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. 1992 Nov;58(11):3488–3493. doi: 10.1128/aem.58.11.3488-3493.1992

Viability of Cryptosporidium parvum oocysts: correlation of in vitro excystation with inclusion or exclusion of fluorogenic vital dyes.

A T Campbell 1, L J Robertson 1, H V Smith 1
PMCID: PMC183133  PMID: 1482174

Abstract

A viability assay for oocysts of Cryptosporidium parvum based on the inclusion or exclusion of two fluorogenic vital dyes, 4',6-diamidino-2-phenylindole (DAPI) and propidium iodide, was developed by using several different isolates of oocysts. Correlation of this assay with viability measured by in vitro excystation was highly statistically significant, with a calculated correlation coefficient of 0.997. In this research, two similar excystation protocols were utilized, and no significant difference between excystation protocols was detected. Percent excystation of oocyst suspensions could be increased or reduced by inclusion of a preincubation treatment in either excystation protocol, and this alteration was also demonstrated in the viability assay. Oocysts which excluded both dyes would not excyst in vitro unless a further trigger was provided and were more resistant to acid or alkali treatment. The results of this research provide a reproducible, user-friendly assay which is applicable to individual oocysts and also provides a useful adjunct for identification of oocysts in water and environmental samples.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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