Encystation in Acanthamoeba castellanii: Development of Biocide Resistance

Since the early 1960s, axenic culture and the development of procedures for the induction of encystation have made Acanthamoeba spp. superb experimental systems for studies of cell biology and differentiation. More recently, since their roles as human pathogens causing keratitis and encephalitis hav...

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Bibliographic Details
Published in:The Journal of eukaryotic microbiology 2001-01, Vol.48 (1), p.11-16
Main Authors: LLOYD, D., TURNER, N. A., KHUNKITTI, W., HANN, A. C., FURR, J. R., RUSSELL, A. D.
Format: Article
Language:English
Subjects:
Acanthamoeba - drug effects
Acanthamoeba - growth & development
Acanthamoeba - ultrastructure
Amebiasis - parasitology
Amebicides - pharmacology
Animals
Antibiotics. Antiinfectious agents. Antiparasitic agents
Antiparasitic agents
Benzalkonium chloride
Biological and medical sciences
Chlorhexidine diacetate
confocal laser scanning microscopy
dibromopropamine isethionate
Drug Resistance
flow cytometry
H2O2
Humans
Medical sciences
oxonol
pentamidine isethionate
Pharmacology. Drug treatments
polyhexamethylene biguanide
propamidine isethionate
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Summary:Since the early 1960s, axenic culture and the development of procedures for the induction of encystation have made Acanthamoeba spp. superb experimental systems for studies of cell biology and differentiation. More recently, since their roles as human pathogens causing keratitis and encephalitis have become widely recognized, it has become urgent to understand the parameters that determine differentiation, as cysts are much more resistant to biocides than are the trophozoites. Viability of trophozoites of the soil amoeba Acanthamoeba castellanii (Neff), is conveniently measured by its ability to form plaques on a lawn of Escherichia coli. Use of confocal laser scanning microscopy with Calcofluor white, Congo Red or the anionic oxonol dye, DiBAC4(3) or flow cytometry with propidium iodide diacetate and fluorescein or oxonol provides more rapid assessment. For cysts, the plaque method is still the best, because dye exclusion does not necessarily indicate viability and therefore the plate count method has been used to study the sequence of development of biocide resistance during the differentiation process. After two hours, resistance to HCl was apparent. Polyhexamethylene biguanide, benzalkonium chloride, propamidine isethionate, pentamidine isethionate, dibromopropamine isethionate, and H2O2 and moist heat, all lost effectiveness at between 14 and 24 h after trophozoites were inoculated into encystation media. Chlorhexidine diacetate resistance was observed at between 24 and 36 h. The molecular biology and biochemistry of the modifications that underlie these changes are now being investigated.
ISSN:1066-5234
1550-7408
DOI:10.1111/j.1550-7408.2001.tb00410.x