In-depth snapshot of the equine subgingival microbiome.

The research article is an in-depth study of the diverse range of bacteria present under the gum-line (subgingival) in horse’s oral cavities. The study, employing 16S rRNA gene amplicon pyrosequencing, made significant discoveries about the number and potential specificity of these bacteria to horses.

Methodology and Results

• Using the 16S rRNA gene amplicon pyrosequencing technique, the researchers collected pooled subgingival plaque samples from nearly 200 sulcus sites from two horses labeled EQ1 and EQ2.
• A total of 14,260 quality-filtered pyrosequencing reads were obtained from the samples, further assigned to 3875 operational taxonomic units (OTUs) at a 99% identity cut-off. These OTUs comprised 1907 units for EQ1 and 2156 units for EQ2.
• The analyze identified a range of diverse bacterial taxa from 12 identified phyla. A significant proportion of these OTUs did not closely resemble known phylotypes, suggesting the possible existence of ‘equine-specific’ bacterial taxa.

Bacterial Taxa Identified

• The bacterial taxa identified included phyla such as Actinobacteria, Bacteroidetes, Chloroflexi, Firmicutes, Fusobacteria, Proteobacteria, Spirochaetes, Synergistetes, Tenericutes, GN02, SR1, and TM7.
• Gamma proteobacteria phylotypes were particularly abundant. They included species like Actinobacillus spp., unspecified Pasteurellaceae, and Moraxella spp.

Synergistetes and Spirochaetes Phyla

• The study conducted PCR tests targeting the Synergistetes and Spirochaetes phyla, and the 16S rRNA gene amplicons were subject to Sanger sequence.
• It revealed 26 Spirochaetes OTUs and 16 Synergistetes OTUs at a 99% identity cut-off. These ‘species-level’ OTUs received the designation of Equine Oral Taxon (EOT) numbers for future reference and investigation.
• Notably, the majority of Spirochaetes taxa belonged to the Treponema genus, including 7 out of 10 human oral treponeme phylogroups. However, certain treponemes associated with animal hoof/foot and non-oral soft tissue infections were not identified in these samples.
• The study also identified diverse Synergistetes taxa corresponding to oral clusters A and B, including species such as Fretibacterium fastidiosum and Pyramidobacter piscolens.

Comparison with Other Animals

• The study concluded that the subgingival plaque microbiota in horses shares considerable similarity with those observed in humans, dogs, and cats, highlighting possible parallels in oral health conditions across species and offering potential opportunities for comparative medical studies.