Airway Bacterial Biodiversity in Exhaled Breath Condensates of Asthmatic Children—Does It Differ from the Healthy Ones?

Abstract

Asthma etiopathology is still not fully determined. One of its possible causes can be found in airway microbiome dysbiosis. The study’s purpose was to determine whether there are any significant differences in the bacterial microbiome diversity of lower airways microbiota of asthmatic children, since knowledge of this topic is very scarce. To the authors’ knowledge, this is the first research using exhaled breath condensates in children’s lower airways for bacterial assessment. Exhaled breath condensates (EBC) and oropharyngeal swabs were obtained from pediatric asthmatic patients and a healthy group (n = 38, 19 vs. 19). The microbial assessment was conducted through genetic material PCR amplification, followed by bacterial 16S rRNA amplicon sequencing. Collected data were analyzed, in terms of taxonomy and alpha and beta diversity between assessed groups. Swab samples are characterized by higher species richness compared to exhaled breath condensates (Shannon diversity index (mean 4.11 vs. 2.867, p = 9.108 × 10−8), observed features (mean 77.4 vs. 17.3, p = 5.572 × 10−11), and Faith’s phylogenetic diversity (mean 7.686 vs. 3.280 p = 1.296 × 10−10)). Asthmatic children had a higher abundance of bacterial species (Shannon diversity index, mean 3.029 vs. 2.642, p = 0.026) but more even distribution (Pielou’s evenness, mean 0.742 vs. 0.648, p = 0.002) in EBC than healthy ones; the same results were observed within pediatric patients born naturally within EBC samples. In children with a positive family history of allergic diseases, alpha diversity of lower airway material was increased (Shannon’s diversity index p = 0.026, Faith’s phylogenetic diversity p = 0.011, observed features p = 0.003). Class Gammaproteobacteria and Bacilli were less abundant among asthmatics in the exhaled breath samples. The most dominant bacteria on a phylum level in both sample types were Firmicutes, followed by Proteobacteria and Actinobacteriota. The obtained outcome of higher bacterial diversity of lower airways among asthmatic patients indicates a further need for future studies of microbiota connection with disease pathogenesis.

Nerolidol attenuates airway inflammation and airway remodeling and alters gut microbes in ovalbumin‐induced asthmatic mice

“…Studies have shown that Proteobacteria are abundant in the respiratory tract of asthmatic patients 43 . In the airway microbiota of asthmatic patients, the most dominant bacteria at the phylum level are Firmicutes, followed by Proteobacteria and Actinobacteriota 44 . In this study, we found that microbial alpha diversity reduced, the abundance of Actinobacteriota and Proteobacteria increased and the abundance of Firmicutes decreased in the gut of asthmatic mice.…”

“…43 In the airway microbiota of asthmatic patients, the most dominant bacteria at the phylum level are Firmicutes, followed by Proteobacteria and Actinobacteriota. 44 In this study, we found that microbial alpha diversity reduced, the abundance of Actinobacteriota…”

Bacterial Microbiota of Asthmatic Children and Preschool Wheezers’ Airways—What Do We Know?

“…The nasal brushes also had greater bacterial richness than that of the washes [ 17 ]. The exhaled breath condensates had lower alpha diversity than that of the oropharyngeal samples [ 44 ]. Because of the sampling procedure, the EBC and induced-sputum samples could be contaminated with upper respiratory bacteria, of which researchers should be aware while assessing the outcomes of studies with those sampling methods.…”

“…Moreover, the presented studies do not provide sufficient information about the influence of asthma treatment on bacterial microbiome. In one study, the asthma medication intake in the lower-airway samples of the asthmatics was statistically relevant in terms of beta diversity ( n = 14 vs. 5, p = 0.014) [ 44 ]. This topic needs further investigation.…”

“…Additionally, Haemophilus was positively correlated with PD-L1, while Porphyromonas and Peptostreptococcus had negative correlation. The researchers also conducted the original research of the lower-airway microbiota using the exhaled breath condensates, which to our knowledge was the first study in pediatric asthmatics [ 44 ]. Exhaled breath condensates (EBCs) and oropharyngeal swabs were obtained from 38 children (19 asthmatics vs. 19 healthy participants).…”