Improved recovery of Cryptosporidium and Giardia in water by optimizing immunomagnetic separation using acid and heat dissociation.

It is important to efficiently recover (oo)cysts in water during the established detection process, as Cryptosporidium and Giardia are known to cause waterborne outbreaks. We investigated the recovery of these (oo)cysts based on the pH of HCl and NaOH used during the immunomagnetic separation (IMS) step. Additionally, we evaluated the efficiency of heat dissociation as a potential alternative to acid dissociation in IMS. The results showed that recovery rates decreased as the final pH deviated from neutral. The highest recovery rates, exceeding 60%, were observed when the pH of 0.1 N HCl and 1 N NaOH fell within the range of 0.9-1.0 and 13.0-13.1, respectively. The pH had a greater impact on cysts than on oocysts. Since the absolute zeta potential of cysts is lower than that of oocysts, cysts may be less stable in water and more sensitive to pH variations. The recovery rates of (oo)cysts were comparable when either acid and heat dissociation was applied. Therefore, to enhance the recovery of (oo)cysts in environmental water, it is essential to regularly monitor the pH of the reagent used in IMS step. Furthermore, the application of heat dissociation without HCl and NaOH may be considered as an alternative method.