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Comparison of Filtration Methods for Primary Recovery of Cryptosporiidum Parvum from Water

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Abstract:Waterborne disease outbreaks from contaminated drinking water have been linked to the protozoan parasite, Cryptosporidium parvum. To improve monitoring for this agent, the USEPA developed Method 1622 for isolation and detection of Cryptosporidium oocysts in water. Method 1622 is performance-based and involves filtration, concentration, immunomagnetic separation (IMS), antibody (FA) and counter dAPI) staining, and microscopic evaluation. Currently, a capsule filter system (1 micrometer nominal pore size, pleated, polethersulphone concentration of water samples by USEPA Method 1622 analysis of water samples.

Four filtration systems were compared for primary concentration of C. parvum oocysts seeded into untreated environmental water samples: the capsule filter, a 1 micrometer absolute pore size, 293 mm diameter, track-etched, polycarbonate membrane filter disk, and two inexpensive, self-contained, disposable hollow fibers. Samples were subsequently processed by IMS, fluorescent antibody and DAPI stained, and microscopically evaluated, as outlined by Method 1622. Additionally, analyst proficiency in our laboratory was validated by performing precision and recovery experiments and method blanks with the capsule and membrane disk filters as directed in Method 1622. Cryptosporidium parvum oocyst recoveries from seeded 10-liter volumes of reagent water in the precision and recovery experiments were 31% (S.D. =10%) and 36% (S.D. = 11%) using the membrane disk and capsule filters, respectively.

Replicate 10-liter field samples of raw waters, unspiked and laboratory spiked, were tested to evaluate the matrix effects from the environmental waters and to compare the recoveries achieved with the different primary concentration methods. Two analysts (O.D.S. III and C.D.H.) microscopically examined in the samples to ensure validity of the counts; oocysts identified in the unspiked field samples were confirmed by DAPI stain and Differential Interference Contrast microscopy. Oocyst recoveries from the environmental samples averaged 26% (S.D. = 25% ) and 16% (S.D. = 6%) with the membrane disk and capsule filters, respectively, and 66% (S.D. = 5%) and 62% (S.D. = 6%) with the two hollow fiber ultrafilters, respectively. These results demonstrate the C. parvum oocysts can be recovered from environmental waters using the filters approved for use with Method 1622 but recoveries are lower and more variable than from reagent grade water. The disposable, hollow fiber ultrafilters recovered C. parvum oocysts more reliably and efficiently than two of the filters now recommended for Method 1622.
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Citation:Simmons, O. D., J. J. Juliano, C. D. Heaney, D. S. Francy, F. W. Schaefer III, and M. D. Sobsey. Comparison of Filtration Methods for Primary Recovery of Cryptosporiidum Parvum from Water. Presented at International Symposium on Waterborne Pathogens, Milwaukee, WI, August 29-September 1, 1999.
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Contact: Mary P. O'Bryant - (919)-541-4871 or obriant.mary@epa.gov
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Division: Microbiological & Chemical Exposure Assessment Division
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Branch: Biohazard Assessment Research Branch
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Product Type: Abstrct/Oral
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Presented: 08/30/1999
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Related Entries:
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Bullet Item Detecting Ccl-Related, Emerging and Regulated Waterborne Human Protozoa for Exposure Assessment
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Last Updated on Monday, October 22, 2007
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