Comparative in vitro activity of the new quinolone sparfloxacin (CI-978, AT-4140) against nosocomial gram-negative bloodstream isolates

The in vitro activity of sparfloxacin (CI-978, AT-4140), a new quinolone which is active against gram-negative and gram-positive bacteria, and nine other broad-spectrum antibiotics was tested against 128 gram-negative nosocomial bloodstream isolates from separate patients. Sparfloxacin and ciprofloxacin were among the most potent antibiotics against Escherichia coli (n=40), Enterobacter cloacae (n=18), Klebsiella oxytoca (n=13), and Klebsiella pneumoniae (n=19), with MIC90 values of ≤ 0.25 μg/ml. Ciprofloxacin was slightly more potent than sparfloxacin against Serratia marcescens (n=14), the MIC90 values being 0.25 and 1.0 μg/ml respectively, although all strains were susceptible to both agents. Sparfloxacin was slightly less potent than ciprofloxacin against Pseudomonas aeruginosa (n=24), the MIC90 values being 4.0 and 0.5 μg/ml respectively. Overall, the in vitro activity of sparfloxacin compared favorably with that of ciprofloxacin and the other broad spectrum agents tested against nosocomial gram-negative bloodstream isolates.