Enterotoxin gene profile and molecular epidemiology of Aeromonas species from fish and diverse water sources.

AIMS: This investigation was undertaken to study the prevalence, enterotoxin gene profile and molecular epidemiology of Aeromonads from various sources of water (182) and fish (173). METHODS AND RESULTS: A total of 116 Aeromonas sp. were isolated, of which 48 (26·37%) were from water and 68 (34·62%) were from fish samples collected from retail markets and fish farms. The Aeromonads were recovered from all types of water sources viz. drinking water (13%), surface waters (26%) and fish ponds (69%). The most prevalent species recovered from drinking water was A. hydrophila, from fish ponds it was A. caviae, from surface water sources A. hydrophila and A. caviae were recovered more frequently, and A. hydrophila and A. veronii bv. sobria were isolated predominantly from gills of fish samples. On multiplex PCR analysis for the detection of enterotoxin genes (act, alt, ast), the above mentioned Aeromonas species frequently contained enterotoxin genes, irrespective of their sources. From isolates across all the sources, act (63%) and alt (57%) genes were encountered more frequently than ast (6%). The enterobacterial repetitive intergenic consensus sequences polymerase chain reaction was used for typing of isolates and most of the isolates from water and fish were related, owing to similar ecosystem. CONCLUSION: A wide distribution of enterotoxin genes in Aeromonads from water and fish is a potential public health threat and molecular genotyping can be helpful to study epidemiology of the pathogen. SIGNIFICANCE AND IMPACT OF THE STUDY: A high proportion of isolates recovered from diverse water sources, particularly potable drinking water and fish samples carried one or more enterotoxin genes thereby indicating a potential pathogenic nature of isolates from these sources. The genetic relatedness was detected amongst many isolates recovered from water sources and fish samples indicating circulation of familiar virulent clones in the aquatic environments.

A multiplex PCR for detection of enterotoxin genes in Aeromonas species isolated from foods of animal origin and human diarrhoeal samples.

AIMS: The present study describes incidence and enterotoxin gene profile of Aeromonas spp. from human diarrhoeal samples (83) and raw meats (171). METHODS AND RESULTS: The samples were screened for isolation of Aeromonads. Aeromonas spp. contaminated raw meats of all kinds under the study and per cent contamination in chicken, mutton and beef was 14·03, 22·89 and 19·35, respectively. Of the 83 diarrhoeal samples from children, 6 (7·22%) were positive for presence of Aeromonas spp. Seven different species of Aeromonas (Aer. hydrophila, Aer. caviae, Aer. veronii bv sobria, Aer. trota, Aer. schubertii, Aer. jandaei and Aer. allosaccharophila) could be identified from foods and from diarrhoeal samples two species (Aer. caviae and Aer. hydrophila) were encountered. Unique primers were designed, and a multiplex PCR was standardized for detection of three enterotoxin genes (act, alt, ast) in the Aeromonas spp. Of the 39 isolates, 35 (89·74%) carried one or more enterotoxin genes: act, alt and ast genes were detected in 30 (76·92%), 31 (79·48%) and 4 (10·25%) isolates, respectively. The enterotoxin genes from a strain recovered from mutton were sequenced and submitted to GenBank and the accession no.s KC687135, KC633828 and KC687134 were provided for alt, ast and act, respectively, by the GenBank. CONCLUSIONS: The occurrence of enterotoxigenic Aeromonads in raw meats and diarrhoeal samples is a public health concern. SIGNIFICANCE AND IMPACT OF THE STUDY: Given the increasing evidence of involvement of Aeromonads in foodborne outbreaks, the standardization of single-step multiplex PCR will be helpful tool for detection of enterotoxin genes in Aeromonas spp.