Journal Article

<i>In vitro</i> antibacterial activity of fluoroquinolones against <i>Porphyromonas gingivalis</i> strains

Sigrun Eick, Andrea Schmitt, Svea Sachse, Karl-Hermann Schmidt and Wolfgang Pfister

in Journal of Antimicrobial Chemotherapy

Published on behalf of British Society for Antimicrobial Chemotherapy

Volume 54, issue 2, pages 553-556
Published in print August 2004 | ISSN: 0305-7453
Published online August 2004 | e-ISSN: 1460-2091 | DOI: http://dx.doi.org/10.1093/jac/dkh354
In vitro antibacterial activity of fluoroquinolones against Porphyromonas gingivalis strains

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Objectives: The objective of the study was to evaluate the in vitro activity of ciprofloxacin, gatifloxacin and moxifloxacin against 16 Porphyromonas gingivalis strains.

Methods: MICs of the quinolones were established by Etest and the agar dilution technique. Experiments focused on determination of the spontaneous mutation rate and the induction of resistant strains, using 0.25-fold MIC of antibiotic. Fragments of gyrA and gyrB as well as of parC were sequenced.

Results: Moxifloxacin and gatifloxacin had very low MIC values. Subinhibitory concentrations of the fluoroquinolones rapidly induced mutations. The spontaneous mutation rate was strain- and quinolone-dependent; the lowest rate was encountered after moxifloxacin. The predicted serum concentrations of the quinolones were bactericidal to wild-type strains, but 100 mg/L of each tested quinolone was insufficient to kill a mutant exhibiting moderate resistance. Often the mutants exhibited high resistance to ≥32 mg/L. All these mutants bore a Ser-83→Phe substitution in GyrA.

Conclusions: DNA gyrase is the primary target of fluoroquinolones in P. gingivalis. In terms of the achievable level in the gingival fluid and the MICs, moxifloxacin might prevent the development of resistance and may be an alternative in the antibiotic treatment of P. gingivalis-associated periodontitis.

Keywords: P. gingivalis; periodontitis; GyrA; quinolones

Journal Article.  1780 words.  Illustrated.

Subjects: Medical Oncology ; Critical Care

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