Class of 2015 Abstract / Objectives: Stenotrophomonas maltophilia is considered one of the most intrinsically resistant opportunistic infections in the hospital setting. Immunocompromised patients are at a significant risk for nosocomial S. maltophilia infection. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry can quickly identify S. maltophilia. This study sought to determine the median and range of time to appropriate therapy of S. maltophilia infections after implementation of MALDI-TOF-MS for rapid species identification. Methods: A retrospective electronic medical record review of patients admitted to UAMC-UC during the study period was utilized to determine time to appropriate therapy. Positive cultures for S. maltophilia were identified by the microbiology laboratory database and assessed for inclusion in the study. Demographic information, time of culture, time to appropriate therapy, and isolate susceptibilities were collected using a data extraction tool. Variables were assessed with medians and ranges. Results: The average time to appropriate therapy was 3.4 days with a median of 3 days (range 0-21). Most isolates were susceptible to sulfamethoxazole-trimethoprim and levofloxacin and resistant to ceftazidime. Of the 20 isolates resistant to sulfamethoxazole-trimethoprim, 14 were susceptible to levofloxacin. Only one isolate was resistant to all four drugs. Immunocompromised patients accounted for only 12% of the study population. Conclusions: After implementation of MALDI-TOF MS, the median time to appropriate therapy in S. maltophilia infection was 3 days. Rapid species identification can lead to a quicker time to appropriate therapy, which is essential for effective treatment of S. maltophilia infection.