For suspected brucellosis, which specimen yields the highest culture sensitivity?

• A. Bone marrow
• B. Nasopharyngeal swab
• C. Sputum
• D. Stool

Answer: (A)

Bone marrow. Brucella are intracellular bacteria that localize in the reticuloendothelial system, especially within bone marrow macrophages, where they reach a higher bacterial load. This makes bone marrow cultures more likely to yield a positive result than other specimens. Nasopharyngeal swabs, sputum, and stool are not typical reservoirs for Brucella and generally have low culture positivity. Blood cultures are useful but can be less sensitive than bone marrow, especially if bacteremia is intermittent or the patient has already begun antibiotics. Because bone marrow culture is more invasive, it’s typically used when brucellosis is strongly suspected and blood culture results are negative or when maximizing yield is critical.