Role of Stenotrophomonas maltophilia isolation in patients with non CF bronchiectasis

Background: Stenotrophomonas maltophilia is a bacteria whose role in patients with cystic fibrosis bronchiectasis has been previously studied; little is known about its role in non-CF bronchiectasis. Aim: Investigate the risk factors for S. Maltophilia acquisition and its clinical impact on bronchiectasis patients. Design: A retrospective observational cohort study enrolling patients attending the Bronchiectasis Clinic at the Royal Infirmary of Edinburgh, Scotland, UK. Methods: 167 bronchiectasis patients undergoing intravenous antibiotic therapy were selected and divided according to single or chronic S. Maltophilia isolation in sputum. The risk factors and prognostic impact was studied. Results: Single isolation was independently associated with lower baseline % predicted FEV1 (OR 0.98; 95%CI 0.970-1,044; p = 0.025) and with less radiological involvement (OR 0.379; 95%CI 0.175-0.819; p = 0.01). Chronic isolation was associated with the number of intravenous antibiotic courses in the year before and after the first isolation (OR 1.2; 95%CI 1.053-1.398; p = 0.007) and with the absence of P. Aeruginosa colonisation (OR 0.207; 95%CI 0.056-0.764; p = 0.02). In the chronic isolation group, there were more exacerbations and more need of intravenous antibiotics in the year after the first isolation. Conclusions: Poor lung function is the main independent risk factor for single isolation of S. maltophilia. For chronic colonisation, the main independent risk factor is the number of intravenous antibiotic courses and the absence of P. aeruginosa chronic colonisation. Only when chronically present, S. maltophilia had a clinical impact with more exacerbations.