In humans, deviation from a core airway microbiota is thought to predispose to development, exacerbation or progression of respiratory diseases. Our objective was to describe changes in the airways and fecal microbiota as cats transitioned from healthy (day 0) to asthmatic, in the early (6 weeks) and chronic (36 weeks) stages. The gut microbiota influences microbial communities at distant sites. However, as asthma is a localized disease, we hypothesized that it would result in decreased richness and diversity of the lower airway microbiota, contributing to a state of dysbiosis, while the fecal microbiota would remain unaffected.

Fecal, oropharyngeal (OP), and bronchoalveolar lavage (BAL) samples were collected from eight healthy research cats before (day 0) and at 6, 12, 24 and 36 weeks after experimental asthma induction using Bermuda grass allergen. Extracted DNA underwent PCR of the 16S rRNA gene. Once sequenced, richness, diversity, and relative abundance of representative operational taxonomic units (OTUs) were determined via RM ANOVA on ranks (p<0.050). Principal component analysis (PCA) was used to visualize relatedness of samples. Differences in community composition between timepoints were tested using PERMANOVA of Bray-Curtis similarity indices.

Feces had decreased richness between day 0 and 6 weeks (p<0.001) only. In OP samples, richness increased at 6 and 36 weeks versus day 0 (p=0.036 and 0.02, respectively). No significant change in relative abundance of predominant taxa was found in fecal or OP samples over time. In BAL, richness significantly decreased from day 0 to 6 and 36 weeks (mean #OTUs 96, 47 and 21, respectively; p<0.001). Relative abundance of Pseudomonadaceae decreased from day 0 to 36 weeks (68% to 0.12%; p<0.001) with increases in Sphingobacteriaceae and Bradyrhizobiaceae (from 0.08% to 52.16% and from 0.40% to 32.58%; p<0.001). Within BAL, PERMANOVA detected significant differences (p<0.001) in diversity between samples collected at day 0 and week 36 compared to all other time-points.

Upper and lower airway communities differ from each other and from the fecal microbiota. In upper airways, increased richness without change in relative abundance of predominant taxa was noted after asthma induction. In contrast, lower airway microbiota undergo significant changes in early and chronic stages of asthma. Decreases in relative abundance of organisms associated with healthy airways supports the concept of airway dysbiosis. Knowledge of changes in asthmatic airway microbial populations opens the door to investigation of modulation of airway microbiota to attenuate disease.

Disclosures

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