Quantitative enumeration of acanthamoeba for evaluation of cyst inactivation in contact lens care solutions.

A simple, quantitative plate assay has been developed for use in the enumeration of Acanthamoeba. The technique uses an agarose overlay and low-nutrient medium to support the growth of amoebae on a bacterial lawn. The authors found that in this assay, individual trophozoites or dormant cysts will cause plaques to form in an Enterobacter aerogenes lawn. With the assay, it is possible to quantitatively assess the effects of various disinfectant compounds on the viability of Acanthamoeba. The authors used this assay to enumerate Acanthamoeba cyst viability after chemical disinfection in contact lens care solutions. The inactivation data indicated major differences among the four test solutions evaluated.