Structure-activity relationships amongst beta-lactamase inhibitors.

Using a variety of beta-lactamases including those from Escherichia coli (TEM-1), Enterobacter cloacae P99 and Staphylococcus aureus the inhibition profiles (I50 values) were determined for various groups of compounds including penicillins, penicillanic acid derivatives (sulphone and beta-halo substitutions), olivanic acids and clavulanic acid derivatives including substituted ethers and amines. Some of the latter compounds had higher activity than clavulanic acid with and without preincubation of enzyme with inhibitor but they still had poor activity against the P99 enzyme. Improvements in activity against Class I cephalosporinases were obtained with some derivatives of clavulanic acid but this was usually achieved at the expense of activity against clavulanate susceptible beta-lactamases. The olivanic acids had the highest activity against the widest range of beta-lactamases.