In vitro-activity of clavulanic acid and amoxicillin combined against amoxicillin-resistant bacteria.

The ability of clavulanic acid to inactivate beta-lactamase was investigated using 47 amoxicillin-resistant bacteria. In the presence of 10 mg/l clavulanic acid most strains of staphylococci, Escherichia coli, Klebsiella and Proteus mirabilis became fully amoxicillin-sensitive. This effect of clavulanic acid was in most instances not observed with Serratia marcescens, Proteus inconstans, Pseudomonas aeruginosa, Enterobacter and indole-positive Proteus species.