Genomic analysis revealed distinct transmission clusters of vancomycin-resistant Enterococcus faecium ST80 in Stockholm, Sweden.

Summary Vancomycin-resistant Enterococcus faecium (VREfm) belonging to sequence type (ST) 80 has become the predominant clonal lineage in Stockholm in the last three years. ST80 accounted for 75% and 46% of VRE cases in 2018 and 2019, respectively, and gave rise to both vanA-type and vanB-type outbreaks. Non-duplicate ST80-VREfm isolates (n=188) were subjected to whole-genome sequencing. Genomic analysis revealed three distinct transmission clusters. Our study indicated that difficulties in detecting low-grade vancomycin-resistant isolates by phenotypic testing might be one of the explanatory factors for the prolonged course of vanB-type outbreaks. Herein, we also report the first optrA-positive linezolid-resistant VRE isolate in Stockholm.