Abstract
Introduction Stenotrophomonas maltophilia (S. maltophilia)is an emerging opportunistic Gram-negative bacillus associated with high morbidity and mortality. However, data on its epidemiology in Portugal are limited. This study evaluated the clinical characteristics, risk factors, and outcomes of patients with S. maltophilia colonization and infection. Methods This retrospective, single-center cohort study was conducted on adult patients with S. maltophilia isolated from clinical specimens between 2020 and 2024. Patients were classified as infected or colonized, with infected cases further divided into survivors and non-survivors. Clinical, microbiological, and treatment data were analyzed using univariate and multivariate methods to identify risk factors for 30-day mortality. Results Among 97 patients, 62.9% had S. maltophilia infection and 37.1% were colonized. Infected patients more frequently had cardiovascular disease (31.1% vs. 13.9%) and immunosuppression (24.6% vs. 11.1%). Targeted antimicrobial therapy was administered to 78.7% of infected patients, primarily with co-trimoxazole. Mortality was higher in infected patients (32.8% vs 8.3%, p=0.003). Non-survivors had significantly higher rates of septic shock (66.7% vs. 12.2%, p < 0.01), recent antibiotic exposure (100.0% vs. 73.2%, p = 0.011), and cardiovascular disease (55.0% vs. 19.5%, p = 0.08). Multivariate analysis identified a lack of appropriate therapy (odds ratio (OR) 20.78, 95% CI 1.35-318.6), cardiovascular disease (OR 11.85, 95% CI 1.39-100.49), and septic shock (OR 13.18, 95% CI 1.10-157.37) as independent predictors of 30-day mortality. Conclusion S. maltophilia infections, especially in critically ill patients, are associated with high mortality, especially in patients with septic shock, recent antibiotic exposure, and cardiovascular disease. Lack of appropriate antibiotics is also an independent risk factor for mortality. Early diagnosis, prompt targeted therapy, and optimal management of comorbidities are crucial to improving outcomes.