Prevalence and Diversity of Integrons and Associated Resistance Genes in Escherichia coliIsolates from Poultry Meat in Tunisia

AbstractFifty-five Escherichia coliisolates were acquired from chicken and turkey meat obtained from two slaughterhouses in Tunis. Eighty-nine percent, 80%, 78%, 67%, 45%, 27%, 7%, 4%, and 2% of these isolates showed resistance to tetracycline, trimethoprim/sulfamethoxazole, streptomycin, nalidixic acid, ampicillin, chloramphenicol, ciprofloxacin, colistine, and gentamicin, respectively. No resistance was detected to cefotaxime, ceftazidime, or amikacin. blaTEMgene was found in 22 of 25 ampicillin-resistant isolates, and 1 isolate harbored blaOXA-1gene. Tetracycline resistance was predominately mediated by the tetAgene. The sul1, sul2, and sul3genes, alone or combined, were detected in 46 of 48 sulfonamide-resistant isolates, and sul1and sul3were included in class 1 integrons in some cases. Sixty percent of isolates harbored integrons (class 1, 30 isolates; class 2, 5 isolates). Class 2 integrons contained in all cases the dfrA1-sat1-aadA1-orfXgene cassette arrangement. Nine gene cassette arrangements have been detected among class 1 integrons, containing different alleles of dfrA(five alleles) and aadA(2 alleles) genes, which encode trimethoprim and streptomycin resistance, respectively. An uncommon gene cassette array (sat-psp-aadA2-cmlA1-aadA1-qacH-IS440-sul3) has been identified in three class 1 integron-positive isolates, and one additional isolate had this same structure with the insertion of IS26inside the aadA1gene (included in GenBank with accession no. FJ160769). The 55 studied isolates belong to the four phylogenic groups of E. coli, and phylogroups A and D were the most prevalent ones. At least one virulence-associated gene (fimA, papC, or aer) was detected in 44 of the 55 (80%) studied isolates. E. coliisolates of poultry origin could be a reservoir of antimicrobial-resistance genes and of integrons, and its evolution should be tracked in the future.