Actinomyces denticolens colonisation identified in equine tonsillar crypts

Area of Science:

• Veterinary Microbiology
• Equine Pathology

Background:

• Submandibular abscesses in horses have been recently linked to Actinomyces denticolens.
• Actinomycotic clumps, indicative of this bacterium, have been observed in equine tonsillar crypts.

Purpose of the Study:

• To investigate and confirm the colonization of Actinomyces denticolens within equine tonsils.
• To establish the tonsil as a potential intrinsic infection site for A. denticolens in horses.

Main Methods:

• Histopathological examination and bacterial isolation from 12 equine tonsils.
• Immunohistochemistry using specific anti-A. denticolens serum to detect bacterial antigens.
• 16S rRNA gene sequencing for precise identification of isolated Actinomyces-like bacteria.

Main Results:

• Actinomycotic clumps were identified in the tonsillar crypts of 91.7% of horses examined.
• A. denticolens antigens were detected in clumps and tonsillar parenchyma in 100% of tonsils.
• Six isolates demonstrated 99.7-99.9% 16S rRNA gene sequence similarity to A. denticolens.

Conclusions:

• Equine tonsils serve as a significant colonization site for Actinomyces denticolens.
• The tonsils are suggested to be the intrinsic infection site for A. denticolens, potentially leading to submandibular abscesses.