The in vitro spectrum of a novel des-fluoro(6) quinolone, BMS-284756, was compared with those of five fluoroquinolones (trovafloxacin, moxifloxacin, levofloxacin, ofloxacin, and ciprofloxacin). BMS-284756 was among the most active and often was the most active quinolone against staphylococci (including methicillin-resistant strains), streptococci, pneumococci (including ciprofloxacin-nonsusceptible and penicillin-resistant strains), and Enterococcus faecalis. BMS-284756 inhibited Ϸ60 to Ϸ70% of the Enterococcus faecium (including vancomycin-resistant) strains and 90 to 100% of the Enterobacteriaceae strains and gastroenteric bacillary pathogens at the anticipated MIC susceptible breakpoint (<4 g/ml). Against the nonfermenters, BMS-284756 inhibited 90 to 100% of Pseudomonas fluorescens, Pseudomonas stutzeri, Stenotrophomonas maltophilia, Flavobacterium spp., and Acinetobacter spp. and 72% of Pseudomonas aeruginosa strains at 4 g/ml. Against anaerobic bacteria, BMS-284756 was among the most active, inhibiting essentially all strains tested. It had very low MICs against the fastidious and atypical microbial species, in particular against mycoplasmas or ureaplasmas, Borrelia burgdorferi, chlamydia, and gonococci. These results indicate that with its broad antibacterial spectrum, BMS-284756 should be evaluated clinically for the treatment of community and nosocomial infections.BMS-284756 is a novel des-fluoro(6) quinolone. This means that BMS-284756 differs from recently approved quinolones (i.e., the fluoroquinolones included in this study and gatifloxacin) in that BMS-284756 lacks a fluorine at the C-6 position. BMS-284756 (also known as T-3811ME) has antibacterial activity similar to those of fluorinated quinolones, but the des-F(6) derivatives are less acutely toxic in mice (K. Hayashi, Y. Todo, S. Hamamoto, K. Ojima, M. Yamada, T. Kito, M. Takahata, Y. Watanbe, and H. Narita, Abstr. 37th Intersci. Conf. Antimicrob. Agents Chemother., abstr. F-158, 1997).Quinolones can differ in their antibacterial spectra and potencies. Notable potency differences among quinolones occur in their activities versus gram-positive bacteria, pseudomonads, anaerobic bacteria, and mycobacteria. In the present study, the antibacterial spectrum of BMS-284756 is compared to those of five fluoroquinolones against 1,150 strains representing 66 bacterial species. While the antibacterial activity of BMS-284756 was reported previously by Takahata et al. (9), the present study included additional bacterial species and was performed using NCCLS-recommended susceptibility test methods, whenever they were available for specific bacterial groups. MATERIALS AND METHODSAntimicrobial agents. BMS-284756 was obtained from Toyama Chemical Co. Ltd., Toyama, Japan, and moxifloxacin (MFX) and ciprofloxacin (CIP) were obtained from Bayer Corporation, West Haven, Conn. Levofloxacin (LVX) and trovafloxacin (TVA) were extracted and purified from commercially available tablets and were determined to be Ն95% pure by high-performance liquid chromatography. Ofloxac...

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The in vitro antibacterial spectrum of gatifloxacin was compared with those of ciprofloxacin and ofloxacin. Gatifloxacin was two- to four-fold more potent than comparator quinolones against staphylococci, streptococci, pneumococci and enterococci (gatifloxacin MIC90s, < or =1 mg/L, except 4 mg/L against methicillin-resistant Staphylococcus aureus and Enterococcus faecium). Gatifloxacin was two-fold less potent than ciprofloxacin, and the same as or two-fold more potent than ofloxacin against Enterobacteriaceae (MIC90s, 0.06-0.5 mg/L against most members of the Enterobacteriaceae and < or =1 mg/L against Proteus/Morganella spp.). Relative to the comparator quinolones, gatifloxacin was two- to four-fold more potent against Providencia spp., and had good potency against Acinetobacter spp. (MIC90s, 0.25-1 mg/L). Gatifloxacin and ofloxacin had similar anti-pseudomonal potency, with corresponding MIC90s of 4, 8 and 0.25 mg/L for Pseudomonas aeruginosa, Pseudomonas fluorescens and Pseudomonas stutzeri, while ciprofloxacin had two- to eight-fold more potency. The three quinolones were equipotent against Burkholderia cepacia (MIC90s, 8 mg/L), but gatifloxacin was two-fold more potent against Stenotrophomonas maltophilia (MIC90, 4 mg/L). Gatifloxacin was highly potent (MIC90s, 0.03-0.06 mg/L) against Haemophilus influenzae, Legionella spp., Helicobacter pylori and had at least eight-fold better anti-chlamydial and anti-mycoplasma potency (gatifloxacin MIC90s, 0.13 mg/L). The higher quinolone MICs for ureaplasma (MIC90s, 4-8 mg/L) may be due to the acidic pH of the ureaplasma test medium, which antagonizes quinolones. Like other quinolones, gatifloxacin had poor potency against Mycobacterium avium-intracellulare, though it was eight- to 16-fold more potent against Mycobacterium tuberculosis (MIC90, 0.25 mg/L). Of the three quinolones, only gatifloxacin had activity against Bacteroides fragilis and Clostridium difficile. In summary, gatifloxacin is a broad-spectrum 8-methoxy fluoroquinolone that is more potent than ciprofloxacin and ofloxacin against Gram-positive bacteria, chlamydia, mycoplasma, mycobacteria and anaerobes.