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Antimicrobial Agents and Chemotherapy, September 2001, p. 2486-2494, Vol. 45, No. 9
Institute of Medical Microbiology, University Hospital of
Frankfurt, D-60596 Frankfurt/Main,1
Pharmaceutical Microbiology, University of Bonn, D-53115
Bonn,2 Merlin GmbH, D-53332
Bornheim-Hersel,3 and Department of
Biological Electron Microscopy, University of Bayreuth, D-95440
Bayreuth,4 Germany
Received 8 March 2001/Returned for modification 25 May
2001/Accepted 14 June 2001
Little is known to date about the in vitro activity of
fluoroquinolones against Borrelia species. Our study
aimed at determining the in vitro activities of 15 quinolones against
nine isolates of the Borrelia burgdorferi sensu lato
complex in addition to one Borrelia valaisiana and one
Borrelia bissettii tick isolate. For the determination
of MICs, a standardized colorimetric microdilution method was applied.
Determination of minimal borreliacidal concentrations providing 100%
killing of the final inoculum (MBCs) after 72 h and time-kill
experiments were performed by conventional culture in
Barbour-Stoenner-Kelly medium in combination with dark-field microscopy. The rank order of potency on a microgram-per-milliliter basis for the substances with in vitro activity against B.
burgdorferi was gemifloxacin (MIC at which 90% of the isolates
tested are inhibited [MIC90], 0.12 µg/ml) > sitafloxacin (MIC90, 0.5 µg/ml), grepafloxacin
(MIC90, 0.5 µg/ml) > gatifloxacin
(MIC90, 1 µg/ml), sparfloxacin (MIC90, 1 µg/ml), trovafloxacin (MIC90, 1 µg/ml) > moxifloxacin (MIC90, 2 µg/ml), ciprofloxacin
(MIC90, 2 µg/ml) > levofloxacin (MIC90,
4 µg/ml) > ofloxacin (MIC90, 8 µg/ml), norfloxacin (MIC90, 8 µg/ml) > fleroxacin
(MIC90, >16 µg/ml), and pefloxacin (MIC90,
32 µg/ml) > nalidixic acid (MIC90, 256 µg/ml).
After 72 h of exposure, gemifloxacin was borreliacidal (100%
killing) against the isolates investigated at a median MBC of 4 µg/ml. In the other compounds tested, median MBCs were higher (
0066-4804/01/$04.00+0 DOI: 10.1128/AAC.45.9.2486-2494.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
In Vitro Activities of Fluoroquinolones against
the Spirochete Borrelia burgdorferi
8
µg/ml). Results of electron microscopy and time-kill studies clearly
support an in vitro activity of some fluoroquinolones against
borreliae. Our study demonstrates for the first time the enhanced in
vitro effectiveness of some of the recently introduced 4-quinolones
against B. burgdorferi.
*
Corresponding author. Mailing address: Institute of
Medical Microbiology, University Hospital of Frankfurt,
Paul-Ehrlich-Str. 40, D-60596 Frankfurt/Main, Germany. Phone:
49-69-6301-6441. Fax: 49-69-6301-5767. E-mail:
K.Hunfeld{at}em.uni-frankfurt.de.
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