Comparative in-vitro susceptibilities of Pseudomonas aeruginosa, Xanthomonas maltophilia, and Pseudomonas spp. to sparfloxacin (CI-978, AT-4140, PD131501) and reference antimicrobial agents
The susceptibility of sparfioxacin, a new broad spectrum fluoroquinolone, was determined for 72 clinical isolates of Pseudomonas aeruginosa, 15 Xanthomonas maltophilia, and 19 Pseudomonas spp. The activity of sparfioxacin was compared with that of ciprofloxacin and other reference antibiotics. Sparfioxacin was the most active antibiotic tested against X. maltophilia (MIC90 1 mg/l) and the most active quinolone against P. cepacia and P. putrifaciens. Ciprofloxacin, however, demonstrated greater activity than sparfioxacin against P. fluorescens and P. stulzeri. P. aeruginosa was most susceptible to ciprofloxacin with an MIC90 of 2 mg/l, compared with an MIC90 of 8 mg/l for sparfioxacin and ofloxacin. Although cross-resistance between quinolones was noted, cross-resistance between antibiotic classes was not seen. Aminoglycoside-resistant and aminoglycoside-susceptible P. aeruginosa strains were equally susceptible to sparfioxacin. Kill curves showed sparfioxacin to be rapidly bactericidal against P. aerugmosa at 1 × MIC. Sparfioxacin demonstrated greater bactericidal activity than ciprofloxacin at 1 × and 2 × their MICs. Unlike ciprofloxacin and gentamicin, sparfioxacin showed sustained bactericidal activity at ≥ 1 MIC for 24 h.