Exploring the epidemiology of mcr genes, genetic context and plasmids in Enterobacteriaceae originating from pigs and humans on farms in Thailand

Abstract

Objectives: In veterinary medicine, colistin has been widely used as therapeutic and prophylactic agent, and for growth promotion. However, colistin has been re-introduced into treatment of human MDR bacterial infections. We assessed the characteristics and spread of plasmid-borne colistin resistance among healthy pigs, workers with animal-contact and their household members in Thailand.Methods: WGS and MIC data of 146 mcr-positive isolates from a cross-sectional One Health study were ana-lysed. Long-read sequencing and conjugation were performed for selected isolates.Results: mcr-carrying isolates were detected in 38% of pooled-pig samples and 16% of human faecal samples. Of 143 Escherichia coli and three Escherichia fergusonii, mcr-1, mcr-3, and mcr-9 variants were identified in 96 (65.8%), 61 (41.8%) and one (0.7%) isolate, respectively. Twelve E. coli co-harboured two mcr variants (mcr-1 and mcr-3). Clonal transmission was detected in five out of 164 farms. mcr-1 was mostly harboured by epidemic IncX4 and IncHI1 plasmids (89.9%). Conversely, mcr-3 was harboured by a range of different plasmids. Comparative plasmid studies suggested IncP and IncFII plasmids as possible endemic mcr-3 plasmids in Asian countries. Moreover, mcr-3 was associated with different mobile genetic elements including TnAs2, ISKpn40 and IS26/15DI. Detected genetic signatures (DRs) indicated recent mcr-3 transpositions, underlining the mobilizable nature of the mcr-3 cassette.Conclusions: The epidemiology of mcr and the possible evolution of successful plasmids and transposition mod-ules should be carefully monitored. Of special concern is the growing number of different horizontal gene trans-ferring pathways encompassing various transposable modules the mcr genes can be shared between bacteria.

Published in

Journal of Antimicrobial Chemotherapy
2023, volume: 78, number: 6, pages: 1395–1405
Publisher: OXFORD UNIV PRESS

SLU Authors

• Lunha, Kamonwan

  • Department of Clinical Sciences, Swedish University of Agricultural Sciences
    

• Jiwakanon, Jatesada

  • Khon Kaen University

• Magnusson, Ulf

  • Department of Clinical Sciences, Swedish University of Agricultural Sciences
    

Associated SLU-program

AMR: Bacteria

UKÄ Subject classification

Microbiology in the medical area
Clinical Science

Publication identifier

• DOI: https://doi.org/10.1093/jac/dkad097

Permanent link to this page (URI)

https://res.slu.se/id/publ/123004