In vitro Susceptibility of Methicillin-Resistant Staphylococcus aureus and Slime-Producing and Non-Slime-Producing Coagulase-Negative Staphylococci to Fusidic Acid

The in vitro susceptibility of 100 oxacillin-resistant Staphylococcus aureus and 100 oxacillin-resistant coagulase-negative staphylococci (CNS; 50 slime-negative and 50 slime-positive strains) was determined by agar dilution technique, with and without the addition of 50% human serum. All strains tested were highly sensitive to fusidic acid. S. aureus and CNS showed MIC50 values of 0.125 and 0.25 mg/l, respectively. MICs of all strains increased significantly in the presence of 50% human serum. Only minor differences were noted between the MICs of slime-producing and slime-deficient CNS.