The dog, valves’ best friend: infective endocarditis due to Capnocytophaga canimorsus—a case report

Capnocytophaga canimorsus is a Gram-negative bacillus found in the oral microbiota of dogs. It is a very rare cause of endocarditis. We hereby present a case of aortic valve endocarditis due to this microorganism.

A 39-year-old male was admitted to hospital with a history of intermittent fever and exertion dyspnoea and showed signs of heart failure on physical examination. Transthoracic and transoesophageal echocardiography confirmed the presence of a vegetation in the non-coronary cusp of the aortic valve, aortic root pseudoaneurysm, and left ventricle-to-right atrium fistula (Gerbode defect). The patient underwent aortic valve replacement with a biological prosthesis. The fistula was closed with a pericardial patch, although a dehiscence of the patch was detected in post-operative echocardiogram. The post-operative period was complicated by acute mediastinitis and cardiac tamponade secondary to a pericardial abscess, requiring emergent surgery. The patient made a good recovery afterwards and was discharged 2 weeks later.

Capnocytophaga canimorsus is a very rare cause of endocarditis, although it can be very aggressive, with high degree of valve damage, necessity of surgery, and high mortality. It mainly affects young men with no previous structural heart disease. Due to its slow growth, blood cultures can be negative, so other microbiological techniques such as 16S RNA sequencing or matrix-assisted laser desorption/ionization and time-of-flight (MALDI-TOF) can be helpful for diagnosis.