Comparative study of mcr-10 plasmids in Enterobacter spp. with the mcr-10_ter locus from wastewater and clinical samples: Implications for antimicrobial resistance and fitness
Liansheng Yu, Shizuo Kayama, Wataru Hayashi, Yo Sugawara, Sayoko Kawakami, Motoyuki Sugai
Abstract
OBJECTIVES: The emergence and dissemination of mobile colistin resistance (mcr) genes among various Enterobacter species found in humans, animals, and the environment have attracted significant global attention. We report the emergence of mcr-10-carrying plasmids in Enterobacter spp. isolated from wastewater in Japan. This study aimed to characterize the genetic environment of mcr-10 detected in Japan. METHODS: Wastewater samples were collected bimonthly from four municipal wastewater treatment plants in Hiroshima, Japan between October 2020 and August 2021, and three mcr-10-harboring isolates were recovered. These isolates were characterized by antimicrobial susceptibility testing, whole-genome sequencing, and comparative analysis of mcr-10-carrying plasmids. RESULTS: The three colistin-resistant strains, JARB-T-NT00029, JARB-T-NT00194, and JARB-T-NT00318 belonged to sequence types 364, 32, and 486, respectively. The mcr-10 genes were located on 118-155 kb plasmids of the IncFIB(K), IncFIA(HI1), and IncFIB(pECLA)/IncFII(pECLA) replicon types. These plasmids showed high similarity to mcr-10-carrying plasmids found in Enterobacter spp. isolated from human samples reported in other countries across Asia and Europe. Further detailed comparative analysis revealed that an mcr-10_ter locus-containing fragment, including genes involved in colistin resistance and the promotion of gut colonization, was conserved in 14 of 30 (46.7%) strains isolated from human samples in Japan. CONCLUSIONS: We reported colistin-resistant Enterobacter spp. harboring plasmids carrying the mcr-10. This is the first detailed characterization of the genetic structures of the mcr-10-carrying plasmids isolated from the environment in Japan. Our investigation suggests the potential spread of a combination of genes for colistin resistance and the promotion of gut colonization.