Bacterial presence in aortic thrombus at elective aneurysm resection: is it clinically significant?

Infected thrombus in an abdominal aortic aneurysm represents a potential source of subsequent aortic graft sepsis. Previous reports have documented a 10 to 15 percent incidence of positive results of culture of the contents of an abdominal aortic aneurysm and have recommended prolonged postoperative organism-specific antibiotic therapy when a positive culture is encountered. In our study, we cultured the intraluminal thrombus during elective aneurysm repair in 64 patients with abdominal aortic aneurysms and found bacterial growth in 9 (14 percent of all patients). Eight of the nine patients received no antibiotic therapy other than the routine prophylaxis regimen, and no evidence of either early or late prosthetic graft sepsis occurred (mean follow-up 25 months). We conclude that a positive result of culture may not imply clinical infection at the time of operation and that prolonged postoperative organism-specific antibiotic therapy does not appear necessary in the patient with an asymptomatic aneurysm and no overt evidence of infection of the aneurysm at the time of operation.