Production of Verocytotoxin and Presence of stx Gene in Escherichia coli Strains from Diarrhoeic and Non-Diarrhoeic Cattle and their Handlers
2013
Rashid, M. | Kotwal, S.K. | Agarwal, R.K. | Ahmad, Mudasir | Sailo, B. | Anjay
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% stx 1 , 16.52% stx 2 and 5.78% both stx 1 and stx . 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 1 st , 2 nd , 3 rd and 4 th 2 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 3 and 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.
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