Pathogenic bacteria enriched in the oral microbiota might be associated with recurrent pulmonary infections in elderly individuals

Background and aims

Pulmonary infections are a major health concern for the elderly, because of their high morbidity and mortality rates. With the growing world’s aging population, it is crucial to prioritize the health of elderly individuals. This study aimed to explore the associations between oral and gut microbiota and pulmonary infections.

Methods

Throat swabs and stool samples were collected from elderly patients aged 78–98 years and divided into four groups: Control, Infection, Re-Infection, and Re-None. The microbiota were analyzed via 16S rRNA gene sequencing, and the functional predictions were imputed using PICRUSt with MetaCyc pathway annotation.

Results

Significant differences were observed in oral and gut microbiota diversity between the control and test groups. Patients with pneumonia showed a significant increase in Staphylococcus aureus abundance in the oral microbiota compared to the Control group, while those with recurrent pneumonia showed elevated, Klebsiella pneumoniae levels. In the gut microbiota, Enterococcus hirae alone that was significantly enriched in all three test groups. Furthermore, PICRUSt2 analysis indicated an increased relative abundance of genes associated with the degradation of D-glucarate and D-galactarate pathways in patients with recurrent infections.

Conclusion

Oral and gut microbiota diversity showed significant differences between patients with recurrent pneumonia and common pneumonia pneumonia-infected patients. The higher prevalence of both S. aureus and K. pneumoniae in the oral microbiota offers crucial insights into the pneumonia etiology. Specifically, the increased abundance of K. pneumoniae may contribute significantly to the heightened lung infections susceptibility among elderly individuals.