Differences in pulmonary microbiota of severe community-acquired pneumonia with different pathogenic microorganisms in children.

Background: Community-acquired pneumonia (CAP) is the leading cause of hospitalization and death in children under 5 years old. Recently, the number of children with severe CAP (SCAP) has increased significantly, and local or systemic complications may occur. However, changes in the pulmonary microbiota of SCAP with different pathogens and their relationship with the clinical features of SCAP remain unclear.

Methods: This study collected bronchoalveolar lavage fluid (BALF) from 105 children with SCAP for metagenomics next generation sequencing (mNGS). According to the first pathogen of mNGS, the enrolled children were divided into the Streptococcus pneumoniae (SP), Mycoplasma pneumoniae (MP) and Haemophilus influenzae (HI) groups. We aimed to explore differences in clinical features and pulmonary microbiota of SCAP with different pathogens, and clarify the correlation between pulmonary microbiota and clinical features.

Results: Fever days and the levels of C-reactive protein (CRP), procalcitonin (PCT), lactate dehydrogenase (LDH), D-dimer and heparin-binding protein (HBP) of children in MP group were significantly higher than those in HI group. The level of LDH of children in MP group was significantly higher than that in SP group. The abundance of MP was also positively correlated with fever days and the levels of PCT, LDH and D-dimer. The α diversity of SP group was significantly increased compared to MP group and HI group.

Conclusion: Compared to SP-infected and HI-infected children with SCAP, children with SCAP infected with MP tend to have a more intense inflammatory response. The α diversity was higher in the lower airways of children with SCAP and SP infections compared to MP-infected and HI-infected children with SCAP.