In vitro activity of sparfloxacin (CI-978), a new broad-spectrum fluoroquinolone.

The in vitro activity of sparfloxacin (CI-978, AT-4140), a new fluoroquinolone, was compared with ciprofloxacin, norfloxacin and other commonly used antimicrobial agents against 650 strains of Enterobacteriaceae, 237 isolates of other gram-negative bacilli and 318 strains of gram-positive cocci. The MICs of sparfloxacin against 90% of the members of Enterobacteriaceae were between 0.12 and 0.5 microgram/ml. All the 48 isolates of notoriously drug-resistant Serratia marcescens were inhibited by less than 0.03-4.0 micrograms/ml of sparfloxacin. All the 90 isolates of Acinetobacter, 80 of the 88 strains of Pseudomonas aeruginosa and all the 28 isolates of Xanthomonas maltophilia were susceptible to sparfloxacin. The MIC90 for all the cocci tested ranged between 0.5 and 4.0 micrograms/ml of sparfloxacin. It inhibited 92% of enterococci as compared with 27% for ciprofloxacin and 22% for norfloxacin. It was better or comparable in activity to other fluoroquinolones and superior to penicillins, cephalosporins and aminoglycosides tested. There was cross-resistance between ciprofloxacin, norfloxacin and sparfloxacin.