Infective Endocarditis Caused by Rhodococcus equi in an Immunocompetent Patient

Rhodococcus equi (R. equi) is a rare zoonotic organism that is found in the feces of grazing animals and in farm soil. It typically causes pulmonary disease, but it can also cause extrapulmonary disease. Immunocompromised patients are at a higher risk of developing the infection, but it has been reported in individuals with competent immune system as well. We present a unique case of infectious endocarditis (IE) due to a R. equi infection in an immunocompetent patient. A 77-year-old male with a history of coronary artery disease, prior myocardial infarction, systolic heart failure, hypertension, hyperlipidemia, aortic stenosis, and benign prostatic hypertrophy was evaluated by cardiothoracic surgery for coronary and valvular heart disease. His transesophageal echocardiogram and cardiac catheterization demonstrated severe aortic stenosis and multivessel coronary artery disease. The patient underwent coronary artery bypass grafting and simultaneous aortic valve replacement. Intraoperatively, there was exudative material covering his aortic valve, which was sent for tissue culture. Tissue culture was positive for R. equi and Enterococcus faecium.  R. equi endocarditis is a rare presentation of this organism. R. equi endocarditis is a very challenging diagnosis due to its varying presentation compared to typical IE. Detailed history taking and physical exam are extremely important to determine if further evaluation is needed. Prolonged oral and intravenous antibiotics are recommended for effective treatment.