Pneumocystis jirovecii in the lower respiratory tract ofimmunocompetent individuals

Abstract

tBackground: Pneumocystis jirovecii colonization rates in healthy patients are unclear. Previously publishedstudies suggest that the fungus could play a role in the physiopathology and progression of chronicrespiratory diseases.Aims: The goal of this study was to determine the prevalence of colonization by this fungus in the lowerrespiratory tract of immunocompetent patients who are not at risk of dysbiosis.Methods: The presence of P. jirovecii was confirmed in the bronchoalveolar lavage (BAL) samples fromadults who underwent bronchoscopy for non-infectious reasons, had no immunosuppressive factors,and had not been on antibiotic treatment for at least one month. The results were compared with thoseobtained in the study on the presence of Pneumocystis in environmental dust samples obtained by swab-bing surfaces in the participating subjects’ domestic settings. Real-time PCR was the technique used fordetecting the fungus in both types of samples.Results: A total of 97 BAL samples and 49 domestic environment samples were studied. The medicalreasons for needing a bronchoscopy were, mainly, the examination of both pulmonary neoplasm in 55patients (57%) and diffuse interstitial lung disease in 21 patients (22%). The overall prevalence of P. jiroveciiin our population was 7.22% in BAL samples and 0% in domestic samples.Conclusions: The presence of P. jirovecii in the lower respiratory tract is relevantly linked with the patient’simmune status, not with an underlying pathology. Prevalence is low in immunocompetent individualswho do not have any infectious pathology and are not having antimicrobial treatments. Our results donot enable us to figure out which the environmental niche of P. jirovecii is.