Abstract
Purpose :
Fungal keratitis (FK) is an infectious disease of the cornea that is increasing in prevalence worldwide. To combat increasing prevalence and improve current therapies, broad-spectrum antifungal agents and models that reliably assess efficacy of topical applied drugs are needed. Current models such as in vitro minimum inhibitory concentration assays can be challenging to interpret due to the lack of established drug breakpoints for many fungal species. These in vitro methods may also fail to correlate well with in vivo application. The purpose of this research is to compare an ex vivo corneal model for antifungal drug efficacy to recent results from a gold-standard MIC assay, with the hypothesis that this method will provide an accurate evaluation of therapeutic efficacy that is better representative of fungal colonization and corneal infection.
Methods :
Archived isolates of Aspergillus flavus, A. fumigatus, Fusarium falciforme, and F. keratoplasticum, sourced from equine FK patients at North Carolina State University, were used for this study. Disinfected porcine cadaver globes were inoculated via intrastromal injection with approximately 500,000 conidia of A. flavus, A. fumigatus, F. keratoplasticum, or F. falciforme. Corneas were excised and incubated in Dulbecco's Modified Eagle Cell Culture Medium (DMEM) with either amphotericin B (AMB), luliconazole (LUL), natamycin (NAT), or voriconazole (VOR) at a concentration equivalent to 0.0X, 0.25X, 1.0X or 2.0X of the previously reported MIC. Radial fungal growth was monitored by imaging corneas and measuring area of colonization by pixel count every 12 hours for 72 hours total.
Results :
All antifungal drugs examined significantly inhibited growth of A. fumigatus and F. keratoplasticum at or below the MIC at all time points. With few exceptions, all drugs inhibited growth of A. flavus below the MIC at all time points. AMB did not inhibit growth of F. falciforme, while all other drugs inhibited growth at or below the MIC for all time points except for LUL at 24 hours.
Conclusions :
Inhibition of radial fungal growth in corneas injected with conidia and incubated in AMB, LUL, NAT, or VOR corresponded well with in vitro MICs in each isolate. With few exceptions, ex vivo fungal growth was significantly inhibited at one-half of the established MIC.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.