Adherence and biofilm formation of Fusarium oxysporum isolated from a corneal ulcer

Nathalie Kira Tamura¹, Giuli Kira², Eliana Valeria Patussi¹, Lucelia Donatti³ and Terezinha Inez Estivalet Svidzinski¹*

¹Department of Clinical Analysis, Division of Medical Mycology, State University of Maringá, Paraná, Brazil.

²Hoftalon, Londrina, Paraná, Brazil.

³Department of Biology, Federal University of Paraná, Curitiba, Brazil.

Corresponding Author E-mail: tiesvidzinski@uem.br, terezinha@email.com; Phone: +5544 3011-4809; Fax: +5544 3011-4860

Accepted 13 January, 2015

Abstract

Fusarium oxysporum is one of the principal agents of fungal keratitis, causing morbidity and loss of vision moreover contact lenses are important cofactor. This study aimed to evaluate the capacity for adherence, invasion, and biofilm formation in vitro of a sample of Fusarium isolated from a human corneal ulcer. The biofilm formation capacity of the fungal isolate was evaluated by the XTT reduction colorimetric method, on polystyrene Microplates at intervals of 1, 2, 4, 8, 24, and 48 hours. The viability of the adhered fungal cells was evaluated by LIVE/DEAD staining in confocal scanning fluorescence microscopy. Hydrophilic contact lenses were inoculated with 10⁶ colony-forming units per milliliter of the fungus to evaluate adherence, by counting of strongly adhered cells, and the capacity for invasion observed by scanning electron microscopy. The formation of a biofilm by F. oxysporum was demonstrated by an increase in the intensity of XTT from 8 to 48 hours. LIVE/DEAD staining and XTT showed that the adhered fungi remained viable and metabolically active. F. oxysporum showed a high adherence capacity within 1 hour of incubation. After 72 hours the fungus had invaded and completely penetrated the contact-lens matrix. Concluding F. oxysporum, isolated from a fungal keratitis, showed a high capacity to adhere, invade, and form a biofilm. In addition, fungal cells remain viable and metabolically active after adhering, suggesting a potential for infection.

Key-words: Fungal keratitis, Fusarium biofilm, Contact lenses, Virulence factors.