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Background: Capnocytophaga canimorsus, a bacterium found in the oral cavities of healthy cats and dogs, is rarely reported as a cause of infective endocarditis. In this report we describe such a case in a young, male dog owner who presented acutely unwell in heart failure. Case summary: A 47-year-old male presented with a subacute onset of fever, night sweats, weight loss, dyspnoea, and peripheral oedema. On clinical examination typical features of infective endocarditis, heart failure, and aortic regurgitation were found. The patient had no conventional risk factors for infective endocarditis but was a dog owner. Transthoracic echocardiography revealed vegetations on the right coronary and non-coronary cusps of the aortic valve causing severe eccentric aortic regurgitation and left ventricular dilatation. Initial blood cultures taken prior to the initiation of antimicrobial therapy showed no growth. The patient underwent aortic valve and root replacement and a 16S ribosomal RNA polymerase chain reaction (16S rRNA PCR) of the resected aortic valve tissue, using the additional primer set 785F/1175R targeting the V5-7 region of 16S rRNA, identified C. canimorsus. The patient was treated post-operatively with a 6-week course of meropenem and made a good recovery. Discussion: Suspicion of C. canimorsus causing infective endocarditis should be considered in culture-negative infective endocarditis in individuals who have close contact with dogs or cats. Those who are immunocompetent can be susceptible to this infection and so this diagnosis should not be disregarded in healthy individuals. A 16S rRNA PCR can help identify this bacterium and should be used early in cases of culture-negative infective endocarditis.

Background : European Society of Cardiology 2015 guidelines approved 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) as a useful diagnostic imaging technique in prosthetic valve endocarditis (PVE) and recent evidence seems to suggest a role of nuclear imaging in the follow-up of cardiovascular infections, but nowadays there are no sufficient data available. Case summary : A 67-year-old male presented with fever, weight loss, and fatigue. His medical history included ulcerative colitis and a previous Bentall-De Bono surgical procedure in 2014. A previous recent hospitalization to a small community hospital did not reveal a clear aetiology for the fever: transeosophageal echocardiography showed dubious peri-prosthetic tissue alterations, interpreted as post-surgical fibrosis; consequently, the patient was discharged with steroid therapy. At admission in our ward, we repeated transoesophageal echocardiography that confirmed the peri-prosthetic alterations. Moreover, 18F-FDG PET/CT showed two hypermetabolic areas, one around the prosthetic tube in the aortic bulb and the other in relation with the prosthetic aortic valve. Serological test was positive for Coxiella burnetii infection with consequent beginning of a targeted antimicrobial therapy with oral doxicycline and hydroxychloroquine. Echocardiography, serology, and 18F-FDG PET/CT follow-up demonstrated a progressive response to treatment and clinical conditions of the patient gradually improved. Discussion : According to guidelines, 18F-FDG PET/CT can be used in ambiguous PVE to improve diagnostic accuracy of standard techniques. In this case, 18F-FDG PET/CT combined with echocardiography and serological tests is used not only to better define diagnosis but also for treatment response monitoring during follow-up.