Prevalence and antibiotic resistance of Escherichia coli O157:H7 in beef at a commercial slaughterhouse in Moro, Kwara State, Nigeria

Background. Gastroenteritis due to foodborne disease is a leading cause of death in developing countries. In Nigeria, there is an increasing demand for beef. Yet, there is no surveillance for Escherichia coli O157:H7 contamination of raw beef and little is known about the carriage of this pathogen in Nigeria’s livestock. 

Methods. A total of 415 samples, including 180 cow carcass swabs, 180 caecal content samples, 16 water samples, 25 hand swabs and 14 knife swabs were collected at a large abattoir in the Moro region of Kwara State, Nigeria. The samples were enriched in modified tryptone broth containing novobiocine, and plated onto Sorbitol–MacConkey agar (Oxoid SR0172E) supple-mented with 0.05 mg l⁻¹ cefixime and 2.5 mg l⁻¹ potassium tellurite (Oxoid) (CT-SMAC). Indole-producing isolates were confirmed serologically by serotyping with antisera specific for the O157 and H7 antigens. The E. coli O157:H7 isolates were further tested for their susceptibility to antibiotic agents using the disc diffusion method. Commercially available Gram-negative multi-discs (Oxoid) comprising nitrofurantoin (30 µg), ampicillin (5 µg), ceftazidime (30 µg), gentamicin (10 µg), ciprofloxacin (5 µg), augmen-tin (30 µg), ofloxacin (5 µg) and cefuroxime (30 µg) were tested. 

Results. Overall, 16 (3.9 %) samples were contaminated with E. coli O157:H7, of which 10 (5.6 %) were isolated from carcass swabs, 4 (2.2 %) from caecal content samples and 2 (12.5 %) from water. All isolates were multidrug-resistant (MDR), with resistance to ampicillin, ceftazidime and cefuroxime being the most common. 

Conclusion. This study provides evidence to suggest that E. coli O157:H7 exists in the beef production chain. The pathogen reveals a high frequency of multidrug resistance, suggesting that consumers and handlers of such meat are at risk of contracting antibiotic-resistant E. coli O157:H7-associated foodborne disease. Routine monitoring of antibiotic resistance is critical to uncovering novel therapeutic strategies that will help inform clinical practice guidelines.