In vitro susceptibilities of Bartonella and Rickettsia spp. to fluoroquinolone antibiotics as determined by immunofluorescent antibody analysis of infected Vero cell monolayers

The in vitro susceptibilities of Bartonella and Rickettsia spp. to differen t concentrations of ciprofloxacin, levofloxacin, ofloxacin and sparfloxacin in Vero cell cultures, were determined by enumeration of immunofluorescent -stained bacilli. After incubation in a CO2-enriched atmosphere, inocula we re replaced and tested with media containing 12 different concentrations of each antibiotic in replicate for each species and the monolayers were re-i ncubated. Growth status was determined by evaluation of immunofluorescent s taining bacilli. Effective inhibitory antibiotic dilution endpoints were de termined by counting Bartonella- and Rickettsia-specific fluorescent foci a cross a range of antibiotic dilutions with an epi-fluorescent microscope, a nd were compared with an antibiotic-negative control, Based upon the use of C-max:MIC and AUC:MIC data, levofloxacin exhibited activity against Barton ella elizabethae and B. quintana. (C) 2001 Elsevier Science B.V. and Intern ational Society of Chemotherapy. All rights reserved.