Discussion    
The morbidity and mortality rates of infectious aortic aneurysm rupture are extremely high, with a poor prognosis for non-operative cases.3 The causes of infectious aneurysms are as follows: bacterial aneurysms caused by an infectious embolus due to endocarditis; arteritis followed by an aneurysm due to bacterial invasion of an arteriosclerotic blood vessel wall; infection of a preexisting aneurysm; and traumatic, infectious pseudoaneurysms including those caused iatrogenically.4 Our patient had arteriosclerosis and a chronic dissecting lesion, which served as a nidus of infection. In absence of a preexisting aneurysm, he was diagnosed with arteritis-type aneurysm formation.
Salmonella is the most common causative organism for this type of infection, followed by Staphylococci andStreptococci .5 In this case, AmpC-producingC. freundii was the causative organism, and required long-term administration of carbapenem antibiotics. However, the antibiotics caused pseudomembranous enteritis due to C. difficile , which prolonged the duration of treatment. We administered Vancomycin and Fidaxomicin to treat the C. difficile ; Fidaxomicin was particularly effective in the patient. C. freundii is most often found in patients who are immunosuppressed; however, our patient’s immune status was normal.
Prevention of infections in prosthetic aortic grafts is important in the overall treatment strategy and the following methods should be considered: 1) meticulous removal of the abscess; 2) muscle and omental flap wrapping;6 3) addition of antibacterial agents to the prosthetic grafts, (e.g., rifampicin soaking);7 4) the use of a homograft;8 and 5) extra-anatomical revascularization.1 In such an emergency situation it was impractical to obtain a homograft. Extra-anatomical reconstruction was also non-viable for a TAAA requiring reconstruction of the major abdominal branch. Therefore, methods 1-3 were used to avoid infection of the grafts. If complete removal of the arterial wall containing the infected tissue is intended in infectious TAAA, reconstruction of the intercostal artery is not viable, and spinal cord ischemia is a concern. In this case, widespread infection made it difficult to reconstruct the intercostal artery and consequently led to paraplegia.