Efficacy of combination therapy versus monotherapy in the treatment of Stenotrophomonas maltophilia pneumonia

Stenotrophomonas maltophilia is intrinsically resistant to several antibiotics, making it potentially challenging to treat. Studies have demonstrated treatment failures and resistance development with monotherapy (MT); however, clinical data are limited with combination therapy (CT). To compare clinical outcomes with CT versus MT for S. maltophilia pneumonia. This was a retrospective cohort study of patients admitted between November 2011 and October 2017 with S. maltophilia pneumonia who received at least 48 h of effective therapy. The primary outcome was clinical response after 7 days of effective therapy with CT versus MT. Secondary outcomes included development of a non-susceptible isolate, 30 day microbiological cure, infection recurrence, infection-related mortality and all-cause mortality. The Wilcoxon rank sum test, the Pearson χ2 test and Fisher’s exact test were utilized for univariate analyses. A multivariable logistic regression model was used to assess clinical response while adjusting for confounding variables. Of 252 patients with S. maltophilia pneumonia included, 38 received CT and 214 received MT. There was no difference in 7 day clinical response with CT versus MT (47.4% versus 39.7%, P = 0.38), even after controlling for immune status, APACHE II score and polymicrobial pneumonia (adjusted OR 1.51, 95% CI 0.63–3.65). Thirty day microbiological cure (P = 0.44), recurrence (P = 0.53), infection-related mortality (P = 0.19) and isolation of a non-susceptible isolate during or after therapy (P = 1.00 each) were also similar between both groups; however, 30 day all-cause mortality was greater with CT (P = 0.03). CT had similar rates of clinical efficacy and resistance development compared with MT for S. maltophilia pneumonia.