Abstract
Probiotics have been advocated as a novel therapeutic approach to respiratory disease, but knowledge of how oral administration of probiotics influences the respiratory microbiota is needed. Using 16S rRNA amplicon sequencing of bacterial DNA our objective was to determine whether oral probiotics changed the composition of the upper and lower airway, rectal, and blood microbiota. We hypothesized that oral probiotics would modulate the respiratory microbiota in healthy cats, demonstrated by the detection and/or increased relative abundance of the probiotic bacterial species and altered composition of the microbial population in the respiratory tract. Six healthy young research cats had oropharyngeal (OP), bronchoalveolar lavage fluid (BALF), rectal, and blood samples collected at baseline and 4 weeks after receiving oral probiotics. 16S rRNA gene amplicon libraries were sequenced, and coverage, richness, and relative abundance of representative operational taxonomic units (OTUs) were determined. Hierarchical and principal component analyses (PCA) demonstrated relatedness of samples. Mean microbial richness significantly increased only in the upper and lower airways. The number of probiotic OTUs (out of 5 total) that significantly increased in relative abundance vs. baseline was 5 in OP, 3 in BAL and 2 in feces. Using hierarchical clustering, BALF and blood samples grouped together after probiotic administration, and PERMANOVA supported that these two sites underwent significant changes in microbial composition. PERMANOVA revealed that OP and rectal samples had microbial population compositions that did not significantly change. These findings were visualized via PCA, which revealed distinct microbiomes in each site; samples clustered more tightly at baseline and had more variation after probiotic administration. This is the first study describing the effect of oral probiotics on the respiratory microbiota via detection of probiotic species in the airways. Finding bacterial species present in the oral probiotics in the upper and lower airways provides pilot data suggesting that oral probiotics could serve as a tool to target dysbiosis occurring in inflammatory airway diseases such as feline asthma, a disease in which cats serve as an important comparative and translational model for humans.
Highlights
Prior to the advent of culture-independent microbiological techniques, the lower airways were considered sterile, and the primary role of bacteria in respiratory disorders was assumed to be as pathogens leading to development, persistence, exacerbation, and/or progression of respiratory diseases (Beigelman et al, 2014)
These data suggest that oral probiotic administration is associated with increased richness and diversity of the airway microbiota, with no concurrent changes detected in the fecal or blood microbiota
Oral probiotics can prevent and/or decrease frequency or severity of diseases outside of the gastrointestinal tract (Alberda et al, 2007; Lappin et al, 2009; Di Nardo et al, 2014; Esposito et al, 2014; Lee et al, 2015; Zuccotti et al, 2015; FuchsTarlovsky et al, 2016; Gruner et al, 2016; Vieira et al, 2016; Zamani et al, 2016), few studies have directly evaluated the appearance of orally administered probiotic species or changes in host microbial communities at distant sites (De Alberti et al, 2015; Mastromarino et al, 2015; Treven et al, 2015)
Summary
Prior to the advent of culture-independent microbiological techniques, the lower airways were considered sterile, and the primary role of bacteria in respiratory disorders was assumed to be as pathogens leading to development, persistence, exacerbation, and/or progression of respiratory diseases (Beigelman et al, 2014). Dysbiosis, or deviations from the healthy microbiota, is associated with overgrowth of pathogens, decreased biodiversity, and stimulation of the host immune system that contributes to disease development (Gollwitzer and Marsland, 2014; Fujimura and Lynch, 2015). Probiotic strains may exert their effects on dysbiosis directly by changing the composition of the host microbiome or indirectly by interacting with the host through the common mucosal immune system (CMIS) (Neish, 2014; Thaiss et al, 2016). Orally administered probiotics modulate immune responses in the lung, promoting a tolerogenic environment of benefit in allergic disease (Rautava and Isolauri, 2002)
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