Comparative in-vitro activity of A-56268 (TE-031), a new macrolide antibiotic

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Abstract
The comparative in-vitro activity of A-56268 (TE-031), a new semisynthetic marcolide antibiotic, was assessed against approximately 400 bacterial isolates. The new drug demonstrated excellent activity against penicillin-susceptible streptococci (MIC90s ≤ 0.06 mg/l) and methicillin-susceptible staphylococci (MIC90 = 0.25 mg/l). Among other Gram-positive organisms tested, a significant number were resistant to A-56268 as well as to erythromycin and clindamycin. A-56268 was at least as active as erythromycin against Pasteurella multocida and Campylobacter jejuni, but was more active than erythromycin against Legionella spp. (MIC90 ≤ 0.06 mg/l), Bacteroides fragilis (MIC90 = 4 mg/l) and Bact. melaninogenicus (MIC90 ≤ 0.125 mg/l). Activity of A-56268 was pH dependent (more active at pH 7 than at pH 6) and was moderately affected by inoculum size. The drug was bactericidal against two strains of Streptococcus pyogenes tested, but exerted a bacteriostatic effect against Staphylococcus aureus and Str. faecalis.