Bacteremia is as unpredictable as clinical manifestations in human brucellosis.

Objectives: Because of the suboptimal recovery rate of brucellae from blood, it has been proposed that cultures of bone marrow, liver tissue, and lymph nodes may improve the recovery rate of the organism. Data in support of these recommendations are limited and not clearly convincing, especially that of bone marrow culture. The main purpose of this work was to evaluate the roles of blood, bone marrow, liver, and lymph node cultures in the diagnosis of human brucellosis.

Methods: Blood and bone marrow cultures were evaluated in parallel in 103 cases of human brucellosis using Castaneda's biphasic technique. Simultaneous cultures of blood, bone marrow, liver, and lymph node aspirates were also carried out for 13 of these 103 cases.

Results: Blood culture identified 47 (45.6%) cases and bone marrow culture identified 85 (82.5%) cases. Faster recovery of Brucella spp was accomplished with the bone marrow culture (2.8+/-0.7 days, p<0.05). When the results of cultures of blood and bone marrow were compared with each other in the 13 cases, it was found that bone marrow specimens could be sterile (six cases (46%)) when bacteremia was present, but Brucella melitensis was detected in liver aspirate in all these six bacteremic cases.

Conclusions: Our data indicate that it is worthwhile practicing bone marrow culture by conventional biphasic technique for the definitive and rapid diagnosis of brucellosis; this is particularly the case in developing countries where diagnostic facilities by advanced technologies such as automated culture systems with PCR are not available. Bone marrow culturing would be a better gold standard in areas where antibiotic pretreatment is common. Also, adopting the practice of culturing liver/lymph node fluids may enhance bacterial isolation and aid in the establishment of a diagnosis of brucellosis in cases for whom blood and bone marrow cultures are negative.