterocolitis is reported in a 23-month-old female infant . The A . hydrophila strain isolated from the patient's stool sample produced cytotoxin against verocells; increasing levels of cytotoxin-neutralizing antibody in the patient's sera were demonstrated, suggesting a recent infection . This report indicates that A . hydrophila should be suspected as a possible cause of HUS, and that this pathogen should be looked for in cases of post-diarrhoeal HUS.

J Gen Microbiol, 1991 May, 137 ( Pt 5), 1185 - 92
Siderophore production by Aeromonas salmonicida; Hirst ID et al.; Growth under conditions of iron-restriction and the production of siderophores was examined in 21 typical and 14 atypical strains of Aeromonas salmonicida . With the exception of one atypical strain, all strains grew and multiplied in the presence of the high-affinity iron chelators ethylenediamine di(o-hydroxyphenylacetic acid), alpha, alpha'-dipyridyl or transferrin . Chrome azurol S agar was used to screen bacterial strains growing under these conditions for the production of siderophores . Siderophore production was detected only in the typical strains . Siderophores were also detected in the iron-restricted culture supernatants of typical strains . Siderophores were also detected in the iron-restricted culture supernatants of typical strains, where they were associated with an iron-binding activity . The siderophore was extracted from iron-restricted culture supernatant of one strain by adsorption onto an XAD-7 resin; it behaved as a 2,3-diphenol-catechol in several colorimetric assays . The results indicate that although both typical and atypical strains of A . salmonicida grow and multiply under conditions of iron-restriction, they use different iron-uptake mechanisms, siderophore-mediated and siderophore-independent, respectively . In cross-feeding assays, growth of typical strains was stimulated only by homologous iron-restricted supernatant, suggesting strain differences in the siderophore produced . However, one strain produced a culture supernatant with growth-stimulating activity for other typical and also atypical strains.

Zentralbl Veterinarmed B, 1991 May, 38(3), 186 - 94
Carp erythrodermatitis (CE) due to an Aeromonas hydrophila infection . Casuistic and experimental results; Sioutas S et al.; In November 1987 high losses of carp (Cyprinus carpio) with the main symptom of skin ulcera were observed in a farm in northern Greece . Sixty-six isolates of bacteria, characterized mainly as Aeromonas hydrophila or Pseudomonas spp . could be isolated from lesions of diseased fish . Transmission experiments with these isolates using mirror carp showed that Aeromonas hydrophila strains induced identical clinical and pathological pictures after intra- or subcutaneous injection . Extracts of these Aeromonas hydrophila isolates, as well as a supernatant of culture bouillon were toxic for carp and mice, indicating the presence of endo- and exotoxins . The results prove that carp erythrodermatitis (CE) may be caused by different bacteria, mainly including A . hydrophila.

Cesk Epidemiol Mikrobiol Imunol, 1991 May, 40(3), 177 - 90
{The Aeromonas genus}; Aldova E et al.; Aeromonas hydrophila manifested itself since its discovery in 1891 as a pathogen of cold-blooded and warm-blooded animals and man . Aeromonads cause intestinal and non-intestinal disease . The genus Aeromonas comprises: A . hydrophila, A . sorbria, A . caviae, A . veronii, A . schubertii, i.e . mesophilie species and as to psychrophilie immobile species . A . salmonicida and A . media . For warm-blooded animals and man mesophilie motile species are important as pathogens . A . veronii is an ornithine-decarboxylase positive species, A . schubertii is mannitol-negative, A . caviae is non-haemolytic and VP-negative . It is difficult to differentiate . A . hydrophila with aerogenic and anaerogenic strains from A . sobria . Several practical differential diagnostic tests were suggested by Janda et al . and Joseph et al.: hydrolysis of esculine, KCN, arabinose and salicin are usually positive in A . hydrophila, in A . sobria usually negative . Existing species of mesophilie aeromonads, however, do not correspond to some strains which are found . Therefore Arduino et al . divided their aeromonads into DNA-hybridization groups: for A . hydrophila there were 5, for A . caviae 2 and for A . sobria 1 hybridization group . Biochemisal characteristics corresponded to the hybridization groups . For isolation of aeromonads from faeces selective media with ampicillin must be used and possibly enrichment in alkaline peptone water . Evidence of pathogenity factors is similar as in E . coli,: detection of adhesins and enterotoxin or cytotoxin by means of tests commonly used in cholera and E . coli . The types of adhesins are differentiated by means of fucose- galactose- and mannose resistant haemagglutination.(ABSTRACT TRUNCATED AT 250 WORDS)

Antonie Van Leeuwenhoek, 1991 May, 59(4), 225 - 8
Comparison of different media for the identification and quantification of Aeromonas spp . in water; Ribas F et al.; In order to assess the suitability of the Starch glutamate ampicillin penicillin-10C agar for the isolation of Aeromonas spp . from waters it was necessary to compare the properties of this medium with those of three others, Starch ampicillin agar, Ampicillin dextrin agar and m-Aeromonas medium, and to monitor different kinds of waters . A selection of forty eight samples were taken from moderately polluted river water, highly polluted river water, polluted sea water (littoral) and treatment & distribution water and monitored using these media . The results were similar with Ampicillin dextrin agar, m-Aeromonas medium and Starch glutamate ampicillin penicillin-10C, but the simplicity of composition and use and its selectivity recommends the last medium as the most adequate for the isolation of Aeromonas spp.

Sci Total Environ, 1991 Apr 15, 103(2-3), 229 - 43
Comparative toxicity of organotin compounds to rainbow trout (Oncorhynchus mykiss) yolk sac fry; de Vries H et al.; The comparative toxicity of various organotin compounds was investigated in early life stages of the rainbow trout . Beginning with yolk sac fry, trout were continuously exposed for 110 days to tributyl- (TBTC), triphenyl- (TPhTC) or tricyclohexyltin chloride (TCHTC) at concentrations of 0.12-15 nM, to trimethyltin chloride (TMTC) at concentrations of 3-75 nM or to dibutyl- (DBTC) or diphenyltin chloride (DPhTC) at 160-4000 nM . The diorganotin compounds DBTC and DPhTC were about three orders of magnitude less toxic than the triorganotin homologs TBTC and TPhTC . Both for DBTC and DPhTC, a no-observable-effect concentration (NOEC) of 160 nM was established, corresponding to 40 and 60 ppb, respectively . Of the triorganotin compounds, TCHTC appeared to be the most toxic, inducing 100% mortality within 1 week at a concentration of 3 nM . Only a few trout survived exposure to 0.6 nM TCHTC for 110 days . TBTC and TPhTC caused acute mortality at a concentration of 15 nM . For both TBTC and TPhTC a NOEC of 0.12 nM was established, corresponding to water concentrations of 40 and 50 ppt, respectively . Histopathological examination revealed depletion of glycogen in liver cells of both di- and triorganotin exposed fish, except in the case of TMTC . No signs of toxicity were observed in fish exposed to up to 75 nM TMTC, the highest concentration tested . Atrophy of the thymus, the most prominent sign of toxicity of di- and tributyltin compounds in mammalian species, was not observed in early life stages of rainbow trout . Tail melanization was observed in the groups exposed to 3 nM TPhTC, 3 nM TBTC, 800 nM DBTC and 800 nM DPhTC . At the end of the exposure period, resistance to infection was examined by an intraperitoneal challenge with Aeromonas hydrophila, a secondary pathogenic bacterium to fish . Resistance of bacterial challenge was found to be decreased even at the lowest-effect concentration of both di- and triorganotin compounds.

J Wildl Dis, 1991 Apr, 27(2), 206 - 13
Effect of Lernaea cyprinacea (Crustacea: Copepoda) on stocked rainbow trout (Oncorhynchus mykiss); Berry CR Jr et al.; Prevalence, intensity and pathogenesis of Lernaea cyprinacea (anchorworm) in stocked rainbow trout (Oncorhynchus mykiss) fingerlings were monitored annually for 4 yr (1981 to 1984) in East Canyon Reservoir, Utah (USA) . Anchorworms were first detected in midsummer each year and were most abundant in the fall . The mean parasite intensity was highest in October 1982 (19 anchorworms per fish); in other years, maximum density was 7 to 9 . The dorsal and caudal areas of the fish were the most heavily parasitized . The histological response to parasite attachment included an infectious granuloma similar to that reported in other fish hosts . Bacteria were not found in the kidneys of fish before stocking, but afterward bacteria that were presumptively identified as belonging to the genus Aeromonas, were found in the kidneys of up to 45% of the parasitized fish . Most (94%) anglers noticed the anchorworms, but few (8%) discarded parasitized fish . Some 28% used special cleaning techniques to prepare fish but 49% did nothing special to clean them . Lernaeosis probably had little effect on the fishery management goals for the reservoir.

Kinderarztl Prax, 1991 Apr, 59(4), 123 - 5
{Liver abscess caused by Aeromonas hydrophila}; Spencker FB et al.; Because of the rare incidence of liver abscess in childhood and of extremely rare observed Aeromonas hydrophila as pathogen of such a disease we report on a 14 7/12 year old girl with a liver abscess . For the last 4 years she had to be enrolled in chronic hemodialysis . The treatment comprised opening of the abscess cavity and drainage, and antibiotic therapy with cefotiam . We were unable to isolate Aeromonas hydrophila in the environment of the hemodialysis center . Some aspects of clinical importance of liver abscess in childhood and of Aeromonas spp . as pathogens in human infections are discussed.

J Infect Dis, 1991 Apr, 163(4), 890 - 4
Biochemical and genetic characterization of autoagglutinating phenotypes of Aeromonas species associated with invasive and noninvasive disease; Kokka RP et al.; The genetic characteristics and biochemical and structural properties of a number of autoagglutinating (AA) strains of Aeromonas associated with invasive and noninvasive disease in humans and infections in animals and from environmental sources were investigated . Of 27 strains analyzed by multilocus enzyme typing and DNA hybridization studies, 25 (93%) were confirmed to belong to either hybridization group 1 (phenospecies and genospecies Aeromonas hydrophila) or 8 (phenospecies Aeromonas sobria; genospecies Aeromonas veronii) . Further analysis of 19 of these strains indicated that four major groups could be identified on the basis of serologic and surface characteristics, protein and lipopolysaccharide composition, and virulence properties; these groupings held true regardless of the site of isolation or disease process involved . The major AA+ group identified was serogroup O:11, whose strains possessed an S layer, were resistant to the bactericidal activity of normal serum, and were pathogenic in mice . The results suggest a set of useful phenotypic and structural markers for identification of specific subsets of mesophilic Aeromonas involved in a wide range of infections in the animal kingdom.

Zentralbl Bakteriol, 1991 Apr, 275(1), 85 - 93
Susceptibilities of motile Aeromonas sp . to antimicrobial agents; Kaznowski A et al.; Resistance to antimicrobial agents of 106 isolates of motile Aeromonas sp . was characterized . The results indicated that in vitro susceptibilities among the three species of the motile Aeromonas sp . were similar, and only the distribution of susceptibility to cephalothin was different . The percentage of resistance of A . sobria strains was lower than the percentage of the resistant strains of A . hydrophila and A . caviae . All of the isolates were susceptible to kanamycin, nalidixic acid, tobramycin, amikacin, netilmicin, cefuroxime, ceftriaxone, cefoperazone and cefotaxime . Three of the tested strains (two A . hydrophila and one A . caviae) transferred resistance plasmids to the Aeromonas hydrophila recipient.

Zentralbl Bakteriol, 1991 Apr, 275(1), 28 - 45
Multilocus enzyme analysis of the genus Aeromonas and its use for species identification; Altwegg M et al.; A total of 153 Aeromonas strains were analyzed by multilocus enzyme electrophoresis . All 11 genetic loci were polymorphic with three to 14 alleles per locus (average 6.55) . The genetic diversity of each locus varied between 0.095 for indophenol oxidase and 0.881 for the fast variety of malic enzyme . Cluster analysis of the 122 enzyme types revealed a good correlation with taxonomic groupings as determined by DNA-DNA hybridization . In conjunction with biochemical analysis, as few as two enzymes may be sufficient for the identification of all species in the genus Aeromonas.

Zentralbl Bakteriol, 1991 Apr, 275(1), 1 - 10
Gas-liquid chromatographic analysis of cellular fatty acid methyl esters in Aeromonas species; Hansen W et al.; The cellular fatty acids of 39 strains belonging to the genus Aeromonas (Aeromonas hydrophila, Aeromonas caviae, Aeromonas sobria, Aeromonas media, Aeromonas schubertii, Aeromonas veronii) were determined by high resolution gas-liquid chromatography . The fatty acid profiles were characterized by major amounts (60% or more) of one saturated (hexadecanoic acid = 16:0) and two unsaturated (hexadecenoic acid = 16:1 and octadecenoic acid = 18:1) acids . While the majority of the strains of the six species exhibited, qualitatively, very similar fatty acid compositions, only minor and inconsistent differences could be observed which would be useful for a distinction of the different taxons . The following fatty acids were qualitatively identified: 12:0, i-13:0, 14:0, 3-OH 13:0, i-15:0, 15:0, 2-OH 14:0, 3-OH 14:0, i-16:0, 16:1, 16:0, i-17:1, i-17:0, a-17:0, 17:0 cyclopropane, 17:1, 17:0, 18:1 (3 isomers), 18:0 and i-20:0 . Excellent congruence was found in reproducibility studies . Fatty acid analyses show a great homogeneity within the group and the technique does not appear to be the ideal method in distinguishing between Aeromonas species.

Fundam Appl Toxicol, 1991 Apr, 16(3), 576 - 89
Development of fish peritoneal macrophages as a model for higher vertebrates in immunotoxicological studies . I . Characterization of trout macrophage morphological, functional, and biochemical properties; Zelikoff JT et al.; The immune defense mechanisms of fish are not as well characterized as those of mammals but seem to be related and similarly competent . Because of this, there is an increased interest in the immune responses of fish as models for higher vertebrates in immunotoxicological studies . Prior to such studies, baseline criteria for specific components of the immune response needed to be established . For this study, we have examined trout macrophage morphology using light and scanning electron microscopy, phagocytic activity, random and stimulus-directed migration, and superoxide anion radical (O2-) production for resident and lipopolysacharide (LPS) or Aeromonas salmonicidae-elicited rainbow trout (Oncorhynchus mykiss) peritoneal macrophages (M phi) . Following peritoneal lavage, greater than 89% of the cells were M phi as determined by differential counts and nonspecific esterase staining . Immunization with LPS and A . salmonicidae increased M phi number approximately 5 and 13-fold, respectively, and overall size . Trout M phi were phagocytically active engulfing serum opsonized latex particles and were mobile, migrating both randomly and in a directed fashion towards formyl-methionine-L-leucine-L-phenylalanine (FMLP) and trout serum-derived complement fragment C5a . Concentrations of FMLP (100 nM) and C5a (0.01-1%) effective for attracting trout M phi are the same as those used to attract rabbit M phi . Resident trout M phi produced negligable quantities of .O2- following stimulation with 1 micrograms/ml phorbol myristate acetate; Aeromonas-elicited M phi produced .O2- in a time-dependent manner which peaked after 60 min at 2.9 nmol per 2 x 10(5) cells and then declined . The results of this study provide a data base for future toxicological studies with trout peritoneal M phi and indicate the usefulness of this system for immunotoxicological studies.

FEMS Microbiol Lett, 1991 Mar 1, 62(2-3), 231 - 7
Genetic variation in related cytolytic toxins produced by different species of Aeromonas; Chopra AK et al.; Comparative analyses were performed at the immunological, biological, and genetic level to establish the degree of relatedness of a group of four cytotoxic enterotoxins and aerolysins produced by different isolates of Aeromonas: SSU {16}, Ah1 {13}, Ah2 {18}, and Ah65 {21} . Results obtained from Western blot analysis, neutralization studies, and Southern blot analysis indicated that although the members of this group of toxins displayed structural similarities they also differed from each other at the immunological, biological and genetic level.

J Clin Microbiol, 1991 Mar, 29(3), 565 - 9
Aeromonas jandaei and Aeromonas veronii dual infection of a human wound following aquatic exposure; Joseph SW et al.; Exudate removed from an infection that developed below the left eye of a 10-year-old male following a previously inflicted wound after aquatic exposure was cultured and revealed two different Aeromonas spp . Further characterization showed that one strain was phenotypically identical to Aeromonas veronii, while the other strain was confirmed by DNA hybridization analysis to be Aeromonas jandaei sp . nov . This is the first report of these more recently described aeromonads, thus far rarely reported from clinical disease, occurring simultaneously in a human infection.

Int J Food Microbiol, 1991 Feb, 12(2-3), 181 - 8
Experimental evidence for toxin production by Aeromonas hydrophila and Aeromonas sobria in a meat extract at low temperatures; Majeed KN et al.; The ability of enterotoxigenic strains of Aeromonas hydrophila and Aeromonas sobria to produce exotoxins (enterotoxin and haemolysin) in a meat extract at low temperatures (5 and 12 degrees C) was investigated . All three strains incubated at 12 degrees C were enterotoxigenic and haemolytic in the meat extract after 5 days . At 5 degrees C, five of the six strains tested were able to produce these exotoxins after 8 days incubation while one strain was neither enterotoxigenic nor haemolytic after 5, 8 and 11 days . The possible involvement of performed toxin(s) in Aeromonas gastroenteritis is also discussed.

Enferm Infecc Microbiol Clin, 1991 Feb, 9(2), 76 - 81
{Phenotypic characteristics of 100 strains belonging to the mesophilic aeromonas group isolated from feces}; Reina J et al.; Phenotypic characteristics of 100 strains pertaining to the group of mesophilic aeromonas isolated in feces of patients with diarrhea (23 A . hydrophila, 34 A . sobria, 19 A . caviae, and 24 considered atypical because produced a the negative esculin reaction and a positive gas formation from glucose {TSI}) . The percentages obtained in the different biochemical tests support the hypothesis that in this group there is a taxonomic complexity . We observed variations in the following tests: LDC, arabinose, Voges-Proskauser, lactose, and motility and hemolytic activity . We compared manual and automatic procedures in detecting esculinase and beta-galactosidase activity (ONPG) . The study of constitutional enzymatic activity by means of API ZYM system can not be used to differentiate the distinct species although the enzyme beta-glucosidase is detected preferentially in A . hydrophila.

J Bacteriol, 1991 Feb, 173(3), 1241 - 9
Mutagenesis and isolation of Aeromonas hydrophila genes which are required for extracellular secretion; Bo JN et al.; Transposon mutagenesis was used to isolate mutants of Aeromonas hydrophila which were deficient in the production of extracellular proteins . The culture supernatants of two of the mutants were essentially devoid of the proteins normally secreted by the parent strain, despite their continued synthesis . Western immunoblot analysis of one of these proteins indicated that normal signal sequence processing occurred but that normal zymogen activation did not, and cell fractionation experiments indicated that both mutants accumulated the three different extracellular proteins assayed in a position external to the cytoplasmic membrane, presumably in the periplasm . The two mutants differed, however, in that one was lysed during the osmotic shock procedures and also contained severely reduced amounts of two of the major protein components of the outer membrane . The wild-type chromosomal regions into which the transposon had been inserted in the two mutants were cloned . In each case, transconjugants of the mutants containing the corresponding cloned fragment were complemented for the defects in secretion, and one of the mutants was complemented by the heterologous clone as well, suggesting the possibility of an interaction between these two genes or gene products . These results indicate that two separate functions which are required for extracellular secretion were interrupted in the insertion mutants and that one of these is also critically important in the biogenesis of the outer membrane.

J Gen Microbiol, 1991 Feb, 137 ( Pt 2), 237 - 41
Acquisition of iron from host sources by mesophilic Aeromonas species; Massad G et al.; The mesophilic Aeromonas species are opportunistic pathogens that produce either of the siderophores amonabactin or enterobactin . Acquisition of iron for growth from Fe-transferrin in serum was dependent on the siderophore amonabactin; 50 of 54 amonabactin-producing isolates grew in heat-inactivated serum, whereas none of 30 enterobactin-producing strains were able to grow . Most isolates (regardless of siderophore produced) used haem as a sole source of iron for growth; all of 33 isolates grew with either haematin or haemoglobin and 30 of these used haemoglobin when complexed to human haptoglobin . Mutants unable to synthesize a siderophore used iron from haem, suggesting that this capacity was unrelated to siderophore production . Some members of the mesophilic Aeromonas species have evolved both siderophore-dependent and -independent mechanisms for acquisition of iron from a host.

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