Effect of Antimicrobial Drug Combinations on Enzymic Lysis of Staphylococcus aureus

Summary Sublethal concentrations of nafcillin, ampicillin, cloxacillin and cephalothin react with growing cells of S. aureus CHP and bring about a characteristic lytic response when these cells are subsequently incubated with lysozyme and trypsin. The same lytic effect is apparent to a much lesser degree with novobiocin but not with inhibitors of protein synthesis, e.g., chloramphenicol, tetracycline, erythromycin or actinomycin D, which in fact antagonize this effect. In combination with nafcillin, novobiocin was shown to antagonize the nafcillin-promoted enzymic lysis, while ampicillin, cloxacillin and cephalothin exerted neither antagonism or significant synergism.