Comparative in vitro activity of A-56268.

The comparative in vitro activity of A-56268 was studied using 1,006 clinical isolates including streptococci, enterococci, staphylococci, Neisseria gonorrhoeae, Haemophilus influenzae and anaerobes. A-56268 showed activity comparable to that of erythromycin and was more active than josamycin and roxithromycin against erythromycin-sensitive aerobic and facultatively anaerobic gram-positive cocci. A-56268 was the most active macrolide against Clostridium spp. and Neisseria gonorrhoeae. Josamycin was more active than either A-56268 or erythromycin against the anaerobic gram-positive cocci and the Bacteroides fragilis group. Staphylococci moderately resistant or resistant to erythromycin (MIC 3.12-50 mg/l) remained susceptible to josamycin but not the other macrolides.