Stenotrophomonas maltophilia: to be or not to be a cystic fibrosis pathogen

Purpose of review Stenotrophomonas maltophilia can cause persistent airway colonization and chronic infection in cystic fibrosis (CF) patients. The clinical effect of chronic S. maltophilia infection is still a matter of debate. The purpose of the review is to summarize studies published during the last 1.5 years with a focus on whether S. maltophilia should be regarded as a 'true' CF pathogen. Recent findings Studies concerning the microbiological characteristics of this microorganism with special focus on identification, virulence factors, cross-infection and resistance pattern, and studies on clinical effects of chronic infection, specifically serological responses to this infection, negative effects on the clinical status and possible effects of antibiotic treatment have been reviewed. Summary S. maltophilia can be identified with certainty, has well-described virulence factors, is capable of cross-infection and often shows multiresistance. Although CF patients with chronic S. maltophilia infection have lower lung function parameters compared with other CF patients and experience more exacerbations, chronic S. maltophilia infection in itself was not associated with a worse clinical outcome. True, pathogenic effects of S. maltophilia could not be found, but the presence of chronic S. maltophilia could be a marker of more pronounced lung disease in affected patients.