Abstract / Description
Pneumonia and diarrhea are the two leading causes of death in children under five years of age, and these two conditions often present as a comorbidity, where the same child experiences respiratory and digestive system infection symptoms simultaneously or sequentially. Clinical data indicate that the incidence of secondary diarrhea in children hospitalized with pneumonia is high, significantly prolonging hospital stays and affecting prognosis. In recent years, the proposal of the gut-lung axis theory has provided a novel perspective for understanding this comorbidity phenomenon. The gut-lung axis refers to the bidirectional regulatory pathway between the gut microbiota and the pulmonary immune system, with the lungs and intestines sharing embryonic origin and a common mucosal immune system. This review systematically reviews the characteristics of gut microbiota dysbiosis and the mechanisms of immune disorders in the context of pediatric pneumonia-diarrhea comorbidity. Clinical studies have shown that children with comorbidity exhibit significant gut microbiota dysbiosis, characterized by a reduction in beneficial bacteria such as Bifidobacterium, an increase in opportunistic pathogens such as Escherichia coli, and decreased microbial diversity. Gut microbiota dysbiosis leads to immune disorders through multiple mechanisms, including reduced short-chain fatty acids, skewed immune cell differentiation, and dysregulated inflammatory factor networks, resulting in Th1/Th2 imbalance, decreased regulatory T cell function, and exacerbated systemic inflammatory responses. Supplementation with microecological preparations such as Saccharomyces boulardii has been shown to significantly shorten hospital stays, diarrhea duration, and fever resolution time, while improving peripheral blood immunoglobulin levels and T-cell subsets, providing evidence-based support for clinical intervention. This review also systematically reviews clinical laboratory indicators associated with comorbidity, including inflammatory markers, immune status indicators, intestinal barrier function markers, and microbiota detection methods, which have important application value in early identification, disease assessment, and treatment monitoring of comorbidity. Future research should further employ metagenomic approaches combined with longitudinal follow-up designs to elucidate the roles of specific bacterial species/strains in gut-lung axis regulation, providing new strategies for precision prevention and treatment of pediatric pneumonia-diarrhea comorbidity.