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Michaela L. Bajenaru, A R. Santos, M A. Shousha, R A. Oechsler, J Maestre, E Hernandez, M E. Fini, Darlene Miller, E C. Alfonso; A Rat Model for Contact Lens Associated Fusarium Keratitis. Invest. Ophthalmol. Vis. Sci. 2011;52(14):2935.
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Fungal keratitis is responsible for significant ocular morbidity and blindness worldwide with higher incidence in regions with warm, humid climates such as in South Florida. Trauma and contact lens wear are major risk factors for the development of the disease. One of the most common and pathogenic isolates for fungal keratitis is Fusarium solani. We developed a highly reproducible rat contact lens model with the help of optical coherence tomography (OCT). The purpose of this study is to induce contact lens (CL)-associated Fusarium keratitis in the rat and to study its molecular pathogenesis.
Hydrogel (38% water, 62% polymacon) contact lenses (Bausch and Lomb, UK) were fitted on immunocompromised female Sprague-Dawley rats (n=24). Fusarium infection was initiated in the experimental eye by performing corneal stromal abrasion on the rat eye and fitting a contact lens soaked in Fusarium solani 108 CFU/ml for 4 hours. The fungal infection was monitored by periodic slit lamp examination, and SD-OCT imaging of the rat eye. One week post infection, the eyes were enucleated, cornea were excised, and submitted for histopathology. Corneal homogenates were cultured on Sabouraud agar plates to quantify the viable fungi in the infected rat cornea. PCR with specific primers for Fusarium solani was performed in corneal homogenates.
Our results revealed a 75% infection rate 1 week post-infection in the CL-associated Fusarium keratitis rat model. The SD-OCT findings confirmed the histopathological and slit lamp results in all the animals with CL-associated fungal keratitis, revealing thickening of the cornea, endothelial plaques, and inflammatory cells infiltrates. Moreover, in one case, SD-OCT was able to detect the infection even without any findings on slit lamp examination. PCR was positive with primers specific for Fusarium. Sabouraud agar plates were culture positive, and we quantified a high infective index of 105 CFU/eye. Fungal hyphae were also observed in cross-sections of the corneal tissue by H&E and Gomori staining.
The clinical presentation of CL associated Fusarium keratitis in the rat model is very similar to humans. SD-OCT proved to be a very valuable tool. It is non-invasive and confirmed a suspected case of keratitis with only subtle clinical manifestation.
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