Studies on the Antibiotic Therapy of Serious Staphylococcal Infections

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Abstract
The antibacterial activity in vitro of phenethicillin and methicillin against 100 Staphylococcus isolates is compared with that of penicillin G and other commonly used antibiotics. Phenethicillin was not significantly more active than penicillin G, probably because phenethicillin is only slightly resistant to the action of penicillinase. Phenethicillin and methicillin were not as active against penicillin-sensitive staphylococci as was penicillin G, but none of the penicillin-resistant staphylococci was resistant to the bacteriostatic action of methicillin. Depending upon the strain, the bactericidal activity of methicillin varied widely and was related to the size of the inoculum used in the sensitivity tests. Methi-cillin has impressive bactericidal activity against most coagulase-positive staphylococci. The bactericidal and bacteriostatic activity of methicillin was equalled only by that of vancomycin. Vancomycin appeared to be more active than methicillin against certain phage type 80/81 staphylococci. Methicillin and vancomycin are the preferred drugs for the initial treatment of serious infections due to staphylococci of unknown antibiotic sensitivity.