Antibacterial properties of AM-1155, a new 8-methoxy quinolone

AM-1155 is a new 8-methoxy quinolonecarboxylic acid with a broad spectrum of antibacterial activity. It inhibited more than 90% of clinical isolates of methicillin-susceptible Staphylococcus aureus, streptococci, Enterococcus faecalis, most of the Enterobacteriaceae, Acinetobacter calcoaceticus and Haemophilus influenzae at the concentration of 0.39 mg/L. AM-1155 was 2- to 16-fold more active than ciprofloxacin against Gram-positive organisms including methicillin-resistant staphylococci. The antibacterial activity of AM-1155 was almost equal to that of sparfloxacin against a wide range of Gram-positive and Gram-negative species. AM-1155 also showed a good activity against anaerobes. The protective efficacy of AM-1155 against experimental systemic infections with Gram-positive and Gram-negative pathogens in mice was almost equal or superior to that of sparfloxacin. AM-1155 was 5- to 28-times more effective than ciprofloxacin, in terms of ED50 at one week, in staphylococcal and streptococcal infections.