Multiple Copies of Tigecycline Gene Cluster tmexC6D6-toprJ1b in Pseudomonas mendocina in a Swine Farm.

Background/

Objectives

The emergence and transmission of the tigecycline resistance efflux pump gene cluster tmexCD-toprJ among humans, animals and the environment have posed a serious threat to public health. The objective of this study was to characterize Pseudomonas strains carrying multiple copies of tmexC6D6-toprJ1b from a pig farm and illustrate the genetic context of tmexC6D6-toprJ1b in the NCBI database.

Methods

The characterization of Pseudomonas strains FJFQ21PNM23 and FJFQ21PNM24 was determined by antimicrobial susceptibility testing, whole-genome sequencing, and RT-qPCR.

Results

The tmexCD-toprJ-positive P. mendocina strains FJFQ21PNM23 and FJFQ21PNM24 were isolated from nasal swabs in a pig farm. Sequence analysis showed that the two P. mendocina strains harbored multiple antimicrobial resistance genes, including tigecycline resistance gene tmexC6D6-toprJ1b. WGS analysis indicated that tmexC6D6-toprJ1b gene was located on a classical transferable module (int1-int2-hp1-hp2-tnfxB-tmexCD-toprJ) and a multiresistance region in FJFQ21PNM24 and FJFQ21PNM23, respectively. Further analysis revealed that 39 additional tmexC6D6-toprJ1b genes in the NCBI database were all identified in Pseudomonas spp., and the genetic features of tmexC6D6-toprJ1b were summarized into three distinct structures.

Conclusions

This study is the first to identify and report the tigecycline resistance gene tmexCD-toprJ in a swine farm. Our findings summarize the three structures in the genetic context of tmexC6D6-toprJ1b and reveal that Pseudomonas serves as the only known reservoir of tmexC6D6-toprJ1b.