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

## TL;DR

This study identifies Pseudomonas bacteria from a pig farm carrying multiple copies of a tigecycline resistance gene, highlighting its potential public health risk.

## Contribution

First report of tmexCD-toprJ in a swine farm and characterization of three distinct genetic structures of tmexC6D6-toprJ1b.

## Key findings

- Two Pseudomonas strains from a pig farm were found to carry multiple tigecycline resistance gene copies.
- The tmexC6D6-toprJ1b gene was located in transferable modules and multiresistance regions in the bacterial genomes.
- 39 additional tmexC6D6-toprJ1b genes in the NCBI database were all found in Pseudomonas species.

## Abstract

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.