In vitro activities of antimicrobials against Brucella abortus isolates from cattle in Korea during 1998-2006.

In vitro activities of 13 antibiotics were assessed against 85 Brucella abortus isolates from naturally infected cattle in the Republic of Korea during 1998-2006, using broth microdilution test. Tetracyclines showed the most excellent activity against B. abortus, displaying MIC values of 0.5 μg/ml or below. In particular, minocycline showed the lowest MIC₅₀/₉₀ values (0.125/0.125 μg/ml) in this study. Among four fluoroquinolones tested, ciprofloxacin (MIC₅₀/₉₀, 0.5/1 μg/ml) and norfloxacin (MIC₅₀/₉₀, 8/8 μg/ml) had the most and the least activities, respectively. Gentamicin (MIC₅₀/₉₀, 1/1 μg/ml) was more effective than streptomycin, erythromycin, rifampin, and chloramphenicol (MIC₅₀/₉₀, 2/2 μg/ml).