BACKGROUND: Pneumocystis jirovecii pneumonia (PJP) is a life-threatening opportunistic infection. Colonization is prevalent but cannot be reliably distinguished from active infection by conventional methods. Metagenomic next-generation sequencing (mNGS) is a promising diagnostic tool, but the value of blood mNGS for diagnosis, microbial community comparison, and outcome-related associations in PJP remains unclear. METHODS: We analyzed 73 suspected PJP patients with paired BALF and blood mNGS. Using strict diagnostic criteria, patients were classified as: PJP (n = 50) and P. jirovecii colonization (PJC, n = 23). Bioinformatic analyses compared compartment-specific microbiota. BALF-blood concordance and associations between P. jirovecii load and outcomes were evaluated. RESULTS: BALF showed higher α-diversity than blood (both Shannon and Simpson, P 4.8), outperforming BALF mNGS (AUC 0.76), blood PCR (AUC 0.64) and BALF PCR (AUC 0.73). Gram-negative bacteria accounted for a large proportion of blood taxa (75% of top 20 taxa), while BALF showed additional fungal taxa including Aspergillus fumigatus. LEfSe identified matrix-specific taxa: oral commensals in PJC-BALF. Blood P. jirovecii load correlated positively with LDH (r = 0.34, P = 0.0035), CRP (r = 0.34, P = 0.0031), and BDG (r = 0.26, P = 0.025), and was higher in non-survivors (P < 0.05). CONCLUSION: Blood mNGS may serve as a non-invasive, highly specific complementary tool for PJP diagnosis and broader microbiological assessment.
Chen et al. (Mon,) studied this question.
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