Effect of Cephalosporin C and Various Penicillin Derivatives on Staphylococcal Penicillinase and Penicillinase-Producing Staphylococcia.∗

Summary and conclusions1. Cephalosporin C is equally inhibitory to penicillinresistant and penicillin-sensitive staphylococci. However, against sensitive strains it is not nearly so effective an antibiotic as penicillin G. 2. Cephalosporin C and penicillin G apparently do not act synergistically in inhibiting the growth of penicillin-resistant staphylococci. 3. Cephalosporin C, dimethoxyphenylpenicillin and 6-aminopenicillanic acid are hydrolyzed slowly, if at all, by staphylococcal penicillinase. 4. Cephalosporin C is an active inducer of penicillinase synthesis in staphylococci, being comparable to dimethoxyphenylpenicillin in this respect but superior to penicillin G. 5. Cephalosporin C, at relatively high concentrations, does not significantly inhibit staphylococcal penicillinase.