Comparison of Molecular and Antifungal Profiles of Fusarium species recovered from patients Treated with Rose Bengal Photodynamic Antimicrobial Therapy vs Antifungal Therapy.

Abstract

Purpose : To compare species diversity, antifungal susceptibility and mycotoxin profiles of Fusarium isolates recovered from patients subjected to RB-PDAT plus antifungal therapy vs those treated with antifungal therapy alone.

Methods : We used a combination of PCR and DNA sequencing to confirm and classify 25 fusarium isolates (5 PDAT-treated; 20 non-PDAT treated) recovered from patients presenting at BPEI with fungal keratitis between July 2016 and November 2021. Primer specific PCR and DNA sequencing were used to screen for the presence of Fumonisin and Trichothecene mycotoxins. Etests were used to evaluate antifungal susceptibility profiles for amphotericin B and voriconazole in accordance with CLSI standards in 21 isolates.

Results : Isolates: In general, 60% (n=15) of isolates belonged to the Fusarium solani species complex (FSSC), of which Fusarium falciforme (20%, n=5) was the most common species. 36% (n=9) belonged to the Fusarium chlamydosporum species complex (FCSC), and 4% (n=1) to the Fusarium dimerum species complex (FDSC), namely Fusarium delphinoides. Of the five PDAT isolates included, 60% (n=3) belonged to the Fusarium solani species complex; one being Fusarium falciforme. The remaining two isolates belonged to the FCSC and FDSC, respectively.

Mycotoxins: At least one mycotoxin was identified in all isolates. Fumonisin toxins were documented in 44% (n=11) of all isolates and in 60% (n=3) of the PDAT-treated species. Trichothecenes were documented in 68% (n=17) of isolates and in all PDAT-treated species.

Antifungal susceptibility testing: None of the isolates demonstrated in vitro susceptibility to voriconazole and amphotericin B with MICs₉₀ of >32 µg/ml (R) at 72 hours, respectively. Mean MICs for voriconazole were similar in the non-PDAT treated group (28.8 µg/mL/R) compared to the PDAT-treated group (27.2 µg/ml/R). Similarly, MICs for amphotericin B in the non-PDAT treated group (14.3 µg/mL/R) showed little variation compared to the PDAT-treated group (14.6 µg/ml/R).

Conclusions : Toxin producing members of the Fusarium solani complex remain the most frequently recovered fusarium species from fungal keratitis in South Florida conferring increased resistance to standard antifungal treatment. Isolates treated with RB-PDAT were more likely to be toxins producers.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.