Objective  To evaluate the application value of metagenomics next-generation sequencing (mNGS) in the detection of pathogens in suspected pulmonary infection cases, and improve clinical understanding of the etiological characteristics of pulmonary infection.

Methods In Hainan province, bronchoalveolar lavage fluid samples were collected from 45 patients with suspected pulmonary infection admitted to Sanya People's Hospital from February to September, 2023, and mNGS and conventional comprehensive microbialcomprehensive test (CMT) were used to screen pathogens, and the microbial characteristics of lower respiratory tract of the patients were retrospectively analyzed. Spearman was used to analyze the correlation between pathogenic reads per million (RPM) and inflammatory factors.

Results In the 45 patients, 41 were positive in pathogen detection by mNGS. A total of 7 single infection cases and 34 mixed infection cases were detected, in which 37 were bacterial infection cases, 19 were fungal infection cases, 26 were viral infection cases, 1 was Mycoplasma pneumoniae infection case and 1 was Chlamydia psittaci infection case. A total of 46 species of pathogens were detected, including 26 bacterial pathogens, 8 fungi pathogens, 10 viral pathogens and 2 other pathogens. CMT detection detected 23 positive cases, a total of 13 cases of single infection and 10 cases of mixed infection were detected, in which 14 were bacterial infection cases, 16 were fungal infection cases and 3 were viral infection cases. In the pathogens detected by mNGS, the top five bacterial pathogens with high detection rates were Pseudomonas aeruginosa (20.00%),Corynebacterium striatum (17.78%), Acinetobacter baumannii (15.56%), Streptococcus pneumoniae (13.33%), and Kebsiella pneumoniae (11.11%). The fungal pathogen with highest detection rate was Candida albicans (24.44%) and the viral pathogen with highest detection rate was human γ herpevirus 4 (22.22%). There was a certain correlation between pathogen RPM and inflammatory factors.

Conclusion In clinical practice, mNGS can be used for pathogen screening in bronchoalveolar lavage fluid to improve the detection rate of pathogen. Inflammatory factors can provide reference for the evaluation of pathogen infections, but further validation is needed.