Alternative methods for collection and isolation of Cryptosporidium from finished water

For over a decade, despite continuous efforts, the methods for collection, isolation and detection of Cryptosporidium have remained time-consuming and inefficient. For example, two standard methods for Cryptosporidium are the United Kingdom Standing Committee of Analysts (SCA) method (Anon, 1990) and the U.S. Environmental Protection Agency (USEPA) Information Collection Rule (ICR) method (1996). Both these methods have relied on large volume filtration, elution using large quantities of a weak detergent solution, concentration with various centrifugation steps and then clarification of the target organisms by using specific density flotation, with either sucrose alone or in conjunction with Percoll. Because of the laborious nature of these methodsand their poor recovery efficiencies, the USEPA instigated the development of improved methodologies, with the objective that commercially available products could be incorporated into methods that would eventually lead to the development of reliable methods, with improved oocyst recoveries. This has resulted in the development of a method for surface waters and is based on collection of small sample volumes (10 L) through cartridge or membrane filters, elution of organisms andclarification by immunomagnetic separation followed by their detection by immunofluorescence. This USEPA method has been collectively termed Method 1622 (USEPA, 1998) and has undergone initial validation work and is currently in the round-robin testing phase. [ABSTRACT FROM AUTHOR]