Figure 1.

Nasopharyngeal microbiome composition in young children with respiratory syncytial virus (RSV) infection and healthy control (HC) subjects and associations with host characteristics. (A) Dendrogram visualizing an average linkage hierarchical clustering of individuals on the basis of the Bray–Curtis dissimilarity matrix. The branches of the tree structure were colored according to health status (HC subjects, green; patients with RSV, yellow). Information on age and disease severity is depicted adjacent to the branch ends. Stacked bar charts show the relative abundance of the 15 highest-ranked operational taxonomic units (OTUs) and of residual bacteria specified by phylum. OTUs are color coded according to phylum: Firmicutes, red; Proteobacteria, blue; Actinobacteria, yellow; and Bacteroidetes, green. On the basis of clustering indices, an optimal number of 11 clusters was identified, 5 of which comprised more than three study participant samples. Classifier taxa for these five clusters (color-coded horizontal panels) were: Streptococcus (STR), light red; Haemophilus influenzae (HPH), dark blue; Corynebacterium (COR), yellow; Moraxella (MOR), light blue; and Staphylococcus aureus (STA), dark red. Gray panels mark individuals not included in any of these five clusters. (B) A nonmetric multidimensional scaling (NMDS) plot was used to visualize the associations between nasopharyngeal microbiota clusters (see color coding in A) and host characteristics: age group (round arrowheads), health status (arrowheads, bold text), and antibiotic treatment (arrowheads, bold italic text), depicting both the individual nasopharyngeal microbiota composition (data points [n = 132] and ellipses [SD of data points] colored according to cluster) and the 10 highest-ranked OTUs. We observed that RSV hospitalization was related to STR- and HPH-enriched profiles. Additionally, we observed an association between outpatients, older age, and MOR enrichment, whereas STA-dominated profiles were observed primarily in young, healthy infants. The orthogonal orientation (∼90°angle) of the vectors associated with health status and age imply that these host characteristics are not highly correlated, which was verified by permutational multivariate analysis of variance (unadjusted R² severity, 5.7%; age, 6.7%; and interaction severity–age, 5.9%). AB = antibiotic treatment; Inp = inpatients; Outp = outpatients.