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PubMed2006

Updated phylogeny of the genus Aeromonas.

Recent phylogenetic studies of the genus Aeromonas based on gyrB and rpoD gene sequences have improved the phylogeny based on 16S rRNA gene sequences first published in 1992, particularly in the ability to split closely related species. These studies did not include the recently described species Aeromonas simiae and Aeromonas molluscorum and only a single strain of Aeromonas culicicola was available for analysis at that time. In the present work, these Aeromonas species and newly isolated strains of A. culicicola were examined. Sequence analysis indicates that A. simiae and A. molluscorum belong to non-described phylogenetic lines of descent within this genus, which supports the original description of both species. The most closely related species are Aeromonas schubertii and Aeromonas encheleia, respectively, which is consistent with 16S rRNA gene sequencing results. However, while the five strains of A. molluscorum showed nucleotide differences in their gyrB and rpoD gene sequences, the only two known A. simiae strains exhibited identical gene sequences, suggesting that they are isolates of the same strain. On the basis of the rpoD gene sequence phylogeny, A. culicicola strains from the original description and new isolates from drinking water and ornamental fish clustered within the species Aeromonas veronii, suggesting inconsistencies with previous results. Other strains with previously controversial taxonomy and new isolates from other studies were included in this study in order to clarify their phylogenetic affiliation at the species level.

Aeromonas↗
PubMed1998

Population dynamics of Aeromonas spp. in an urban river watershed.

Density of Aeromonas spp. at one site in the Buffalo River and at four sites on its upstream tributaries was followed from June 1992-June 1993. Membrane filtration counts of Aeromonas during the summer ranged between 18 and 4000 ml-1, which were one to two logs higher than faecal coliform and faecal streptococci densities. Aeromonas spp. in the Buffalo River, and faecal coliforms, faecal streptococci, and the heterotrophic plate count throughout the watershed, increased by approximately one log during summer rainstorms. However, Aeromonas spp. increased only by a factor of two during rainstorms at the upstream sites. Aeromonas spp. showed a strong positive correlation with both indicator bacteria and total suspended solids at the upstream sites during the summer but not the winter. Correlations between Aeromonas and indicator bacteria remained strong in the Buffalo River during the winter, signifying that different conditions exist in the Buffalo River and its upstream tributaries. The strong correlation between Aeromonas spp. and indicator bacteria in the Buffalo River suggest that, in the absence of media capable of the quantitative recovery of potentially pathogenic aeromonads, standard faecal coliform analyses may adequately assess public health risks from Aeromonas spp. in an urban river used for recreational purposes.

Aeromonas↗
PubMed1984

Isolation of Aeromonas spp. from an unchlorinated domestic water supply.

The recovery of Aeromonas spp. from the unchlorinated water supply for a Western Australian city of 21,000 people was monitored at several sampling points during a period of 1 year. Membrane filtration techniques were used to count colonies of Aeromonas spp., coliforms, and Escherichia coli in water sampled before entry to service reservoirs, during storage in service reservoirs, and in distribution systems. Aeromonas spp. were identified by subculture on blood agar with ampicillin, oxidase tests, and the use of Kaper medium and then were tested for production of enterotoxins and hemolysins. During the same period, two-thirds of all fecal specimens sent for microbiological examination were cultured on ampicillin-blood agar for Aeromonas spp. Recovery of Aeromonas spp. from water supplies at distribution points correlated with fecal isolations and continued during autumn and winter. Coliforms and E. coli were found most commonly in late summer to autumn. This pattern differs from the summer peak of Aeromonas isolations both from water and from patients with Aeromonas spp.-associated gastroenteritis in Perth, Western Australia, a city with a chlorinated domestic water supply. Of the Aeromonas strains from water, 61% were enterotoxigenic, and 64% produced hemolysins.

Aeromonas↗
PubMed2000

Impact of an urban effluent on antibiotic resistance of riverine Enterobacteriaceae and Aeromonas spp.

In order to evaluate the impact of an urban effluent on antibiotic resistance of freshwater bacterial populations, water samples were collected from the Arga river (Spain), upstream and downstream from the wastewater discharge of the city of Pamplona. Strains of Enterobacteriaceae (representative of the human and animal commensal flora) (110 isolates) and Aeromonas (typically waterborne bacteria) (118 isolates) were selected for antibiotic susceptibility testing. Most of the Aeromonas strains (72%) and many of the Enterobacteriaceae (20%) were resistant to nalidixic acid. Singly nalidixic acid-resistant strains were frequent regardless of the sampling site for Aeromonas, whereas they were more common upstream from the discharge for enterobacteria. The most common resistances to antibiotics other than quinolones were to tetracycline (24.3%) and beta-lactams (20.5%) for Enterobacteriaceae and to tetracycline (27.5%) and co-trimoxazole (26.6%) for Aeromonas. The rates of these antibiotic resistances increased downstream from the discharge at similar degrees for the two bacterial groups; it remained at high levels for enterobacteria but decreased along the 30-km study zone for Aeromonas. Genetic analysis of representative strains demonstrated that these resistances were mostly (enterobacteria) or exclusively (Aeromonas) chromosomally mediated. Moreover, a reference strain of Aeromonas caviae (CIP 7616) could not be transformed with conjugative R plasmids of enterobacteria. Thus, the urban effluent resulted in an increase of the rates of resistance to antibiotics other than quinolones in the riverine bacterial populations, despite limited genetic exchanges between enterobacteria and Aeromonas. Quinolone resistance probably was selected by heavy antibiotic discharges of unknown origin upstream from the urban effluent.

Aeromonas↗
PubMed1998

Role of a cytotoxic enterotoxin in Aeromonas-mediated infections: development of transposon and isogenic mutants.

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

Aeromonas hydrophila↗
PubMed1991

Aeromonas spp. and their association with human diarrheal disease.

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.

Aeromonas↗
PubMed1986

Clinical associations of Aeromonas spp. in fecal specimens from children.

Human infections caused by Aeromonas spp. are being reported with increased frequency. We examined 1012 unselected stool specimens from 799 children for various pathogens, including Aeromonas spp., to evaluate the clinical associations of Aeromonas spp. in the stools of children in the East End of London. A total of 33 children had positive cultures for Aeromonas spp. These were identified as: Aeromonas hydrophila (16), A. sobria (9), A. caviae (8). Aeromonas spp. were identified by being oxidase positive in character, a property that distinguishes Aeromonas spp. from Enterobacteriaceae. Associated pathogens included Salmonella typhimurium (1), Campylobacter spp. (3), Enteropathogenic Escherichia coli (2), and Giardia lamblia (1). Electron microscopic examination of the stool of 13 children revealed viral particles in two, rotavirus (1), and coronavirus-like particles (1). The associated clinical features in the 25 children with only Aeromonas excretion were diarrhea (21), vomiting (10), abdominal pain (9), fever (4), and mild dehydration (2). Five patients had macroscopic blood loss in the stools. The illness was generally mild and lasted only a short time.

Aeromonas↗
PubMed1995

Role of aeromonas isolated from feces of Finnish patients.

Aeromonas species were isolated from 249/13,027 (1.9%) stool samples submitted to the Dept. of Bacteriology and Immunology, University of Helsinki, during 1 year, to be cultured for bacterial enteropathogens. Aeromonas was the third most common enteropathogen isolated, after campylobacter (3.6%) and salmonella (3.3%). Isolates and clinical information from 234 Aeromonas patients were available for further study. A. caviae (41%), A. hydrophila (27%), and A. veronii biovar sobria (22%) were the most frequent isolates. In 15% of the patients, other enteropathogens were found along with aeromonas. Only 2% of all aeromonas-positive patients were found to be asymptomatic, whereas no aeromonas isolates were detected in the stools of 343 asymptomatic individuals. Almost all (96%) patients with aeromonas in their feces had gastroenteritis. Patients infected with A. veronii biovar sobria had a shorter illness course and had more often travelled abroad. In conclusion, Aeromonas spp. were found to be a potential cause of diarrhea in Finnish patients.

Adult↗
PubMed2003

Aeromonas isolates from human diarrheic stool and groundwater compared by pulsed-field gel electrophoresis.

Gastrointestinal infections of Aeromonas species are generally considered waterborne; for this reason, Aeromonas hydrophila has been placed on the United States Environmental Protection Agency Contaminant Candidate List of emerging pathogens in drinking water. In this study, we compared pulsed-field gel electrophoresis patterns of Aeromonas isolates from stool specimens of patients with diarrhea with Aeromonas isolates from patients' drinking water. Among 2,565 diarrheic stool specimens submitted to a Wisconsin clinical reference laboratory, 17 (0.66%) tested positive for Aeromonas. Groundwater isolates of Aeromonas were obtained from private wells throughout Wisconsin and the drinking water of Aeromonas-positive patients. The analysis showed that the stool and drinking water isolates were genetically unrelated, suggesting that in this population Aeromonas gastrointestinal infections were not linked with groundwater exposures.

Aeromonas↗
PubMed2026

Genomic insights into Aeromonas infections in diarrheal patients: high diversity, emerging resistance, and potential outbreak in Beijing.

BACKGROUND: Aeromonas species are ubiquitous aquatic bacteria that have emerged as significant foodborne enteric pathogens worldwide, yet their genomic landscape in clinical settings remains poorly delineated, particularly in Beijing. METHODS: To address this gap, we performed active surveillance for Aeromonas among 691 consecutive diarrheal outpatients in a Beijing district from January to December 2024. Isolates were recovered using enrichment culture coupled with PCR screening and identified by MALDI-TOF MS. Antimicrobial susceptibility was tested against 17 agents. Whole-genome sequencing was conducted on all isolates, enabling average nucleotide identity (ANI) analysis, comprehensive annotation of antimicrobial resistance and virulence genes, multilocus sequence typing (MLST), and core-genome SNP (cgSNP)-based phylogenetics. RESULTS: Aeromonas was detected in 3.3% (23/691) of patients, with Aeromonas veronii (56.52%, 13/23) and Aeromonas caviae (26.09%, 6/23) predominating. Co-infections with other enteric pathogens occurred in 65.2% of positive cases. Resistance rates were notably high for ampicillin/ampicillin-sulbactam (78.26%), nalidixic acid (56.52%), and ertapenem (21.73%), and 65.21% of isolates were multidrug-resistant. Genotypic-phenotypic concordance was robust, with β-lactamase genes ampS (60.87%) and blaCEPH-A3 (47.83%) being most prevalent. Strikingly, mcr-3.25 and mcr-3.3, which belong to the mcr family (originally described as mobile colistin resistance genes), were identified in 8.70% of isolates, exhibiting perfect correlation with phenotypic resistance. Plasmer analysis suggested both mcr genes to be chromosomally encoded. Comparative genomic analysis of virulence-associated genes revealed striking species-specific specialization: A. veronii predominantly carried complete T3SS clusters (61.5%), A. caviae and Aeromonas enteropelogenes were enriched in T6SS genes, and a single A. dhakensis isolate possessed an extensive arsenal including T3SS, T6SS, and a full RTX toxin cluster. MLST resolved the 23 isolates into 22 sequence types, 18 of which were novel. Phylogenetic reconstruction identified a tight monophyletic cluster of three A. veronii isolates (9-27 SNP differences) recovered within a 96-h window, suggestive of a potential cluster that warrants further epidemiological investigation. Comparative genomic analysis of the rare species Aeromonas allosaccharophila demonstrated that the Beijing clinical isolate S14 differs from the U.S. clinical strain ATCC 35942 by 42,099 SNPs, confirming its distinct genetic lineage. CONCLUSION: Collectively, this study delineates high genetic diversity, emerging chromosomal colistin resistance, and species-specific virulence specialization among Aeromonas isolates from diarrheal patients in Beijing. The detection of a potential outbreak cluster and a rare clinical isolate underscores the power of genomics-based surveillance for detecting and mitigating foodborne pathogen threats.

Aeromonas↗
PubMedDate not supplied

Hemolytic properties of some Aeromonas strains.

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.

Aerobiosis↗
PubMedDate not supplied

[Discordancies between classical and API 20E microtest biochemical identification of Vibrio and Aeromonas strains].

The present study reveals some discordancies of diagnosis considering Vibrionaceae strains when tested by comparison with API 20E (BioMerieux) system and classical biochemical reactions, aspects already mentioned in the literature by other authors. If any misidentification has not an important impact (e.g. identification of Aeromonas schubertii as A. sobria), others as misidentification of Aeromonas as Vibrio strains or the failure to recognize Vibrio strains raise major epidemiological problems. The present study was performed on 25 aquatic strains, comparatively identified by means of API 20E system and classical biochemical tests (using media prepared in Vibrio Laboratory of Cantacuzino Institute). All 25 strains were identified as Vibrio fluvialis by API 20E system, while using the classical tests one strain proved to belong to Pseudomonadaceae (O/F test of oxidative type), one was identified as Aeromonas schubertii, 2 Aeromonas hydrophila and 4 Aeromonas caviae. Discordancies between API 20 E system and classical tests were registered for: gelatinase (20%), LDC 12% and ADH, ODH, O/F test, saccharose, manite, inosite (4% each). The misidentification of Aeromonas as Vibrio strains by API 20E hinders the recognition of Aeromonas infections implicated more and more frequently in human pathology in immunodeficient as well as in immunocompetent hosts. Our results demonstrate that the use of API 20E system has some limits in the diagnostic of some bacterial genera (Vibrio, Aeromonas), and the introduction of these systems in the current laboratory practice requires previous information and studies regarding their efficiency and availability for the diagnostic of particular bacterial genera and species.

Aeromonas↗
PubMedDate not supplied

Aspects of constitutive and acquired antibioresistance in Aeromonas hydrophila strains isolated from water sources.

Over the last three decades, the literature pointed out the implications of Aeromonas species in human pathology. These species were described as being involved in intestinal (several outbreaks of acute gastroenteritis of choleric/dysenteric form or chronic diarrhoea, ulcerative colitis, etc.) in normal adults or children, as well as in extraintestinal infections in immunocompromised hosts. This last aspect included a large range of cutaneous injuries (micronecrosis, abscesses, bums, cellulites, furunculosis), joint, bones, respiratory, urinary tract, ocular infections up to meningitis, endocarditis, peritonitis, hepatobilliary disease, endotoxic shock and septicemia (as consequence of leech microvascular surgery). During the last decade, the literature reported a high mortality in Aeromonas infections determined by certain phenospecies (A. hydrophila and A. veronii) especially in extraintestinal infections in immunocompromised patients. In microbiologists' opinion this high rate of mortality was probably due to poor knowledge concerning the aspects of antibioresistance in Aeromonas strains, to empiric treatments with antibiotics to which these bacteria exhibiting constitutive resistance lead to insuccessful results, and at last to the increasing trend of aeromonads resistance to certain antibiotics after 1996. The literature mentioned also that for a great number of Beta-lactamase producing Aeromonas strains, the use of microdilution method (by comparison to disk diffusion in agar medium) giving false results made more difficult the true knowledge of Aeromonas antibioresistance patterns. At the same time, in 2002, the literature mentioned 4 ecological compartments considered as "reservoirs for dissemination and transfer of microbial antibioresistance i.e. humans, animals, plants and natural soil and water. In the last time, more and more data of the literature revealed that some bacteria with role of reservoir of antibioresistance in the natural environment, even without a direct medical impact, however they could play an indirect one remaining permanent sources of R genes for bacterial strains with pathogenic abilities implicated in human pathology (i.e. Aeromonas infections in man related to different professional activities such as fishing, surfing, swimming, diving, etc.). The purpose of this work was to determine the aspects related to constitutive and acquired antibioresistance in 35 A. hydrophila strains isolated in aquatic environment of Danube Delta (10 salmaster waters, 5 aquatic plants, 5 fish intestinal content, 5 fish sapling, 5 snake and oyster shells). The strains were biochemically identified by using API20E and API20NE kits. The antibioresistance spectrum was determined by disk diffusion method following NCCLS 2000 recommendations. The choice and disposal of antibiotics on the Mueller Hinton plate was done to allow the interpretive reading and the phenotypic detection of different antibioresistance mechanisms, as follows: beta-lactamases (PEN, ME, AMX, AMC, CAZ) and carbapenemase (IMP) production; porin deficiency (FOX); efflux mechanism (C, TE, NOR). All tested strains exhibited high resistance to penicillin, aspect pleading for constitutive penicillinase production in Aeromonas strains. With reference to other penicillins (ME, AMX, AMC) and cephalosporins (CAZ, FOX) the tested strains exhibited 2 different antibioresistance patterns: AMX-R, AMC-S, CAZ-S (65%) indicating the presence of beta-lactamase sensitive to inhibitors and AMX-R, AMC-R, CAZ-S (22%) indicating the presence of beta-lactamase resistant to inhibitors. Resistance to FOX in 8% of strains signifies a phenotypical marker for the presence of porin deficiency. Only one Aeromonas strain (2.8%) was resistant to IMP. Three strains (8%) were simultaneous resistant to TE and TMP/SMX, NOR and CHL probably due to the presence of a resistance plasmid (codifying an efflux/ enzymatic mechanism). These aspects are pleading for the necessity to investigate the bacterial antibioresistance patterns of bacterial strains isolated from the environment, in the purpose to identify the factors responsible for the spreading of certain antibioresistance mechanisms in the external medium as risk factors for the colonization process with possible impact upon the human pathology.

Aeromonas hydrophila↗
PubMed1995

[New species of Aeromonas isolated in Cuba].

One hundred and fifty-five strains of Aeromonas isolated in the stools of children under 5 years presenting with acute diarrheal disease were studied. Using the Aerokey II system for the identification of species, 47 strains were identified as Aeromonas caviae, 58 as Aeromonas hydrophila, 23 as Aeromonas veronii biovar sobria, 14 as Aeromonas trota, 9 as Aeromonas veronii biovar veronii, 2 as Aeromonas jandaei and 2 as Aeromonas shubertii, Emphasis is placed on the advantages of this method which allowed for the classification of new species not identified previously in our country.

Acute Disease↗
PubMed1998

Optimisation of the protocol for detection of Aeromonas species in ready-to-eat salads, and its use to speciate isolates and establish their prevalence.

Aeromonas spp. are detected in more than 500 cases of gastrointestinal infection each year in England and Wales. This study aimed to identify their prevalence in ready-to-eat salads, which are a potential source of aeromonas infection. The protocol for isolation of mesophilic Aeromonas spp. from salads was optimised. Using the improved method, Aeromonas spp were isolated from 19 of 25 samples (25 g) of ready-to-eat salad products. Aeromonas organisms were counted, isolates were identified to species level, and the effect of pH on colonisation of salads was assessed. Aeromonas was present at high levels in six salads (> or = 100 cfu/g). The major species present in salads was Aeromonas caviae, but A.hydrophila and A.sobria, which have more pathogenic potential, were also isolated. It is hoped that this study will help to assess the risk to public health of aeromonas in salads.

Aeromonas↗
PubMed1995

Distribution of Aeromonas species in the intestinal tracts of river fish.

Aeromonas isolates were obtained from fish intestines, water, and sediments from an urban river and identified by the DNA-DNA microplate hybridization method. The isolates were Aeromonas veronii (22%), Aeromonas caviae (18%), Aeromonas hydrophila (13%), Aeromonas sobria (8%), Aeromonas jandaei (7%), and other Aeromonas spp. (33%). Aeromonas species occurred at high densities with high incidences, regardless of season. The results strongly suggest that aeromonads are indigenous in fish intestines, water, and sediments of rivers and have the potential to be predominant in aquatic environments.

Journal Article↗
PubMed1994

Aeromonas species in septicemia: laboratory characteristics and clinical observations.

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.

Adolescent↗
PubMed1998

Incidence of non-01 Vibrio cholerae and Aeromonas spp. in fresh water in Araraquara, Brazil.

The occurrence of Aeromonas spp., Vibrio cholerae, and Plesiomonas shigelloides in fresh water from various sources in Araraquara, State of São Paulo, Brazil was determined. Samples from ten distinct irrigation systems used in vegetable cultivation, from five distinct streams, from two reservoirs, from one artificial lake, and from three distinct springs were analyzed. All isolates were serotyped and tested for hemolysin, cytotoxin, heat-stable (ST) and heat-labile (LT) enterotoxins production; presence of plasmid; autoagglutination and drug resistance. V. cholerae isolates were also tested for cholera enterotoxin (CT) production, and Aeromonas isolates for suicide phenomenon. No P. shigelloides was found. V. cholerae non 01 was found in five irrigation water samples and in three stream samples. Aeromonas sp. were isolated in two samples of irrigation water, in three streams, and in one reservoir. All the V. cholerae and Aeromonas isolates were positive for beta-hemolysin production, and all Aeromonas isolates were positive for suicide phenomenon; cytotoxic activities were observed in two Aeromonas strains. Cholera enterotoxin was not found in eight V. cholerae non-01 isolates tested by the Y-1 mouse adrenal cell. All isolates were also negative for the other virulence markers. V. cholerae isolates were found to be sensitive to the majority of drugs tested, while Aeromonas strains presented multiple drug resistance.

Aeromonas↗