Clinical associations with carriage of pulmonary Stenotrophomonas maltophilia

Background: Stenotrophomonas maltophilia causes opportunistic respiratory infections and is associated with declining lung function in patients with cystic fibrosis (CF). Risk factors for carrying S. maltophilia remain unclear. Methods: We conducted a retrospective study of patients yielding >= 1 respiratory S. maltophilia isolate at the Oxford University Hospitals Trust between 2014 and 2019 and a cohort study of S. maltophilia carriage in CF patients attending annual review in 2018. Results: Seven hundred and forty isolates were identified from 238 patients (median 1.0 isolate/patient). Predisposing conditions included invasive ventilation (29.8%). CF (25.6%) and non-CF bronchiectasis (24.4%). The rates of Stenotrophomonas isolates and co-trimoxazole resistance were stable over time. About 10.8% of isolates were co-trimoxazole-resistant, with resistance more common in CF than in other diagnoses (29.5% vs 5.8%, p < 0.001). No clinical features were significantly associated with S. maltophilia carriage in the CF population. Discussion: We present new insight into the epidemiology of Stenotrophomonas colonisation/infection and identify increased co-trimoxazole resistance in CF isolates.