Disrupted gut microbial profiles in Vietnamese children under 5 years of age with community-acquired pneumonia

<h2>Abstract</h2><h3>Problem considered</h3> Pneumonia remains a major cause of morbidity and mortality in children under five years. Emerging evidence highlights the critical role of the gut-lung axis in respiratory diseases; however, data on gut microbial alterations in pediatric community-acquired pneumonia (CAP) are scarce, especially in Southeast Asia. <h3>Methods</h3> We conducted a cross-sectional study involving 78 Vietnamese children aged 2 months to 5 years, including 30 patients with CAP and 48 healthy controls (HC). Stool samples were collected prior to antibiotic administration and analyzed by 16S rRNA gene sequencing, targeting the V3–V4 region. Gut microbial diversity (alpha and beta) and taxonomic composition were compared between the groups. Linear discriminant analysis effect size (LEfSe) was performed. <h3>Results</h3> Children with CAP exhibited significantly reduced microbial richness (Chao1, ACE, observed features, all p < 0.001) but preserved evenness along with distinct community structures (PERMANOVA, p=0.001). CAP was associated with the enrichment of potentially pathogenic genera (<i>Escherichia</i>, <i>Shigella</i>, <i>Eggerthella</i>) and the depletion of butyrate-producing taxa (<i>Ruminococcus</i> and <i>Coprobacillus</i>). These alterations may impair mucosal immunity by disrupting the gut–lung axis. <h3>Conclusion</h3> Vietnamese children with CAP display marked gut microbiota dysbiosis, with reduced richness and an imbalance favoring pro-inflammatory taxa. These results support the pivotal role of the gut-lung axis in the pathogenesis of pediatric pneumonia and suggest that microbiota-targeted interventions may hold promise for prevention and adjunctive treatment strategies.