Streptococcus henryi sp. nov. and Streptococcus caballi sp. nov., isolated from the hindgut of horses with oligofructose-induced laminitis.

The research discovered two novel bacterial species, Streptococcus henryi and Streptococcus caballi, in the digestive system of horses suffering from oligofructose-induced laminitis, providing new directions for understanding the disease.

Isolation of Novel Bacterial Strains

• In this research study, the researchers isolated four catalase-negative and Gram-positive bacterial strains from the cecum and rectum of horses that were suffering from oligofructose-induced laminitis.
• The bacteria, which were coccoid in shape, were studied for their phenotypic characteristics and genetic relationships with recognized Streptococcus species.

Characterization and Gene Sequence Analysis

• The initial biochemical profiling linked two of the four isolates to Streptococcus bovis, a known species of Gram-positive bacteria belonging to the genus Streptococcus.
• The remaining two isolates could not be definitively linked to any known species based on their biochemical characteristics. The analysis thus included a genetic sequencing comparison to known Streptococcus species.
• The gene sequence analysis, focused on the 16S rRNA gene and the manganese-dependent superoxide dismutase gene (sodA), indicated that the new isolates were closely related to Streptococcus suis and Streptococcus orisratti.

Phylogenetic and Phenotypic Analyses

• The sequence divergence from known Streptococcus species, based on both the 16S rRNA gene and the sodA gene, were significantly high for all four isolates, exceeding 3% and 13%, respectively.
• This significant divergence in genetic sequence, complemented by the distinct phenotypic characteristics, implied that the isolates were unique and hitherto unrecognized species of Streptococcus.

Identification of New Species

• Based on these comprehensive analyses, the researchers concluded that the four isolates constituted two distinct clonal groups, each representing a novel species within the Streptococcus genus.
• The researchers proposed the names Streptococcus henryi and Streptococcus caballi for these newfound organisms, distinguishing them by their strain type.

Significance

• The identification and classification of these two new species of bacteria offer a better understanding of the disease and may pave the way for more definitive treatments for oligofructose-induced laminitis in horses.