Abstract
BACKGROUND: Stenotrophomonas maltophilia, a MDR pathogen, causes healthcare-associated infections in critically ill patients. Deep-seated infections pose treatment challenges due to high bacterial inocula and biofilms. Prior studies often include polymicrobial or colonization cases, complicating evaluations. This study compares monotherapy versus combination therapy in deep-seated, monomicrobial infections to clarify optimal treatment. METHODS: This single centre, retrospective study evaluated patients admitted from 2010 to 2023 with deep-seated, monomicrobial S. maltophilia infections receiving in vitro active antimicrobials within 72 h of culture collection. The primary outcome was clinical failure, defined as 30-day all-cause mortality, infection-related readmission, or recurrent infection. Regression models used inverse probability of treatment weighting and time-varying covariates. RESULTS: Among 190 patients, 99 (52.1%) received monotherapy and 91 (47.9%) received combination therapy. Clinical failure occurred in 30.3% of monotherapy and 34.1% of combination therapy patients (P = 0.579). In propensity-weighted regression, combination therapy with levofloxacin plus minocycline (adjusted odds ratio [aOR] 0.44, 95% CI 0.17-0.94, P = 0.022) and levofloxacin plus trimethoprim/sulfamethoxazole (aOR 0.19, 95% CI 0.08-0.76, P = 0.035) was associated with reduced odds of clinical failure. Higher SOFA scores (aOR 1.89, 95% CI 1.25-2.12, P = 0.033), prior carbapenem use (aOR 2.02, 95% CI 1.54-2.24, P = 0.014) and empyema (aOR 2.77, 95% CI 2.18-3.96, P = 0.011) increased the odds of clinical failure. CONCLUSION: Levofloxacin-based combination therapies may reduce clinical failure in deep-seated S. maltophilia infections, while SOFA scores, carbapenem use and empyema increase risk. Prospective trials are warranted to confirm the efficacy of levofloxacin-based combinations.