A Newly Incompatibility F Replicon Allele (FIB81) in Extensively Drug-Resistant Escherichia coli Isolated from Diseased Broilers

Multiple drug resistance (MDR) has gained pronounced attention among . The transfer of multiple antimicrobial resistance genes, frequently carried on conjugative incompatibility F (IncF) plasmids and facilitating interspecies resistance transmission, has been linked to spp. and in broilers. In Egypt, the growing resistance is exacerbated by the limited clinical efficacy of many antimicrobials. In this study, IncF groups were screened and characterized in drug-resistant spp. and isolated from broilers. The antimicrobial resistance profile, PCR-based replicon typing of bacterial isolates pre- and post-plasmid curing, and IncF replicon allele sequence typing were investigated. Five isolates of (5/31; 16.13%) and spp. (5/36; 13.89%) were pan-susceptible to the examined antimicrobial agents, and 85.07% of tested isolates were MDR and extensively drug-resistant (XDR). Twelve MDR and XDR and spp. isolates were examined for the existence of IncF replicons (FII, FIA, and FIB). They shared resistance to ampicillin, ampicillin/sulbactam, amoxicillin/clavulanate, doxycycline, cefotaxime, and colistin. All isolates carried from one to two IncF replicons. The FII-FIA-FIB+ and FII-FIA+FIB- were the predominant replicon patterns. FIB was the most frequently detected replicon after plasmid curing. Three XDR isolates that were resistant to 12-14 antimicrobials carried a newly FIB replicon allele with four nucleotide substitutions: C99→A, G112→T, C113→T, and G114→A. These findings suggest that broilers are a significant reservoir of IncF replicons with highly divergent IncF-FIB plasmid incompatibility groups circulating among XDR Supporting these data with additional comprehensive epidemiological studies involving replicons other than the IncF can provide insights for implementing efficient policies to prevent the spreading of new replicons to humans.