IN-VITRO ACTIVITY OF BAY-12-8039, A NEW FLUOROQUINOLONE

The in vitro activity of BAY 12-8039, a new fluoroquinolone, was studi ed in comparison with those of ciprofloxacin, trovafloxacin (CP 99,219 ), cefpodoxime, and amoxicillin-clavulanate against gram-negative, gra mpositive, and anaerobic bacteria, Its activity against mycobacteria a nd chlamydia was also investigated, BAY 12-8039 was active against mem bers of the family Enterobacteriaceae (MIG at which 90% of strains tes ted were inhibited [MIC(90)s] less than or equal to 1 mu g/ml, except for Serratia spp, MIC(90) 2 mu g/ml), Neisseria spp, (MIC(90)s, 0.015 mu g/ml), Haemophilus influenzae (MIC(90), 0.03 mu g/ml), and Moraxell a catarrhalis (MIC(90), 0.12 mu g/ml), and these results were comparab le to those obtained for ciprofloxacin and trovafloxacin. Against Pseu domonas aeruginosa, the quinolones were more active than the beta-lact am agents but BAY-12-8039 was less active than ciprofloxacin. Strains of Stenotrophomonas maltophilia were fourfold more susceptible to BAY 12-8039 and trovafloxacin (MIC(90)s, 2 mu g/ml) than to ciprofloxacin, BAY 12-8039 was as active as trovafloxacin but more active than cipro floxacin against Streptococcus pneumoniae (MIC(90), 0.25 mu g/ml) and methicillin-susceptible Staphylococcus aureus (MIC(90)s, 0.12 mu g/ml) . The activity of BAY 12-8039 against methicillin-resistant S. aureus (MIC(90), 2 mu g/ml) was lower than that against methicillin-susceptib le strains. BAY 12-8039 was active against anaerobes (MIC(90)s less th an or equal to 2 mu g/ml), being three- to fourfold more active agains t Bacteroides fragilis, Prevotella spp,, and Clostridium difficile tha n was ciprofloxacin. Against Mycobacterium tuberculosis, BAY 12-8039 e xhibited activity comparable to that of rifampin (MICs less than or eq ual to 0.5 mu g/ml). Against Chlamydia trachomatis and Chlamydia pneum oniae BAY 12-8039 was more active (MICs less than or equal to 0.12 mu g/ml) than either ciprofloxacin or erythromycin and exhibited a greate r lethal effect than either of these two agents, The protein binding o f BAY 12-8039 was determined at 1 and 5 mu g/ml as 30 and 26.4%, respe ctively, The presence of human serum (at 20 or 70%) had no marked effe ct on the in vitro activity of BAY 12-8039.