Emergence and dissemination of multidrug-resistant harboring the novel RND efflux pump operon.

The global emergence of multidrug-resistant (MDR) , particularly carbapenem-resistant (CRKP), presents a severe public health threat, limiting available treatment options. Tigecycline and eravacycline, have been considered a last-resort therapeutic against MDR . However, strains were resistant to these antibiotics increased recently. The , a plasmid-encoded resistance-nodulation-division (RND)-type efflux pump, has emerged as a critical factor conferring resistance to tigecycline and eravacycline. In this study, we reported the emergence of 11 CRKP isolates harboring , isolated from two lung transplant patients in a tertiary hospital in eastern China. Most of the isolates (82%) exhibited high-level resistance to tigecycline and eravacycline, along with other common antibiotics. Whole-genome sequencing (WGS) and phylogenetic analysis indicated these strains are not clonal, and resistance phenotypes were associated with the operon and other crucial resistance elements. We also found the operon was located on a conjugative plasmid, sharing high sequence similarity with the operon identified in Our results showed that the t-harboring plasmid is efficiently transferable, which contributes to the dissemination of tigecycline and eravacycline resistance. At the same time, the plasmid can coexist with the -carrying plasmid, which may cause multidrug resistance. The emergence of -positive CRKP in lung transplant patients highlights the potential for rapid nosocomial dissemination and reduced treatment efficacy of last-line antimicrobials. Our findings emphasize the need for enhanced genomic surveillance, infection control measures, and alternative therapeutic strategies to combat the spread of -mediated resistance in clinical settings.