Multiple Copies of Mobile Tigecycline Resistance Efflux Pump Gene Cluster tmexC2D2.2-toprJ2 Identified in Chromosome of Aeromonas spp.

The appearance and prevalence of novel plasmid-encoded tigecycline resistance efflux pump gene clusters and in have raised a threat to public health. Here, another tigecycline resistance gene cluster, , was identified in two isolates recovered from fish meat and vegetables. Cloning confirmed the expression of mediated the resistance to tigecycline and decreased susceptibility to tetracyclines and cephalosporins in both Escherichia coli and . In an Aeromonas veronii strain, four copies of were located on the chromosome. Further analysis revealed that has been detected in the chromosomes of , Aeromonas hydrophila, and Aeromonas caviae with one to four copies due to the insertion of a potential integrative transferable unit. The occurrence of multiple copies of chromosomal may act as a sink for this tigecycline resistance gene cluster, which requires continuous monitoring. Tigecycline is regarded as one of the few effective drugs against multidrug-resistant bacterial infection. However, mobile tigecycline resistance efflux pump gene clusters such as and its variants have been identified in both animal- and human-origin e. In this study, we first found another efflux pump gene cluster, , in the chromosome. This gene cluster could mediate tigecycline resistance and decrease susceptibility to tetracyclines and cephalosporins in the host strain. Meanwhile, was detected with multiple copies in spp. This multidrug resistance efflux pump gene cluster with multiple copy numbers might stably exist in and serve as a reservoir for , facilitating its persistent presence and spread.