Exploratory analysis of nasal and gut microbial community structure in preschool children with recurrent wheeze

Early-life wheezing has been associated with microbial alterations along the gut-airway axis, yet few studies have examined bacterial communities in both compartments within the same children. This cross-sectional exploratory pilot study (n=25) characterized nasal and stool bacterial communities in children aged 1-4 years with recurrent wheeze and healthy controls using 16S rRNA gene metabarcoding. Across participants, nasal and stool bacteriomes were highly individualized and taxonomically diverse. Overall richness, evenness, and global community composition did not differ significantly between healthy controls and children with recurrent wheeze in either compartment. Nasal communities in the recurrent-wheeze group showed greater within-group dispersion, although the comparison did not reach the conventional significance threshold (p=0.054). Exploratory distance-based stratification identified a subgroup with nasal profiles farther from the healthy-control centroid; these profiles had lower richness and evenness, higher Moraxella abundance, and lower abundances of Prevotella spp., Alloprevotella, and Veillonella. No statistically supported genus-level differences were detected in stool samples. Community-assembly and co-occurrence analyses yielded group-specific descriptive patterns in both compartments. Different sets of cross-compartment correlations passed the multiple-testing threshold in healthy controls and children with recurrent wheeze, including correlations of stool Lactococcus with several nasal taxa in the recurrent-wheeze group. Because these analyses were performed in small groups, they are considered hypothesis-generating. These findings identify nasal microbial heterogeneity and exploratory differences in community organization in preschool children with recurrent wheeze, while providing no evidence for causal or Moraxella-driven effects. Larger longitudinal studies with functional measurements are required for validation.