Patients’ characteristics
During the year following the fibreoptic bronchoscopy, 20/80 (25.0%) preschool children had no exacerbation (No-Ex), 27/80 (33.7%) experienced 1 or 2 exacerbations (Low-Ex) and 33/80 (41.3%) experienced 3 or more exacerbations (High-Ex). The prevalence of atopic dermatitis was higher in the “High-Ex” than in the “Low-Ex” groups (Figure 1A) and the age at the first episode of wheezing was lower in the “High-Ex” than in both the “No-Ex” and “Low-Ex” groups (Figure 1B). Conversely, there was no significant difference between groups with respect to the other clinical and biological characteristics (Table 1).
Regarding the BALF parameters (Table E1), “No-Ex” had a lower prevalence of positive bacterial culture than both “Low-Ex” and “High-Ex” (Figure 1C). The genera identified in the BALF were in descending order of frequency Haemophilus , Streptococcus ,Neisseria , Moraxella , Corynebacterium ,Staphylococcus and Pseudomonas (Table E1). The prevalence of Haemophilus sp . was significantly more elevated in “Low-Ex” than in “High-Ex” than in “No-Ex” (Figure 1D) and the prevalence of Streptococcus sp. was significantly higher in both “Low-Ex” and “High-Ex” than in “No-Ex” (Figure 1E). At the species level, the most frequently identified bacteria were in descending order of frequency Haemophilus influenzae, Streptococcus α-hemoliticus, Haemophilus parainfluenza, Moraxella catarrhalis, Streptococcus pneumoniae, Streptococcus oralis/mitis (Table E1). Among these bacteria species, only the prevalence of Streptococcus pneumoniae was significantly higher in “Low-Ex” than in “No-Ex” (Table E1). There was no significant difference between groups according to the BALF cytology (Table E1).
Regarding bronchial biopsies, RBM-BSM distance was significantly decreased (Figure 1F) whereas both the BSM area (Figure 1G) and the RBM thickness (Figure 1H) were significantly increased in High-Ex compared to the two other groups (Table E1). There was no significant difference between groups according to all other remodelling parameters or inflammatory cell densities on bronchial biopsies (Table E1).