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United States Department of Agriculture

Agricultural Research Service


item Graczyk, Thaddeus - JOHNS HOPKINS UNIV
item Fayer, Ronald
item Cranfield, Michael - THE BALTIMORE ZOO
item Owens, Rebecca - THE BALTIMORE ZOO

Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 9, 1996
Publication Date: N/A

Interpretive Summary: Cryptosporidium parvum has recently been recognized as the most important contaminant of drinking water in the United States. The oocyst stage of the parasite is the infectious form transmitted in the environment. The ability to determine if oocysts recovered from water are infectious or dead is an important public health and veterinary medical issue. Of 3 methods used to recover waterborne oocysts a membrane filter dissolved by acetone proved to be the best for recovery; but it was not determined if oocysts recovered by this method were live or dead. The present study showed that both live and dead oocysts were retained by the method permitted further testing for viability and infectivity.

Technical Abstract: Cryptosporidium parvum oocysts infectious to neonatal BALB/c mice were processed by the cellulose acetate membrane (CAM) filter dissolution method to determine if the procedure, that utilizes acetone incubation and alcohol centrifugations, alters their viability (determined by in vitro excystation) or infectivity (determined by infectivity bioassay). In addition, most oocysts with viability altered by desiccation, heat inactivation, and snap freezing that were processed by the CAM filter dissolution method were non-refractile, unstained oocyst ghosts. The remaining organisms were lightly stained with the acid-fast stain and resembled oocyst shells. Infectious oocysts retained their infectivity and nonviable oocysts (oocyst shells) retained their morphology when processed by the CAM dissolution method. Infectious oocysts, oocyst shells, and oocyst ghosts produced positive reactions of similar intensity in direct immunofluorescence antibody staining, utilizing the MERIFLUOR tm test. In summary cryptosporidium oocysts recovered from drinking water by the CAM dissolution method can be subjected to testing for their viability and infectivity.

Last Modified: 9/3/2015
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