A comparison of four fluorescent antibody-based methods for purifying, detecting, and confirming Cryptosporidium parvum in surface waters

Cryptosporidiosis has been traced to drinking contaminated surface water, w hich was either not treated or was ineffectively treated. Testing to detect Cryptosporidium parvum in surface water has been suggested to help prevent future outbreaks. In the present study, the same sample collection and fil tration methods were used to compared sample processing and detection steps from 4 testing methods: a modified information collection rule (ICR) metho d and method 1623 (both developed by the U.S. Environmental Protection Agen cy), a flow cytometric method, and a solid-phase cytometric method. All of these methods use fluorescent antibody staining, which is only a presumptiv e indication of the presence of this parasite. Confirmation requires anothe r assay. Methods were evaluated for both presumptive and confirmed detectio n. Solid-phase cytometry had the highest presumptive and confirmed detectio n rates. Flow cytometry had the next highest presumptive detection rate in reagent water but was third in spiked surface and tap waters, with no confi rmation procedure. The ICR method had the third highest presumptive detecti on rate in reagent water and the second highest in spiked surface and tap w aters but failed to confirm any oocysts. Method 1623 had significantly lowe r presumptive detection than any other method and a significantly lower con firmation rate than the solid-phase cytometry method.