Polymicrobial Keratitis: Acanthamoeba and Infectious Crystalline Keratopathy

Purpose To report the early presentation, cause, and successful medical management of combined Acanthamoeba keratitis (AK) and infectious crystalline keratopathy (ICK). Design Interventional case series. Methods Retrospective review of 111 AK patients diagnosed and managed at the University of Illinois Eye and Ear Infirmary between June 1, 2003 and November 30, 2008 for an additional diagnosis of infectious keratitis. Results Of 5 AK patients with microbiologic evidence of an additional bacterial keratitis during their active AK treatment, concomitant ICK developed in 3 patients. All patients were examined within 3 weeks of their AK diagnosis and were found to have characteristic signs and symptoms consistent with ICK. Bacterial culture results at the time of AK diagnosis were negative in 2 patients, but subsequent culture results were positive for Streptococcus oralis. Initial culture results demonstrated light growth of methicillin-sensitive Staphylococcus aureus in the remaining patient, who had received partial antibiotic treatment. Topical corticosteroids were used before diagnosis in 2 patients and were in use in only 1 patient after AK diagnosis. All infections resolved with medical therapy alone. One patient later required penetrating keratoplasty for visual rehabilitation. Conclusions In patients with AK, ICK can develop early and without either the use of corticosteroids or a preexisting epithelial defect, inconsistent with previously suggested mechanisms and major risk factors for secondary infection. Combined AK and ICK may exhibit increased pathogenicity with the onset of severe, often new, pain and acceleration of localized tissue loss and resultant scarring. Although early recognition and aggressive medical treatment were successful in resolving the combined infections in our cases, Acanthamoeba coinfection, and perhaps endosymbiosis, should be considered in the evaluation and clinical management of AK, especially in those cases progressing atypically. Further research is needed to understand the precise mechanism of the introduction of coinfectious pathogens and their role in the pathogenicity of AK.