Epidemic characteristics of the SXT/R391 integrated conjugative elements in multidrug-resistant Proteus mirabilisisolated from chicken farm

This study was designed to depict prevalence and antimicrobial resistance characteristics of Proteus mirabilis(P. mirabilis) strains in 4 chicken farms and to probe the transfer mechanism of resistance genes. A total of 187 P. mirabilisisolates were isolated from 4 chicken farms. The susceptibility testing of these isolates to 14 antimicrobials showed that the multidrug resistance (MDR) rate was as high as 100%. The β-lactamase resistance genes blaOXA-1, blaCTX-M-1G, blaCTX-M-9Gand colistin resistance gene mcr-1were highly carried in the P. mirabilisisolates. An MDR strain W47 was selected for whole genome sequencing (WGS) and conjugation experiment. The results showed that W47 carried 23 resistance genes and 64 virulence genes, and an SXT/R391 integrated conjugative elements (ICEs) named ICEPmiChn5 carrying 17 genes was identified in chromosome. ICEPmiChn5 was able to be excised from the chromosome of W47 forming a circular intermediate, but repeated conjugation experiments were unsuccessful. Among 187 P. mirabilisisolates, 144 (77.01%, 144/187) isolates carried ICEPmiChn5-like ICEs, suggesting that ICEs may be the major vector for the transmission of resistance genes among MDR chicken P. mirabilisstrains in this study. The findings were conducive to insight into the resistance mechanism of chicken P. mirabilisstrains and provide a theoretical basis for the use of antibiotics for the treatment of MDR P. mirabilisinfections in veterinary clinic.