NGS analysis of unexplained Community-Acquired Pneumonia (CAP) cases in South Korea

Abstract

In general, pneumonia has known to be closely associated with respiratory infection of viruses, bacteria, fungi, and parasites. In South Korea, pneumonia is a leading cause of death that continues to threaten public health every year. Through the tertiary hospital-based influenza surveillance system in South Korea, nasopharyngeal swab specimens were obtained from patients with unexplained cases of Community-Acquired Pneumonia (CAP) between 2011 and 2017. After real-time PCR screening using respiratory viral panels, the samples were found negative for 16 common respiratory pathogens including adenovirus, influenza viruses, rhinovirus, respiratory syncytial virus, coronavirus, metapneumovirus, and parainfluenza viruses. The aim of this study was to investigate the patient microbiota and examine the etiology of CAP requiring hospitalization. The nasopharyngeal microbiome of adult patients during CAP was analyzed using Next-Generation Sequencing (NGS) on the Illumina MiSeq platform and a subsequent bioinformatics pipeline. Viral nucleic acids were nearly absent in the samples and failed to generate any sequence reads. On the other hand, samples were enriched with a diverse bacterial community, which was mainly comprised of Corynebacterium, Staphylococcus, Streptococcus, Haemophilus, Moraxella, Acinetobacter, and Rhizobium genera. Despite the diversity of bacterial composition, only a few dominant species with > 1% abundance were identified in each patient sample. Population analysis at the genus level showed that microbial diversity varied according to age, sex, and location.