Development and Evaluation of Three Real-Time PCR Assays for Genotyping and Source Tracking Cryptosporidium spp. in Water.

The occurrence of Cryptosporidium oocysts in drinking source water can present a serious public health risk. To rapidly and effectively assess the source and human-infective potential of Cryptosporidium oocysts in water, sensitive detection and correct identification of oocysts to the species level (genotyping) are essential. In this study, we developed three real-time PCR genotyping assays, two targeting the small-subunit (SSU) rRNA gene (18S-LC1 and 18S-LC2 assays) and one targeting the 90-kDa heat shock protein (hsp90) gene (hsp90 assay), and evaluated the sensitivity and Cryptosporidium species detection range of these assays.

Antigenic differences within the Cryptosporidium hominis and Cryptosporidium parvum surface proteins P23 and GP900 defined by monoclonal antibody reactivity.

The biological basis for the specificity of host infectivity patterns of Cryptosporidium spp., in particular C. hominis and C.

Immunomagnetic separation (IMS)-fluorescent antibody detection and IMS-PCR detection of seeded Cryptosporidium parvum oocysts in natural waters and their limitations.

Detection and enumeration of Cryptosporidium parvum in both treated and untreated waters are important to facilitate prevention of future cryptosporidiosis incidents. Immunomagnetic separation (IMS)-fluorescent antibody (FA) detection and IMS-PCR detection efficiencies were evaluated in two natural waters seeded with nominal seed doses of 5, 10, and 15 oocysts. IMS-FA detected oocysts at concentrations at or below the three nominal oocyst seed doses, illustrating that IMS-FA is sensitive enough to detect low oocyst numbers.

Cryptosporidium parvum mixed genotypes detected by PCR-restriction fragment length polymorphism analysis.

Combinations of 10 Cryptosporidium parvum oocysts, with various ratios of genotype I to genotype II, were isolated and subjected to PCR-restriction fragment length polymorphism analysis. Amplification of both genotypes in these samples ranged from 31 to 74% and yielded no information about the genotype proportions. In addition, since both genotypes were not always detected, amplification of a single genotype is not conclusive evidence that the sample contains only a single genotype.