LAUSR

Pneumocystis jirovecii colonisation is frequent during COPD and patients constitute potential contributors to its interhuman circulation. However, the existence of an environmental reservoir cannot be excluded. We assessed the prevalence and factors associated with Pneumocystis colonisation during COPD, and studied circulation between patients and their domestic environment. Pneumocystis molecular detection and mtLSU genotyping were performed in oro-pharyngeal washes (OPW) sampled in 58 patients with COPD acute exacerbation, and in indoor dust, sampled in patients' homes using electrostatic dust collectors (EDCs). Lung and systemic inflammation was assessed. Pneumocystis carriage was evaluated in 28 patients after 18 months at stable state. Pneumocystis was detected in 11/58 OPWs during exacerbation (19.0%). Colonised patients presented a significantly lower body mass index, and higher serum IL-17 and CD62P. One patient presented positive detection of typable isolates in both OPW and EDC, with both isolates harbouring mtLSU genotype 3. Pneumocystis genotype 1 was further detected in EDCs from 3 non-colonised patients and 1 colonised patient with non-typable isolate. Genotypes 1 and 2 were predominant in clinical isolates (both 42%), with genotype 3 representing 16% of isolates. Pneumocystis was detected in 3/28 patients at stable state (10.7%). These data suggest that Pneumocystis colonisation could be facilitated by a lower BMI and be related to acute alteration of lung function during COPD exacerbation. It also suggests Th17 pathway and platelet activation could be involved in the anti-Pneumocystis response during colonisation. Lastly, Pneumocystis detection in EDCs supports its potential persistence in indoor dust. LAY SUMMARY COPD patients tend to be more frequently colonised by Pneumocystis during exacerbation (19.0%) than at stable state (10.7%). Factors associated with colonisation include lower BMI, higher IL-17 and CD62P. Pneumocystis detection in patients' dwellings suggests potential persistence in indoor dust.