Exhaled Pneumocystis jirovecii output and detection of asymptomatic exhalation by facemask sampling in HIV-uninfected, immunocompromised patients.

Pneumocystis jirovecii pneumonia (PJP) transmission is poorly defined. Previous studies have sampled air of rooms occupied by HIV-infected patients with PJP, while natural and direct exhalations of HIV-uninfected subjects remain under-investigated. Here, clinical facemasks were used to examine and quantify potential P. jirovecii exhalations from HIV-uninfected patients with suspected PJP and to determine whether pathogen exhalation was definable clinically or radiologically. Forty-five patients in Leicester (England), highly suspected of having PJP based on European Conference on Infections in Leukaemia (ECIL-5) guidelines, each wore one facemask carrying a gelatine/PVA sampling matrix for 1 h while respiring normally. Mask contamination with P. jirovecii was assessed using a modified quantitative polymerase chain reaction targeting mitochondrial large subunit (MtLSU). Radiological findings on chest X-ray (CXR) and computed tomography (CT) were graded and analysed for correlation with P. jirovecii signals alongside relevant clinical and laboratory findings. P. jirovecii was detected in seven of 20 patients diagnosed with PJP and three of 19 patients with suspected but undiagnosed PJP. The median captured signal was 8.59 × 104 MtLSU copies/mask (interquartile range (IQR) = 3.01 × 105-1.81 × 104). Blood β-D-glucan test results correlated with the mask detection data (r = 0.65; P<0.0001) but other clinical indices and radiological features did not. Five of the 10 P. jirovecii-exhalers exhibited normal CXR with a median exhalation burden 1.28 × 105 copies/mask (IQR = 1.51 × 105-2.27 × 104). Two P. jirovecii-exhalers (7.64 × 104 copies/mask) were asymptomatic. P. jirovecii was exhaled sufficiently during normal respiration to be detectable in facemasks worn by HIV-uninfected patients. Neither clinical nor radiological features correlated with P. jirovecii exhalation.