Escherichia coli O157:H7 Contamination of Cattle Carcass at Slaughter from Abattoirs in Lagos, Nigeria

Meat obtained from cattle serve as a major source of protein in Nigeria, ensuring its safety will therefore be of great importance. This study was carried out to investigate the contamination of cattle carcass with E. coli O157:H7 and determine the antimicrobial susceptibility of the organism. Twenty meat samples from bowel, aitch bone, hide, rib and hunch back were collected from abattoirs in Lagos, Nigeria. MacConkey agar and Eosine methylene blue agar were used for isolation of E. coli. Isolates were sub-cultured on sorbitol MacConkey agar and E. coli O157:H7 were differentiated from other strains due to its inability to ferment sorbitol. Identification was based on cultural, morphological and biochemical characteristics. Susceptibility of the isolates to amoxicillin, ceftazidime and cefuroxime was also investigated. All E. coli isolates were catalase and indole positive, oxidase, citrate and urease negative. The mean total coliform count varied from 4.45x107 cfu/g (hunch back) to 9.20x107 cfu/g (bowel). E. coli O157:H7 occurred in 37% of the meat samples while other E. coli strains occurred in 63%. They both occurred in meat samples from the different parts of the carcass investigated. Among the fourteen E. coli O157:H7 isolates 57.14% were resistant to ceftazidime, 42.86% to cefuroxime and 78.57% to amoxicillin. E. coli, although an enteric bacterium, was found to contaminate different parts of cattle carcass as a result of slaughtering. Of greater concern was the antibiotic resistance and isolation of the pathogenic strain, E. coli O157:H7.