Factors affecting recovery efficiency in isolation of Cryptosporidium oocysts and Giardia cysts from vegetables for standard method development

While recently published techniques for recovering parasites from fruits and vegetables demonstrate a marked increase in efficiency and utility, there is still scope for further improvement in developing a standard method, particularly with difficult, but important, sample matrices such as bean sprouts. Herein, a number of parameters used in published techniques are investigated more closely. While sample size reduction may improve recovery efficiency because of a range of factors, it is important to keep the sample large enough for detection of low-level contamination. Age of sample is also important, and samples should be as fresh as possible. Elution procedures may contribute to losses of Giardia and should be more thoroughly investigated. Improved immunomagnetic separation techniques currently coming onto the market also have the potential to increase recovery efficiency substantially, even with difficult samples such as aged bean sprouts. However, merely increasing magnetic strength of the capturing magnet does not affect recovery efficiency, which must be reliant on a superior bead system, buffering system, or both.