INVITRO ANTIMICROBIAL ACTIVITY OF SPARFLOXACIN (AT-4140, CI-978, PD-131501) COMPARED WITH NUMEROUS OTHER QUINOLONE COMPOUNDS

Sparfloxacin (AT-4140, CI-978, PD 131501) was tested against over 800 recent bacteremic strains and compared with ciprofloxacin and six other fluoroquinolones. The 90% minimum inhibitory concentration (MIC90) ranges for the Enterobacteriaceae species were (a) sparfloxacin, 0.03-1-mu-g/ml and (b) ciprofloxacin, 0.015-0.25-mu-g/ml. Moraxella catarrhalis, Haemophilus influenzae, and Neisseria gonorrhoeae were very susceptible to sparfloxacin (MIC90S, 0.004-less-than-or-equal-to 0.03-mu-g/ml) and the other comparison drugs. Staphylococcus aureas and other staphylococci were generally susceptible to the tested fluoroquinolones but very susceptible to sparfloxacin and WIN 57273. All beta-hemolytic streptococci, enterococci, and pneumococci had sparfloxacin MICs of less-than-or-equal-to 1-mu-g/ml. Sparfloxacin was quite active against anaerobic bacteria including Bacteroides fragilis gr. and Gram-positive strains (MIC90S, less-than-or-equal-to 2-mu-g/ml). The most resistant enteric bacilli were among Serratia marcescens and the Proteae, especially the Providencia spp. (two- to eightfold higher MICs). Pseudomonas aeruginosa strains were also susceptible to sparfloxacin (MIC90, 2-mu-g/ml). Magnesium ions, CO2 incubation, and low pH had some adverse effect on sparfloxacin MICs, and resistance development was documented among current clinical isolates of staphylococci, pseudomonas, and some enteric species.