Characterization of TMexCD3-TOprJ3, an RND-Type Efflux System Conferring Resistance to Tigecycline in Proteus mirabilis, and Its Associated Integrative Conjugative Element.

The emergence and transmission of novel antimicrobial resistance genes pose a great threat to public health globally. Recently, the plasmid-encoding RND efflux pump TMexCD1-TOprJ1 in Klebsiella pneumoniae was reported to reduce the sensitivity of multiple antimicrobials. Here, we identified a pandrug-resistant Proteus mirabilis isolate that harbored the novel tmexCD3-toprJ3 gene cluster located on SXT/R391 ICE. This study expands current knowledge of the transfer mechanisms of tmexCD1-toprJ1-like gene clusters among P. mirabilis isolates and warrants further genomic epidemiology investigations.