Staphylococcus pseudintermedius isolated from atopic dogs with pyoderma induces mast cell degranulation.

Area of Science:

• Veterinary Dermatology
• Microbiology
• Immunology

Background:

• Staphylococcus pseudintermedius is a common cause of pyoderma in dogs.
• Canine atopic dermatitis (cAD) is a prevalent allergic skin disease.
• Staphylococcal toxins are implicated in skin inflammation and barrier dysfunction.

Purpose of the Study:

• To sequence the δ-toxin (hld) and accessory gene regulator (agr) locus in S. pseudintermedius isolates from atopic dogs.
• To assess the mast cell degranulation potential of S. pseudintermedius δ-toxin in vitro and in vivo.
• To investigate the quorum sensing regulation of δ-toxin gene expression (RNAIII).

Main Methods:

• Whole genome sequencing of four S. pseudintermedius isolates.
• In vitro mast cell degranulation assay using synthetic δ-toxin.
• In vivo assessment of mast cell degranulation in canine skin following injection of bacterial filtrate.
• Quantitative PCR to measure RNAIII expression under varying bacterial densities.

Main Results:

• Sequences of hld and agr elements were determined.
• Synthetic S. pseudintermedius δ-toxin induced mast cell degranulation comparable to S. aureus δ-toxin.
• Canine mast cell degranulation was confirmed in vivo upon exposure to S. pseudintermedius filtrate containing δ-toxin.
• RNAIII expression significantly increased with bacterial cell density, indicating quorum sensing control.

Conclusions:

• S. pseudintermedius isolates from atopic dogs possess genes for δ-toxin.
• δ-toxin can degranulate mast cells in vitro and in vivo, potentially contributing to cAD.
• Quorum sensing likely regulates δ-toxin production in these isolates.