Virulence genes, serobiotypes and antibiotic resistance profile of Escherichia coli strains isolated from aquaculture and other sources

Abstract

Virulence genes, serobiotypes and antibioticresistance profile ofEscherichia colistrains isolatedfrom aquaculture and other sourcesSurendra raj Alagarsamy, Nirmala Thampuran & Toms C. JosephCentral Institute of Fisheries Technology, Cochin, IndiaCorrespondence: Surendraraj Alagarsamy, Institute of Food and Dairy Technology, TANUVA S, Alamathi P.O., Red Hills (via), Chennai600 052, India. E-mail: asurendraraj@redi¡mail.comAbstractIn order to determine the prevalence of pathogenicEsche richia coli, a total number of 155 E. coli isolatesfrom aquaculture, clinical and veterinary sourceswere screened for s even pathogenic virulence mar-kers and a house-keeping gene by a polymerasechain reaction. The targeted virulence genes in-cluded ea eA of enteropathogenic E. coli, elt and est ofenterotoxigenic E. coli (ETEC), ipaH of e nteroinvasiveE. coli, pCVD432 of enteroaggregative E. coli, stx, hlyAand eaeA of shigatoxigenic E. coli (STEC) and Entero-haemorrhagic E. coli. All the isolates were positive forphoA, the house-keeping gene for E. coli.Amongthe155 isolates, seven numbers (4.5%) harboured thevirulence markers belonging to the pathogenic groupETEC and STEC. The virulent genes detected in thesegroups were elt, est, hlyA and stx. The sources of thesevirulence genes were ¢sh (hlyA), shrimp (elt), feedercanal water (hlyA and elt) of aquaculture origin andfrom diarrhoea a¡ected cow (hlyA, est and stx). Theisolates w ith pathogenic traits belonged to t he ser-ogroups O6 or O29 a nd the remaining cou ld not betyped. They showed resistance to two to four antibio-tics out of the 12 antibiotics tested. Biotyping re-vealed that three isolates belonged to a singlebiotype (7333) and the remaining isolates were of di-verse types. In conclusion, a molecular tool such asPCR proves as more e¡ective tool for detection of thispathogen than the conventional methods. Detectionof these eme rging pathogens in aquaculture sampleswar rants for strict adherence to hygienic handling atretail outlets and proper cooking by the consumerbefore consumpt ion.