Background: Stenotrophomonas maltophilia is an emerging opportunistic pathogen. The increasing incidence is of particular concern in patients with cystic fibrosis (CF). Since 2012, the Western France has witnessed high annual prevalence of S. maltophilia colonization/infection. This retrospective cohort study investigated the epidemiology of S. maltophilia emergence in the CF center of Roscoff, Western France, a region of high prevalence of CF in Europe.

Methods: All CF patients with S. maltophilia isolated in respiratory samples between December 2013 and February 2017 were included. For each patient the colonization status with S. maltophilia was determined. The epidemiological and microbiological characteristics collected were compared between colonization statuses.

Results: S. maltophilia was isolated in 90 patients (42 males, 48 females). Mean age at first colonization was 24.4±13.5 years. Annual prevalence since 2013 was high (16-17.9%), but stable. This high prevalence is mainly due to a high rate of intermittent colonization. Only 2.8% of CF patients showed chronic colonization, with significantly more frequent co-colonization by methicillin-susceptible Staphylococcus aureus (p<0.0001) and Pseudomonas aeruginosa (p<0,05). During chronic colonization, S. maltophilia acquired resistance to cotrimoxazole and β-lactams. Interestingly, there were cases of decolonization.

Conclusion: This is the first epidemiological report of S. maltophilia in a French CF center. Prevalence was stable but above the national average. Most cases were intermittent; chronic colonization was rare.