Emergence of the resistance‐nodulation‐division efflux pump tmexCD3‐toprJ3 gene confers resistance to tigecycline in Pseudomonas juntendi and Proteus terrae isolated from a pig farm in China

Background Tigecycline is regarded as a last‐resort antimicrobial agent against multidrug resistance (MDR). However, resistance‐nodulation‐division efflux pump resistance genes, such as tmexCD3‐toprJ3, that confer resistance to tigecycline have emerged. Objectives This study aimed to characterise the tmexCD3‐toprJ3 gene cluster in Pseudomonas juntendi and Proteus terrae isolated from a pig farm. Methods Samples were obtained from a Chinese piggery and included 92 pig faecal samples, 56 wastewater samples, 23 drinking water samples, 28 sow vagina samples and nine sow uterus swabs. The presence of tmexCD3‐toprJ3 was detected using a polymerase chain reaction assay, and the antimicrobial susceptibility profile of the tmexCD3‐toprJ3‐positive isolates was determined using the broth dilution method. Genomic locations were identified using whole‐genome sequencing and bioinformatics. Results We identified two tmexCD3‐toprJ3‐positive isolates, and both isolates were highly resistant to antibiotics such as tigecycline. In addition, we identified several mobile elements (ISPa7, ISCfr1, ISVsa3) and insertion sequences (TnAs2, TnAs3) in tmexCD3‐toprJ3‐positive isolates that could increase the potential for the spread of MDR. Conclusions To the best of our knowledge, this study is the first to report the detection of tmexCD3‐toprJ3 in P. juntendi and P. terrae isolated from a pig farm. This is the first report of the emergence of the tmexCD3‐toprJ3 gene in Pseudomonas juntendi and Proteus terrae isolated from a pig farm in China. The tmexCD3‐toprJ3 efflux pump cluster conferred multidrug resistance, including resistance to tigecycline, demonstrating pathogenicity and transmission.