Acanthamoeba castellanii amoeba, computer illustration. This is the reproductive and infective stage of the organism, or trophozoite form. A. castellanii, a free-living single-celled organism, is found in all aquatic habitats and soil. It can infect the eye causing Acanthamoeba keratitis, a potentially blinding inflammation of the cornea. Although rare, infection is more common amongst contact lens wearers.