Abstract
This study was designed to systematically evaluate the diagnostic performance of metagenomic next-generation sequencing (mNGS) using blood and bronchoalveolar lavage fluid (BALF) samples in patients with severe pneumonia complicated by bloodstream infections. A retrospective analysis of 30 patients with severe pneumonia-bloodstream infection admitted to our hospital from January 2018 to December 2022 was conducted, and the potential pathogens in both BALF and blood samples were simultaneously detected by conventional microbial examination (traditional group) and mNGS tests (mNGS group), comparing the differences in pathogen species and detection rates between the two methods. There was no significant difference in the positivity of pathogen detection in BALF and blood samples using mNGS (p = 0.492). The proportion of bacteria (p = 0.005) and fungi (p = 0.037) detected by BALF mNGS was higher than that by blood mNGS, but there was no significant difference in the proportion of viruses (p = 0.121). In addition, the positive rate of pathogen detection by mNGS in BALF and blood samples was significantly higher than that by traditional methods (p < 0.01). BALF mNGS demonstrated superior diagnostic sensitivity for bacterial and fungal pathogen detection compared to blood mNGS and conventional culture methods. Notably, blood specimens retained distinct advantages in identifying specific viral infections. Future prospective studies with larger sample sizes are warranted to validate these findings.