Staphylococcal Enterotoxins Promote Virulence in Bacterial Keratitis

Area of Science:

• Microbiology
• Ophthalmology
• Infectious Diseases

Background:

• Staphylococcus aureus is a leading cause of infectious keratitis.
• Secreted enterotoxins are more prevalent in ocular S. aureus isolates.
• Enterotoxins are known for toxic shock syndrome and food poisoning but their role in keratitis is unestablished.

Purpose of the Study:

• Investigate the role of staphylococcal enterotoxins in the virulence of S. aureus keratitis.
• Determine if enterotoxins contribute to bacterial adhesion, invasion, or cytotoxicity in corneal infections.
• Assess the impact of enterotoxins on disease severity in vivo.

Main Methods:

• Utilized clinical S. aureus isolates, including enterotoxin-positive and negative strains, and their mutants.
• Evaluated bacterial adhesion, invasion, and cytotoxicity in a primary corneal epithelial cell model.
• Assessed bacterial burden, enterotoxin gene expression, and host cytokine response in an in vivo keratitis model.

Main Results:

• Staphylococcal enterotoxins do not affect bacterial adhesion or invasion but cause direct cytotoxicity to corneal epithelial cells.
• Enterotoxin gene expression (sed, sej, sek, seq, ser) varied during infection.
• Strains encoding enterotoxins exhibited increased bacterial burden and reduced host cytokine response in vivo.

Conclusions:

• Staphylococcal enterotoxins play a novel role in promoting S. aureus virulence during keratitis.
• Enterotoxins contribute to corneal tissue damage and modulate the host immune response.
• Findings suggest enterotoxins are potential therapeutic targets for S. aureus eye infections.