Clostridium septicum Triad Infected Aortic Aneurysm, Empyema, and Colon Cancer

Infected aortic aneurysm is a rare occurrence accounting for 2.6% of described aneurysms. Staphylococcus species and Salmonella species are the most frequently isolated microbes, with Clostridium septicum being decidedly less commonly detected. It is well documented that C. septicum bacteremia in the presence of an infected aneurysm is strongly associated with gastrointestinal cancer, particularly colorectal adenocarcinoma. Although blood cultures were repeatedly negative, a left pleural effusion culture grew C. septicum. The patient was treated with an endovascular prosthesis and prolonged antibiotic therapy including lifelong suppression. Serial abdominal computed tomographic scans with contrast displayed an enlarging appendiceal lesion that was described as a mucocele. Surgical histopathology revealed an invasive moderately differentiated adenocarcinoma. This case highlights both the association of C. septicum with malignancy and the utility of pleural effusion culture in the presence of culture-negative infected aortic aneurysm.