Shiga Toxin and Non-Shiga Toxin-Producing Escherichia coli O157 from Cattle, Goats and Chickenin Ado-Ekiti, South West, Nigeria

Background: Illnesses due to contaminated food, particularly food of animal origin, are perhaps the most widespread health problem in the contemporary world.
Aims: To detect Shiga toxin-producing Escherichia coli (STEC) in food animals in Ado-Ekiti, Nigeria and the possible risk to human health.
Study Design: Non-repeat faecal samples from various animals and poultry birds were examined for STEC.
Place and Duration of Study: Department of Microbiology, Ekiti State University, Ado-Ekiti, between January 2010 and December 2011.
Methodology: We investigated 722 non-repeat faecal samples from animals and poultry birds for the presence of STEC using bacteriological, serological, and tissue culture techniques. Detection of virulence genes was performed by PCR.
Results: Overall, 316 isolates of E. coli were recovered from 62.3% cattle, 19.6% local chicken, 10.1% goats, 4.1% broiler, 2.9% layers, and 0.9% cockerels. Of the non-sorbitol fermenting E. coli phenotype selected from the isolates, 13.3% were presumptively identified as O157 serotype based on inability to ferment sorbitol on sorbitol MacConkey agar (SMAC).
Serotyping using commercial kits capable of detecting O157 and non-O157STEC confirmed 6.6% of these as O157 comprising 4.1% from cattle and 2.5% from local chicken. Only 4.7% of the strains were serologically confirmed as non-O157 of which 0.9% was from cattle, 3.2% from goat and 0.6% from local chicken. Verocytotoxicity test and the presence of virulence genes stx1, stx2 and eae assayed by PCR showed the complete absence of virulence genes in the 13 serologically confirmed strains of O157 from cattle. The virulence gene stx1 was detected only in non-O157 strain from goat and local chickens.
Conclusion: This study has shown that the prevalence of E. coli O157 is low in food animals in the study area compared to reports from the developed countries. Furthermore, our study is the first to report the isolation of non-O157STEC in goat, a very common domestic animal, in the study area.