Clinical and microbiological characteristics of mycotic aneurysms in a medical center in southern Taiwan

Background and Purpose: Mycotic aneurysm poses a high risk of mortality. This study evaluated the demographic and clinical characteristics and outcomes of hospitalized patients with mycotic aneurysm. Methods: Patients with mycotic aneurysm hospitalized between March 1996 and May 2006 at a medical center in southern Taiwan were retrospectively analyzed. Results: Fifty two patients (38 men and 14 women; mean age, 64.5 ± 15.6 years) were included. The leading underlying diseases were diabetes mellitus (40.4%), hypertension (21.2%), and renal disease and heart disease (19.2% each). The most common pathogens isolated from blood and/or resected tissue were Salmonella spp. (34.6%), Klebsiella pneumoniae (11.5%) and Staphylococcus aureus (11.5%). Mycotic aneurysms caused by Gram-negative bacilli were significantly more likely to occur in older patients (p=0.018) and at infrarenal sites (p=0.021). There were trends suggesting that mycotic aneurysms were more likely to be caused by Gram-negative bacilli in patients receiving steroid treatment and in those with underlying diabetes mellitus. Mycotic aneurysms caused by Gram-positive cocci were significantly more likely to occur in suprarenal arteries (p=0.048), especially intracranially (p=0.002), in younger patients (p=0.018) and in patients with concurrent endocarditis (p=0.008). The overall in-hospital mortality rate was 30.6%, and there was no significant difference in in-hospital mortality between mycotic aneurysms caused by Gram-negative bacilli and those due to Gram-positive cocci. Conclusions: The relationship between the anatomic site of mycotic aneurysm and the spectrum of culprit bacteria may help clinicians promptly choose appropriate antibiotic regimens on an empirical basis. Further study is required to understand better the role of K. pneumoniae in mycotic aneurysm in Taiwan.