Retrospective investigation of 43 necropsy cases of Tyzzer disease in foals and partial genome sequence of Clostridium piliforme by shotgun metagenomics.

This research conducted a retrospective investigation to understand more about Tyzzer disease caused by Clostridium piliforme in foals. Using a shotgun metagenomics approach, they were able to partially sequence the genome of this bacterium from the liver of a deceased foal affected by the disease.

Research Background and Objective

• The research focused on understanding Tyzzer disease (TD), a severe infection in many animals, including foals, caused by the obligate intracellular bacterium Clostridium piliforme. The disease is severe in foals and often leads to death.
• The main objective of the research was to retrospectively analyze necropsy cases of foals from 2012 to 2024 that died of TD and provide a partial genome sequence of C. piliforme.

Findings from the Retrospective Investigation

• The study analyzed 43 equine necropsy cases where C. piliforme was detected. These cases were prevalent from February to July, hit a peak in May.
• The foals affected ranged from 4 days to 2 months old. In all cases, the disease was manifested as necrotizing hepatitis with distinct markers.

Genome Sequencing and Comparison

• Due to the lack of a complete genome sequence for C. piliforme in horses, shotgun metagenomics was employed to sequence the bacterium’s genome from the liver tissue collected during the necropsy of a foal afflicted with TD.
• The sequences obtained were matched against the NCBI NT/NR database, and the highest number of reads and contigs aligning to Clostridium species were found.
• A complete 16S rRNA gene was obtained, which showed a strong genetic resemblance to the horse strain of C. piliforme, followed by the rabbit and rodent strains, indicating variations among species.
• Additional genes identified, including the alveolysin, exo-α-sialidase, and flagellar, provided the first genetic evidence of virulence factors of C. piliforme.

Implications and Future Directions

• The study revealed the presence of genes encoding for multidrug export and multidrug resistance proteins in the bacterium, suggesting that C. piliforme could potentially develop resistance against certain antimicrobials such as beta-lactams and fluoroquinolones.
• The researchers provided the first partial genome sequence of C. piliforme utilizing a shotgun metagenomics method, providing valuable data for future research on understanding this bacterium, its pathogenicity, and potential medical interventions for TD.