Efficacy of apalcillin alone and in combination with four aminoglycoside antibiotics against Pseudomonas aeruginosa.

The in vitro activity of apalcillin against 258 Pseudomonas aeruginosa strains was compared with that of 3 penicillins and 5 aminoglycosides using agar dilution tests. Apalcillin showed the highest activity of all the penicillins investigated, and of the aminoglycosides tested tobramycin and amikacin were most active. On testing the combined efficacy of apalcillin with aminoglycosides by the checkerboard technique, combinations with tobramycin or amikacin were less synergistic than combinations with gentamicin or netilmicin. Antagonistic or even only additive effects were found with none of the P. aeruginosa strains.