Free living amoebae (FLA) keratitis

Purpose: To describe the clinical features and treatment results in 41 consecutive patients with microbiologically proven free-living amoebae (FLA) keratitis. Methods: Corneal scrapings from patients with suspected amoebic keratitis were plated on non-nutrient agar seeded with E. coli. Amoebic isolates were identified morphologically and by PCR. All patients were treated with PHMB 0.02% eye-drops. Results: 41 corneal scrapings from 41 patients were found to be culture-positive for FLA; 39 (95%) were from contact lens (CL) wearers, 2 (5%) from non-CL wearers. Microscopic examination identified 3 Acanthamoeba spp, 20 Hartmannella spp, 13 Vahlkampfidae, and 3 mixed infections with Hartmannella/Vahlkampfidae. Morphological results were confirmed by PCR. Patients with Acanthamoeba, Hartmannella and Vahlkamfidae keratitis had indistinguishable clinical features. In 37 eyes with keratitis at an early stage, treatment with PHMB 0.02% eye-drops was fully successful. In 4 patients with advanced keratitis, topical PHMB 0.02% controlled the infection, but all of them developed a central corneal scar with visual deterioration. Conclusions: Acanthamoeba is not the only cause of amoebic keratitis, because this condition may also be caused by other FLA, such as Hartmannella and Vahlkampfidae. This finding is epidemiologically interesting, suggesting a possible different geographical prevalence of the different FLA responsible for keratitis. Early diagnosis and proper anti-amoebic treatment are crucial to yield a cure.