Emergence of Extended-spectrum Beta-lactamase Producer and Colistin-resistant E. coli in Animal-origin Foods in Libya

The increasing prevalence of Escherichia coli (E. coli) infection poses significant health challenges worldwide. Understanding the genetic, pathogenic, and antimicrobial resistance profiles of E. coli is crucial for effective diagnosis and treatment. The present study aimed to assess the prevalence and antimicrobial susceptibility patterns of E. coli isolated from different samples of food products from animals, with specific attention to identifying and characterizing extended-spectrum beta-lactamase (ESBL)-producing isolates. The present study analyzed 92 E. coli isolates obtained from 1120 food samples, including milk, dairy products, meat, and meat products, collected randomly from retail markets in Libya. The isolates were tested for antimicrobial susceptibility, and the antibiotic resistance profiles were evaluated using 32 antibiotics from 12 different classes. Multiple antibiotic resistance (MAR) and antibiotic resistance index were calculated, with MAR ≥ 0.2 indicating high antibiotic resistance. Isolates were categorized as multidrug resistant (MDR), extensively drug-resistant (XDR), or pan drug-resistant (PDR) based on standard definitions. The ESBL production was assessed using the double-disc synergy test, and colistin resistance was tested using the agar diffusion method. Antimicrobial susceptibility testing of E. coli isolates revealed 100% resistance to penicillin and cloxacillin, with high resistance rates observed against neomycin (93.4%), rifampicin (86.9%), and methicillin (75%). However, all isolates were susceptible to chloramphenicol, whereas carbapenems (imipenem, meropenem, ertapenem) indicated the lowest resistance (3.2%). Cefepime demonstrated the highest effectiveness among cephalosporins, with a resistance rate of 1.08%. The MAR ranged from 0.09 to 0.6, with the highest MAR value (0.6) observed in isolates resistant to 20 antibiotics. All isolates were MDR, but no XDR or PDR strains were detected. Among the 92 isolates, 43 were confirmed as ESBL producers, primarily originating from raw milk, lben (fermented milk), and other dairy products. In addition, 83 isolates demonstrated phenotypic resistance to colistin. The present study highlighted the significant presence of MDR E. coli in food products of animal origin, particularly raw milk, fermented milk, and chicken meat in Libya, emphasizing the urgent need for antimicrobial stewardship, stronger regulatory frameworks, and integrated One Health surveillance approaches to combat AMR in Libya.