Inhibitory and bactericidal activities of amifloxacin, a new quinolone carboxylic acid, compared with those of seven other antimicrobial agents.

The activity of amifloxacin, a new quinolone carboxylic acid compound, against 147 strains of microorganisms was studied and was compared with the activities of cinoxacin, trimethoprim, amikacin, and four beta-lactam antimicrobials. The minimal concentration at which 90% of strains were inhibited by amifloxacin was lowest for Escherichia coli and Klebsiella sp (less than or equal to 0.125 microgram/ml), followed by Proteus sp (less than or equal to 0.25 microgram/ml), Enterobacter sp and Citrobacter sp (less than or equal to 0.5 microgram/ml), Providencia sp (less than or equal to 2 micrograms/ml), and Pseudomonas aeruginosa, Serratia sp, and Acinetobacter calcoaceticus var anitratus (less than or equal to 8 micrograms/ml). When compared with the ranges of activity of seven reference antimicrobials, the range of amifloxacin activity was lowest for P aeruginosa, Citrobacter sp, Proteus sp, and A calcoaceticus var anitratus and similar to aztreonam's activity against Enterobacter sp. For amikacin-resistant P aeruginosa, the minimal inhibitory concentrations (MICs) of amifloxacin ranged from 1 to 16 micrograms/ml. The MICs and minimal bactericidal concentrations (MBCs) of amifloxacin were similar. For all strains tested, microbial susceptibilities to amifloxacin were greater than those to currently available oral antimicrobial drugs, such as cinoxacin and trimethoprim.