JAC Advance Access originally published online on August 17, 2006
Journal of Antimicrobial Chemotherapy 2006 58(4):784-788; doi:10.1093/jac/dkl341
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In vitro susceptibility of Bartonella species to 17 antimicrobial compounds: comparison of Etest and agar dilution
1 Institute for Medical Microbiology and Hygiene, University of Freiburg Germany 2 Department of Medical Microbiology, UMC St Radboud, Radboud University Nijmegen The Netherlands
Received 16 June 2006; returned 28 June 2006; revised 27 July 2006; accepted 30 July 2006
*Correspondence address. Institute for Medical Microbiology, Immunology and Hygiene, University of Cologne, Goldenfelsstrasse 1921, 50935 Cologne, Germany. Tel: +49-221/478-32100; Fax: +49-221/478-32134; E-mail: christina.doerbecker{at}uk-koeln.de
Objectives: In vitro susceptibility testing of 31 Bartonella spp. strains including 21 Bartonella henselae isolates was performed for 17 antimicrobial agents (telithromycin, four macrolides, five fluoroquinolones, five aminoglycosides, doxycycline and rifampicin).
Methods: MICs were determined by agar dilution and Etest using chocolate agar containing 5% defibrinated sheep blood as assay medium. Longer incubation periods of 35 days in a humid atmosphere with 5% CO2 were required until bacterial growth became visible and MICs could be read.
Results: The ketolide telithromycin was the most active agent exhibiting the lowest MICs. The Bartonella spp. were also highly susceptible to macrolides, particularly clarithromycin, and to doxycycline and rifampicin, with MICs of
0.12 mg/L. Gatifloxacin, gemifloxacin and moxifloxacin were the most potent fluoroquinolones, with MICs ranging from 0.06 to 2 mg/L. Netilmicin was the most active agent among the aminoglycosides. Etest MICs correlated well with MICs determined by agar dilution.
Conclusions: Telithromycin, macrolides, doxycycline and rifampicin were the most effective agents against Bartonella spp. Our data confirm that Etest may be a reliable method for determining susceptibility of Bartonella spp.
Keywords: MICs , telithromycin , macrolides , fluoroquinolones , aminoglycosides