Clavulanic acid in combination with ticarcillin: an in-vitro comparison with other beta-lactams

The in-vitro activity of ticarcillin in combination with clavulanic acid was compared with that of ticarcillin alone, piperacillin, cefotaxime and, where appropriate, other beta-lactams against a total of 301 recent clinical isolates and characterized beta-lactamase producers. An agar dilution procedure was used to determine MICs and two inocula (10(4) and 10(6) cfu) were used throughout. MICs of the combination of ticarcillin and clavulanic acid were expressed as MICs of ticarcillin in the presence of 5 or 10 mg/l of clavulanic acid. Against most members of the Enterobacteriaceae (Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Providencia stuartii and Serratia marcescens), ticarcillin plus clavulanic acid was as active as or more active than piperacillin. Against Staphylococcus aureus. Haemophilus influenzae and the Bacteroides fragilis group the combination was considerably more active than piperacillin. Piperacillin was more active than the ticarcillin/clavulanic acid combination against Pseudomonas aeruginosa.