Molecular Tracking of Emerging Fusarium Species in Keratitis: F. veterinarium, F. contaminatum, and F. curvatum

Fungal keratitis, which is caused primarily by Neocosmospora and Fusarium species, is a significant global health issue that affects more than a million people annually in tropical and subtropical regions. Neocosmospora solani (formerly Fusarium solani) is a leading cause of corneal infections, along with members of the Fusarium oxysporum species complex (FOSC). This study provides new insights by reporting a series of ocular fusariosis cases caused by FOSC members and presenting molecular evidence linking specific haplotypes within FOSC to human infections. We describe three cases of Fusarium keratitis selected from a comprehensive review of clinicopathological data in our institution's archives. These cases were chosen for their distinctive clinical presentations and the involvement of less common Fusarium species. Two of these patients were diagnosed with keratitis and anterior endophthalmitis, and the third patient had a corneal ulcer previously treated with topical antivirals and antibiotics. All patients were successfully treated with topical amphotericin B. The Fusarium isolates from these patients were subjected to detailed molecular characterization, including DNA sequencing (tef1 alpha, rpb2, CaM, tub2, and LSU), amplified fragment length polymorphism (AFLP) marker analysis, and MALDI-TOF MS analysis. Remarkably, our study reports the first case of human infection by F. veterinarium, alongside cases involving F. contaminatum and F. curvatum. Furthermore, a molecular survey using haplotypic networks based on tef1 alpha sequences identified genotypes associated with human infections and revealed the emergence of F. veterinarium clade VII. Our findings emphasize the need for vigilance regarding emerging species within the FOSC, particularly F. veterinarium. This highlights the need for improved diagnostic tools and targeted research to combat fusarioid-related infections effectively.