ANTIMICROBIAL ACTIVITY OF DV-7751A, A NEW FLUOROQUINOLONE

We compared the in vitro antibacterial activity of DV-7751a against gr am-positive and -negative bacteria with those of quinolones currently available. MICs for 90% of the strains tested (MIC90s) against clinica l isolates of methicillin-susceptible and -resistant Staphylococcus au reus and Staphylococcus epidermidis were 0.20, 0.39, 0.20, and 0.78 mu g/ml, respectively. Moreover, MIC50s for DV-7751a against ofloxacin-re sistant methicillin-resistant S. aureus were 4-, 8-, 16-, 32-, and 64- fold lower than those for tosufloxacin and sparfloxacin, levofloxacin, ofloxacin and fleroxacin, ciprofloxacin, and lomefloxacin, respective ly. DV-7751a inhibited the growth of all strains of Streptococcus pneu moniae, Streptococcus pyogenes, and Peptostreptococcus spp. at 0.39, 0 .39, and 0.78 mug/ml, respectively, and was 4- to > 16-fold more activ e against enterococci at the MIC90 level than the other quinolones tes ted. The activity of DV-7751a against Pseudomonas aeruginosa was rough ly comparable to those of levofloxacin and sparfloxacin at the MIC90 l evel and was two- to fourfold less than that of ciprofloxacin. DV-7751 a showed activity comparable to those of levofloxacin and ciprofloxaci n against the other glucose-nonfermenting bacteria Haemophilus influen zae, Neisseria gonorrhoeae, and Moraxella catarrhalis (MIC90s of 0.025 , 0.20, and 0.10 mug/ml, respectively). DV-7751a activity was not affe cted by medium, inoculum size, or the addition of human serum but was decreased under acidic conditions and in human urine, as were the othe r quinolones tested. Time-kill curve studies demonstrated the rapid ba ctericidal action of DV-7751a against S. aureus, S. pneumoniae, Escher ichia coli, and P. aeruginosa. The frequency of spontaneous resistance to DV-7751a was less than or equal to those of the reference drugs. D V-7751a inhibited the supercoiling activity of DNA gyrases from S. aur eus, E. coli, and P. aeruginosa at concentrations comparable to those of levofloxacin and sparfloxacin.