Metagenomic NGS for Diagnosis of Pneumonia

Metagenomic NGS testing for pathogen identification will be done for airway and blood specimens using APGseq ® (Asia Pathogenomics, New Taipei City, Taiwan). The sample preparation for mNGS testing was as follows: 5-10 mL of whole blood were centrifuged at 1,600g for 10 min at 4°C to separate the plasma. Plasma samples were transferred to 2 mL sterile tubes for the following DNA or RNA extraction. In general, 300ul of plasma sample was used for DNA extraction. Total genomic DNA from samples were extracted using the column-based method (e.g. QIAamp DNA Microbiome Kit, Qiagen for DNA extraction; or QIAamp Viral RNA Mini Kit, Qiagen for RNA extraction, respectively), following the manufacturer's operational manual. The RNA was reverse transcribed and synthesized to double-stranded complementary DNA (ds cDNA) with SuperScript II Reverse Transcription Kit (Invitrogen).

Endotracheal aspirates, blood samples, urine samples, and nasopharyngeal swabs were obtained from the patients as soon as possible after ICU admission. Bacterial culture was performed, with the use of standard techniques, on blood samples and endotracheal aspirates. Urine antigen detection was performed for detection of L. pneumophila and S. pneumoniae. A PCR assay was performed on nasopharyngeal swabs for the detection of influenza A and B viruses and SARS-CoV-2 viruses. Fungal or mycobacterial detections, and whether to use multiplex PCR for pathogen detection, such as the FilmArray system, were determined at the discretion of the physicians.