In vitro activity of moxifloxacin, a new 8-methoxyquinolone, against gram-positive bacteria

The in vitro activity of moxifloxacin,formerly BAY 12-8039, against gram-po sitive bacteria was tested by the agar dilution method. A total of 189 isol ates that included Staphylococcus aureus, Enterococcus faecalis, Enterococc us faecium, streptococci, rhodococci, leuconostocs, pediococci, lactobacill i, and diphtheroids were tested. Moxifloxacin showed greater potency than c iprofloxacin against S. aureus, streptococci, and enterococci, having Minim al Inhibitory Concentrations (MICs) lower than those of ciprofloxacin by 2- to 64-fold. This improved activity was most prominent for S. aureus. Moxif loxacin was active against Leuconostoc and Rhodococcus species. Time-kill s tudies using moxifloxacin at a concentration of 3 mu g/mL against one isola te each of methicillin-resistant S. aureus (MSSA) (MIC, 0.031 mu g/mL), MRS A (MIC, 1 mu g/mL), two isolates off. faecalis (MICS, 0.25 and 2 mu g/mL), and two isolates of vancomycin-resistant E. faecium (MICs, 0.25 and 2 mu g/ mL) revealed an average decrease in colony forming unit (CFU) by 3.8, 0.4, 4.0, 2.0, 4.2, and 1.8 log(10) CFU/mL at 24 h, respectively. Moxifloxacin i s a new 8-methoxyquinolone with improved in vitro activity against gram-pos itive bacteria. Further studies of the in vivo activity of this compound ap pear warranted. (C) 1999 Elsevier Science Inc.