Intensive care unit-acquired Stenotrophomonas maltophilia: incidence, risk factors, and outcome

Introduction The aim of this study was to determine incidence, risk factors, and impact on outcome of intensive care unit (ICU)acquired Stenotrophomonas maltophilia. Methods This prospective observational case-control study, which was a part of a cohort study, was conducted in a 30-bed ICU during a three year period. All immunocompetent patients hospitalised > 48 hours were eligible. Patients with non-fermenting Gram-negative bacilli (NF-GNB) at ICU admission were excluded. Patients without ICU-acquired S. maltophilia who developed an ICU-acquired NF-GNB other than S. maltophilia were also excluded. Screening ( tracheal aspirate and skin, anal, and nasal swabs) for NF-GNB was performed in all patients at ICU admission and weekly. Univariate and multivariate analyses were performed to determine risk factors for ICU-acquired S. maltophilia and for ICU mortality. Results Thirty-eight (2%) patients developed an S. maltophilia ICU-acquired colonisation and/or infection and were all successfully matched with 76 controls. Chronic obstructive pulmonary disease ( COPD) and duration of antibiotic treatment ( odds ratio [ OR] [ 95% confidence interval (CI)] = 9.4 [ 3 to 29], p < 0.001, and 1.4 [ 1 to 2.3], p = 0.001, respectively) were independently associated with ICU-acquired S. maltophilia. Mortality rate (60% versus 40%, OR [ 95% CI] = 1.3 [ 1 to 1.7, p = 0.037]), duration of mechanical ventilation ( 23 +/- 16 versus 7 +/- 11 days, p < 0.001), and duration of ICU stay ( 29 +/- 21 versus 15 +/- 17 days, p < 0.001) were significantly higher in cases than in controls. In addition, ICU-acquired infection related to S. maltophilia was independently associated with ICU mortality ( OR [ 95% CI] = 2.8 [ 1 to 7.7], p = 0.044). Conclusion COPD and duration of antibiotic treatment are independent risk factors for ICU-acquired S. maltophilia. ICU-acquired S. maltophilia is associated with increased morbidity and mortality rates. ICU-acquired infection related to S. maltophilia is an independent risk factor for ICU mortality.