antibiotic rifampin Rifampicin is active in vitro against Brucella species, is remarkably lipid soluble, and it accumulates within eukaryotic cells. In order to provide a completely oral regimen with which to treat brucellosis, the combination of doxycycline (200 mg/day orally) plus rifampicin (60000 mg/day orally), with both drugs administered for six weeks, was recommended by the WHO Expert Committee in 1986. This regimen has generally been found to be of similar efficacy to doxycycline plus streptomycin for patients with uncomplicated brucellosis. Caution is advised when considering this regimen for patients with complications, such as spondylitis. An analysis of various treatment regimens concluded that overall the regimen of doxycycline plus streptomycin was likely to be the most effective. In addition, some data have been reported indicating that rifampicin might enhance the plasma clearance of doxycycline, thus yielding subtherapeutic levels a possible explanation of treatment failures with this regimen. (http://www.who.int/csr/resources/publications/Brucellosis.pdf p37) YH.YL B.abortus RB 51 is resistant to rifampicin.