The pharmacodynamic properties of a new veterinary
fluoroquinolone antimicrobial agent,
ibafloxacin, were evaluated. Minimal inhibitory concentrations (MIC), time-kill kinetics, postantibiotic effect (PAE) and postantibiotic subminimal inhibitory concentration effects (PA-SME) were determined against pathogenic canine Gram-negative and Gram-positive bacterial isolates from dermal, respiratory and
urinary tract infections. The synergistic interactions between
ibafloxacin and its main metabolite, 8-hydroxy-ibafloxacin were investigated. Finally, the efficacy of
ibafloxacin was tested in in vivo canine
infection models.
Ibafloxacin had good activity against Pasteurella spp., Escherichia coli, Klebsiella spp., Proteus spp. and Staphylococcus spp. (MIC90=0.5 microg/mL), moderate activity against Bordetella bronchiseptica, Enterobacter spp. and Enterococcus spp. (MIC50=4 microg/mL) and low activity against Pseudomonas spp. and Streptococcus spp. The time-killing analysis confirmed that
ibafloxacin was bactericidal with a broad spectrum of activity. The PAE and PA-SME were between 0.7-2.13 and 1-11.5 h, respectively. Finally, studies in dog models of
wound infection and
cystitis confirmed the efficacy of once daily oral
ibafloxacin at a dosage of 15 mg/kg. Additional studies are needed to better define the importance of AUC/MIC (AUIC) and Cmax/MIC ratios on the outcome of
fluoroquinolone therapy in dogs.