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Concentrating Toxoplasma gondii and Cyclospora cayetanensis from Surface Water and Drinking Water by Continuous Separation Channel Centrifugation
Citation:
Borchardt, M., S. Spencer, P. D. Bertz, M. W. WARE, J. P. Dubey, AND H. LINDQUIST. Concentrating Toxoplasma gondii and Cyclospora cayetanensis from Surface Water and Drinking Water by Continuous Separation Channel Centrifugation. JOURNAL OF APPLIED MICROBIOLOGY. Blackwell Publishing, Malden, MA, 107(4):1089-1097, (2009).
Impact/Purpose:
The overall objective of this task is the development of improved occurrence detection methods for protozoan parasites and Microsporidia. Since this work is a primary focus of the Branch, this task supports several individual projects related to sample preparation and protozoan detection. Together these projects will lead to complete methods able to support the UCMR and the CCL2 and CCL3.
Description:
Aims: To evaluate the effectiveness of continuous separation channel centrifugation for concentrating Toxoplasma gondii and Cyclospora cayetanensis from drinking water and environmental waters. Methods and Results: Ready-to-seed vials with known quantities of Toxoplasma gondii and Cyclospora cayetanensis oocysts were prepared by flow cytometry. Oocysts were seeded at densities ranging from 1 to 1000 oocysts l-1 into 10 to 100 l test volumes of finished drinking water, water with manipulated turbidity, and the source waters from nine drinking water utilities. Oocysts were recovered using continuous separation channel centrifugation and counted on membrane filters using epifluorescent microscopy. Recovery efficiencies of both parasites were ≥84% in 10 l volumes of drinking water. In source waters, recoveries ranged from 64-100%, with the lowest recoveries in the most turbid waters. Method precision was usually between 10% and 20% coefficient of variation. Conclusion: Toxoplasma gondii and Cyclospora cayetanensis are effectively concentrated from various water matrices by continuous separation channel centrifugation. Significance and Impact of the Study: Waterborne transmission of Toxoplasma gondii and Cyclospora cayetanensis has been documented, presenting another challenge in producing clean drinking water and protecting public health. Detection of these parasites relies on effectively concentrating oocysts from an ambient water sample, otherwise false negatives may result. While several concentration methods are available, validation data specific to Toxoplasma gondii and Cyclospora cayetanensis recoveries are limited. Using continuous separation channel centrifugation, oocysts are recovered with high efficiency and precision, the method attributes required for accurately assessing the risk of waterborne transmission.