Genetic Background of Antimicrobial Resistance in Multiantimicrobial-Resistant Isolates from Feces of Healthy Broiler Chickens in Tunisia.

Multiantimicrobial-resistant isolates are a global human health problem causing increasing morbidity and mortality. Genes encoding antimicrobial resistance are mainly harbored on mobile genetic elements (MGEs) such as transposons and plasmids as well as integrons, which enhance their rapid spread. The aim of this study was to characterize 83 multiantimicrobial-resistant isolates recovered from healthy broiler chickens. Among 78 tetracycline-resistant isolates, the , , and genes were detected in 59 (75.6%), 14 (17.9%), and one (1.2%) isolates, respectively. The , , and genes were detected 31 (46.2%), 16 (23.8%), and 6 (8.9%) isolates, respectively, among 67 sulfonamide-resistant isolates. The PCR-based replicon typing method showed plasmids in 29 isolates, IncFIB (19), IncI1-I (17), IncF (14), IncK (14), IncFIC (10), IncP (8), IncY (3), IncHI2 (1), and IncX (1). The class 1 and 2 integrons were detected in 57 and 2 isolates, respectively; one isolate harbored both integrons. Seven and one gene cassette arrays were identified in class 1 and class 2 integrons, respectively. Our findings show that multiantimicrobial-resistant isolates from chickens serve as reservoirs of highly diverse and abundant and genes and plasmid replicons. Such isolates and MGEs pose a potential health threat to the public and animal farming.