Failure of daptomycin ß-Lactam combination therapy to prevent resistance emergence in Enterococcus faecium.

Daptomycin ß-Lactam combination therapy offers "protection" against daptomycin non-susceptibility (DNS) development in Enterococcus faecium. We report failure of this strategy and the importance of source control. Mutations were detected in the LiaF and cls genes in DNS isolates. A single DNS isolate contained an unrecognized mutation, which requires confirmation.