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Three sample preparation protocols for polymerase chain reaction based detection of Cryptosporidium parvum in
M Kostrzynska1, M Sankey, E Haack
1Laboratory Services Division, University of Guelph, Ontario, Canada.
Abstract:
Cryptosporidium parvum is a protozoan parasite responsible for an increasing number of outbreaks of gastrointestinal illness worldwide. In this report, we describe development of sample preparation protocols for polymerase chain reaction (PCR)-based detection of C. parvum in fecal material and environmental water samples. Two of these methods were found adequate for isolation of Cryptosporidium DNA from filtered water pellet suspensions. The first involved several filtration steps, immunomagnetic separation and freeze-thaw cycles. The second method involved filtration, addition of EnviroAmp lysis reagent, freeze-thaw cycles and precipitation of the DNA with isopropanol. Using nested PCR, we detected 100 oocysts/ml of filtered water pellet suspension, with either of the above sample preparation procedures. Nested PCR increased sensitivity of the assay by two to three orders of magnitude as compared to the primary PCR. The detection limit for seeded fecal samples was 10-fold higher than for filtered environmental water pellet suspension. Nested PCR results showed 62.4 and 91.1% correlation with immunofluorescence assay (IFA) for fecal samples and filtered environmental water pellet suspensions, respectively. This correlation decreased to 47.2% and 44.4%, respectively, when only IFA positive samples were analyzed. However, in fecal samples contaminated with a high number (> 10(5)/g) of C. parvum oocysts, this correlation was 100%.
Insights
This study developed effective sample preparation methods for detecting Cryptosporidium parvum DNA using nested PCR in water and fecal samples. Nested PCR significantly improved detection sensitivity for this important gastrointestinal pathogen.
Area of Science:
- Environmental microbiology
- Parasitology
- Molecular diagnostics
Background:
- Cryptosporidium parvum is a significant cause of global gastrointestinal illness outbreaks.
- Accurate detection methods are crucial for public health surveillance and water quality monitoring.
Purpose of the Study:
- To develop and validate sample preparation protocols for Cryptosporidium parvum detection.
- To assess the sensitivity and correlation of PCR-based methods with traditional assays.
Main Methods:
- Development of two distinct sample preparation protocols involving filtration, immunomagnetic separation, lysis reagents, and DNA precipitation.
- Application of nested PCR for enhanced sensitivity in detecting Cryptosporidium parvum DNA.
- Comparison of PCR results with immunofluorescence assay (IFA) for fecal and water samples.
Main Results:
- Two sample preparation methods effectively isolated Cryptosporidium DNA from water samples.
- Nested PCR achieved a detection limit of 100 oocysts/ml in filtered water, with sensitivity increased by 2-3 orders of magnitude.
- Correlation with IFA varied, but was high for samples with high oocyst loads (> 10(5)/g).
Conclusions:
- Optimized sample preparation protocols combined with nested PCR offer a sensitive method for Cryptosporidium parvum detection.
- This approach is valuable for monitoring environmental water and diagnosing fecal infections.
- Further validation is needed for samples with low oocyst concentrations.
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