The in-vitro activity of Bay y 3118, a new chlorofluoroquinolone

The in-vitro activity of Bay y 3118, a new quinolone antimicrobial was compared with that of ciprofloxacin, sparfloxacin and three beta-lactams against 620 clinical isolates. Bay y 3118 was the most active quinolone against the majority of Enterobacteriaceae and Staphylococcus spp. The MIC90 for the members of the Enterobacteriaceae were < or = 0.12 mg/L except for Serratia spp. (1 mg/L) and in general Bay y 3118 was two-fold more active than ciprofloxacin or sparfloxacin. Strains of Pseudomonas aeruginosa were more susceptible to ciprofloxacin (MIC90 0.25 mg/L) than to Bay y 3118 (MIC90 0.5 mg/L) or sparfloxacin (MIC90 1.0 mg/L). Staphylococcus aureus was more susceptible to Bay y 3118 (MIC90 0.03 mg/L) and sparfloxacin (MIC90 0.06 mg/L) than to ciprofloxacin (MIC90 1 mg/L) and similar differences were noted for Staphylococcus saprophyticus and Staphylococcus epidermidis. Streptococcus pneumoniae was susceptible to Bay y 3118 (MIC90 0.03 mg/L) as were other streptococci. Enterococcus spp. was four-fold more susceptible to Bay y 3118 and sparfloxacin than to ciprofloxacin. All strains of Haemophilus influenzae and Moraxella spp. were inhibited by Bay y 3118 < or = 0.015 mg/L. Anaerobes were more susceptible to Bay y 3118 than to other quinolones; the MIC90 of Bay y 3118 for Bacteroides fragilis being 0.06 mg/L. Little effect was seen by increasing the inoculum from 10(4) cfu to 10(6). Bay y 3118 inhibited Chlamydia sp. at concentrations < or = 0.015 mg/L.