Daptomycin <i>In Vitro</i> Activity against Methicillin-Resistant Staphylococcus aureus Is Enhanced by <scp>d</scp> -Cycloserine in a Mechanism Associated with a Decrease in Cell Surface Charge

Abstract

ABSTRACT The killing activity of daptomycin against an isogenic pair of daptomycin-susceptible and daptomycin-nonsusceptible (DNS) methicillin-resistant Staphylococcus aureus (MRSA) strains was enhanced by the addition of certain cell wall agents at 1× MIC. However, when high inocula of the DNS strain were used, no significant killing was observed in our experiments. Cytochrome c binding assays revealed d -cycloserine as the only agent associated with a reduction in the cell surface charge for both strains at the concentrations used.