A rare case of Listeria monocytogenes causing mycotic aneurysm of the common femoral artery: A case report

INTRODUCTION: Mycotic aneurysms are an uncommon occurrence, withStaphylococcus and Salmonella species found to be the causative pathogen in up to 95% of cases. We believe this is the first described case of a common femoral artery mycotic aneurysm due to Listeria monocytogenes. PRESENTATION OF CASE: A 66-year-old male presented with a two-month history of an increasing painful mass in his left groin, on the background of immunosuppression treatment for ankylosing spondylitis. He was afebrile on assessment, with a normal white cell count. Contrast enhanced CT scan showed a common femoral artery aneurysm, with no infective features. His aneurysm was excised and repaired with a Dacron tube graft. L. monocytogenes was cultured from the aneurysm tissue, and he was commenced on appropriate antibiotic treatment. The prosthetic graft was also replaced with a venous bypass of the aneurysm. DISCUSSION: L. monocytogenes is a rare cause of mycotic aneurysm with less than 40 cases reported in the literature. Immunosuppression is a recognised risk factor for Listerial infections. Immunocompromised patients may not display typical clinical or biochemical features associated with a mycotic aneurysm. Prosthetic graft infections are associated with significant mortality, with excision of the prosthetic material and venous reconstruction associated with good outcomes for eradicating infection. CONCLUSION: This report highlights the importance of obtaining intraoperative tissue samples for microbiological and histopathological assessment in immunocompromised patients. This is important for the detection of rare organisms such as L.monocytogenes, requiring targeted antibiotic therapy. Inappropriate treatment of Listerial infections can result in serious invasive illness.