1) to determine the risk factors for first acquisition of Stenotrophomonas. maltophilia in people with CF
2) to characterize the patterns of S. maltophilia infection in different groups of patients.
Why is this important?
S. maltophilia is an increasingly common bacterium infecting the lungs of individuals with CF. Chronic S. maltophilia infection in patients with CF is an independent risk factor for pulmonary exacerbation requiring hospitalization, and is associated with an increased risk of mortality or lung transplantation. It is therefore important to understand who is at risk of infection.
What did you do?
Children and adults followed at our Toronto CF clinics all contribute their medical information to our CF Database. We used this database to identify patients who had not been infected with S. maltophilia before 1997, and followed this group of 751 patients until 2008 to see who would become infected and what happened to them after their first infection.
What did you find?
We found that 25% of our patients had at least one positive respiratory culture for S. maltophilia during the study period. We identified that younger patients and those with a steeper rate of lung function decline were at increased risk of S. maltophilia infection. S. maltophilia was less likely to occur in patients who received oral antibiotics. Three infection patterns were identified: 1) those with persistent infection, 2) those with sporadic positive cultures and 3) those who appeared to clear the infection.
What does this mean and reasons for caution?
There were several important observations drawn from this study. The first is that children with CF were found to be at increased risk of acquiring S. maltophilia infection, contrary to previous beliefs that this bacterium was more of a problem in older patients with CF and end stage lung disease. In addition, there has previously been a reluctance to treat patients with CF with oral antibiotics due to the risk of selecting out multi-drug resistant pathogens such as S. maltophilia. However, this study demonstrated that antibiotic therapy may actually be protective against S. maltophilia by slowing lung function decline.
Further study is required to confirm these findings in other, larger CF populations. Treatment trials are also needed to determine the best management of this infection, to minimize its negative clinical consequences.