Quantitative polymerase chain (QPCR) reaction using the MIMIC approach to estimate Cryptosporidium parvum oocysts, an intestinal pathogen, in municipal water treatment sludge samples

An accurate estimation of the number of Cryptosporidium parvum oocysts in w ater treatment plant sludge was determined using the Quantitative Polymeras e Chain Reaction (QPCR) method. Approximately 8 x 10(6) purified viable ooc ysts were spiked into raw water and treated by conventional water treatment methods. The settled sludge was collected and the DNA extracted. The QPCR Mimic produced two competing products that were 300 and 435 base pairs in s ize. The log ratio of the products were used in the standard curve to deter mine a final estimation of oocysts in the sludge sample. The final number o f oocysts in the sludge sample was estimated at 258 oocyst per two litres o f treated water. This is the first lime sludge from a water treatment proce ss has been tested for presence of C. parvum oocysts, which is a known cont aminant of drinking water. The QPCR method can be used to test other sludge samples and help estimate the sanitary risks associated with using sludge to fertilize agricultural lands. (C) 2000 Academic Press.