title: Nucleic acid stains as indicators of Giardia muris viability following cyst inactivation.
abstract: A reliable viability assay for Giardia is required for the development of disinfection process design criteria and pathogen monitoring by water treatment utilities. Surveys of single-staining nucleic acid dyes (stain dead parasites only), and double-staining vital dye kits from Molecular Probes (stain live and dead parasites) were conducted to assess the viability of untreated, heat-killed, and chemically inactivated Giardia muris cysts. Nucleic acid staining results were compared to those of in vitro excystation and animal infectivity. Nucleic acid stain, designated as SYTO-9, was considered the best among the single-staining dyes for its ability to stain dead cysts brightly and its relatively slow decay rate of visible light emission following DNA binding. SYTO-9 staining was correlated to animal infectivity. A Live/Dead BacLight was found to be the better of 2 double-staining viability kits tested. Logarithmic survival ratios based on SYTO-9 and Live/Dead BacLight were compared to excystation and infectivity results for G. muris cysts exposed to ozone or free chlorine. The results indicate that SYTO-9 and Live/Dead BacLight staining is stable following treatment of cysts with chemical disinfectants.
authors.affiliation: Department of Biological Sciences, University of Alberta, Edmonton, Canada.
authors.forename: R
authors.initials: R
authors.lastname: Taghi-Kilani
authors.forename: L L
authors.initials: LL
authors.lastname: Gyürék
authors.forename: P J
authors.initials: PJ
authors.lastname: Millard
authors.forename: G R
authors.initials: GR
authors.lastname: Finch
authors.forename: M
authors.initials: M
authors.lastname: Belosevic
mesh_terms: D000818:Animals; D000890:Anti-Infective Agents / Q000494:pharmacology; D002713:Chlorine / Q000494:pharmacology; D004396:Coloring Agents; D006224:Cricetinae; D004203:Disinfection / Q000379:methods*; D005260:Female; D005872:Giardia / Q000187:drug effects / Q000302:isolation & purification* / Q000472:pathogenicity; D051379:Mice; D008828:Microbiological Techniques; D009696:Nucleic Acids / Q000302:isolation & purification*; D009930:Organic Chemicals; D016877:Oxidants / Q000494:pharmacology; D010126:Ozone / Q000494:pharmacology; D013194:Staining and Labeling / Q000379:methods*
chemical_list: D000890:Anti-Infective Agents; D004396:Coloring Agents; D009696:Nucleic Acids; D009930:Organic Chemicals; D016877:Oxidants; C103389:SYTO 9; D002713:Chlorine; D010126:Ozone