Clostridium septicum–Infected Aortic Aneurysm
An 81-year–old man with a history of resection of anterior mediastinal tumor, hypertension, and paroxysmal atrial fibrillation was admitted to our hospital for high fever and disturbed consciousness. He was in shock state. The chest x-ray film showed enlarged aortic arch with extended pneumomediastinum along the descending aorta (Figure, A), and laboratory data indicated severe infection, liver injury, acute renal failure, and disseminated intravascular coagulation. Computed tomography scans showed a saccular thoracic aortic aneurysm with periaortic emphysema and left pleural effusion (Figure, B). There were no apparent masses implying recurrence of mediastinal tumor. Three-dimensional computed tomography angiogram more clearly demonstrated aneurysm and periaortic gas (Figure, C). Blood cultures were all positive for anaerobic Clostridium septicum. Gas production in the culture bottle was consistent with perianeurysmal gas (Figure, D). Because of multiple organ failure associated with septic shock, surgical repair was abandoned. Despite antibiotic therapy with penicillin G and clindamycin, aortic aneurysm had been rapidly enlarged from 45 to 55 mm in diameter in 5 days, and the patient died 6 days after admission. Autopsy imaging with computed tomography revealed shrunk aortic aneurysm and left hemothorax indicating rupture of the aortic aneurysm.
Infected aortic aneurysm constitutes 2.6% of aortic aneurysm.1 Staphylococcus and Salmonella species are the most commonly detected pathogens from infected aortic aneurysm, and less-common pathogens include anaerobic bacteria, such as Bacteroides and Clostridium species.2 Clostridium septicum is a Gram-positive and spore-forming bacillus and 1 of the causative organisms of gas gangrene and atraumatic myonecrosis.3 Its high virulence depends on cytolytic and lethal α-toxin.3 Because C septicum infection is highly associated with malignancy, especially cecal or colonic adenocarcinoma, it is likely that mucosal ulcerative lesion of tumor provides a portal for the bloodstream.4 Necrotic atheromatous vascular tissues may be susceptible to Clostridial infection because of their hypoxic environment. Once entered into the bloodstream, Clostridia can settle and proliferate extensively in the atherosclerotic vascular walls. Although computed tomography scan failed to detect colon tumors in the present case, we cannot exclude the possibility that the patient had a colon carcinoma. It has been reported that the rate of rupture of infected aortic aneurysm was ≤85% and that the mortality of the patients with aortic C septicum infection was 100% if surgical intervention was not performed.4 Aortic débridement and surgical repair with high-dose and long-term antibiotic treatment should be considered as early as possible.
- © 2014 American Heart Association, Inc.