Genetic epidemiology and plasmid-mediated transmission of by ST155 from wastewater of long-term care facilities.

Long-term care facilities (LTCFs) for older people play an important and unique role in multidrug-resistant organism transmission. Herein, we investigated the genetic characteristics of mobile colistin resistance gene ()-carrying strains isolated from wastewater of LTCFs in Shanghai. Antimicrobial susceptibility test was carried out by agar dilution methods. Whole-genome sequencing and plasmid sequencing were conducted, and resistance genes and sequence types of colistin in isolates were analyzed. Core genome multilocus sequence typing (cgMLST) analysis was performed by the Ridom SeqSphere+ software. Phylogenetic tree through the maximum likelihood method was constructed by MEGA X. Out of 306 isolates, only 1 named ECSJ33 was found, and the plasmid pECSJ33 from ECSJ33 harbored the gene that was located with 59,080 bp belonging to IncI2 type. The plasmid pECSJ33 was capable of conjugation with an efficiency of 2.9 × 10. Bioinformatic analysis indicated pECSJ33 shared backbone with the previously reported -harboring pHNGDF93 isolated from fish source. Moreover, the cgMLST analysis revealed that ECSJ33 belongs to different lineages from those reported from previous strains but shared high similarity to NCTC11129 in cluster 11. The phylogenetic tree revealed MCR-1 of ECSJ33 in this study was mostly of animal food origin and that they were closely related. Our study firstly reports detection of genome sequence of a multidrug-resistant -harboring ST155 from wastewater of LTCF source in China. The data may prove that the plasmid pECSJ33 belongs to food origin and help to understand the antimicrobial resistance mechanisms and genomic features of colistin resistance under One Health approach.IMPORTANCEOne named ECSJ33 was found from wastewater of a long-term care facility (LTCF) and the plasmid pECSJ33 from ECSJ33 harbored the mobile colistin resistance gene () that was located with 59,080 bp belonging to IncI2 type, which was capable of conjugation with an efficiency of 2.9 × 10. This paper firstly reports an -carrying strain ST155 isolated from LTCF in China. Comparative genomics analysis indicated pECSJ33 shared backbone with the previously reported -harboring pHNGDF93 isolated from fish source. The phylogenetic tree revealed MCR-1 protein of ECSJ33 in this study was mostly of animal food origin and that they were closely related. Therefore, the pECSJ33 could be considered as food-origin transmission -harboring plasmid.