THE INVITRO 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, sparfioxacin and three β-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 ≤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 sparfioxacin. 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 sparfioxacin (MIC90 1·0 mg/L). Staphylococcus aureus was more susceptible to Bay y 3118 (M1C90 0·03mg/L) and sparfioxacin (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 sparfioxacin than to ciprofloxacin. All strains of Haemophilus influenzae and Moraxella spp. were inhibited by Bay y 3118 ≤ 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 cfu to 106. Bay y 3118 inhibited Chlamydia sp. at concentrations ≤ 0·015 mg/L. © 1993 The British Society for Antimicrobial Chemotherapy.