Differences in virulence between two Candida albicans strains in experimental keratitis

Area of Science:

• Ophthalmology
• Mycology
• Infectious Diseases

Background:

• Contact lens-related microbial keratitis is a significant cause of vision loss.
• Candida albicans is an opportunistic fungal pathogen that can cause severe keratitis.
• Understanding strain-level virulence differences is crucial for predicting disease severity.

Purpose of the Study:

• To compare the virulence of two wild-type Candida albicans strains (SC5314 and VE175) in a rabbit model of contact lens-facilitated keratitis.
• To assess differences in corneal invasion and clinical disease severity between the two strains.

Main Methods:

• Dutch belted rabbits were inoculated with standardized inocula of either SC5314 or VE175 on a debrided cornea.
• Contact lenses were applied and removed after 24 hours, with clinical assessment and histological analysis performed six days post-infection.
• Corneal fungal invasion depth and clinical disease scores were quantified.

Main Results:

• Strain SC5314 demonstrated significantly higher virulence, causing deeper corneal stromal penetration (mean 24.4%) compared to VE175 (mean 2.6%).
• SC5314 led to more severe clinical disease (P = 0.0048), with hyphae penetrating the full corneal thickness in some cases.
• No significant difference in fungal isolate recovery was observed between the two strains.

Conclusions:

• Wild-type Candida albicans strains exhibit significant variations in virulence, impacting corneal invasion depth and clinical outcomes.
• Identifying genetic factors underlying these virulence differences could elucidate mechanisms of fungal pathogenesis.
• These findings highlight the importance of strain-specific characteristics in fungal keratitis.