Chronic Stenotrophomonas maltophilia infection and mortality or lung transplantation in cystic fibrosis patients.

BACKGROUND: Chronic Stenotrophomonas maltophilia infection is an independent risk factor for severe pulmonary exacerbations in cystic fibrosis (CF) patients. The goal of this study was to determine the effect of chronic S. maltophilia infection on mortality and the need for lung transplantation in a longitudinal study of children and adults with CF.
METHODS: This was a cohort study of CF patients from the Hospital for Sick Children and St Michael's Hospital (Toronto, Canada) from 1997 to 2008. A Cox Regression model was used to estimate the hazard ratio (HR) to time of death or lung transplantation adjusting for age, gender, genotype, pancreatic status, CF related diabetes (CFRD), forced expiratory volume in 1 s (FEV1), body mass index, number of pulmonary exacerbations, Pseudomonas aeruginosa, Burkholderia cepacia complex, Aspergillus and chronic S. maltophilia infection.
RESULTS: A total of 687 patients were followed over the 12 year study period; 95 patients underwent a lung transplantation (of which 26 died) and an additional 49 patients died (total 144 events). In a Cox Regression model adjusting for baseline FEV1, baseline infection with B. cepacia complex (HR 1.72, 95% CI 1.09-2.71) and baseline chronic S. maltophilia infection (HR 2.80, 95% CI 1.65-4.76) were significantly associated with death or lung transplant. However, in a time-varying model, infection with B. cepacia complex and chronic S. maltophilia infection were no longer significant.
CONCLUSIONS: Baseline chronic S. maltophilia infection is associated with an almost three-fold increased risk of death or lung transplant in CF patients. It is still unclear, however, whether chronic S. maltophilia infection is simply a marker of severity of disease and ultimate mortality or whether it is causally related to disease progression.