INHIBITORY EFFECT OF CLINDAMYCIN ON PRODUCTION OF BETA-LACTAMASE IN BETA-LACTAM-RESISTANT BACTERIA

The inhibitory effect of clindamycin on beta-lactamase biosynthesis wa s investigated in beta-lactam resistant bacteria with inducible and/or constitutive production of the enzyme(s). Clinical isolates of Entero bacter cloacae (E. cloacae) and Pseudomonas aeruginosa (P. aeruginosa) were examined. Three strains of each, against which sulbactam at 8 mu g/ml reduced the minimum inhibitory concentration (MIC) of cefoperazon e (CPZ) at least 4 fold, were studied in greater detail. Although clin damycin had no appreciable effect on bacteria growth at concentrations up to 50 mug/ml, it suppressed inducible beta-lactamase biosynthesis almost completely at a concentration of 20 mug/ml. There was also a si gnificant reduction of constitutive enzyme biosynthesis by clindamycin at 50 mug/ml. Thus, it was estimated that a high concentration of cli ndamycin was required to suppress beta-lactamase biosynthesis in beta- lactamase producing bacteria of the constitutive type.