In vitro activity of daptomycin against Gram-positive cocci: the first multicentre study in Greece

Abstract

A total of 10 420 Gram-positive cocci (including staphylococci, enterococci and various groups of streptococci) collected from clinically significant specimens in ten Greek hospitals during 2006–2007 were tested for their susceptibility to daptomycin. The minimum inhibitory concentration (MIC) was determined by the broth microdilution method. Daptomycin demonstrated very high activity against Enterococcus faecalis (MIC at which 50% of the isolates were inhibited (MIC 50) = 1 mg/L and MIC at which 90% of the isolates were inhibited (MIC 90) = 1.36 mg/L), Enterococcus faecium (MIC 50 = 1.36 mg/L and MIC 90 = 1.90 mg/L), Streptococcus pyogenes (MIC 50 = 0.12 mg/L and MIC 90 = 0.50 mg/L), Streptococcus agalactiae (MIC 50 = 0.09 mg/L and MIC 90 = 0.12 mg/L), Streptococcus pneumoniae (MIC 50 = 0.24 mg/L and MIC 90 = 0.5 mg/L) and viridans group streptococci (MIC 50 = 0.50 mg/L and MIC 90 = 0.89 mg/L). Resistance to linezolid and vancomycin for enterococci and to penicillin for streptococci appears to be independent of reduced susceptibility to daptomycin. On the other hand, daptomycin was also active against meticillin-resistant Staphylococcus aureus (MIC 50 = 0.44 mg/L and MIC 90 = 0.78 mg/L) and meticillin-resistant coagulase-negative staphylococci (MIC 50 = 0.24 mg/L and MIC 90 = 0.44 mg/L); however, 0.9% of the staphylococci tested had an MIC > 1 mg/L, which is the Clinical and Laboratory Standards Institute breakpoint proposed for susceptibility. For all tested organism groups, resistance to daptomycin was not associated with glycopeptide resistance.