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PubMed1995

Relationship between enterotoxicity and multiple drug resistance in Aeromonas spp.

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

Adult↗
PubMed1995

Improved glutaminate-starch-penicillin agar for the isolation and enumeration of Aeromonas hydrophila from seawater by membrane filtration.

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

Aeromonas hydrophila↗
PubMed1996

Colonization of streptomycin-treated mice by Aeromonas species.

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

Aeromonas↗
PubMed1996

[Gastroenteritis due to Aeromonas in pediatrics].

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

Acute Disease↗
PubMedDate not supplied

Haemolytic activity of Aeromonas species isolated in Libya.

Twenty seven Aeromonas strains (5A. hydrophila, 8A. sobria and 14A. caviae) isolated from children with diarrhoea and 34 Aeromonas strains (9A. hydrophila, 7A. sobria an 18A. caviae) isolated from children without diarrhoea were tested from haemolysin production. The results obtained showed that haemolysin production using human, horse or sheep erythrocytes was significantly associated with A.hydrophila and A sobria but not with A.caviae, regardless of whether these strains were isolated from children with or without diarrhoea. Human or horse rather than sheep erythrocytes are recommended for use in the haemolysin assay.

Aeromonas↗
PubMed1996

[Purification and characterization of S-layer protein from Aeromonas hydrophila].

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

Aeromonas hydrophila↗
PubMed1996

Metabolism of proteins and glycoproteins in tumour bearing mice treated with Aeromonas L-asparaginase.

L-asparaginase, isolated in our laboratory, from Aeromonas had been found to be antileukaemic. In the present study, changes in the levels of proteins and glycoproteins in leukaemic mice and under treatment with Aeromonas L-asparaginase have been compared. Levels of protein bound hexose, fucose and sialic acid which were increased during leukaemia attained normal levels when treated with L-asparaginase. The increased blood urea level declined significantly during enzyme therapy. Effects of L-asparaginase are compared with 'Leunase', a commercially available drug used in the treatment of leukaemia.

Aeromonas↗
PubMedDate not supplied

[Bacteria of the genus Aeromonas as the causative agents of saprophytic infection].

The bacteriological study of feces from 458 patients with acute enteric diseases revealed that in 3.2% of cases (in summer in 8.1% of cases) the disease was caused by Aeromonas. In Aeromonas strains isolated from river water in the Volga delta, from fish and from raw meat the same pathogenicity factors occurred as in strains isolated from patients (hemolysin, DNA-ase, protease, lecithinase, amylase, adhesins, capacity of binding Congo red).

Aeromonas↗
PubMed1996

Association of Aeromonas hydrophila and Vibrio alginolyticus with Larval Mortalities of Scallop (Argopecten purpuratus)

A bacteriological study was carried out in a hatchery of Argopecten purpuratus located in northern Chile which had been affected by severe larval mortalities. The phenotypic characterization of the bacterial strains revealed that Vibrio alginolyticus was the predominant species isolated in the majority of samples taken from the different units of the hatchery (microalgae, swimming larvae, seawater of larval culture tanks, and a reservoir tank of 50-μm filtered seawater). However, the bacterial population of dying larvae was composed of only Aeromonas hydrophila strains which proved to be resistant to most of the chemotherapeutic agents tested. The bioassays conducted to evaluate the effect of these bacteria on larval survival showed that all of the isolated Vibrio and Aeromonas strains possessed a high degree of pathogenicity, since they produced dying larvae on concentrations ranging from 5.5 x 10(4) to 5.5 x 10(2) cells/ml. The possible virulence mechanism of these bacteria is discussed, as well as the potential use of drugs to prevent larval mortalities.

Journal Article↗
PubMed1998

Reduction of diverse electron acceptors by aeromonas hydrophila

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

Journal Article↗
PubMed1981

Nonselectivity of Rimler-Shotts Medium for Aeromonas hydrophila in Estuarine Environments.

Thirty presumptive Aeromonas hydrophila isolates were collected from estuarine sources using Rimler-Shotts media. Many of the isolates, especially the strains from a low-salinity site, were also identified as A. hydrophila using the API 20E system and two differential techniques devised for the identification of A. hydrophila. All of the isolates, however, had deoxyribonucleic acid base compositions with guanine-plus-cytosine ratios between 40 and 49 mol%, which excludes these strains from the genus Aeromonas.

Journal Article↗
PubMed1994

An Outbreak of Aeromonas hydrophila Infection in Turtles (Pseudemis scripta).

An outbreak of Aeromonas hydrophila infection with a high rate of mortality (95%) in turtles (Pseudemis scripta) in Italy is reported. Pure cultures of the pathogen were isolated from liver, lung, kidney, and heart specimens of the turtles. The A. hydrophila isolate was resistant to amoxicillin, ampicillin, cephalothin, and trimethoprim-sulfamethoxazole but was sensitive to a number of other antibiotics tested. The study indicates that pet turtles can act as reservoirs of this pathogen and may play an important role in the etiology of Aeromonas-associated human infections.

Journal Article↗
PubMed1995

Comparison of the Growth and Survival of Larval Turbot in the Absence of Culturable Bacteria with Those in the Presence of Vibrio anguillarum, Vibrio alginolyticus, or a Marine Aeromonas sp.

Larval turbot (Scophthalmus maximus) were reared on rotifers (Brachionus plicatilis) in the absence of culturable bacteria for up to 14 days and exhibited growth and high rates of survival (>55% in five experiments). Low numbers of known bacteria were introduced into similar cultures by exposure of the rotifers to a suspension of bacteria prior to addition of rotifers to the larval cultures; Vibrio anguillarum 91079 caused a highly significant decrease (P <0.01) in the proportion of survivors in two separate trials. With an Aeromonas sp. previously isolated from a healthy batch of copepod-fed larvae, there was no significant difference in survival compared with control larvae, even though the density of bacteria in the water of larval cultures reached 10(sup7) ml(sup-1). Bacteria colonized the gut of larvae exposed to Aeromonas-treated rotifers to levels similar to those in conventionally reared fish (>4 x 10(sup4) CFU per larva). Rearing of larvae in the presence of known bacteria provides a means of investigating the interaction of specific bacteria with turbot larvae and could provide a method for the selection of bacteria which may restrict the growth of opportunistic pathogens which would be harmful to turbot larvae.

Journal Article↗
PubMed1999

Cloning and Nucleotide Sequencing of Prolyl Endopeptidase Gene from Aeromonas punctata subsp. punctata.

Prolyl endopeptidase activity was found in Aeromonas punctata subsp. Punctata. The genomic DNA was partially digested with EcoRI and the recovered 8-16 kb DNA fragments were inserted into the EcoRI site of plasmid pUC19, and were transformated into Escherichia coli DH5alpha. The resulted clones were screened by using Benzyloxycarbonyl-Gly-Pro-beta-naphthylamide, the specific substrate of prolyl endopeptidase and a positive clone was obtained. The 12 kb insertion fragment of recombinant plasmid was digested with HincII and subcloned. The PEP gene was found in the 3.5 kb HincII/EcoRI fragment. Nucleotide sequence of the gene was completely sequenced by Auto Sequencer. The complete gene consisted of 2 073 bp corresponding to 690 amino acid residues with a calculated molecular weight of 76 467 Da. The amino acid sequence was 92.3% 53.2% 33.5% 33.2% and 20.5% homologous to those of Aeromonas hydrophila, Flavobacterium meningosepticum, porcine brain, human lymphocytes and Pyrococcus furiosus respectively. From a survey of sequence homology with other members of the prolyl endopeptidase family, the amino acid residues involved in the catalytic triad were deduced to be Ser(538) Asp(622) and His(657).

Journal Article↗
PubMedDate not supplied

Pyrolysis mass spectrometry characterisation and numerical taxonomy of Aeromonas spp.

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.

Aeromonas↗
PubMed1992

Variation in growth kinetics and phenotype of Aeromonas spp. from clinical, meat processing and fleshfood sources.

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.

Aeromonas↗
PubMedDate not supplied

A C1q-binding 40 kDa porin from Aeromonas salmonicida: cloning, sequencing, role in serum susceptibility and fish immunoprotection.

A 40 kDa C1q-binding outer membrane protein from Aeromonas salmonicida was identified by direct-binding assay with biotinylated C1q, a subcomponent of the complement classical pathway component C1. The 40 kDa porin structural gene from the A450 A. salmonicida typical strain (A+:O+) was cloned in Escherichia coli and sequenced. The amino acid sequence of the 40 kDa A. salmonicida porin, its ability to bind C1q in an antibody independent process, and its immunological cross-reaction with the A. hydrophila AH-3 porin II, allow us to determine the role of this protein in serum susceptibility. Furthermore, we obtained defined A. salmonicida 40 kDa porin insertion mutants in serum sensitive or resistant strains, and we complemented these mutants with a plasmid harboring only the 40 kDa porin gene from A. salmonicida A450 in order to define its role as an important surface molecule involved in serum susceptibility and C1q binding. Similar complementation was obtained using the A. hydrophila AH-3 porin II gene. The 40 kDa porin gene and/or protein was present in all the A. salmonicida typical or atypical strains tested. Furthermore, the A. hydrophila AH-3 porin II seems to be an important molecule for fish immunoprotection against either A. salmonicida or A. hydrophila strains.

Aeromonas hydrophila↗
PubMed1993

Haemagglutinating activity, serum sensitivity and enterotoxigenicity of Aeromonas spp.

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.

Adult↗