Blood Culture Negative Endocarditis (BCNE)

Definition:

Endocarditis without etiology following 3 sets of blood cultures with negative results after 5 days of incubation. Consult microbiologist and Infectious Diseases physician in all cases of BCNE.

- Cultures are negative for 2 major reasons:

• previous administration of antibiotics - in these cases, viridans group streptococci most likely pathogen and should be treated empirically - see relevant Empiric Therapy recommendations (native valve, IVDU, prosthetic valve)

• infection with highly fastidious bacteria (see below) or nonbacterial pathogens.

- If previous open heart surgery, consider Legionella spp or Mycobacterium spp. Consult microbiologist and Infectious Diseases.

- Also consider noninfectious causes of valvular vegetations:

• anti-phospholipid antibody (APA) syndrome

• neoplasia – atrial myxoma, marantic endocarditis, carcinoid

• autoimmune – rheumatic carditis, systemic lupus erythematosus, polyarteritis nodosa, Behcet disease

• post valvular surgery changes.

- For potential etiologic agents based on epidemiological risks; refer to Table 6 in Circulation 2015;132:1435-86.