Bactericidal synergistic effect due to chloramphenicol-induced inhibition of staphyloccal penicillinase.

A synergistic bactericidal effect of chloramphenicol and penicillin-G was observed with 17 out of 20 beta-lactamase producing strains of Staphylococcus aureus. The synergism was due to chloramphenicol-induced inhibition of beta-lactamase production. With seven of the strains the synergistic effect was operative only with subinhibitory concentrations of chloramphenicol, while higher concentrations produced antagonism.