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M. Shoff, C. Joslin, G. Booton, E. Tu, P. Fuerst; Prevalence of Acanthamoeba in Chicago Area Tap Water. Invest. Ophthalmol. Vis. Sci. 2007;48(13):338.
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A significant recent increase in Acanthamoeba keratitis (AK) has been documented in the greater Chicago, Ill. area. It was hypothesized that changes in water treatments may have led to an increase in biofilms and thus an increase in Acanthamoeba in the water supply. This study was done to identify the prevalence of naked amoebae in tap water in the Chicago area to determine the risk for amoebal infections of the cornea in contact lens wearers.
Over the course of 5 months (June 2006-Nov. 2006), water samples were collected from sites in the greater Chicago area. Because most American homes have mixer faucets and do not have storage tanks, water was sampled in all cases using sterile swabs from the inside surface film of the lavatory cistern reservoir tank. Further, 50mL of tank water serving the lavatory was also sampled. In all cases, the ultimate source of water was cold municipal mains water. The presence of amoebae in samples was assayed using an enrichment cultivation method appropriate for Acanthamoeba. Amoebae were identified based on diagnostic features discernable by light microscopy.
A total of 116 households’ samples were processed and amoebae were noted in 62 of these. Acanthamoeba were found on 18 occasions (15.8 %). Amoebae (regardless of genus) were present in 54.4 % of all samples.
Previous surveys in England and Korea have shown that acanthamoebae are found in 15 to 30% of tap water samples in the home and have been associated with corneal infection in contact lens wearers who have exposed their lenses to tap water. The incidence of acanthamoebae infection in the US has been lower than that of the UK. It has been postulated that this is related to the lack of a storage water tank in the loft in US homes. A previous study of South Florida tapwater indicating a low incidence of Acanthamoeba (2.8%) supported this view. The recent outbreak of AK in the Chicago area prompted a study of the tapwater in that area. Initial findings reported here indicate a much higher incidence of Acanthamoeba (as well as other amoebae) in the tap water of Chicago than was observed in S. Florida, possibly a link to the higher incidence of AK in the Chicago area. These initial findings support the hypothesis that the new water treatments may be permitting increased biofilms which result in an increase of Acanthamoeba, as well as other protists, which in turn increases the rate of AK.
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