Research

A new system for higher recovery rate of water borne Cryptosporidium and Giardia

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Abstract

The two most common water borne pathogenic protozoa, Cryptosporidium and Giardia, are a common cause of outbreaks of diarrhea. Detecting these parasites in water samples depends on effective parasite recovery from the water matrix. The recovery rates of the currently used filter methods are low and the procedures are expensive and time consuming. These facts have motivated us to develop a new robust system for higher recovery of protozoan cysts from any fluid matrix. The new system consists of a sample collection chamber in which the fluid passes through a specially coated metallic filter with a carefully chosen pore size. On the reverse side of the filter a transducer delivers ultrasound waves in order to release trapped cysts and particles from the filter and break up parasite clusters. Purified Cryptosporidium oocysts and Giardia cysts were injected into the concentration unit and exposed to varying levels of ultrasonication. The concentrated parasite suspension was backwashed using air and the change in viability of the parasites was assessed by flowcytometry. Without sonication, the recovery rate of Cryptosporidium was around 2%. After short term sonication for 5, 10 or 20 seconds, the recovery rates were stable and ranging from 75-83%. While sonication is usually used for cell lyses, it can be tuned into a useful tool for enhanced separation of retinates of parasites using a specially constructed filter unit and a sonication protocol. The filtration chamber further facilitated the concentration of parasites by ensuring a backwash volume of less than 1ml. The collected parasites may be used for molecular typing and other diagnostic and research purposes. The presented design of the filter system can be used as a robust, cheap, and time effective method of isolating water borne parasites in the laboratory.