| Summary: | Dalbavancin is a lipoglycopeptide antibiotic that shows potent activity against Gram-positive bacteria. It circumvents <i>vanB</i>-type glycopeptide resistance mechanisms; however, data on the in vitro activity of dalbavancin for <i>Enterococcus faecium</i> (<i>E. faecium</i>) are scarce, and thus, no breakpoints are provided. In recent years, there has been a continuing shift from <i>vanA</i>-type to <i>vanB</i>-type vancomycin-resistance in enterococci in Central Europe. Therefore, we aimed to investigate the in vitro activity of dalbavancin against different <i>van</i>-genotypes, with particular focus on <i>vanB</i>-type <i>E. faecium</i>. Dalbavancin susceptibility was determined for 25 <i>van</i>-negative, 50 <i>vanA</i>-positive, and 101 <i>vanB</i>-positive clinical <i>E. faecium</i> isolates (typed by cgMLST). Epidemiological Cut-Off Values (ECOFFs) were determined using ECOFFinder. For <i>vanB</i>-type <i>E. faecium</i> isolates, dalbavancin MICs were similar to those of vancomycin-susceptible isolates reaching values no higher than 0.125 mg/L. ECOFFs for <i>van</i>-negative and <i>vanB</i>-positive isolates were 0.5 mg/l and 0.25 mg/L respectively. In contrast, <i>E. faecium</i> possessing <i>vanA</i> predominantly showed dalbavancin MICs >8 mg/L, therefore preventing the determination of an ECOFF. We demonstrated the potent in vitro activity of dalbavancin against vancomycin-susceptible and <i>vanB</i>-type <i>E. faecium</i>. On the basis of the observed wildtype distribution, a dalbavancin MIC of 0.25 mg/L can be suggested as a tentative ECOFF for <i>E. faecium</i>.
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