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Page No. : 33-38

ABSTRACT

The present study was conducted to know the cytopathic effect of verotoxin producing E. coli on the vero cells. A total of 230 samples from animal and animal handlers were processed for the isolation of E. coli. Out of 121 E. coli isolated from those samples, 77 were serogrouped into 25 serovars and all the 121 isolates were screened by PCR, where 52 (42.97%) were found possessing stx genes, which comprised of 20.66% stx1, 16.52% stx2 and 5.78% both stx1 and stx2. The cell free supernatant of ten Verotoxin Producing E. coli isolates (O15, O22, O55, O60, O71, O86, O102, O111, O116 and O139) possessing stx genes were tested for cytotoxicity on vero cell lines. Microscopically undiluted culture filtrates of all the ten strains induced the cytopathic effect within 24 h. A dilution of 1/4, 1/16, 1/64 and 1/256 affected 50% of the vero cells on 1st, 2nd, 3rd and 4th day post-inoculation, respectively, in O15, O55, O60, O71, O86, O102, O111, O116 and O139 strains. The strain O22 affected 50% of the cells on day 3and 4 with a dilution of 1/4 and 1/16, respectively. The cytopathic effect advanced with time, maximum effect was observed in 4 days and varied with strain dilution from 16 to 256.

Keywords: E. coli, serogroups, verocytotoxicity, verotoxic E. coli