COMPARATIVE KILLING KINETICS OF METHICILLIN-RESISTANT STAPHYLOCOCCUS-AUREUS BY BACITRACIN OR MUPIROCIN

The in vitro activities of bacitracin and mupirocin were compared for seven different strains of methicillin-resistant Staphylococcus aureus . Six of seven strains showed bacitracin minimum inhibitory concentrat ions (MICs) of 0.5 to 1.0 units/mL, and all seven had mupirocin MICs o f 0.5 to 2 mu g/mL. Time-kill studies revealed 2.6- to 4.5-log reducti on in 24 hours with strains susceptible to bacitracin (4 units/mL) and 0 to 2.2 reduction with mupirocin (16 mu g/mL). Bacitracin should be considered further for in vivo studies because of enhanced bacteriocid al effect and lower cost.