Effect of inoculum size on the induction of endophthalmitis in aphakic rabbit eyes

Area of Science:

• Ophthalmology
• Microbiology
• Infectious Diseases

Background:

• Bacterial endophthalmitis requires reproducible animal models for antimicrobial research.
• Current models may lack consistency in inducing infection.

Purpose of the Study:

• To determine the minimum bacterial inoculum sizes of Staphylococcus aureus and Pseudomonas aeruginosa required for consistent endophthalmitis induction in aphakic rabbit eyes.
• To compare intravitreal and anterior chamber injection routes for model reproducibility.

Main Methods:

• Aphakic rabbit eyes were injected with varying inocula of S. aureus and P. aeruginosa.
• Injections were administered into the anterior chamber and intravitreally immediately post-surgery.
• The consistency of induced endophthalmitis was evaluated based on inoculum size and injection site.

Main Results:

• For Staphylococcus aureus, a minimum intravitreal inoculum of 19.3 ± 7.5 CFU and an anterior chamber inoculum of 50.5 ± 4.0 CFU consistently produced endophthalmitis.
• For Pseudomonas aeruginosa, an intravitreal inoculum of 5.5 ± 2.6 CFU and an anterior chamber inoculum of 97.5 ± 10.7 CFU consistently produced fulminant infection.
• Lower bacterial inocula resulted in inconsistent endophthalmitis in both injection sites.

Conclusions:

• Specific, reproducible inoculum sizes for S. aureus and P. aeruginosa have been identified for inducing bacterial endophthalmitis in aphakic rabbit eyes.
• This data is vital for developing and testing antimicrobial agents for endophthalmitis prophylaxis and treatment.
• The findings provide a foundation for standardized experimental protocols in endophthalmitis research.