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Applied and Environmental Microbiology, April 2003, p. 1898-1903, Vol. 69, No. 4
0099-2240/03/$08.00+0     DOI: 10.1128/AEM.69.4.1898-1903.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.

Effect of Particles on the Recovery of Cryptosporidium Oocysts from Source Water Samples of Various Turbidities

Yao Yu Feng, Say Leong Ong,* Jiang Yong Hu, Lian Fa Song, Xiao Lan Tan, and Wun Jern Ng

Center for Water Research, Department of Civil Engineering, National University of Singapore, Singapore 119260, Singapore

Received 19 August 2002/ Accepted 6 January 2003

Cryptosporidium parvum can be found in both source and drinking water and has been reported to cause serious waterborne outbreaks which threaten public health safety. The U.S. Environmental Protection Agency has developed method 1622 for detection of Cryptosporidium oocysts present in water. Method 1622 involves four key processing steps: filtration, immunomagnetic separation (IMS), fluorescent-antibody (FA) staining, and microscopic evaluation. The individual performance of each of these four steps was evaluated in this study. We found that the levels of recovery of C. parvum oocysts at the IMS-FA and FA staining stages were high, averaging more than 95%. In contrast, the level of recovery declined significantly, to 14.4%, when the filtration step was incorporated with tap water as a spiking medium. This observation suggested that a significant fraction of C. parvum oocysts was lost during the filtration step. When C. parvum oocysts were spiked into reclaimed water, tap water, microfiltration filtrate, and reservoir water, the highest mean level of recovery of (85.0% ± 5.2% [mean ± standard deviation]) was obtained for the relatively turbid reservoir water. Further studies indicated that it was the suspended particles present in the reservoir water that contributed to the enhanced C. parvum oocyst recovery. The levels of C. parvum oocyst recovery from spiked reservoir water with different turbidities indicated that particle size and concentration could affect oocyst recovery. Similar observations were also made when silica particles of different sizes and masses were added to seeded tap water. The optimal particle size was determined to be in the range from 5 to 40 µm, and the corresponding optimal concentration of suspended particles was 1.42 g for 10 liters of tap water.

* Corresponding author. Mailing address: Centre for Water Research, Department of Civil Engineering, National University of Singapore, 10 Kent Ridge Crescent, Singapore 119260, Singapore. Phone: (65) 68742890. Fax: (65) 68742890. E-mail: CVEONGSL{at}nus.edu.sg.

Applied and Environmental Microbiology, April 2003, p. 1898-1903, Vol. 69, No. 4
0099-2240/03/$08.00+0     DOI: 10.1128/AEM.69.4.1898-1903.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.



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  • Ochiai, Y., Takada, C., Hosaka, M. (2005). Detection and Discrimination of Cryptosporidium parvum and C. hominis in Water Samples by Immunomagnetic Separation-PCR. Appl. Environ. Microbiol. 71: 898-903 [Abstract] [Full Text]  
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