Importance of bacterial growth phase in determining minimal bactericidal concentrations of penicillin and methicillin

The minimal inhibitory concentrations of penicillin against 96 strains of group B streptococci and of methicillin against 10 strains of Staphylococcus aureus were unrelated to the growth phase of test bacteria. However, the minimal bactericidal concentrations were significantly higher in the stationary phase than the logarithmic phase for both organisms (P less than 0.001 and less than 0.05, respectively).