Susceptibility of Polish Bartonella henselae strains

Due to the fastidious nature of B. henselae and the limited number of available isolates worldwide, there are few data on its in vitro susceptibility to antibiotics. We determined the minimal inhibitory concentrations (MIC) of ten antimicrobial agents against 11 feline isolates of B. henselae by Etest method. The lowest MICs were obtained for rifampicin < or = 0.002 mg/L. MICs of all isolates were < 0.016 mg/L for ampicilin, amoxicillin/clavulanic acid, tetracycline and ranged from 0.016 to 0.032 mg/L for azithromycin. The MICs for two tested fluoroquinolones: ciprofloxacin and levofloxacin ranged from 0.016 to 0.125 mg/L. The highest MICs were obtained for gentamicin ranging from 0.025 to 2.0 mg/L. Sulphonamide resistance genes sul 1, sul 2, sul 3 were not found in any of the tested isolates. Etest methodology seems to be a reliable method for determination of B. henselae susceptibility, however standardization is strongly desired.