Diagnosing pathogenic DNA fromPneumocystis jiroveciiin exhaled breath condensate: a feasibility study

Pathogen identification in pneumonia is achieved in less than 25% of cases. Diagnosis of Pneumocystis pneumonia relies on a multimodal approach combining clinical, radiological, and immunological assessment with microbiological confirmation, most often by polymerase chain reaction. However, the method cannot reliably distinguish between active infection and colonization because of limited assay standardization and lack of universally accepted interpretive criteria. This pilot study explored whetherPneumocystis jiroveciiDNA could be detected in patients with suspected infection (PcP) in exhaled breath condensate (EBC). Ten patients with suspected PcP and ten healthy controls provided oral mouthwash (OW) and EBC samples for real-time PCR.P. jiroveciiDNA was detected in both OW and EBC in four patients. Ongoing PcP therapy associated with absence of detectable DNA (p =0.048). DetectingP. jiroveciiDNA in EBC is feasible, supporting its potential as a non-invasive diagnostic and monitoring tool. The study was approved by the North Denmark Regional Committee on Health Research Ethics (Journal number N-20190070).