1484. Impact of Combination Vs. Monotherapy on Clinical Outcomes Associated with Stenotrophomonas maltophilia Pneumonia

BACKGROUND: Stenotrophomonas maltophilia is an emerging nosocomial pathogen with intrinsic resistance to several antibiotics, making it potentially challenging to treat. Studies have demonstrated treatment failures and resistance development with monotherapy (MT); however, limited clinical data have demonstrated improved outcomes with combination therapy (CT). The aim of this study was to compare clinical outcomes with CT vs. MT for S. maltophilia pneumonia. METHODS: This was a retrospective cohort study of patients admitted to OSUWMC between November 2011 and October 2017 with S. maltophilia pneumonia who received at least 48 hours of effective therapy. Data collected included baseline characteristics, APACHE II, immune status, and therapy received. The primary outcome was clinical response after seven days of effective therapy with CT vs. MT (i.e., improvement in signs and symptoms of infection, absence of fever for 24 hours, WBC normalization if immunocompetent, and negative blood cultures if concurrently bacteremic). Secondary outcomes included development of a nonsusceptible isolate; adverse drug events (ADEs); and 30-day microbiological cure, infection recurrence, and all-cause mortality. The Wilcoxon Rank-sum test, Pearson chi-squared test, and Fisher’s exact test were utilized as appropriate. A multivariable logistic regression model was used to assess clinical response while adjusting for confounding variables. RESULTS: There were 252 patients with S. maltophilia pneumonia who met inclusion criteria, of which 38 received CT and 214 received MT. There was no difference in clinical response with CT vs. MT (47.4% vs. 39.7%, P = 0.38), even after controlling for immune status, APACHE II, and polymicrobial pulmonary infection (adjusted OR 1.49, 95% CI 0.62–3.60). Thirty-day microbiological cure (P = 0.44), recurrence (P = 0.53), all-cause mortality (P = 0.07), and isolation of a nonsusceptible isolate during (P = 0.96) or after (P = 0.85) therapy were also similar when comparing CT vs. MT. The most commonly reported ADEs were hyperkalemia and GI intolerance with trimethoprim/sulfamethoxazole and fluoroquinolones, respectively. CONCLUSION: CT had similar efficacy and development of nonsusceptibility compared with MT for S. maltophilia pneumonia. DISCLOSURES: All authors: No reported disclosures.