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Page No. : 97-102

ABSTRACT

The study was undertaken to determine the prevalence and characteristics of necrotoxigenic E. coli (NTEC) isolated from diarrhoeic and healthy calves. Faecal samples from 75 diarrhoeic and 50 healthy calves were screened for the presence NTEC. NTEC strains were further characterised by determining their serotypes, virulence determinants, plasmid profile and antibiotic resistance patterns. A total of 300 colonies of E. coli were obtained from the calves with diarrhoea and 120 colonies from the healthy calves. The prevalence of NTEC was found to be 35.3% in diarrhoeic calves and 15.0% in healthy calves. The prevalence of NTEC2 was more than NTEC1. Genes like pap, aer, afa, sfa and hly were found to be associated with the NTEC isolates. The common serotypes associated with NTEC were O2, O4, O12, O18, O29, O113 and O123. All the NTEC isolates were found to harbour plasmids with molecular weights from 3 kb to 26 kb. All the isolates exhibited different degrees of antibiotic resistance; the highest degree of resistance was to ampicillin and least resistance to furazolidone. It is concluded that a large number of isolates associated with diarrhoea were NTEC. Further, healthy cattle may act as a reservoir for NTEC.

Keywords: Antibiogram, calves, diarrhoea, NTEC, plasmid profile, serotyping, virulence genes (nf, pap, aer, afa, sfa and hly)