Ventilator-Associated Tracheobronchitis Versus Pneumonia Due to Stenotrophomonas maltophilia in Critically Ill Patients: Outcomes and Antimicrobial Treatment Patterns in a Two-Center Cohort

Background/Objectives: Stenotrophomonas maltophilia is a common cause of lower respiratory tract infection (LRTI) in critically ill patients, but differences between ventilator-associated tracheobronchitis (VAT) and ventilator- or hospital-acquired pneumonia (VAP/HAP) remain unclear. We aimed to compare clinical outcomes between VAT and VAP/HAP and, secondarily, to explore antimicrobial treatment patterns and their association with treatment failure. Methods: We conducted a retrospective two-center cohort study of adults admitted to intensive care units (ICUs) in Madrid, Spain, between August 2021 and December 2025 with clinically significant S. maltophilia VAT, VAP, or HAP. The primary analysis included only the first (index) episode per patient. Results: Sixty-seven patients contributed 90 episodes. Among index episodes, therapeutic failure was more frequent in VAP/HAP than in VAT (40.6% vs. 14.3%; absolute risk difference, 26.3 percentage points; 95% confidence interval [CI], 5.0–45.2; p = 0.026). In a parsimonious Firth’s penalized logistic regression, VAP/HAP remained associated with therapeutic failure (adjusted odds ratio, 4.06; 95% CI, 1.32–14.25; p = 0.014). Results were consistent after adjustment for SOFA score at infection onset and when the analysis was restricted to VAP. ICU mortality was numerically higher in VAP/HAP (46.9% vs. 25.7%). In an exploratory Firth’s model, laboratory-reported in vitro active antimicrobial therapy was associated with lower odds of failure (adjusted odds ratio, 0.19; 95% CI, 0.05–0.72; p = 0.014); however, this exposure was susceptible to time-dependent bias, and empirical anti-S. maltophilia therapy, defined at treatment initiation, was not associated with failure (26.7% vs. 26.9%). Conclusions: The clinical and prognostic significance of respiratory S. maltophilia infection appears to differ by syndrome. VAP/HAP was associated with more therapeutic failure than VAT. The association between in vitro active therapy and lower failure was exploratory and requires confirmation, and no comparative effectiveness conclusions can be drawn for individual antimicrobial agents.