Epidemiology and genetic diversity of linezolid resistant enterococci clinical isolates in Belgium from 2013 to 2021

Olivier Mortelé; Stefanie van Kleef-van Koeveringe; Sarah Vandamme; Hilde Jansens; Herman Goossens; Veerle Matheeussen

doi:10.1016/j.jgar.2024.04.010

Epidemiology and genetic diversity of linezolid resistant enterococci clinical isolates in Belgium from 2013 to 2021

J Glob Antimicrob Resist. 2024 May 6:S2213-7165(24)00084-5. doi: 10.1016/j.jgar.2024.04.010. Online ahead of print.

Authors

Olivier Mortelé¹, Stefanie van Kleef-van Koeveringe², Sarah Vandamme¹, Hilde Jansens², Herman Goossens², Veerle Matheeussen³

Affiliations

¹ National Reference Centre for Enterococci and Microbiology Department, University Hospital Antwerp, Edegem, Belgium.
² National Reference Centre for Enterococci and Microbiology Department, University Hospital Antwerp, Edegem, Belgium; Laboratory of Medical Microbiology, Vaccine & Infectious Disease Institute (VAXINFECTIO), University of Antwerp, Wilrijk, Belgium.
³ National Reference Centre for Enterococci and Microbiology Department, University Hospital Antwerp, Edegem, Belgium; Laboratory of Medical Microbiology, Vaccine & Infectious Disease Institute (VAXINFECTIO), University of Antwerp, Wilrijk, Belgium; Laboratory of Medical Biochemistry, University of Antwerp, Wilrijk, Belgium. Electronic address: Veerle.matheeussen@uza.be.

PMID: 38719188
DOI: 10.1016/j.jgar.2024.04.010

Abstract

Objectives: Linezolid resistant opportunistic human pathogens Enterococcus faecalis and Enterococcus faecium are an emerging health threat as limited therapeutic options remain. The aim was to investigate the epidemiology, resistance mechanisms and genetic diversity of Belgian linezolid resistant enterococci (LRE) isolated between 2013 and 2021 received at the Belgian National Reference Centre (NRC) for Enterococci.

Methods: Linezolid susceptibility testing was performed upon request on 2458 submitted Enterococci strains. Whole genome sequencing was performed on all LRE strains.

Results: Seventy-eight LRE human isolates, of which 63 (81%) E. faecalis and 15 (19%) E. faecium strains, were submitted to the Belgian NRC for Enterococci. Of the linezolid resistant E. faecalis strains, 97% harboured the optrA (56% wild-type pE349) and 3% the poxtA gene. Of the linezolid resistant E. faecium strains, 54% harboured the G2576T point mutation in the V domain of the 23S rRNA genes, 23% the poxtA and 23% the optrA gene. Furthermore two E. faecium strains were identified with a combination of two resistance mechanisms ((i) optrA and poxtA and (ii) cfr(B) and G2576T point mutation respectively). Vancomycin resistance was observed in 15% (n=12) of the LRE. ST480 (n=42/63 typed strains, 67%) was the most frequently detected sequence type (STs) in linezolid resistant E. faecalis strains, while ST203 (n=5/15 typed strains, 33%) was the most frequently detected STs in linezolid resistant E. faecium strains.

Conclusions: E. faecalis isolates harbouring optrA were the predominant LRE in Belgium with ST480 as the most prominent MLST. Linezolid resistance in E. faecium could be attributed to either chromosomal mutations or transferable resistance determinants.

Keywords: Enterococci; LRE; Linezolid; optrA; poxtA.