In vitro activity of BAY 12-8039, a new fluoroquinolone, against species representative of respiratory tract pathogens

The in vitro antibacterial activity of BAY 12-8039, a novel 8-methoxy-quinolone, was compared with those of other quinolones, amoxicillin/clavulanate, cefuroxime and erythromycin against species commonly implicated in respiratory tract infections as well as viridans group streptococci. The new compound was highly active against methicillin-susceptible staphylococci (MIC90 0.125 mu g/ml), penicillin-susceptible and penicillin-resistant pneumococci (MIC90 0.5 and MIC50 0.25 mu g/ml, respectively), penicillin-susceptible and penicillin-resistant viridans group streptococci (MIC90 0.5 and 0.25 mu g/ml, respectively), group A streptococci (MIC,, 0.25 mu g/ml), M. catarrhalis (MIC90 0.125 mu g/ml) and H. influenzae (MIC90 0.063 mu g/ml), irrespective of beta-lactamase production. It was, however, less active against methicillin-resistant staphylococci (MIC50 and MIC90, 2 and 4 mu g/ml, respectively). The new compound demonstrated bactericidal activity at concentrations 2, 4, 8 times the MIC against representative isolates of the above collection. At a concentration of eight times the MIG, the frequency of spontaneous resistance ranged from 2.5 x 10(-7) to <4 x 10(-8). These results suggested that BAY 12-8039 would be a promising agent for the eradication of respiratory tract pathogens and that clinical trials assessing its efficacy for the management of infections caused by these organisms are warranted. (C) 1998 Elsevier Science B.V./International Society of Chemotherapy. All rights reserved.