Long-term follow-up of positive cultures in 500 abdominal aortic aneurysms.

Routine aneurysm culture is frequently performed as it is thought that a positive culture could be a risk factor for secondary graft infection. Five hundred aneurysms, in a series of 796 patients, had microbiologic examination of the thrombus and/or aneurysm wall. Cultures were positive in 185 cases (37%), mostly due to normal skin flora microorganisms (80%), whereas 16 patients (3.2%) had infectious aortitis. Gram-stained smears were positive in nine of these 16 patients compared with two of the other 169. Of the 185 patients with positive culture, after a mean length of follow-up of 35 months, only one had a graft infection that occurred 6 years later and was not due to the same microorganism. Graft sepsis was diagnosed in six of the 296 patients who did not have a positive culture, and was related to clinically obvious locoregional or systemic foci. In this series, positive cultures from aneurysm without rupture or signs of infection were not a risk factor for secondary graft sepsis. Therefore, in cases of asymptomatic unruptured aneurysm, routine culturing is not necessary as a positive result has no pathogenic significance or therapeutic implication.