In vitro activity of apalcillin compared with those of piperacillin and carbenicillin against 6,797 bacterial isolates from four separate medical centers.

Quantitative susceptibility tests were performed in four separate medical centers, in which apalcillin was compared with piperacillin and carbenicillin. Data from tests of 6,797 isolates confirmed that apalcillin and piperacillin had nearly identical spectra of activity but that apalcillin was significantly more active against Pseudomonas aeruginosa (MIC required to inhibit 90% of strains, 2.0 versus 64 micrograms/ml) and Acinetobacter calcoaceticus subsp. anitratus (MIC required to inhibit 90% of strains, 2.0 versus 16 micrograms/ml). Against 166 anaerobic bacterial isolates, apalcillin demonstrated in vitro activity.