Objective: Stenotrophomonas maltophilia is a nosocomial infection agent that has been isolated more frequently in recent years. Treatment is quite difficult because of its intrinsic resistance to the majority of antimicrobial agents. This study was carried out to determine the antimicrobial resistance rates of S. maltophilia strains isolated from various clinical specimens.

Method: All culture samples submitted to our laboratory between 1st January 2017 and 31st December 2018 from services were included in our study. A total of 105 strains evaluated as pathogenic microorganisms were identified as S. maltophilia with the Matrix-Assisted Laser Desorption/Ionization Time of Flight Mass Spectrometry (MALDI-TOF MS, bioMérieux, France). Antimicrobial susceptibility tests for trimethoprim-sulfamethoxazole were conducted in paralel with the Vitek 2 compact (bioMérieux, France) device and Kirby-Bauer method. The results were processed, and evaluated according to ?The European Committee on Antimicrobial Susceptibility Testing? (EUCAST) criteria Antibacterial susceptibilities of levofloxacin and ceftazidim were studied, and evaluated based on antibiotic gradient test (E-test, bioMérieux, France) and CLSI standards.

Results: Total of 105 S. maltophilia strains isolated from 41 tracheal aspirates, 16 blood, 14 urine, 12 sputum samples, seven wound sites, six bronchoalveolar lavage samples, five aspirates, two tissue, and two bile samples were analyzed. While, 12.6% of the strains were resistant to trimethoprim-sulfamethoxazole. Resistance rates for levofloxacin and ceftazidime as alternative antibiotics were e 14.5% and 65.9%, respectively. The resistance profiles of the isolates obtained from blood culture for trimethoprim-sulfamethoxazole, levofloxacin and ceftazidime were 43.8%, 8.3% and 33.3% respectively.

Conclusion: In S. maltophilia infections, levofloxacin appears to be a good alternative to trimethoprim-sulfamethoxazole. As antimicrobial resistance rates may vary, each hospital should follow its own antimicrobial resistance rates, and empirical treatment policy should be determined according to each hospital?s own antimicrobial resistance status.