Prevalence of Escherichia coli O157 isolated from marketed raw cow milk in Kwara State, Nigeria

Escherichia coli (E. coli) is a common cause of poor milk microbial quality, often resulting from unhygienic milk handling. Here, a cross-sectional study was performed to determine the prevalence and antibiotic susceptibility profile of E. coli O157 in raw cow milk sold in Kwara State. Raw cow milk (n = 1225) samples from 11 selected markets within the agro-ecological zones of Kwara State (known for vending milk) were collected across rainy (n = 548) and dry (n = 677) seasons. Isolation and identification of E. coli were done using standard procedures. The Polymerase Chain Reaction was utilized to detect E. coli O157 targeting 16S RNA and its virulence (eaeAO157) and toxigenic (Shiga-toxin 1 (stx1)) genes. The antimicrobial susceptibility profile of E. coli O157 isolates was determined by multi-disc diffusion. The total prevalence of E. coli was 48.9% (n = 599), of which 2.3% (n = 28) were E. coli O157. The prevalence of E. coli was significantly higher during the dry (58.8%) than during the rainy (36.7%) season. Twenty-six E. coli O157 isolates possessed the eaeAO157 gene, while all the 28 isolates carried the stx1. E. coli O157 were susceptible to nitrofurantoin (50.0%) and ciprofloxacin (46.5%), but resistant to cefotaxime (96.4%), ampicillin (89.3%), gentamicin (89.3%) and chloramphenicol (71.4%). This study established the presence of E. coli O157 with virulence, toxigenic genes, and antimicrobial resistance in raw cow milk in Kwara State. Improved hygienic practices during milk handling are recommended.