Activity and postantibiotic effect of marbofloxacin, enrofloxacin, difloxacin and ciprofloxacin against feline Bordetella bronchiseptica isolates

The minimum inhibitory concentration (MIC) and postantibiotic effect (PAE) of marbofloxacin, enrofloxacin, difloxacin and ciprofloxacin were evaluated in vitro against 43 feline-source Bordetella bronchiseptica strains. All s trains tested were susceptible to marbofloxacin and enrofloxacin (MIC90 0.5 mg/l), while 93 and 84% of the strains were susceptible, respectively, to ciprofloxacin and difloxacin with MIC90 values of, respectively, 1 and 8 mg /l. The PAE was studied in 10 strains by exposure of bacteria to marbofloxa cin. enrofloxacin, difloxacin and ciprofloxacin at 5 and 10 times minimum i nhibitory concentration (MIC) for 1 and 2 h. Regrowth was determined by mea suring the viable counts after drug removal by a 10(3) dilution procedure. PAEs increased as a function of concentration and exposure time. The mean d uration of PAEs varied between 1.1 and 8.2 h, showing the following order: marbofloxacin > enrofloxacin > ciprofloxacin > difloxacin. These data are e ncouraging since fluoroquinolones have a possible role in the clinical trea tment of B. bronchiseptica infections, and the strong PAE caused by quinolo nes may contribute to the in vivo efficacy of these drugs. (C) 2001 Elsevie r Science B.V. All rights reserved.