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Applied and Environmental Microbiology, March 2000, p. 1057-1061, Vol. 66, No. 3
Department of Biology, Georgia State
University, Atlanta, Georgia 30303
Received 2 August 1999/Accepted 10 December 1999
Flow cytometric analyses of cellular staining with fluorescent
viability dyes and direct microscopic observations of methylene blue
exclusion were compared for evaluation of the effects of a
chlorhexidine gluconate-based contact lens disinfectant solution and a
polyhexamethylene biguanide solution against cysts and trophozoites of
Acanthamoeba castellanii and Acanthamoeba
polyphaga. The flow cytometric procedure with propidium iodide
(used to stain dead cells) indicated that more than 90% of
trophozoites of both species (inocula of 105 to
106/ml) at 22°C lost their viability after 4 h of
exposure to chlorhexidine. When propidium iodide was used in
combination with fluorescein diacetate (for live cells), the apparent
number of propidium iodide-stained cells was reduced, but the relative
efficacies of the two biguanide solutions appeared unchanged from those
evident with the single dyes; the chlorhexidine solution was more
effective than the polyhexamethylene biguanide solution. Similar data
were obtained with the more cumbersome methylene blue exclusion
procedure. Flow cytometric analyses provided a statistically
reproducible and rapid procedure for determining the relative
antiamoebal efficacies of the disinfecting solutions.
0099-2240/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Flow Cytometry for Determination of the Efficacy of
Contact Lens Disinfecting Solutions against
Acanthamoeba spp.

*
Corresponding author. Mailing address: Department of
Biology, Georgia State University, P.O. Box 4010, Atlanta, GA
30302-4010. Phone: (404) 651-3110. Fax: (404) 651-2509.
Present address: Bausch & Lomb, Rochester, NY 14603-0450.
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