Antimicrobial susceptibility of Francisella noatunensis subsp. noatunensis strains isolated from Atlantic cod Gadus morhua in Norway.

A total of 30 isolates of Francisella noatunensis subsp. noatunensis isolated from Atlantic cod Gadus morhua L. were tested for susceptibility, in the form of minimal inhibitory concentration (MIC) values, against the following antibacterial agents: flumequine, oxolinic acid, ciprofloxacin, florfenicol, oxytetracycline, erythromycin, streptomycin sulphate, trimetoprim/sulphadiazine and rifampin. All the isolates had a low susceptibility to oxytetracycline, trimetoprim/sulphadiazine (Tribrissen®), erythromycin, ciprofloxacin and streptomycin with MIC values of 64, 64 to 128, 16, 8 and 32 to 128 µg ml-1, respectively. The strains were, on the other hand, susceptible to florfenicol, oxolinic acid, flumequine and rifampin with MIC values of 0.5, 0.25, 0.25 and 0.25 to 1 µg ml-1, respectively.