Comparative activity of the new fluoroquinolone Bay y3118 against 177 penicillin susceptible and resistant pneumococci.

The activity of a new fluoroquinolone, Bay y3118, was evaluated in comparison to three quinolones (ciprofloxacin, ofloxacin, lomefloxacin) and four broad-spectrum oral cephalosporins (cefpodoxime, cefuroxime, cefaclor, cefixime) against 49 penicillin-susceptible pneumococci, 77 pneumococci with intermediate resistance and 51 penicillin-resistant pneumococci. Quinolone activity was not affected by the penicillin susceptibility status of the organisms. Bay y3118 was very active against all strains, with an MIC90 of 0.015 microgram/ml. Other quinolones were less active, with MIC90s of 4 micrograms/ml (ciprofloxacin and ofloxacin) and 8 micrograms/ml (lomefloxacin). Cephalosporin MICs rose parallel to those of penicillin. Cefuroxime and cefpodoxime were the most active cephalosporins, with MIC90s for strains showing susceptibility, intermediate resistance and resistance of 0.125-0.25, 2-4 and 4 micrograms/ml, respectively. Cefaclor and cefixime were less active, with corresponding MIC90s of 1-2, 8-16 and > 16 micrograms/ml, respectively.