Fig. 5

Validation of the IgA-seq outcomes. A, C, D Correlation between sIgA deposition from filtered and concentration-adjusted nasal eluates on cultured nasal isolated of a selection of bacterial species, as assessed by flow cytometry, and the IgA probability ratio calculated for the same species of the matching study participants. All strains were grown in nutrient-rich TSB (for Staphylococcus spp.) or BHI-Tween-80 (BHI-T; for Corynebacterium and Cutibacterium spp.) (A, C) or in nutrient-limiting 10% THB (D). All samples were normalized to 10 μg/ml sIgA, except for S. aureus 35-1 (0.3 μg/ml sIgA). Fluorescence intensity (FI) was measured by flow cytometry in triplicates and normalized to the corresponding unstained controls, with a fold change of one (no detectable deposition) being represented by a dashed horizontal line. Correlations were analyzed by non-linear regression. B, E sIgA deposition of nasal sIgA of individual study participants on nasal isolates of S. epidermidis, S. lugdunensis, and C. accolens grown in nutrient-rich conditions (B), and S. aureus 35-1 and C. simulans grown in nutrient-limiting conditions (10% THB) (E), stratified by colonization status. Statistical differences were tested by Mann–Whitney test