Comparative in vitro bacteriostatic and bactericidal activity of trovafloxacin, levofloxacin and moxifloxacin against clinical and environmental isolates of Legionella spp.

The susceptibility of 140 Legionella spp isolates (106 clinical and 34 envi ronmental isolates) to trovafloxacin (TRFX), levofloxacin (LEVX), moxifloxa cin (MOFX), ciprofloxacin (CIPX), ofloxacin (OFLX), erythromycin (ERY), azi thromycin (AZI) and rifampicin (RIF) was studied using a standard microdilu tion method and buffered yeast extract broth (BYE) supplemented with 0.1% a lpha -ketoglutarate. The post-antibiotic effects (PAEs) of the study drugs against 10 clinical isolates of Legionella pneumophila sg.1 were compared. The MIC inhibiting 90%, of strains tested on BYE alpha broth were 0.008, 0. 016, 0.016, 0.06, 0.125, 0.5, 0.5, and 0.004 mg/l for TRFX. LEVX, MOXX, CIP , OFLX, ERY, AZI, and RIF, respectively. The MBC/MIC ratios ranged from one to eight depending on the antibiotic tested: TRFX [1x-2xMIC], LEVX, MOM CI PX and OFLX [1x-4xMIC], RIF [2x-4xMIC], ERY and AZI [2x-8xMIC]. TRFX, RIF, LEVX, MOM CIPX, OFLX, ERY and AZI showed similar activity against Legionell a species other than L. pneumophila. One-hour exposures to the study antimi crobial agents at a concentration of 4 x MIC resulted in PAEs as follows (a verage in hours): TRFX: 2.68 h; RIF: 2.63 h; CIPX: 2.62 h; MOFX: 2.56 h; LE VX: 2.41 h; OFLX: 2.25 lt AZI: 1.65 h, and ERY: 1.54 It. In conclusion, our in vitro data confirm that trovafloxacin, levofloxacin, moxifloxacin and r ifampicin have excellent bacteriostatic and bactericidal activity against L egionella spp and show significant post-antibiotic effect. (C) 2001 Elsevie r Science B.V. and International Society of Chemotherapy. All rights reserv ed.