A link between the newly described colistin resistance gene mcr-9 and clinical Enterobacteriaceae isolates carrying blaSHV-12 from horses in Sweden

Stefan Börjesson; Christina Greko; Mattias Myrenås; Annica Landén; Oskar Nilsson; Karl Pedersen

doi:10.1016/j.jgar.2019.08.007

A link between the newly described colistin resistance gene mcr-9 and clinical Enterobacteriaceae isolates carrying bla_SHV-12 from horses in Sweden

J Glob Antimicrob Resist. 2020 Mar:20:285-289. doi: 10.1016/j.jgar.2019.08.007. Epub 2019 Sep 5.

Authors

Stefan Börjesson¹, Christina Greko², Mattias Myrenås², Annica Landén², Oskar Nilsson², Karl Pedersen²

Affiliations

¹ Department of Animal Health and Antimicrobial Strategies, National Veterinary Institute (SVA), Uppsala, Sweden; Department of Biomedical and Clinical Sciences, Linköping University, Linköping, Sweden. Electronic address: stefan.borjesson@liu.se.
² Department of Animal Health and Antimicrobial Strategies, National Veterinary Institute (SVA), Uppsala, Sweden.

PMID: 31494305
DOI: 10.1016/j.jgar.2019.08.007

Abstract

Objectives: The aim of this study was to investigate the occurrence of the newly described transferable colistin resistance gene mcr-9 in extended-spectrum β-lactamase (ESBL)-producing clinical Enterobacteriaceae isolates from horses in Sweden.

Methods: A total of 56 whole-genome sequenced ESBL-producing Enterobacteriaceae isolates from horses were subjected to in silico detection of antimicrobial resistance genes and identification of plasmid replicons types. The colistin minimum inhibitory concentration (MIC) for mcr-positive isolates was determined by broth microdilution. Relatedness between Enterobacteriaceae carrying mcr genes was determined by multilocus sequence typing (MLST) and core genome MLST.

Results: Thirty ESBL-producing Enterobacteriaceae isolates from horses were positive for the colistin resistance gene mcr-9. These isolates included Enterobacter cloacae, Escherichia coli, Klebsiella oxytoca and Citrobacter freundii and belonged to diverse MLST sequence types within each species. Two of the mcr-9-containing isolates originated from the same horse. All mcr-9-positive isolates had colistin MICs below or equal to the EUCAST epidemiological cut-off value of 2 mg/L and were negative for the two potential regulatory genes qseB-like and qseC-like for mcr-9. Except for one isolate carrying only bla_TEM_-_1B, all of the isolates carried bla_SHV-12 and bla_TEM-1B, and were all considered multidrug-resistant as they harboured genes encoding resistance to aminoglycosides, chloramphenicol, fosfomycin, macrolides, quinolones, sulfonamides, trimethoprim and tetracyclines. Plasmid replicon types IncHI2 and IncHI2A were detected in all mcr-9-positive isolates.

Conclusion: The occurrence of mcr-9 was common among clinical ESBL-producing Enterobacteriaceae isolates from horses in Sweden and was linked to the ESBL-encoding gene bla_SHV-12 and plasmid replicon types IncHI2 and IncHI2A.

Keywords: Colistin resistance; ESBL; Horses; Plasmid; bla(SHV-12); mcr-9.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Animals
Bacterial Proteins / genetics
Colistin / pharmacology*
Computer Simulation
Drug Resistance, Multiple, Bacterial*
Enterobacteriaceae / classification
Enterobacteriaceae / drug effects
Enterobacteriaceae / genetics
Enterobacteriaceae / isolation & purification*
Enterobacteriaceae Infections / microbiology
Enterobacteriaceae Infections / veterinary*
High-Throughput Nucleotide Sequencing
Horse Diseases / microbiology*
Horses
Microbial Sensitivity Tests
Multilocus Sequence Typing
Plasmids / genetics
Sweden
Whole Genome Sequencing
beta-Lactamases / genetics*

Substances

Bacterial Proteins
beta-Lactamases
Colistin