Clinical Pearls & Morning Reports
Infection with bartonella species is among the most common causes of culture-negative endocarditis in the United States. Read the NEJM Clinical Problem-Solving Article here.
Q: Name some of the causes of palpable purpura.
A: Palpable purpura are a hallmark of cutaneous vasculitis. Causes include autoimmune disorders, cryoglobulinemia caused by infection or an autoimmune disorder, antineutrophil cytoplasmic antibody (ANCA)–associated vasculitis, bacterial endocarditis, cancer, and certain medications, such as allopurinol.
Q: Which bartonella species, in addition to Bartonella henselae, is responsible for most of the clinical infections caused by these bacteria?
A: Bartonella species are gram-negative bacilli that cause a range of diseases in humans, including bacillary angiomatosis, cat scratch disease, bacteremia, and endocarditis. Of the more than 30 known bartonella species, B. quintana, transmitted by body lice, and B. henselae, transmitted by cats with claws that are contaminated with B. henselae–infected flea feces, cause most clinical infections.
A: Bartonella endocarditis typically involves the aortic valve. Bartonella endocarditis can lead to vasculitic manifestations, such as glomerulonephritis. The renal-biopsy findings in patients with bartonella endocarditis–associated glomerulonephritis are variable, but most case reports describe an immune-complex pattern of glomerular injury, sometimes with positive test results for ANCAs. Less commonly, patients with bartonella endocarditis present with a pauci-immune glomerulonephritis and have positive test results for ANCAs, findings that mimic primary ANCA-associated vasculitis. Immune-mediated complications of bartonella infection usually diminish with appropriate antibiotic therapy; in most cases, immunosuppression is not required.
A: Randomized, controlled trials are lacking to guide the treatment of bartonella endocarditis. Some experts recommend a combination of doxycycline plus gentamicin for initial treatment of bartonella endocarditis. A 2003 retrospective report of a heterogeneous group of patients with bartonella endocarditis suggested that patients receiving at least 14 days of an aminoglycoside had improved outcomes. Although 2004 treatment guidelines were based on that report, it is prudent to avoid aminoglycosides in patients with associated glomerulonephritis or other conditions that may result in renal complications, given the potential for the development of irreversible renal failure. A regimen of rifampin (which has excellent intracellular penetration as well as bactericidal properties) plus doxycycline is recommended as an alternative. Because relapse is a risk in patients with endovascular and disseminated bartonella infections, the treatment of bartonella endocarditis should be prolonged. Bartonella antibody titers should be obtained every 4 to 8 weeks. Titers should decrease over a period of months.