Population analysis in strains of Staphylococcus aureus and Staphylococcus epidermidis. II. Cefuroxime and cefotaxime.

Population analyses of susceptibility to cefuroxime and cefotaxime in penicillin-susceptible, penicillin-resistant, and methicillin-resistant strains of Staphylococcus aureus (S. aureus) and Staphylococcus epidermidis (S. epidermidis) were carried out. All strains were clinical isolates. Both antibiotics were shown to be more penicillinase-stable than cephalothin in studies of the penicillin-resistant strains of S. aureus, but less stable than methicillin. The studies of penicillin-resistant strains of S. epidermidis showed no differences in penicillinase-stability between cephalothin and the new cephalosporins. From the methicillin-resistant strains of S. aureus and S. epidermidis it was possible to select highly-resistant mutants against both antibiotics with a frequency of c. 10(-5) although MIC determinations had shown the strains to be susceptible.