This observational study is to learn about the predictive value of targeted next-generation sequencing(tNGS) in pathogen resistance phenotype of patients with lower respiratory tract infection ,by detecting antimicrobial-resistant genes.

Inclusion Criteria:

• Aged 18 years and above
• Lower respiratory tract infection based on at least two of the followings: abnormal temperature (body temperature greater than 38.5°C or less than 36.5°C), leucocyte count abnormality (leucocyte count greater than 10*10^9/L or less than 4*10^9/L), and the presence of purulent tracheal secretions.
• Patients have been performed tNGS test in-hospital, with the criterion that the reads per kilobase per million mapped reads(RPKM) for staphylococcus aureus exceeds 200, acinetobacter baumannii exceeds 300, klebsiella pneumoniae exceeds 20, or pseudomonas aeruginosa exceeds 100.

Exclusion Criteria:

• Klebsiella pneumoniae，acinetobacter baumannii,pseudomonas aeruginosa or staphylococcus aureus were not cultured in BALF.

The study population description specifies individuals diagnosed with LRTI (Lower Respiratory Tract Infection) who were enrolled based on culture-confirmed klebsiella pneumoniae，acinetobacter baumannii,pseudomonas aeruginosa or staphylococcus aureus.