Antimicrobial susceptibility profile and resistance patterns of Escherichia coli O157:H7 isolated from beef in Lafia and Akwanga, Nasarawa State, Nigeria

Antimicrobial resistance (AMR) in foodborne pathogens is a global public health crisis, particularly in low- and middle-income countries where antibiotic use in livestock is poorly regulated. The World Health Organization (WHO) has classified antimicrobial-resistant Enterobacterales, including resistant Escherichia coli, as a priority for surveillance. This study determined the antimicrobial susceptibility profile and resistance patterns of E. coli O157:H7 isolated from beef in Lafia and Akwanga, Nasarawa State, Nigeria, addressing a specific knowledge gap, as no previous AMR data for this pathogen existed in the study area. Twenty-nine confirmed E. coli O157:H7 isolates were tested against nine antimicrobial agents using the Kirby–Bauer disk diffusion method. Results were interpreted using Clinical and Laboratory Standards Institute (CLSI) guidelines. Resistance patterns were analyzed, and exact binomial 95% confidence intervals were calculated for resistance prevalence. Inhibition zone diameters were recorded in millimeters. All 29 isolates (100%) were susceptible to gentamicin, ciprofloxacin, and kanamycin. High resistance was observed for ampicillin (58.6%, 95% CI: 38.9–76.5%), erythromycin (27.6%, 95% CI: 12.7–47.2%), streptomycin (24.1%, 95% CI: 10.3–43.5%), chloramphenicol (20.7%, 95% CI: 8.0–39.7%), and tetracycline (17.2%, 95% CI: 5.8–35.8%). Two isolates (6.9%) exhibited resistance to three antimicrobial classes, thus meeting the definition of multidrug resistance (MDR). No isolate was susceptible to all tested agents. E. coli O157:H7 isolates from beef in Nasarawa State remain susceptible to clinically important antibiotics such as gentamicin and ciprofloxacin. However, the presence of MDR (6.9%) and high ampicillin resistance is concerning. Continued surveillance and antibiotic stewardship are urgently needed. Key words: Antimicrobial resistance, Escherichia coli O157:H7, beef, Nigeria, multidrug resistance, ampicillin resistance.