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Antimicrobial Agents and Chemotherapy, 06 1997, 1326-1330, Vol 41, No. 6
Y Takahashi, N Masuda, M Otsuki, M Miki and T Nishino
The in vitro activity of the new fluoroquinolone HSR-903 was compared with
those of ciprofloxacin, lomefloxacin, sparfloxacin, and levofloxacin.
HSR-903 inhibited 90% of methicillin-susceptible and - resistant
Staphylococcus aureus (MRSA) clinical isolates at 0.78 and 1.56 microg/ml,
respectively, and its activity against MRSA was 16-fold higher than those
of sparfloxacin and levofloxacin and 64-fold higher than that of
ciprofloxacin. The MICs at which 90% of the isolates are inhibited (MIC90s)
of HSR-903 for Streptococcus pyogenes and penicillin G-susceptible and
-resistant Streptococcus pneumoniae (PRSP) were 0.10, 0.05, and 0.05
microg/ml, respectively. Against PRSP, the activity of HSR-903 was 4-fold
higher than that of sparfloxacin and 32- to 256-fold higher than those of
the other quinolones. The MIC90 of HSR-903 for Enterococcus faecalis was
0.20 microg/ml, and HSR-903 was more active than the other quinolones
against enterococci. The activity of HSR-903 against members of the family
Enterobacteriaceae and Pseudomonas aeruginosa was roughly similar to that
of ciprofloxacin and greater than those of the other quinolones. Against
Haemophilus influenzae, Moraxella catarrhalis, and Helicobacter pylori,
HSR-903 was the most potent of the quinolones tested. The activity of
HSR-903 was not affected by the medium, the inoculum size, or the addition
of serum, but decreased under acidic conditions, as did those of the other
quinolones tested. HSR-903 exhibited rapid bactericidal action and had a
good postantibiotic effect on S. aureus and P. aeruginosa. HSR-903
inhibited supercoiling by DNA gyrase from Escherichia coli, but it was much
less active against human topoisomerase II.
Copyright © 1997 by the American Society for Microbiology. All rights reserved.
In vitro activity of HSR-903, a new quinolone
Department of Microbiology, Kyoto Pharmaceutical University, Yamashina- ku, Japan.
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