Comparison of animal infectivity, excystation, and fluorogenic dye as measures of Giardia muris cyst inactivation by ozone

Labatiuk, Charles W.; Schaefer, Frank W.; Finch, Gordon R.; Belosevic, Miodrag

doi:10.1128/aem.57.11.3187-3192.1991

Cited by 44 publications

(26 citation statements)

References 17 publications

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“…The single cyst that was resistant to dye penetration caused considerable alarm because it was found in a treated water sample. This situation is the same as that discussed by Labatiuk et al (20) who concluded that viable cysts as indicated by fluorogenic dyes may not be able to complete their life cycle and produce an infection. The actual risk of giardiasis infection presented by this possibly viable cyst must have been low, because there was no detectable increase in human cases of giardiasis in the months following the report of the positive sample.…”

Section: Viability and Infectivitysupporting

confidence: 77%

“…Water treatment studies have shown that viability testing by nucleic acid staining is not well correlated with animal infection experiments at high levels of water treatment and low numbers of cysts. (20,21) Dye exclusion can, however, be a good indicator of viability in the absence of disinfectants. (22,23) Because penetration of cells by nucleic acid dyes demonstrates abnormal membrane permeability rather than the status of metabolic activity, a cell that admits dye may not yet be dead and could cause an infection if ingested.…”

Section: Viability and Infectivitymentioning

confidence: 99%

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Application of Monitoring Data forGiardia andCryptosporidium to Boil Water Advisories

Wallis

Matson²,

Jones³

et al. 2001

Risk Analysis

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Despite the problems associated with analyzing water samples for Giardia cysts and Cryptosporidium oocysts, the data can be very useful if their strengths and weaknesses are understood. Two municipalities in northern Ontario, Temagami and Thunder Bay, both issued boil water advisories for Giardia contamination. Data from these two cities are compared to show that only one municipality experienced a real outbreak, whereas the other did not. The concentration of Giardia cysts was much higher than background during the outbreak at Temagami, and the postoutbreak concentrations of cysts were very similar to the long-term average cyst concentration at Thunder Bay. The waterborne outbreak of giardiasis at Temagami was characterized by consistent positive results from water samples, concentrations two to three orders of magnitude higher than normal, and an obvious increase in the number of cases of giardiasis in the population. No outbreak was experienced at Thunder Bay, but a boil water advisory (BWA) was set in place for more than a year on the basis of a single sample from Loch Lomond in which only two cysts were detected but the sample equivalent volume was low. This gave the impression of a sudden increase in concentration, but 39 of 41 subsequent samples were negative. Additional factors that led to a BWA at Thunder Bay are described, and recommendations are presented to help determine when a BWA is necessary and when it should be rescinded.

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Section: Viability and Infectivitysupporting

confidence: 77%

Section: Viability and Infectivitymentioning

confidence: 99%

Application of Monitoring Data forGiardia andCryptosporidium to Boil Water Advisories

Wallis

Matson²,

Jones³

et al. 2001

Risk Analysis

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“…Using human isolates, FDA staining consistently overestimated cyst viability, and this probe was found to be totally unreliable in predicting the viability of C. parvum when compared with animal infection tests (17). Labatiuk et al (18), using cyst samples inactivated by ozone, also found a significant difference between the FDA-staining method and the animal infectivity test for G. muris.…”

Section: Introductionmentioning

confidence: 99%

Fluorescence decay of dyed protozoa: differences between stressed and non‐stressed cysts

et al. 2015

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Several series of tests have shown that fresh, intact samples of Giardia duodenalis and Cryptosporidium parvum (oo)cysts are not marked by fluorescent probes such as carboxyfluorcein-succinimidyl-diacetate-ester (CFDA-SE), C12-resazurin and SYTOX® Green, probably because of their robust cell walls. These dyes fail to indicate the viability of such protozoa and allow negative responses to be recorded from living and infectious samples. Cryptosporidium parvum showed stronger isolation from chemicals, with living oocysts remaining unstained by the probe for up to 90 days after extraction. However, in further fluorescence decay (FD) experiments run with G. duodenalis samples stained using CFDA-SE (comprising living, non-stressed but aged cysts, heat-killed samples and UV-C-stressed samples) each showed a different FD decay profile, here studied in seven series of tests of five replicates each. The FD profiles were fitted by double-exponential decay kinetics, with the decay constant k2 being five times higher than k1. This FD procedure is fast and can be easily reproduced in 10 steps, taking ~ 1 h of laboratory work for already purified samples.

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“…Evaluating the public health risk by the application of viability dyes is considered inaccurate as it seems to lack reproducibility when conducted in different laboratories (Clancy et al 1994) and, like IFA, does not enable speciation. In vitro excystation (Rice and Schaefer 1981) and subjecting cysts to animal infectivity models (Labatiuk et al 1991) are considered too expensive, time consuming and impractical to be employed for routine testing of water supplies. Such animal or in vitro methods also may not correlate with infectivity in humans.…”

Section: Introductionmentioning

confidence: 99%

Oligonucleotide probes for specific detection of Giardia lamblia cysts by fluorescent in situ hybridization

Dorsch

Veal

2001

J Appl Microbiol

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Aims: Our study focused on the design of oligonucleotide probes and a suitable hybridization protocol that would allow rapid and speci®c identi®cation of potentially viable cysts of the waterborne parasite Giardia lamblia. Methods and Results: Comparative analysis of ribosomal RNA (rRNA) sequences of Giardia lamblia and a number of closely and more distantly related species identi®ed six regions that appear to be speci®c for the G. lamblia 16S rRNA. Fluorescently labelled probes targeting these regions were produced and employed in¯uorescent in situ hybridization (FISH) experiments.Two of the six probes tested successfully. Conclusions: Our study provides the ®rst reported probes for speci®c FISH detection of G. lamblia. The method depends on suf®cient amounts of intact rRNA in the target organism, which is unlikely to be present in nonviable cysts that have been exposed to the environment for a prolonged period. Signi®cance and Impact of the Study: Currently, detection of G. lamblia cysts is largely based on immuno¯uorescence assays (IFA) targeting cyst wall surface antigens. These assays lack speci®city and will detect species others than G. lamblia. Further, IFA will detect nonviable cysts and cyst wall fragments that do not pose a public health risk. In contrast, FISH probes allow speci®c detection and are likely to only detect viable, infectious cysts.

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Comparison of animal infectivity, excystation, and fluorogenic dye as measures of Giardia muris cyst inactivation by ozone

Cited by 44 publications

References 17 publications

Application of Monitoring Data forGiardia andCryptosporidium to Boil Water Advisories

Application of Monitoring Data forGiardia andCryptosporidium to Boil Water Advisories

Fluorescence decay of dyed protozoa: differences between stressed and non‐stressed cysts

Oligonucleotide probes for specific detection of Giardia lamblia cysts by fluorescent in situ hybridization

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