Antibiotic resistance phenotypes and virulence-associated genes in Escherichia coli isolated from animals and animal food products in Tunisia

Livestock and food products of animal origin constitute important reservoirs of intestinal and extraintestinal pathogenic Escherichia coli including antibiotic-resistant E. coli isolates. To assess potential risks to public health related to E. coli strains of animal origin in Tunisia, 65 E. coli isolates recovered from healthy animals and food products of animal origin were studied. Antimicrobial susceptibility was determined according to CLSI guidelines and genes encoding antibiotic resistance as well as virulence factors were investigated by PCR. High rates of antibiotic resistance were observed to kanamycin (78.4%), gentamicin (75.3%), and streptomycin (75.3%; encoded by strA-strB (7 isolates)), amoxicillin (64.6%), amoxicillin/clavulanic acid (60%), tetracycline (44.6%; tetA (8 isolates) and tetB (7 isolates)), nalidixic acid (27.6%; qnrS (3 isolates), qnrB (2 isolates), and qnrA (one isolate)), and sulfonamides (36.9%; sul1 (1 isolate), sul2 (4 isolates), and sul3 (1 isolate)). Virulotypes classified some isolates as STEC (3%), MNEC (1.5%), and atypical EPEC (1.5%). This study demonstrated high rates of antimicrobial resistance and the presence of some pathogenic pathovars from animal origins that are a cause of concern for public health.