A Two-Phase Separation Method for Recovery of Cryptosporidium Oocysts from Soil Samples
2009
Zilberman, Alla | Zimmels, Yoram | Starosvetsky, Jeanna | Zuckerman, Udi | Armon, Robert
Cryptosporidium parvum oocysts may reach soil through direct deposition of human or animal fecal material, irrigation with raw wastewater or untreated effluents, and contaminated runoff. Examination of soil samples for oocyst presence is of primary importance in order to prevent secondary contamination of crops and groundwater. Several methods were proposed for oocyst recovery from soil samples; however, their efficiency was very low. In the present study, four known methods used to recover oocysts from water and fecal samples (sedimentation, sedimentation with reduced water content, sucrose floatation, water-ether separation) were compared to a method used in the past to recover bacterial spores from bottom sediments (two-phase separation). The two-phase separation technique proved to be the best method of choice resulting in a recovery average of 61.2 ± 15.6%. According to this method, the lowest and highest recoveries were 37% to 95%, respectively. Two other important outcomes were observed with the soil experimental set-up: (1) recovery efficiency is influenced by oocyst viability (high viability was directly correlated with increased recovery efficiency) and (2) high sand content of soil samples reduced oocyst recovery by its detrimental effect on oocyst viability.
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