Comparative in-vitro activities of azlocillin, ticarcillin and ticarcillin plus clavulanic acid against Staphylococcus aureus, Klebsiella pneumoniae and Pseudomonas aeruginosa.

Azlocillin (5 g), ticarcillin (5 g) and ticarcillin (5 g) plus clavulanic acid (200 mg) were administered intravenously on separate days to human volunteers. Serum levels 1 h after the infusion were (mean +/- S.E.): 263 +/- 40 mg/1 for azlocillin, 238 +/- 56 mg/l for ticarcillin and 5.5 +/- 1.9 mg/l for clavulanic acid. Serum withdrawn at 0.5 h was titrated against ten strains of Staphylococcus aureus, ten Klebsiella pneumoniae and nine Pseudomonas aeruginosa of which four were resistant to ticarcillin. Against Staph. aureus and K. pneumoniae, median serum bactericidal activity (SBA) and percentage of sera with SBA greater than or equal to 1:8 were greater with ticarcillin plus clavulanic acid (median SBA 1:32 and 85% of sera with SBA greater than or equal to 1:8) than with the other two regimens. There were no differences in activity against Ps. aeruginosa.