MIC and serum bactericidal activity of clindamycin against methicillin-resistant and -sensitive staphylococci

Six volunteers were given 600 mg clindamycin intravenously to investigate the serum bactericidal activity (SBA) against 50 methicillin susceptible (MSSA) and 50 methicillin resistant Staphylococcus aureus (MRSA) strains. Minimal inhibitory concentrations (MIC) against MSSA, MRSA and 50 methicillin resistant strains of Staphylococcus epidermidis (MRSE), of which 50% were slime-producing, were determined. SBA of clindamycin against MSSA and MRSA was equally high (mean reciprocal SBA titer against MSSA vs MRSA 1 h after application was 13.0 vs 13.45), although MICs against MRSA were markedly higher than against MSSA (MIC 90 of MRSA vs MSSA: 0.06 vs > 32 mg/l). There was no difference in MICs between slime- and non-slime-producing MRSE.