The Synergistic Action of Cephalosporin C and Benzyl-penicillin against a Penicillinase-producing Strain of Staphylococcus aureus

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Abstract
Cephalosporin C, a hydrophilic, penicillin-like antibiotic which is insensitive to penicillinase, is much less active than benzylpenicillin against the Oxford strain of S. aureus but much more active against a penicillinase-producing strain of S. aureus (D3R). When used together, cephalosporin C and benzylpenicillin act synergistically against the later strain in vitro, presumably because cephalosporin C is a competitive inhibitor of penicillinase. When grown under certain conditions in the presence of cephalosporin C, benzylpenicillin, or bacitracin, the Oxford staphylococcus gives rise during a single culture to a resistant bacterial population consisting largely or partly of gram-negative bacilli. In the presence of bacitracin a similar change also occurs with S. aureus strain D3R.