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Purpose: To report a novel clinical presentation of corneal biofilms, consisting of formation of superficial and recurrent corneal plaques. Methods: Interventional case report. A 9-year-old boy presented with subepithelial, whitish, avascular, and recurrent corneal plaques without any clinical manifestations of active corneal inflammation and/or infection. He had a history of minor ocular trauma; otherwise, his medical history was unremarkable. Results: An excisional biopsy was performed under topical anesthesia. Histological analysis identified these plaques as clusters of gram-negative bacilli surrounded by an extracellular matrix. Samples were further evaluated with special stains (calcofluor white, Flamingo fluorescent dye, propidium iodide, and Gomori–Grocott) that demonstrated biofilm structures. Conclusions: Corneal plaques are a very rare clinical presentation of corneal biofilms that allow prolonged survival of microorganisms even in the absence of prosthetic material and clinical signs or symptoms of corneal active inflammation and/or infection.

BackgroundInfectious keratitis is the main cause of preventable blindness worldwide, with about 1.5–2.0 million new cases occurring per year. This inflammatory response may be due to infections caused by bacteria, fungi, viruses or parasites. Fungal keratitis is a poorly studied health problem.ObjectivesThis study aimed to identify a new fungal species by molecular methods and to explore the possible efficacy of the three most common antifungals used in human keratitis in Mexico by performing in vitro analysis. The capacity of this pathogen to cause corneal infection in a murine model was also evaluated.MethodsThe fungal strain was isolated from a patient with a corneal ulcer. To identify the fungus, taxonomic and phylogenetic analyses (nrDNA ITS and LSU data set) were performed. An antifungal susceptibility assay for amphotericin B, itraconazole and voriconazole was carried out. The fungal isolate was used to develop a keratitis model in BALB/c mice; entire eyes and ocular tissues were preserved and processed for histopathologic examination.Results and conclusionThis fungal genus has hitherto not been reported with human keratitis in Mexico. We described a new species Purpurecillium roseum isolated from corneal infection. P roseum showed resistance to amphotericin B and itraconazole and was sensitive to voriconazole. In vivo study demonstrated that P roseum had capacity to developed corneal infection and to penetrate deeper corneal tissue. The global change in fungal infections has emphasised the need to develop better diagnostic mycology laboratories and to recognise the group of potential fungal pathogens.

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