The role of domestic tap water on Acanthamoeba keratitis in non-contact lens wearers and validation of laboratory methods

Abstract

Acanthamoeba is increasingly recognized as an important cause of keratitis in non-contact lens wearers while contact lens wear is the leading risk factor for Acanthamoeba keratitis (AK). It is unlikely that the Acanthamoeba colonization is a feature which is effective only in patient's homes with infectious keratitis since the organism has been isolated from domestic tap water. Two hundred and thirty-one (231) corneal scrapings were taken from infectious keratitis cases, and four contact lens solutions and domestic tap waters were taken from 22 out of 44 AK-diagnosed patient's homes. Microscopic examination, culture, PCR, real-time PCR and DNA sequencing analyses were used for AK-diagnosed samples. The real-time PCR was the most sensitive (100 %) one among the methods used in diagnosis of AK. The 44 (19.0 %) out of 231 corneal scrapings, 4/4 (100 %) contact lens solution and 11/22 (50 %) of domestic tap water samples were found to be positive by real-time PCR for Acanthamoeba. A. griffini (T3), A. castellanii (T4) and A. jacobsi (T15) genotypes were obtained from corneal scrapings, contact lens solutions and domestic tap water samples taken from the patient's homes diagnosed with AK. The isolation of Acanthamoeba containing 6/22 (27.3 %) A. griffini (T3), 14/22 (63.6 %) A. castellanii (T4) and 2/22 (9.1 %) A. jacobsi (T15) from the domestic tap water outlets of 22 of 44 (50 %) of patient's homes revealed that is a significant source of these organisms. A. griffini (T3) and A. jacobsi (T15) genotypes have not been determined from AK cases in Turkey previously. Thus, we conclude that Acanthamoeba keratitis is associated with exposition of patients who has ocular trauma or ocular surface disease to domestic tap water in endemic or potentially endemic countries.