Antipneumococcal activity of BAY 12-8039, a new quinolone, compared with activities of three other quinolones and four oral beta-lactams.

Activities of BAY 12-8039 against 205 pneumococci were tested by agar dilution. MICs (in micrograms per milliliter) at which 50 and 90% of the isolates are inhibited (MIC50s and MIC90s, respectively) were 0.125 and 0.25 (BAY 12-8039), 2.0 and 4.0 (ciprofloxacin and ofloxacin), and 0.25 and 0.5 (sparfloxacin). Beta-lactam MIC50s and MIC90s for penicillin-susceptible, -intermediate, and -resistant strains, in that order, were 0.016 and 0.03, 0.25 and 2.0, and 2.0 and 4.0 (amoxicillin); 0.03 and 0.06, 0.25 and 4.0, and 4.0 and 8.0 (ampicillin); 0.03 and 0.06, 0.5 and 4.0, and 4.0 and 8.0 (cefuroxime); and 0.03 and 0.125, 0.25 and 2.0, and 4.0 and 8.0 (cefpodoxime). At two times their MICs after 24 h, BAY 12-8039, ciprofloxacin, ampicillin, and cefuroxime were uniformly bactericidal (99.9% killing) against 12 strains; other compounds were bactericidal at four times their MICs.