Differentiating Ocular Pathogenic Staphylococcus epidermidis Isolates Using a Human Corneal Epithelial Cell Coculture...

Area of Science:

• Ophthalmology
• Microbiology
• Cell Biology

Background:

• Staphylococcus epidermidis is a common cause of bacterial keratitis.
• Distinguishing pathogenic from nonpathogenic strains is crucial for effective treatment.
• Current methods for strain differentiation can be time-consuming.

Purpose of the Study:

• To develop an in vitro human corneal epithelial cell (HCEC) coculture model.
• To differentiate pathogenic from nonpathogenic ocular Staphylococcus epidermidis isolates.
• To evaluate HCEC viability as a predictor of S. epidermidis pathogenicity.

Main Methods:

• HCECs were cocultured with S. epidermidis strains (104-108 CFU/mL) for 12-72 hours.
• Cell viability was assessed using calcein AM staining.
• The model was validated against mouse keratitis models and receiver operating characteristic analysis.

Main Results:

• The 24-hour HCEC coculture assay reliably quantified bacterial cytotoxicity.
• Pathogenic S. epidermidis strains induced significantly lower HCEC viability compared to nonpathogenic strains at 106 CFU/mL (P = 0.006).
• A 91.36% HCEC viability cutoff distinguished pathogenic strains with 91.7% sensitivity and 100% specificity.

Conclusions:

• The HCEC coculture assay is a rapid and reliable method for differentiating pathogenic from nonpathogenic S. epidermidis ocular isolates.
• The in vitro results showed strong concordance with in vivo keratitis outcomes.
• This model serves as a practical diagnostic tool for bacterial keratitis.