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Prevalence, serotype distribution, antibiotic susceptibility and genetic profiles of mesophilic Aeromonas species isolated from hospitalized diarrhoeal cases in Kolkata, India.

A comprehensive study was performed to examine incidence, species distribution, drugs sensitivity, virulence genes and molecular fingerprints of Aeromonas species isolated from patients with acute diarrhoea over a period of 2 years in Kolkata, India. Following the Aerokey II scheme, more than 95 % of strains were identified to species level. Seven different species were encountered in this study, with Aeromonas caviae being dominant, followed by Aeromonas hydrophila and Aeromonas veronii biovar sobria. Thirty different serotypes were encountered, with O16, O83 and O85 being dominant, but no serotype was associated specifically with a single species. The majority of Aeromonas strains exhibited multidrug resistance. The alt and act genes, which encode heat-labile cytotonic and cytotoxic enterotoxins, were respectively found in 71.9 and 20.1 % of strains examined. Only 2.4 % of strains carried the heat-stable cytotonic enterotoxin (ast) gene. The hlyA gene was found in 28 % of Aeromonas strains. With few exceptions, genomic diversity of Aeromonas strains belonging to the same serotype was observed by random amplification of polymorphic DNA PCR and ribotyping. Different species of Aeromonas and different clones of Aeromonas species seem to be associated with hospitalized cases of diarrhoea in Kolkata, India.

Aeromonas↗

Isolation of Aeromonas hydrophila from a metropolitan water supply: seasonal correlation with clinical isolates.

The occurrence of Aeromonas spp. in the metropolitan water supply of Perth, Western Australia, Australia, was monitored at several sampling points during a period of 1 year. Water within the distribution system conformed to international standards for drinking water but contained Aeromonas spp. in numbers comparable to those in raw surface water, although this water was free of Escherichia coli. Coliforms and E. coli were found in raw surface waters, and Aeromonas spp. were found in raw water from surface and underground sources. Chemical treatment, followed by chlorination at service reservoirs, resulted in water free of E. coli and a decrease in the number of Aeromonas spp. Aeromonas spp. were found in the greatest numbers in summer. Multiple regression analysis showed that growth of Aeromonas spp. in chlorinated water was related to water temperature, residual chlorine, and interaction between these variables. The incidence of Aeromonas-associated gastroenteritis, determined from isolates referred to us for enterotoxin testing, paralleled the pattern of isolation of Aeromonas spp. in water within the distribution systems. We suggest that the presence of Aeromonas spp. in drinking water needs public health appraisal and that further work should be undertaken to permit reevaluation of standards for the quality of drinking water.

Aeromonas↗

Distribution and survival of motile Aeromonas spp. in brackish water receiving sewage treatment effluent.

The spatiotemporal distributions of Aeromonas spp. and fecal coliforms in a cove receiving sewage treatment effluent and draining into a brackish lagoon were studied for 34 months with sampling at six stations. A total of 452 strains of Aeromonas spp. were isolated and identified at the outflow of the treatment system and at stations in the cove. Hemolytic activity of 289 Aeromonas strains was determined. The Aeromonas spp. and fecal coliform distributions showed seasonal cycles in the pond effluent. These seasonal bacterial cycles were persistent in effluent, at the discharge point, and in the cove. However, the abundance levels of these bacterial distributions decreased gradually from the coast to the open lagoon. A dilution model showed that the Aeromonas spp. and fecal coliform distributions in the cove water were subject not only to dilution effect but also to other environmental factors, such as salinity. A. sobria is the most common species identified in the Aeromonas population present in the cove water. Survival studies confirmed that Aeromonas spp., especially A. sobria, were more sensitive to saline and/or marine stress than fecal coliforms. Among the Aeromonas hydrophila and A. sobria strains, 96 and 97%, respectively, produced hemolysin, whereas among the Aeromonas caviae strains, 95% were nonhemolytic.

Aeromonas↗

Diversity, persistence, and virulence of Aeromonas strains isolated from drinking water distribution systems in Sweden.

The Aeromonas populations in 13 Swedish drinking water distribution systems, representing different treatments, were investigated. From each system, water samples were collected four times during the period from May to September 1994 from raw water and water after treatment and at two to five sites within the distribution system. In total, 220 water samples were collected. From samples containing presumptive Aeromonas, up to 32 colonies were analyzed by the PhenePlate Aeromonas (PhP-AE) system, which is a highly discriminating biochemical fingerprinting method. Selected isolates from different phenotypes (PhP types) were further identified by the API 20 NE system and by gas-liquid chromatography analysis of fatty acid methyl esters (FAMEs). Selected isolates were also assayed for their potential to produce hemolysin and cytotoxin and for their ability to adhere to human intestinal cells. In total, 117 water samples (53%) contained presumptive Aeromonas which numbered up to 10(6) CFU/100 ml in raw water and up to 750 CFU/100 ml in tap water. Among the 2,117 isolates that were subjected to typing by the PhP-AE system, more than 300 distinct PhP types were found, of which the majority occurred only sporadically. Raw (surface) water samples usually contained many different PhP types, showing high diversity indices (Di) (median Di = 0.95). The Aeromonas populations in samples collected from within the distribution systems were less diverse (median Di = 0.58) and were often dominated by one major PhP type that was found on several sampling occasions. Seventeen such major PhP types could be found and were represented in 1,037 isolates (49%). Identification by API 20 NE and FAME analysis revealed that most of the major PhP types were Aeromonas hydrophila or belonged to unidentified Aeromonas species. Hemolysin and cytotoxin production was observed in most major PhP types (representing 87 and 54% of the assayed isolates, respectively), and adherence was found in 89% of the isolates that produced cytotoxin. Thus, the data presented here show that although raw water may contain very diverse Aeromonas populations, the populations seemed to be remarkably stable within the studied water distribution systems, and that some potentially pathogenic Aeromonas strains could persist for several months in drinking water.

Aeromonas↗

Prevalence, species differentiation, and toxigenicity of Aeromonas strains in cases of childhood gastroenteritis and in controls.

In a 1-year period (January to December 1984), Aeromonas strains were isolated from feces of 21 of 561 (3.7%) children with gastroenteritis and from 12 of 576 (2.1%) children without intestinal disturbances (controls). The difference between the two isolation rates was not significant (X2 = 2.2; P greater than 0.05). In five cases of illness other intestinal pathogens were isolated together with Aeromonas in the same stool sample. A total of 39 Aeromonas strains were detected since in some cases aeromonads with different biochemical characteristics were obtained from the same stool sample. Of the 39 Aeromonas isolates, 6 strains (5 from patients) were Aeromonas hydrophila, 5 strains (3 from patients) were Aeromonas sobria, and 26 strains (18 from patients) were Aeromonas caviae; 2 strains isolated from controls did not ferment sucrose and were considered a distinct group of Aeromonas. We found no significant difference between the prevalence of each of these species from patients and the prevalence from controls. We found no significant difference in the prevalence of enterotoxin-producing strains (suckling mouse model), cytotoxin-producing strains (HEp-2 cell model), or hemolysin-producing strains (rabbit erythrocyte model) between patients and controls. In our geographical region there is no evidence that Aeromonas species are primary intestinal pathogens in children.

Adolescent↗

The prevalence of Aeromonas species in feces of horses with diarrhea.

Feces collected from 40 horses with diarrhea and 34 horses without diarrhea were examined to determine if an association existed between isolation of Aeromonas spp. and diarrhea. Samples were also examined for Salmonella spp., and identification of viruses and parasite ova. Neither Salmonella spp. nor Aeromonas spp. were isolated from the feces of 34 control horses. Aeromonas spp. were isolated from feces of 22 of 40 (55%) horses with diarrhea. Salmonella spp. were isolated from feces of 8 (20%) horses, and of these, 5 (12.5%) were also positive for Aeromonas spp. Twenty-nine isolates of Aeromonas spp. were recovered from the feces of 22 diarrheic horses. Of these isolates, more than 80% were susceptible on in vitro testing to amikacin, ceftiofur, chloramphenicol, and gentamicin. All isolates were susceptible to enrofloxacin. Diarrheic horses positive for Aeromonas were significantly (P = .04) older than diarrheic horses negative for Aeromonas spp. A significantly greater number of fecal samples were positive for Aeromonas spp. during March through August than samples examined in other months (P = .014). Results of this study indicate that Aeromonas spp. should be considered as a cause of diarrhea in horses.

Aeromonas↗

Prevalence, in-vitro secretory activity, and cytotoxicity of Aeromonas species associated with childhood gastroenteritis in Chennai (Madras), India.

An investigation on the prevalence of Aeromonas in gastrointestinal illnesses of pediatric inpatients 1 month to 3 years of age was conducted from February 1997 through January 1998 in Madras. Sixteen Aeromonas spp. were isolated from 11 male and five female children among the 341 pediatric inpatients suffering from acute diarrhoea. A. caviae, which was isolated from nine cases, was found to be the most predominant isolate, followed by A. veronii biovar sobria, isolated from six cases, and A. hydrophila, isolated from one case. Shigella flexneri was recovered along with Aeromonas veronii biotype sobria serotype 035 from one 5-month-old female child. We did not notice any seasonal pattern in the association between Aeromonas and childhood gastroenteritis. None of the 147 stool samples obtained from age-matched non-diarrhoeic control children yielded Aeromonas spp. Isolation of Aeromonas spp. from patients suffering from gastroenteritis was found to be significant (chi 2 = 7.1312; P = 0.008, < 0.01). Among the 16 Aeromonas isolates, seven isolates of A. caviae and two isolates of A. veronii biovar sobria induced a secretory response in rabbit intestinal mucosa mounted in Ussing chambers as demonstrated by a significant increase in the short circuit current. Nine of the 16 Aeromonas isolates, including three isolates of A. caviae, five isolates of A. veronii biovar sobria, and the solitary isolate of A. hydrophila were also cytotoxic to CHO cells. Five of the six isolates of A. veronii biovar sobria and the A. hydrophila isolate produced hemolysin. The results of this study indicate that Aeromonas species are important causative agents of diarrhoea in childhood gastroenteritis and are prevalent throughout the year in Madras.

Aeromonas↗

Occurrence of haemolytic & cytotoxic Aeromonas species in domestic water supplies in Chennai.

A study on the occurrence of Aeromonas species in the domestic water supplies in Chennai showed that as much as 37.9 per cent of the water samples analyzed from various sources harbored Aeromonas spp. Majority of the isolates belonged to Aeromonas sobria (13.7%), A. caviae (11.6%) and A. hydrophila (9.5%). Among the 37 metropolitan water samples analyzed, 11 samples yielded Aeromonas spp. inclusive of three isolates of A. hydrophila, four of A. sobria and two isolates each of A. caviae and A. jandaei. From a total of 28 bore well water samples analyzed, Aeromonas spp. were recovered from 15 samples, comprising five isolates of A. hydrophila, six of A. sobria and four isolates of A. caviae. Aeromonas spp. inclusive of one isolate of A. hydrophila, five of A. caviae, three of A. sobria and one isolate of A. veronii were isolated from 10 of the 30 water packets of various commercial brands sold in Chennai. Of a total of 36 isolates obtained, 32 (89%) produced beta-haemolysin with the titres ranging from 2-32 and 20 isolates (56%) were cytotoxic to vero cell monolayers. All the Aeromonas isolates were resistant to ampicillin and polymyxin B. All A. hydrophila and A. caviae isolates were also resistant to cephalothin and erythromycin and 83.3 per cent of Aeromonas isolates were resistant to erythromycin. Aeromonads resistant to tetracycline, gentamycin, co-trimoxazole and nalidixic acid appear to be emerging. The study revealed that Aeromonas spp. occur in the potable and domestic water supplies and even in the chlorinated water supplies in Chennai city, which are potentially enteropathogenic and hence may be hazardous to public health. In view of these findings drinking and domestic water quality standards need to be re-evaluated.

Aeromonas↗

Characterization of virulence factors of Aeromonas isolated from children with and without diarrhoea in Tripoli, Libya.

During September 1992-August 1993, stool samples from 157 children with diarrhoea and 157 matched healthy controls were examined for the presence of Aeromonas and other enteropathogens. Aeromonas strains were tested for haemolytic activity, haemagglutination patterns, and antibiotic susceptibility. In total, 62 Aeromonas were isolated, of which 27 (17.2%) were from children with diarrhoea and 35 (22.3%) from healthy controls. Only 23 (14.6%) of the diarrhoeal children and 28 (17.8%) of the healthy controls were positive for Aeromonas; of which, 4 (2.5%) of the diarrhoeal children and 6 (3.8%) of the healthy controls showed multiple species. Aeromonas hydrophila was isolated from 5 (3.2%) children with diarrhoea and from 9 (6.4%) controls, A. veronii bv sobria from 8 (5.1%) and 7 (4.5%), A. caviae from 13 (8.3%) and 17 (10.8%), and A. schubertii from 1 (0.6%) and 2 (1.3%) respectively. No significant difference in the haemolytic activity of Aeromonas was found between diarrhoeal and healthy children. However, a significant difference (p < 0.002) was observed in mannose-resistant haemagglutination (MRHA) by diarrhoeal isolates of Aeromonas (7/27, 26%) compared to the healthy controls (1/35, 3%). Aeromonas strains were uniformly sensitive to ciprofloxacin, gentamicin, and nalidixic acid. The results of this study suggest that A. caviae strains may be associated with diarrhoea in children and MRHA may be used as one of the virulence markers for distinguishing between Aeromonas isolated from diarrhoeal children and healthy controls or environmental isolates.

Aeromonas↗

Typing of Aeromonas isolates from children with diarrhoea & water samples by randomly amplified polymorphic DNA polymerase chain reaction & whole cell protein fingerprinting.

BACKGROUND & OBJECTIVES: Aeromonas spp. are water-borne organisms, often associated with childhood diarrhoea. The present study was conducted to examine the epidemiological relationship among the Aeromonas spp. isolated from water and children with acute diarrhoea in Chennai. METHODS: Thirty six Aeromonas isolates inclusive of 16 from children with diarrhoea, 15 from domestic water samples and 5 reference strains were studied by randomly amplified polymorphic DNA polymerase chain reaction (RAPD-PCR). Twenty eight Aeromonas isolates, 15 from children with diarrhoea, 10 from domestic water samples and three reference strains were analysed by SDS-PAGE for their whole cell protein profiles. RESULTS: The 36 Aeromonas isolates examined by RAPD-PCR generated RAPD fingerprints with majority of the bands ranging from about 250 to 2800 bp. The RAPD fingerprints did not correspond with the phenospecies and varied greatly among the strains within the phenospecies. Cluster analysis revealed two major groups at 75 per cent hierarchical level, comprising 18 Aeromonas isolates, mainly recovered from domestic water samples, while the clinical isolates were scattered in different hierarchical levels in the dendrogram. The whole cell protein fingerprints examined by SDS-PAGE did not correspond with the phenospecies. Only four isolates of A. caviae were found to produce similar protein fingerprints allowing them to form a cluster at about 90 per cent hierarchical level, while the rest of the isolates were scattered at various hierarchical levels in the dendrogram. INTERPRETATION & CONCLUSIONS: In the present study, RAPD fingerprinting was found to be useful in distinguishing Aeromonas isolates recovered from clinical and domestic water supplies. However, RAPD-PCR could not distinguish the phenospecies of the genus Aeromonas. Whole cell protein fingerprinting and cluster analysis could neither differentiate isolates from clinical and domestic water sources nor the phenospecies of the genus Aeromonas.

Aeromonas↗

[Detection of multiresistance Aeromonas with TEM type resistant genes in patients with cirrhosis].

OBJECTIVE: To study the status of beta-lactamase produced by multiresistant Aeromonas selected from cirrhosis patients to provide reference for treatment and reduce resistance and control spreading. METHODS: Four multiresistant Aeromonas strains isolated from serious liver cirrhosis patients from the No. 302 hospital. The TEM resistant genes were detected by PCR and agarose gel electrophoresis. RESULTS: Three TEM-1 positive strains were detected from four multiresistant Aeromonas isolates consisting of one Aeromonas sobria and three Aeromonas hydrophila isolated from blood and ascites. This was further confirmed by gene sequencing. The multiresistance to antibiotics was higher in four Aeromonas isolates. All strains tested were resistant to ampicillin, cefazolin and cefmetazole.The cirrhosis patients who suffered from Aeromonas infection had poor prognosis and had mortality rate of 3/4. CONCLUSION: The beta-lactamase TEM-1 resistant genes was detected in clinical multiresistant Aeromonas strain isolated from serious cirrhosis patients.The results suggested that TEM-1 was the main resistance mechanism of Aeromonas strain and was reduced by adding enzyme inhibitor.

Adult↗

The occurrence of enteric pathogens and Aeromonas species in organic vegetables.

A range of commercially available organic vegetables (n = 86) was examined for the presence of Salmonella, Campylobacter, Escherichia coli, E. coli O 157. Listeria and Aeromonas spp., to provide information on the occurrence of such organisms in organic vegetables in Northern Ireland. The study was not designed to quantify such organisms or to compare occurrence with conventionally farmed vegetables. Standard enrichment techniques were used to isolate and identify enteric pathogens and Aeromonas species. No Salmonella, Campylobacter, E. coli. E. coli O 157, Listeria were found in any of the samples examined. Aeromonas species were isolated from 34% of the total number of organic vegetables examined. Many (64%) of the organic vegetables examined were "ready-to-eat" after minimal processing, i.e., washing. Aeromonas spp. was isolated from 41% of these vegetables. Aeromonas spp. was not recovered from certain vegetable types. The most commonly isolated species of Aeromonas was Aeromonas schubertii with 21.0% of all samples contaminated with this species; 5.8% of samples contained A. hydrophila, 5.8% A. trota, 3.5% A. caviae and 2.3% contained A. veronii biovar veronii. Although Aeromonas species are frequently detected in organic vegetables, the absence of accepted enteric pathogens was encouraging, and does not support the allegation of organic foods being of high risk due to the farming methods used.

Aeromonas↗

The usefulness of molecular techniques to assess the presence of Aeromonas spp. harboring virulence markers in foods.

A total of 78 raw and 123 processed and ready-to-eat retail food samples were used to assess the presence of motile Aeromonas spp. harboring virulence genes (cytotoxic enterotoxin and hemolysin genes) using a recently described PCR method in comparison with the conventional cultivation method based on the use of Ampicillin-Dextrin Agar (ADA) medium. With the ADA-based method, 65/201 (32.3%) samples showed presumptive Aeromonas spp. colonies whereas the PCR method revealed the presence of Aeromonas spp. harboring the targeted virulence genes in 51/201 (25.4%) of the tested samples. The rate of contaminated samples and the presence of pathogenic Aeromonas were significantly lower with both methods for processed than in case of raw samples. A polyphasic identification approach including biochemical and molecular techniques was applied to a selection of 34 PCR-positive presumptive Aeromonas isolates. Following fatty acid methyl ester (FAME) analysis and amplified fragment length polymorphism (AFLP) fingerprinting, a total of 33 isolates (97%) could be identified to the DNA hybridization group (HG) level. The majority of these isolates belonged to the species Aeromonas hydrophila HG3 (50%) and Aeromonas veronii biovar sobria (HG8/10) (38%). Molecular characterization of PCR amplicons obtained from these strains by PCR-Restriction Fragment Length Polymorphism (PCR-RFLP) fingerprinting and PCR-Amplicon Sequence Analysis (PCR-ASA) allowed classification of all strains in a known PCR-RFLP and PCR-ASA type. In conclusion, the current findings demonstrate that the combined use of PCR-based virulence marker detection, PCR-RFLP and PCR-ASA offers a rapid, sensitive, and specific system to assess the presence and prevalence of Aeromonas spp. harboring virulence markers in food samples.

Aeromonas↗

Gas-liquid chromatographic analysis of cellular fatty acid methyl esters in Aeromonas species.

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.

Aeromonas↗

Incidence of mesophilic Aeromonas within a public drinking water supply in north-east Scotland.

The motile mesophilic Aeromonas are ubiquitous to a wide variety of aquatic environments including drinking water distribution systems. Concern over the presence of mesophilic Aeromonas in public drinking water supplies has been expressed in recent years as it has been regarded as a pathogenic organism of importance in gastroenteritis. A major drinking water distribution system in north-east Scotland was monitored over a 12 month period to determine the prevalence of mesophilic Aeromonas. These data were examined in relation to chlorine concentration, pH, temperature, rainfall and the standard bacteriological indicators of water quality. Aeromonas were isolated to varying degrees from 21 of the 31 reservoirs investigated. The maximum recovery observed during the study was 605 cfu in 300 ml. The probability of isolation generally decreased with increasing levels of chlorination, although this oxidant was found to be ineffective in many reservoirs. Certain reservoirs with poor chlorination profiles yielded very few isolates, whereas some highly chlorinated sites liberated Aeromonas frequently and in relatively high numbers. A seasonal pattern in the incidence of Aeromonas emerged with infrequent isolation during the winter period increasing to a peak during the summer, with most isolates recovered when water temperature was > 12 degrees C. An association was demonstrated between the pattern of Aeromonas isolations and that of rainfall. No relationship was apparent between incidence of Aeromonas and total heterotrophic plate counts.

Aeromonas↗

Clinical features and therapeutic implications of 104 episodes of monomicrobial Aeromonas bacteraemia.

OBJECTIVES: Aeromonas bacteraemia is not a common infectious disease, but can cause a grave outcome in infected cases. In this study, clinical presentations and prognostic factors of cases of monomicrobial Aeromonas bacteraemia were analysed. Also, the impact of beta-lactam and aminoglycoside in combination and of emerging cephalosporin-resistance during therapy was discussed. METHODS: From 1989 to 1998 in a medical centre in southern Taiwan, those cases with monomicrobial Aeromonas bacteraemia were included for study. RESULTS: A total of 104 episodes of monomicrobial Aeromonas bacteraemia, accounting for 74% of all Aeromonas bacteraemia, were encountered. The infections usually occurred in the patients with hepatic cirrhosis (54%) or malignancy (21%) and were community-acquired (74%). Cases of community-acquired bacteraemia were more likely to have cirrhosis, a high severity score at onset, and a worse prognosis than those of nosocomial bacteraemia did and nosocomial isolates were less susceptible to cefoxitin and cefotaxime. Forty-three percent of cases had a concomitant infection focus, such as primary peritonitis, invasive cellulitis or necrotizing fasciitis, biliary tract or burn wound infections. Crude fatality rate within 2 weeks after the onset was 30%. Secondary bacteraemia and a higher severity score ( > or = 4) for illness at the first presentation were independently associated with a fatal outcome. The therapeutic superiority of beta-lactam and aminoglycoside in combination cannot be demonstrated in patients with Aeromonas bacteraemia. Cefotaxime resistance emerged in 3.4% of 58 patients treated with a cephalosporin for at least 72 h. None of the community-acquired isolates, but one-quarter of the nosocomial isolates, were resistant to cefotaxime. CONCLUSIONS: Aeromonas bacteraemia usually occurred in patients with liver cirrhosis or malignancy, and heralded a poor prognosis, especially while associated with a relevant infectious source or with a higher severity score at presentation. The superiority of aminoglycoside and beta-lactam in combination cannot be demonstrated while treating those patients, and the emergence of antimicrobial resistance to cephalosporin was a rare event during cephalosporin therapy. Thus, a broad-spectrum cephalosporin remains one of the antimicrobial alternatives for invasive community-acquired Aeromonas infections.

Adolescent↗

Aeromonas-associated diarrhea in children.

In a 27-month prospective study, Aeromonas spp. were isolated from 7.3% of children with diarrhea and from 2.2% of controls. In 32 patients with diarrhea, ranging in age from 1 to 27 months old, Aeromonas spp. were the only potential bacterial enteropathogens isolated. Principal symptoms of Aeromonas-associated diarrhea were vomiting, fever and bloody stools. Diarrhea was often self-limiting and lasted for 10 days or less in 90% of patients. No secondary spread of diarrhea among close contacts was observed and no clear-cut seasonal patterns of Aeromonas isolation were found. Aeromonas caviae was the most frequently isolated species in fecal samples of patients (24 of 29 isolates) as well as controls (5 of 7 isolates). Cholera toxin cross-reactive cytotoxic enterotoxin was produced by a vast majority of Aeromonas isolates, as compared to a non-cholera toxin cross-reactive cytotonic enterotoxin. In addition no significant correlation was observed between severity of the diarrheal disease and different Aeromonas or the quantity of enterotoxins produced. In our geographic area Aeromonas spp., and A. caviae in particular, seem to be an important and frequent cause of diarrhea in young children.

Aeromonas↗

Aeromonas molluscorum sp. nov., isolated from bivalve molluscs.

Five Aeromonas strains (848T(T), 93M, 431E, 849T and 869N), which were isolated from bivalve molluscs and were recognized previously by numerical taxonomy as members of an unknown Aeromonas taxon, were subjected to a polyphasic taxonomic study. DNA-DNA hybridization experiments showed that DNA of strain 848T(T) was <70 % similar (27-45 %) to that of the type/reference strains of the current Aeromonas hybridization groups (HGs), but 93 % similar to that of strain 93M. The DNA G+C content of the five strains ranged from 59.0 to 59.4 mol%. 16S rRNA gene sequence analysis confirmed that the strains belonged to the genus Aeromonas and showed high similarity to Aeromonas encheleia. Amplified fragment length polymorphism fingerprinting clustered the novel strains in a homogeneous group with low genotypic relatedness to other Aeromonas species. Useful phenotypic features for differentiating the five isolates from other Aeromonas species include their negative reactions in tests for indole production, lysine decarboxylase, gas from glucose and starch hydrolysis. From the results of this study, the name Aeromonas molluscorum sp. nov. is proposed for these strains, with the type strain 848T(T) (=CECT 5864(T)=LMG 22214(T)).

Aeromonas↗