This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bacteria, Subject name: Microbiology
Fever of unknown origin in a farmer who raises goats would most likely be caused by which of the following organisms? 
Select and explain. 
A. Brucella melitensis, B. Clostridium novyi, C. T. pallidum, D. Histoplasma capsulatum
A: Brucella melitensis
Answer: A: Brucella melitensis 
Explanation: Brucella are small, aerobic, Gram-negative coccobacilli. Of the four well-characterized species of Brucella, only one-B. melitensis-characteristically infects both goats and humans. Brucellosis may be associated with gastrointestinal and neurologic symptoms, lymphadenopathy, splenomegaly, hepatitis, and osteomyelitis.