Clinical Information

Brucella species are facultative intracellular, gram-negative bacilli that cause brucellosis in humans. Human disease is likely acquired by contact with animals infected with the organism (Brucella abortus, Brucella suis, Brucella melitensis, and occasionally Brucella canis) either by direct contact or by ingestion of meat or milk. The signs and symptoms associated with brucellosis may include fever, night sweats, chills, weakness, malaise, headache, and anorexia. The physical examination may reveal lymphadenopathy and hepatosplenomegaly. A definitive diagnosis of brucellosis is made by recovering the organism from bone marrow, blood, fluid (including urine), or tissue specimens.

In cases of suspected brucellosis, serology may assist in the diagnosis and play a supplementary role in routine culture. Antibodies to Brucella species may not become detectable until 1 to 2 weeks following the onset of symptoms, so serum specimens collected during acute disease may be negative by serology in patients with brucellosis. If serology is performed, the Centers for Disease Control and Prevention currently recommends that specimens testing positive or equivocal for IgG or IgM by a screening enzyme immunoassay be confirmed by a Brucella-specific agglutination method.