Immune response to Staphylococcus epidermidis-induced endophthalmitis in a rabbit model

Area of Science:

• Ophthalmology
• Immunology
• Microbiology

Background:

• Staphylococcus epidermidis is a leading cause of postoperative pseudophakic endophthalmitis.
• The immune response to S. epidermidis-induced endophthalmitis is not well understood.

Purpose of the Study:

• To investigate the immune response to S. epidermidis-induced endophthalmitis using a rabbit model.
• To compare the clinical and histopathologic inflammatory reactions and humoral immune responses between different bacterial inoculums.

Main Methods:

• Rabbits received intravitreal injections of either 7000 (group 1) or 30,000 (group 2) S. epidermidis organisms.
• Clinical and histopathologic evaluations assessed inflammation.
• Vitreous cultures identified bacterial presence.
• Skin tests evaluated delayed hypersensitivity.
• Serum, aqueous, and tear fluid antibody levels (IgG, IgA) to S. epidermidis and glycerol teichoic acid (GTA) were measured.

Main Results:

• Group 2 exhibited more severe conjunctival, corneal, iris, and vitreous inflammation than group 1.
• Histopathology confirmed more intense inflammation in both anterior and posterior segments in group 2.
• Vitreous cultures were positive for longer in group 1, but group 2 had higher initial bacterial loads.
• A significant IgG antibody response to S. epidermidis and GTA was observed in serum, vitreous, and aqueous humor, peaking at days 10-14.
• No delayed hypersensitivity or detectable IgA response was found in serum, vitreous, or tears.

Conclusions:

• S. epidermidis-induced endophthalmitis elicits a humoral immune response.
• The severity of inflammation and antibody response correlates with the bacterial inoculum size.
• A delayed hypersensitivity response to S. epidermidis is not a feature of this experimental model.