DISTINCT changes in the lung microbiome and metabolism may be associated with progression from community-acquired pneumonia (CAP) to acute respiratory distress syndrome (ARDS) in children, according to new research.
The study identified reduced microbial diversity and altered concentrations of dozens of metabolites in children who developed ARDS, potentially offering new insights into the biological processes underlying severe pneumonia.
ARDS is a serious complication of pneumonia characterised by severe inflammation and lung injury which can lead to respiratory failure. However, the biological mechanisms that determine why some children with CAP progress to ARDS remain incompletely understood.
Researchers at Qilu Hospital of Shandong University, China, investigated whether changes in microorganisms and metabolites within the lower respiratory tract could be involved.
The single-centre retrospective study included 81 children with CAP, including children whose illness progressed to ARDS. Researchers analysed bronchoalveolar lavage fluid, collected from the lower respiratory tract, using genetic sequencing to characterise bacterial communities and metabolomic techniques to identify small molecules produced during biological processes.
Stool samples from a subset of children were also analysed to explore possible interactions between microorganisms in the gut and lungs.
Children who developed ARDS had significantly lower microbial diversity in their lungs than those with CAP alone. Researchers also identified differences in the types of bacteria present.
In particular, Pseudomonas bacteria were more abundant amongst children who developed ARDS, while Streptococcus was less abundant.
The researchers also identified 83 metabolites that differed between the two groups. Further analysis highlighted changes in several metabolic pathways, including those involved in pantothenate and coenzyme A biosynthesis, indole alkaloid biosynthesis, and steroid degradation.
One potentially important finding involved terpenoid metabolism. Seven terpenoid compounds differed between the groups, while analysis of the microbiome also suggested alterations in pathways involving terpenoids and polyketides.
Using machine-learning approaches, the researchers identified combinations of metabolites that showed potential for distinguishing children who progressed to ARDS from those with CAP alone.
Analysis of paired lung and stool samples also suggested a possible connection between microorganisms in the gut and lungs.
The researchers identified overlapping microbial patterns that they suggest could be consistent with bacteria moving from the gut to the respiratory tract. However, the analysis does not demonstrate that this translocation occurred or establish that gut bacteria contributed directly to the development of ARDS.
The findings instead provide potential avenues for further research into the mechanisms responsible for severe lung injury in children with pneumonia.
Importantly, the study was retrospective and conducted at a single hospital, limiting the conclusions that can be drawn. The relatively small sample size and exploratory nature of the analyses also mean that the proposed microbial and metabolic markers require validation in larger, independent patient populations.
The researchers conclude that children with CAP who progress to ARDS show substantial differences in their lower respiratory microbiome and metabolic profiles. Further research could determine whether these biological signatures can ultimately help identify children at increased risk of severe disease and provide new targets for diagnosis or treatment.
Wang Y et al. Lower respiratory microbiome and metabolome alterations in pediatric ARDS secondary to community-acquired pneumonia. Respir Res. 2026.
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