**Resistome and plasmidome genomic features ofmcr-1.1-harboringEscherichia coli: aOne Healthapproach**

de Oliveira, Gabriela Simões
Mayer Lentz, Silvia Adriana
Müller, Camila Zanfelice
Guerra, Rafaela Ramalho
Dalmolin, Tanise Vendruscolo
Zempulski Volpato, Fabiana Caroline
de Lima-Morales, Daiana
Wink, Priscila Lamb
Barth, Afonso Luís
Rabinowitz, Peter
Martins, Andreza Francisco

¹Hospital de Clínicas de Porto Alegre, Porto Alegre, Rio Grande do Sul, 90035-903, Brazil
²Programa de Pós-Graduação em Ciências Farmacêuticas, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, 90610-000, Brazil
³Laboratório de Microbiologia e Saúde Única, Instituto de Ciências Básicas de Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, 90035-003, Brazil
⁴Programa de Pós-Graduação em Microbiologia Agrícola e do Ambiente, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, 90035-003, Brazil
⁵Programa de Pós-Graduação em Ciências Médicas, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, 90035-003, Brazil
⁶Laboratório de Microbiologia e Imunologia Clínica, Departamento de Farmácia, Faculdade de Ciências da Saúde, Universidade de Brasília, Brasília, Distrito Federal, 70910-900, Brazil
⁷Departamento de Biociências, Universidade Federal do Paraná - Setor Palotina, Palotina, Paraná, CEP 85953-128, Brazil
⁸Laboratório de Pesquisa em Resistência Bacteriana, Hospital de Clínicas de Porto Alegre, Porto Alegre, Rio Grande do Sul, 90035-903, Brazil
⁹Department of Environmental and Occupational Health Sciences, Center of One Health Research, University of Washington, Seattle, WA, 98195, United States

^*Corresponding author. Ramiro Barcelos 2600, Laboratório 538—Instituto de Ciências Básicas da Saúde (ICBS), Universidade Federal do Rio Grande do Sul (UFRGS), Code 90035-003 Porto Alegre, Brazil. E-mail: [email protected]

^‡These two authors contributed equally to this work.

Received July 4, 2024; revised December 2, 2024; accepted January 13, 2025

Journal of Applied Microbiology 136(1):p lxaf019, January 2025. | DOI: 10.1093/jambio/lxaf019

Abstract

Aims:

This study evaluated the phenotypic and genotypic traits of mcr-1.1-harboring Escherichia coli isolates from chickens, pigs, humans, and farm environments. The resistome and the mobile genetic elements associated with the spread of mcr-1.1 in Southern Brazil were also characterized.

Methods and results:

The 22 mcr-1.1-harboring E. coli isolates from different origins were selected for antimicrobial susceptibility testing and whole genome sequencing for characterization of the resistome, plasmids, and sequence types. All isolates presented several resistance genes and harbored the mcr-1.1 gene in a highly similar IncX4 plasmid. Furthermore, the mcr-1.1 gene co-occurred with the mcr-3.12 gene in a multidrug-resistant isolate from the farm environment.

Conclusions:

These findings demonstrate that the mcr-1.1 gene in E. coli isolates from Brazil is spreading mainly by horizontal transfer of the IncX4 plasmid. The co-occurrence of mcr-1.1 and mcr-3.12 highlights pig farming as an important reservoir of colistin resistance.

Impact Statement

Our findings contribute to a better understanding of the dissemination of the mcr-1 gene by the IncX4 plasmid in southern Brazil and highlights the high similarity of the genetic background of the mcr-1 gene in isolates from different sources.