Thank you to PGY2 Shawn Shah for presenting an interesting case of a 66 year old homeless male who presented with fevers, productive cough, and chronic intermittent chest pain. The patient had a transthoracic echocardiogram done which showed an EF of 35%, as well as a 1.6×1.4cm aortic valve vegetation. The patient had repeatedly negative blood cultures and culture-negative endocarditis was suspected.
What is culture negative endocarditis?
-3 negative blood cultures (after 5 days of incubation) **Remember that administration of antibiotics before obtaining blood cultures decreases the recovery rate of bacteria by 35-40%!!!
-HACEK organisms previously thought to be the most common causes, however can be easily isolated when cultured fro more than 5 days
-Certain exposures/conditions can point to a specific diagnosis such as: farm animals (Brucella, Coxiella), homeless shelters (bartonella quintana), cats (Bartonella henselae), unpasteurized milk (Brucella/Coxiella)
-Immunocompromised and HIV+ patients are at risk for fungal and Coxiella endocarditis
Remember to consider causes of noninfective endocarditis as well such as anti-phospholipid antibody syndrome (sterile valvular vegetations, most commonly affecting the mitral valve), atrial myxoma, marantic endocarditis
-ID consult is recommended for the empiric therapy of culture negative endocarditis.
-For acute presentations of native valve endocarditis (NVE), coverage for Staph aureus, beta-hemolytic strep and aerobic gram negative bacilli should be initiated (vancomycin + cephalosporin)
-For subacute presentations of NVE, coverage for Staph aureus, viridans group strep, HACEK and enterococci should be initiated (vancomycin + ampicillin-sulbactam).
**These regimens do not cover organisms for all organisms that cause culture negative endocarditis. If other organisms suspected, need additional coverage such as Doxycycline.
The patient was subsequently found to have elevated Bartonella titers and had an aortic valve replacement surgery performed, with the native valve staining positive for Warthin-Starry stain (supportive of Bartonella).
Treatment for confirmed Bartonella endocarditis: Doxycycline + Gentamicin (Rifampin if cannot use gentamicin) for 14 days. If valve surgery is performed, doxycycline alone is continued for 6 weeks. If surgery is not performed and infected tissue is still present, doxycycline is continued for 3 months.
On a semi-related note, check out the POET trial (https://www.nejm.org/doi/full/10.1056/NEJMoa1808312) which discusses the use of partial oral antibiotics in the treatment of left sided endocarditis. We will be discussing this in journal club on December 20th!