While overall antifungal minimum inhibitory concentrations (MICs) do not appear to correlate with clinical outcomes in fungal keratitis, a recent study published in the Journal of Ocular Inflammation and Infection suggests that higher voriconazole MICs are associated with poorer outcomes in cases specifically involving Fusarium species. The research, which analyzed data from 141 patients with fungal keratitis, highlights the importance of species-specific antifungal susceptibility testing.
The study, a retrospective analysis of a clinical trial cohort, examined the relationship between MICs of natamycin and voriconazole and various clinical outcomes, including best-corrected visual acuity, infiltrate/scar size, corneal perforation, need for therapeutic penetrating keratoplasty, and time to re-epithelialization. The most commonly cultured organisms were Aspergillus (47%) and Fusarium (45%).
Key Findings in Fusarium Keratitis
Overall, the analysis of all cultured isolates showed no significant association between antifungal MICs and the clinical outcomes studied. However, subgroup analysis focusing on Fusarium-positive cases revealed a significant correlation between voriconazole MIC and adverse outcomes. Specifically, a two-fold increase in voriconazole MIC was significantly associated with:
- Increased odds of needing therapeutic penetrating keratoplasty (odds ratio, 1.92; 95% CI, 1.11–3.89; P = 0.04)
- Worse three-month best-corrected visual acuity (95% CI, 0.02–0.34; P = 0.03)
- Prolonged time to re-epithelialization (95% CI, -8.66–[-0.55]; P = 0.03)
No significant correlations were found among Aspergillus-positive cases, and natamycin MIC was not a significant predictor of any studied clinical outcomes in either subgroup.
Implications for Treatment Strategies
These findings suggest that in vitro susceptibility testing, particularly for voriconazole in Fusarium keratitis, may provide valuable information for guiding treatment decisions. While natamycin remains a common first-line treatment for fungal keratitis, the study underscores the potential importance of considering voriconazole susceptibility when Fusarium is identified as the causative organism. Further research is warranted to validate these findings and explore alternative treatment strategies for Fusarium keratitis with elevated voriconazole MICs.
