Abstract

Cattle can harbour enterohaemorrhagic Escherichia coli O157:H7 serotype in their faecal matters. This study aimed to isolate E. coli O157:H7 from the intestinal digesta, cattle dungs and water; and assess the antibiotic susceptibility and production of shiga toxins by the isolates. The counts of viable bacteria and faecal coliforms in 13 each of intestinal digesta and cattle dung and the 12 water samples were determined using nutrient agar and Eosin methylene blue agar respectively. Sorbitol MacConkey agar (SMAC) was used to screen for E. coli O157:H7 among the 38 E. coli isolates. PCR amplification of uidA genes was used to authenticate the isolates as enterohaemorrhagic E. coli O157:H7 serotype while amplification of stx1 and stx2 showed the production of shiga toxins. The antibiotic susceptibility patterns of the isolates were determined using standard disk diffusion method. The count of viable bacteria and faecal coliform was highest in the intestinal digesta followed by cattle dungs. There was 100% susceptibility to ofloxacin coupled with 100% resistant to augmentin by all the 8 E. coli O157 and 10 non-O157 isolates. The E. coli O157 isolates were more susceptible to ciprofloxacin, gentamicin, ampicillin and cefuroxime than non-O157 isolates but were less susceptible to nitrofurantoin and ceftazidime than non-O157. Eight (44.4%) out of the 18 presumptive E. coli O157 on SMAC amplified uidA genes and were confirmed as E. coli O157. They were isolated only from intestinal digesta and cattle dung. The prevalence of stx1 and stx2 genes among the E. coli O157 was 37.5% and 12.5% respectively. It is concluded from this study that intestinal digesta and cattle dung harboured E. coli O157: H7 some of which possessed shiga toxin.

Key words: Cattle faeces, E. coli O157:H7, Shiga toxins, uidA genes, amplification