Abstract
Aims To develop a filtration unit for efficient recovery of waterborne Cryptosporidium oocysts and Giardia cysts ((oo-)cysts) in drinking water. Methods and Results This unit utilizes a metallic filter and an ultrasound transducer for eluting (oo-)cysts, with a fixed retentate backwash volume; approx. 400 mu l. Changes in the viability was evaluated by seeding wild type (oo-)cysts (1 10 super(4)) followed by sonication for 5, 10, 20 or 40 s (five replicates for each period). Flow cytometry analysis showed negligible increase in the mortality of (oo-)cysts exposed to 5-10 s of sonication. Recovery rate was assessed by seeding ColorSeed super((TM)) (10 replicates) into the filter unit followed by air backwash to a glass slide and counting of (oo-)cysts by epifluorescent microscopy. High recovery rates (mean plus or minus SD) were found: 84.9% plus or minus 4.8 for Giardia cysts and 70% plus or minus 6.5 for Cryptosporidium oocysts. DNA of seeded wild type (oo-)cysts (1 10 super(2); 10 replicates) was successfully amplified using real-time PCR. Conclusions The use of a metallic filter, sonication and 'air backwash' were key factors for creating a highly efficient system for recovery of apparently undamaged protozoa. Significance and Impact of the Study This reagent-less system can be used for monitoring of parasite contamination in drinking water.