Activity of linezolid and daptomycin against methicillin-resistant coagulase-negative staphylococci with increased MIC for vancomycin isolated from blood cultures in pediatric patients.

We evaluated minimal inhibitory concentration (MIC) for vancomycin, daptomycin, and linezolid in methicillin-resistant coagulase-negative staphylococci (MR-CoNS). Minimal inhibitory concentration of 2-4 mg/l for vancomycin was observed in 16% of strains, and among them 19% had MIC at breakpoint for daptomycin or linezolid. Among strains completely susceptible to vancomycin, 16% had MIC at breakpoint for daptomycin and 11% had for linezolid. This large proportion of pathogens with MIC around the breakpoint suggests a possible risk of treatment failure with these drugs. This phenomenon is worth further and constant monitoring.