Objective: Stenotrophomonas maltophilia is a significant opportunistic pathogen, especially in immunocompromised and long-term hospitalized patients due to its extensive resistance to various antibiotics and chemotherapeutic agents. Treatment of S. maltophilia infections is challenging. In the present, it is aimed to investigate the antibiotic resistance rates and risk factors of S. maltophilia isolates in a tertiary-care university hospital.

Methods: A total of 1784 S. maltophilia isolates collected from various clinical samples between January 2013 and December 2023 were included in the study. Bacterial identification and antibiotic susceptibility testing were performed using conventional methods as well as automated systems (Microscan Beckman Coulter, USA, and VITEK 2 BioMerieux, France). Resistance rates of isolates and patient data were retrospectively analyzed.

Results: Thirteen percent of S. maltophilia isolates were from outpatient clinics, while 87% were from hospitalized patients. Among the isolates from hospitalized patients, 29.7% were from adult intensive care units. This was followed by internal medicine wards (20.3%), hematology-oncology services (14.6%), surgical wards (8.6%), and neonatal intensive care units (8.4%). The majority of isolates were obtained from respiratory samples (50.5%). Antibiotic resistance rates were determined as 2.1% for trimethoprim-sulfamethoxazole (TMP-SXT) and 5.1% for levofloxacin.

Conclusion: Hospitalization in intensive care units and immunosuppression are significant risk factors for S. maltophilia infections. Antibiotic susceptibility testing should be performed before prescribing antibiotics to prevent the development of resistance to TMP-SXT and levofloxacin, which are still effective in the treatment of S. maltophilia infections with limited antibiotic treatment options.