Associate Professor of Medicine Equine Field Service University of Pennsylvania New Bolton Center Kennett Square, PA, United States
Abstract: Background- Exploring the guttural pouch bacterial microbiota during Streptococcus equi equi (S. equi) infection may determine indicators that can lead to biofilm formation.Hypothesis/Objectives- To assess the effects of S. equi status on the equine upper respiratory microbiota.Animals- 10 healthy university-owned (S. equi negative), 9 strangles convalescent client-owned (S. equi negative), and 9 strangles convalescent client-owned (S. equi positive) horses were enrolled.Methods- In this prospective observational study, oral wash (OW), nasopharyngeal lavage (NPL), and guttural pouch lavage (GPL) samples were collected and processed for genomic DNA extraction. PCR amplification and Illumina sequencing was performed followed by data analysis using QIIME2 pipelines.Results- Observed species and Shannon diversity metrics showed significant differences between OW, NPL and GPL samples (P=0.001). GPL had much higher diversity compared to OW and NPL (P=0.005). The extent of interaction between commonly present bacterial populations (beta diversity) resulted in a separation by sample type (P=0.001) and a difference between S. equi positive and negative samples (P=0.046). Firmicutes was the most abundant phylum across all sample types. Proteobacteria were reduced in GPL S. equi positive samples. S. equi negative OW and NPL samples had more Gemellaceae whereas Streptococcus was proportionally increased in S. equi positive GPL samples.Conclusions and Clinical Importance- While genera such as Gemellaceae are commonly shared between the upper respiratory tract microbiota, the microbiome associated with the guttural pouch appear distinct with a rich diversity of Streptococcus related genera. Despite low sample size, S.equi positive guttural pouch microbiome differed from negative horses.
