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United States Department of Agriculture

Agricultural Research Service

Research Project: ZOONOTIC PARASITES AFFECTING FOOD SAFETY AND PUBLIC HEALTH

Location: Environmental Microbial and Food Safety Laboratory

Title: Are adequate methods available to detect protist parasites on fresh produce?

Authors
item Macarisin, Dumitru
item Santin-Duran, Monica
item Bauchan, Gary
item Fayer, Ronald

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: February 14, 2012
Publication Date: N/A

Technical Abstract: Human parasitic protists such as Cryptosporidium, Giardia and microsporidia contaminate a variety of fresh produce worldwide. Existing detection methods lack sensitivity and specificity for most foodborne parasites. Furthermore, detection has been problematic because these parasites adhere tenaciously to plant surfaces and cannot be enriched in culture medium like bacteria to produce large numbers that facilitate detection. Cryptosporidium parvum oocysts and microsporidia spores were seeded onto spinach leaves. Using laser scanning confocal microscopy it was shown that both parasites strongly adhered to plant surfaces and resisted vigorous washing. Low temperature electron microscopy analysis of the seeded leaves revealed attachment of large numbers of parasites and frequent cases of infiltration of oocysts into natural openings of the leaf. Additional attempts to remove C. parvum oocysts from leaves with tetrasodium pyrophosphate detergent (Alconox), which was recently reported to be superior in Cryptosporidium recovery from fresh produce, were conducted. Alconox wash (P=0.05) improved the percentage of oocyst recovery from 53.7 ± 7.2% in water to 73.6 ± 3.2% in 0.1% Alconox solution. However, after all washing treatments, samples were still positive for C. parvum DNA, suggesting that in spite of the improved recovery some oocysts were not removed from the contaminated leaves. Because some oocysts remained adherent on all contaminated samples the new Alconox elution technique must be further enhanced before it can be recommended as a standard method for removal of protozoan parasites from fresh produce.

Last Modified: 8/1/2014