Microorganism-Specific Outcomes in Infective Native Aortic Aneurysm: A Comparative Analysis of Salmonella, Melioidosis, and Culture-Negative Disease in a Tropical Tertiary Centre

Background Infective native aortic aneurysm (INAA) is a rare but life-threatening vascular condition associated with substantial morbidity and mortality. The microbiological spectrum differs geographically, with Salmonella spp. predominating in East Asian populations. In tropical Southeast Asia, Burkholderia pseudomallei represents an additional endemic pathogen whose clinical behaviour in INAA remains poorly characterised. Methods A retrospective observational cohort study was performed involving patients treated for INAA at a tertiary vascular referral centre in Malaysia between January 2018 and December 2024. Patients were categorised into four microbiological groups: culture-negative, Salmonella spp., melioidosis caused by Burkholderia pseudomallei, and other organisms. Baseline demographics, anatomical characteristics, operative strategies, perioperative complications, infection-related complications, reintervention, and survival outcomes were analysed. Results Eighty-six patients were included, comprising 29 culture-negative, 27 Salmonella, 15 B. pseudomallei, and 15 other-organism cases. Melioidosis patients were significantly younger (58 ± 10 years; p=0.041), with the highest prevalence of diabetes mellitus (80.0%; p=0.038), most frequent emergency presentation (86.7%; p=0.049), and highest pre-operative C-reactive protein (median 188 mg/L; p<0.001). Thirty-day mortality was uniformly low across all groups (0 to 6.7%; p=0.62). Persistent post-operative sepsis (33.3%; p=0.047), infection-related complications (46.7%; p=0.049), and aneurysm-related death (26.7%; p=0.044) were highest in the melioidosis group. Kaplan-Meier analysis demonstrated divergence in long-term survival from 24 months onwards: estimated three-year overall survival was 95% (95% CI 76-99%) for Salmonella, 82% (95% CI 64-93%) for culture-negative disease, 67% (95% CI 41-86%) for other organisms, and 50% (95% CI 26-74%) for B. pseudomallei; however, the overall log-rank comparison did not reach conventional statistical significance (p=0.083). Conclusions INAA in tropical Southeast Asia demonstrates a distinct microbiological spectrum dominated by Salmonella spp. and B. pseudomallei. B. pseudomallei-caused INAA appears to represent a clinically high-risk phenotype characterised by severe systemic inflammation, a high rate of late infection-related complications, and worse estimated long-term survival. These survival findings should be interpreted as a clinically important trend that did not reach statistical significance in this cohort.