Oral and oropharyngeal bacterial microbiota in children with obstructive mouth breathing: a pilot cross-sectional study

Abstract

Obstructive mouth breathing (OMB) is a common pediatric condition associated with oral and systemic health problems. OMB may alter the oral and oropharyngeal environment through mucosal dryness, reduced salivary clearance, altered airflow and gas exchange, and impaired local mucosal defense. However, its association with pediatric oral and oropharyngeal bacterial microbiota remains unclear. This pilot study aimed to characterize the oral and oropharyngeal bacterial microbiota in children with OMB and to explore candidate OMB-associated taxa. This pilot cross-sectional study included 23 children with OMB and 16 age-matched nasal breathing (NB) controls. Combined oral and oropharyngeal swabs were collected from multiple sites and analyzed using partial 16 S rRNA gene sequencing. Alpha diversity was compared using the Wilcoxon rank-sum test with false discovery rate correction. Beta diversity was assessed by principal coordinate analysis (PCoA) and PERMANOVA. LEfSe was used to identify differentially abundant taxa. Random Forest and receiver operating characteristic (ROC) analyses were used to evaluate exploratory candidate microbial marker panels. Children with OMB showed lower microbial richness and phylogenetic diversity than NB controls, reflected by reduced Chao1 and PD indices, whereas community evenness did not differ significantly. Beta diversity differed between groups only for unweighted UniFrac distance ( R² = 0.180, PERMANOVA P = 0.001), whereas weighted UniFrac and abund-Jaccard distances were not significant. At the genus level, the relative abundances of Moraxella , Rothia , and Corynebacterium were lower in the OMB group, whereas Actinomyces was enriched. LEfSe analysis identified 10 differentially abundant taxa (LDA score > 3.5, P < 0.05). Among the three exploratory microbial marker panels, the Random Forest-derived five-genera panel showed the highest apparent discriminatory performance, with an AUC of 0.90 (95% CI: 0.78-1.00). Children with OMB exhibited altered oral and oropharyngeal bacterial microbiota, including reduced richness and phylogenetic diversity and differences in community structure and taxonomic composition. Several candidate taxa were identified, and exploratory genus-level microbial marker panels showed discriminatory potential in this dataset. These findings should be interpreted cautiously given the pilot design. Larger longitudinal studies integrating functional and multi-omics analyses are needed to validate these findings and clarify their clinical relevance.