Antimicrobial susceptibility of Bordetella avium and Ornithobacterium rhinotracheale strains from wild and domesticated birds in Hungary.
The antimicrobial susceptibility of 19 Bordetella avium and 36 Ornithobacterium rhinotracheale strains was tested by the Kirby-Bauer disk diffusion method, and the minimal inhibitory concentrations (MIC) of amoxicillin, doxycycline and erythromycin were also determined. Most O. rhinotracheale strains were resistant to nalidixic acid, sulphamethoxazole-trimethoprim and gentamicin, and were susceptible to ampicillin, chloramphenicol, spectinomycin and tilmicosin. All B. avium strains were resistant to ceftiofur and lincomycin and susceptible to doxycycline, gentamicin, polymyxin B, spectinomycin and sulphonamides. The MICs ranged widely for all three antibiotics tested against O. rhinotracheale strains, from 0.12 µg/ml to 32 µg/ml for amoxicillin and erythromycin, and from 0.6 µg/ml to 32 µg/ml for doxycycline. For B. avium isolates, the MIC values ranged from ≤0.03 µg/ml to 1 µg/ml for amoxicillin, from ≤0.03 µg/ml to 0.12 µg/ml for doxycycline and from 8 µg/ml to 16 µg/ml for erythromycin. These findings support the idea that the use of antibiotics in a region or a farm may affect antimicrobial resistance and underline the need for prudent application of antibiotic therapy based on proper antimicrobial susceptibility testing.