Two cases of endocarditis as a result of Brucella have been reported in people who inject drugs without zoonotic exposure, according to a study published in Open Forum Infectious Diseases.

A rare complication of systemic Brucella infection is endocarditis, which occurs in 2% to 3% of cases and has been reported in < 400 cases since 1966. Although rare, infective endocarditis causes 80% of deaths in patients with brucellosis. Brucellosis presents with nonspecific symptoms, including fevers, malaise, arthralgia, and night sweats. Subsequent to these symptoms, focal disease develops in 30% to 90% of patients with osteoarticular, genitourinary, neurologic, or cardiovascular involvement. Although endocarditis is most commonly seen in relation to injection drug use, to date, infective endocarditis has been exclusively reported in individuals who had a clear history of animal exposure. However, the 2 cases presented in this study are thought to be the first cases associated with injection of drugs with no clear or identifiable zoonotic risk factors.

The first case was that of a 24-year-old woman who was admitted with fever. She had a history of injection heroin use and hepatitis C infection, and underwent a tricuspid valve replacement following endocarditis due to methicillin-susceptible Staphylococcus aureus. Transesophageal echocardiography demonstrated vegetation on the tricuspid prosthesis with associated regurgitation and stenosis; cardiac surgery recommended surgical intervention but this was deferred due to injection drug use. Five months after symptom onset, serologic testing for Brucella spp showed positive immunoglobulin (Ig) M, negative IgG, and positive serum agglutination test (SAT) at 1:640—two weeks later this was 1:320. Therapy with oral rifampin and doxycycline was initiated for treatment of brucellosis; however, buprenorphine therapy for opioid use disorder was refused. She was received follow-up intermittently with cardiology, cardiac surgery, and infectious diseases. Her most recent follow-up visit was 2 months after discharge, at which time she reported adherence to therapy, but refused follow-up serologic testing.

The second case occurred 8 months after the initial presentation of case 1 and involved a 44-year-old man with a history of injection drug use and chronic hepatitis C. He presented with several months of subjective fevers, malaise, night sweats, back pain, weight loss, and intermittent abdominal pain. Evaluation revealed anemia, thrombocytopenia, hepatosplenomegaly with enlargement of the portocaval and porta hepatis lymph nodes. Transesophageal echocardiography demonstrated mitral valve vegetation with associated mitral regurgitation. Rheumatoid factor was elevated (58 IU/mL), but antinuclear antibody testing was negative. After consultation with a hematologist, the patient received treatment with glucocorticoids for presumed autoimmune hemolytic anemia and thrombocytopenia. Serologic testing for Brucella spp, results showed positive IgM, negative IgG, and positive SAT at 1:320. Therapy with rifampin, doxycycline, and gentamicin was initiated. Once discharged, he was to complete 6 weeks of rifampin, doxycycline, and prednisone taper, but has been lost to follow-up.

Both patients reported living in urban areas in the Midwest and denied any zoonotic exposures, including cats, dogs, sheep, or goats. They both also denied any visits or periods of residence in rural areas or exposures to farm animals, or the consumption of unpasteurized milk or cheeses. Both patients were unwilling to discuss their sources of opioids or injective equipment.

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It is possible that there were zoonotic sources for both patients as they occurred in the same area during a narrow time frame and that it could have been connected to the source of drugs or injection equipment. Overall, the study authors concluded that, “Given these cases, we suggest consideration of brucellosis when evaluating culture-negative infective endocarditis in persons who inject drugs.”

Reference

Cafardi JM, Haas D, Lamarre T, Feinberg J. Brucella Endocarditis in persons who inject drugs. Open Forum Infect Dis. 2020;7(4):ofaa063