Acanthamoeba keratitis: an increasingly common infectious disease of the cornea

Acanthamoeba, a free-living protist that is ubiquitously distributed in the environment, is also an opportunistic pathogen and a host of phylogenetically distinct bacteria, fungi, viruses, and other protists. Acanthamoeba causes keratitis, a sight-threatening, painful, and difficult-to-treat ocular infection that is linked to contact-lens wear.1 The pathogen can also cause infections of the CNS and skin, which are associated with immunodeficiency,2 although these types of infection are less common than keratitis.