Significance of positive bacterial cultures from aortic aneurysm contents

Aneurysm contents were cultured in 275 patients out of a series of 546 cases undergoing infrarenal aortic aneurysm repair between 1961 and 1981. The incidence of positive cultures was 8 per cent. Cultures were more likely to be positive if taken from ruptured (16.7 per cent) and acute (9.1 per cent) aneurysms than from elective (4.2 per cent) cases (X2 = 6.69, P < 0.01). Gram-positive organisms predominated with Micrococcus being the commonest isolate. Positive cultures were seen at an annual rate of 1–3 cases up to 1976 since which time all have been negative and we believe this may be due to prophylactic antibiotics being given preoperatively rather than postoperatively. The incidence of subsequent graft sepsis was greater in patients with positive aneurysm contents cultures (7 out of 22) than in those with negative cultures (6 out of 253) (X2 = 32.7, P <0.001). We recommend the routine culture of aneurysm contents to identify patients who are at high risk of developing graft sepsis and suggest that those cases with positive cultures receive prolonged organism-specific antibiotic therapy. In addition, there is evidence that pre-operative antibiotics may eliminate organisms from aneurysms, thus reducing the subsequent risk of graft sepsis.