Upper and lower respiratory tract microbiota in horses: bacterial communities associated with health and mild asthma (inflammatory airway disease) and effects of dexamethasone

Abstract

BackgroundThe microbial composition of the equine respiratory tract, and differences due to mild equine asthma (also called Inflammatory Airway Disease (IAD)) have not been reported. The primary treatment for control of IAD in horses are corticosteroids. The objectives were to characterize the upper and lower respiratory tract microbiota associated with respiratory health and IAD, and to investigate the effects of dexamethasone on these bacterial communities using high throughput sequencing.ResultsThe respiratory microbiota of horses was dominated by four major phyla, Proteobacteria (43.85%), Actinobacteria (21.63%), Firmicutes (16.82%), and Bacteroidetes (13.24%). Fifty genera had a relative abundance > 0.1%, with Sphingomonas and Pantoea being the most abundant. The upper and lower respiratory tract microbiota differed in healthy horses, with a decrease in richness in the lower airways, and 2 OTUs that differed in abundance. There was a separation between bacterial communities in the lower respiratory tract of healthy and IAD horses; 6 OTUs in the tracheal community had different abundance with disease status, with Streptococcus being increased in IAD horses. Treatment with dexamethasone had an effect on the lower respiratory tract microbiota of both heathy and IAD horses, with 8 OTUs increasing in abundance (including Streptococcus) and 1 OTU decreasing. ConclusionsThe lower respiratory tract microbiota differed between healthy and IAD horses. Further research on the role of Streptococcus in IAD is warranted. Dexamethasone treatment affected the lower respiratory tract microbiota, which suggests that control of bacterial overgrowth in IAD horses treated with dexamethasone could be part of the treatment strategy.Electronic supplementary materialThe online version of this article (doi:10.1186/s12866-017-1092-5) contains supplementary material, which is available to authorized users.

Tracheal microbial populations in horses with moderate asthma

“…This has been documented in children and adults with asthma, and dysbiosis is now associated not only with asthma prevalence and acute exacerbation, but also with asthma severity and airway hyperresponsiveness . Dysbiosis of the airways was also described recently using next‐generation sequencing in horses with moderate and severe asthma, using inclusion criteria in line with the current ACVIM recommendations. Tracheal microbiota was altered in horses with moderate asthma, with a greater relative abundance of the genus Streptococcus spp., and pulmonary microbiota was also altered in horses with severe asthma, but without overrepresentation of specific pathogens in bronchoalveolar lavages .…”

“…Dysbiosis of the airways was also described recently using next‐generation sequencing in horses with moderate and severe asthma, using inclusion criteria in line with the current ACVIM recommendations. Tracheal microbiota was altered in horses with moderate asthma, with a greater relative abundance of the genus Streptococcus spp., and pulmonary microbiota was also altered in horses with severe asthma, but without overrepresentation of specific pathogens in bronchoalveolar lavages . Neither studies attempted to quantify the absolute amount of specific pathogens.…”

“…For example, there is an association between tracheal bacterial count and cough, and between tracheal mucus and bacteria isolated from tracheal aspirates in racehorses . The pulmonary microbiome of horses with asthma is different from that of healthy horses, and the pulmonary microbiome is influenced both by the presence of the disease and by the environment . In human asthma, bacteria have received less attention than viruses for their role in clinical exacerbations, but infections with Haemophilus influenzae , Moraxella catarrhalis , and Streptococcus pneumoniae are now recognized as opportunistic pathogens associated with acute asthma exacerbations .…”

Sputum microbiota is predictive of long-term clinical outcomes in young adults with cystic fibrosis

“…Bacterial communities in CF sputum and reagent blanks were characterised by amplification and sequencing the V3-V4 region of the 16S rRNA 11. The sequencing reads were processed and analysed to construct the operational taxonomic unit (OTU) table using a UPARSE pipeline 18. After removing singleton OTUs 8 320 948 total reads remained (average 80 009 reads/sample; IQR: 57 168–102 441).…”

Efficacy of dexamethasone, salbutamol, and reduced respirable particulate concentration on aerobic capacity in horses with smoke‐induced mild asthma

“…Horses were then endoscopically scored for tracheal mucus (Karl Storz, Mississauga, ON, Canada). A blind BAL was then performed as previously described . Lavage fluid was stored immediately after collection at 4°C.…”