Emergence of a plasmid-borne tigecycline resistance in in Vietnam.

Tigecycline is a last-resort antimicrobial used to treat multidrug-resistant Gram-negative bacterial infections. One of the common antimicrobial resistance mechanisms is the efflux pump system composed of membrane protein complexes to excrete xenobiotic substrates. Recently, a novel gene cluster, , encoding the resistance-nodulation-cell division (RND) efflux pump was identified on plasmids in isolates in China. TMexCD1-TOprJ1 was found to be capable of excreting multiple antimicrobials, including tigecycline, which contributed to the strain's resistance. In this study, we identified isolates harbouring the genes outside of China for the first time. Two tigecycline-resistant isolates belonging to ST273 by multilocus sequence typing were collected from different patients in a medical institution in Hanoi, Vietnam, in 2015. Whole-genome sequence analysis revealed that these isolates harboured a 288.0 kb -carrying plasmid with IncFIB and IncHI1B replicons. The gene cluster was surrounded by several mobile gene elements, including IS, and the plasmids had high sequence identity with that of isolated in China. Our finding suggests that the horizontal spread of tigecycline resistance mediated by -carrying plasmids has occurred in Vietnam and other countries, and raises concern about the further global dissemination.