Lower extremity mycotic aneurysm in a patient with Listeria monocytogenes - associated prosthetic valve endocarditis.

Introduction. Listeria monocytogenes is a rare etiology of infectious endocarditis with only 30 cases of prosthetic valve and about twice as many native valve infections described in the literature. We describe an unusual presentation of an endovascular embolic phenomenon with associated lower extremity mycotic aneurysm due to Listeria monocytogenes prosthetic aortic valve and aortic endograft infection. Case presentation. This is a case of an elderly gentleman with prior history of bioprosthetic aortic valve placement and aortic arch repair who was admitted with several weeks of constitutional symptoms and left lower leg pain. Diagnostic work-up was consistent with thrombosed popliteal artery aneurysm. Blood cultures were positive for Listeria monocytogenes . A transesophageal echocardiogram revealed vegetation on the bioprosthetic valve. The patient underwent arterial bypass and ligation of the aneurysm as well as redoing of his aortic valve and aortic graft replacement. Histopathology of the aortic valve was remarkable for acute inflammation and Gram-positive coccobacilli and bacilli occupying intracellular spaces. The results of broad-range bacterial 16S rRNA PCR and sequence analysis of unfixed aortic valve tissue confirmed detection of L. monocytogenes . Conclusion. Infective endocarditis attributable to species of the genus Listeria is a rare entity. As such, there are no specific guidelines for treatment of Listeria monocytogenes endocarditis. However, combination of penicillin or ampicillin with gentamicin is the most acceptable approach described in the literature. Our patient was treated with ampicillin and gentamicin for 6 weeks followed by life-long amoxicillin suppression therapy. The patient remained asymptomatic at a 6 months follow up visit.