Abstract
The accurate determination of the presence of Giardia cysts and Cryptosporidium oocysts in surface waters requires a reliable method for the detection and enumeration of these pathogenic organisms. Published methods have usually reported recovery efficiencies of less than 50% for both cysts and oocysts. Typically, the losses are greater for Cryptosporidium oocysts than they are for Giardia cysts. The purpose of this study was to examine procedures used for sample collection, elution, concentration, and clarification to determine when losses of cysts and oocysts occurred during processing. The results showed that major losses of cysts and oocysts occurred during centrifugation and clarification. Depending on the centrifugation force, oocyst losses of as high as 30% occurred for each centrifugation step. A 1.15-specific-gravity Percoll-sucrose gradient was needed to optimize recovery of oocysts from natural water samples. Minor improvements in the procedure could be accomplished by selecting a filter other than the recommended 1-micron-pore-size (nominal-porosity) polypropylene filter.
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Selected References
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- LeChevallier M. W., Norton W. D., Lee R. G. Giardia and Cryptosporidium spp. in filtered drinking water supplies. Appl Environ Microbiol. 1991 Sep;57(9):2617–2621. doi: 10.1128/aem.57.9.2617-2621.1991. [DOI] [PMC free article] [PubMed] [Google Scholar]
- LeChevallier M. W., Norton W. D., Lee R. G. Occurrence of Giardia and Cryptosporidium spp. in surface water supplies. Appl Environ Microbiol. 1991 Sep;57(9):2610–2616. doi: 10.1128/aem.57.9.2610-2616.1991. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Musial C. E., Arrowood M. J., Sterling C. R., Gerba C. P. Detection of Cryptosporidium in water by using polypropylene cartridge filters. Appl Environ Microbiol. 1987 Apr;53(4):687–692. doi: 10.1128/aem.53.4.687-692.1987. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Vesey G., Slade J. S., Byrne M., Shepherd K., Fricker C. R. A new method for the concentration of Cryptosporidium oocysts from water. J Appl Bacteriol. 1993 Jul;75(1):82–86. doi: 10.1111/j.1365-2672.1993.tb03412.x. [DOI] [PubMed] [Google Scholar]