Shifting Epidemiology of Stenotrophomonas maltophilia: Specimen-, Ward-, and Time-Dependent Patterns in a Tertiary Hospital 2020-2025-An Observational Study.

Background/Objectives: Stenotrophomonas maltophilia is a critical opportunistic pathogen, yet its long-term epidemiology remains underrepresented in global surveillance frameworks like WHO GLASS. We aimed to analyze its six-year epidemiological trend in a large Polish tertiary hospital. Methods: A retrospective study (2020-2025) of 399 non-duplicate isolates was conducted. Identification was performed using MALDI-TOF MS, and susceptibility was analyzed according to EUCAST breakpoints. Antibiotic consumption (DDD/100 patient-days) was correlated with isolation trends. Results: Wound/skin (36.8%) and lower respiratory tract (35.8%) samples predominated. A significant rise in respiratory isolates was observed post-2020, coinciding with peak carbapenem consumption in ICU and surgical wards. Ward-level analysis demonstrated that intensive care unit status (β = 68.9, 95% CI 46.1-91.8, p < 0.001) and carbapenem consumption (β = 0.080, 95% CI 0.004-0.156, p = 0.041) were independently associated with S. maltophilia isolation burden after adjustment for ward type (adjusted R2 = 0.80). While trimethoprim-sulfamethoxazole remained highly active, levofloxacin susceptibility showed high interannual variability. Conclusions: S. maltophilia is a stable and clinically significant threat in high-intensity hospital environments. Our findings support the inclusion of this pathogen in international AMR monitoring (GLASS) and emphasize strict carbapenem stewardship to curb its emergence.