Emergence of vancomycin-resistant Enterococcus faecium vanA ST612 with reduced daptomycin susceptibility, Switzerland, 2018 to 2024.

We describe the emergence of vancomycin-resistant Enterococcus faecium (VREfm) vanA ST612 in Switzerland from 2018 to 2024 that resulted in a national outbreak investigation. This clone has predisposing genetic alterations associated with reduced daptomycin susceptibility. The National Nosocomial Outbreak Investigation Center was commissioned to assess the temporospatial distribution of this clone in Switzerland and evaluate its clinical impact. Core genome multi-locus sequence typing (cgMLST) revealed five separate VREfm vanA ST612 clusters of different sizes across different healthcare regions, but predominantly in the German-speaking part. The broad geographic dissemination and temporal variation in detection suggests multiple introductions to the healthcare system. One of these cgMLST clusters (n = 79 cases) with an infection rate of 12.8% was ongoing, mainly affecting patients with extensive contact to the Swiss healthcare system or prior antibiotic exposure. The detection of daptomycin non-susceptibility in patients without prior daptomycin exposure suggests ongoing E. faecium adaptation due to external pressures. Future prevention efforts should emphasise assessing barriers for active surveillance cultures, developing a national standard for cost-effective sequencing methods and promoting the sharing of sequencing results together with epidemiological metadata. Our report intends to raise awareness as this sequence type might already be spreading undetected in European countries.