Inhibitory Effect of Clindamycin on Production of β-Lactamase in β-Lactam-Resistant Bacteria

Abstract

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