Purpose: This study evaluated the validated method to detect C. cayetanensis in commodities, other than cilantro and raspberries, and compared the results.
Methods: A total of 25 grams shredded carrots and cilantro and 50 grams raspberries were seeded with 5, 10, 20, and/or 200 C. cayetanensis oocysts from Nepal. Unseeded produce were used as negative controls. The method included washing of the produce, extraction of C. cayetanensis DNA, and molecular detection using a TaqMan assay targeting the 18S rRNA gene.
Results: Detection rates in shredded carrots were 26.7% of 15 samples seeded with 10 oocysts and 56.2% of 16 samples seeded with 20 oocysts. All carrot samples seeded with 200 oocysts (n=11) were positive and all unseeded carrot samples (n=11) were negative. Comparatively, C. cayetanensis oocysts detection rates for cilantro and raspberries seeded with 5 and 10 oocysts were 31.3% and 80.0%, and 50.0% and 90.0%, respectively, in a multilaboratory validation study.
Significance: The method was slightly less sensitive for detection of C. cayetanensis in shredded carrot samples when compared to the results observed in cilantro and raspberries. This study highlights the importance of evaluating the performance of the C. cayetanensis detection method in different food matrices as the U.S. FDA advances with the implementation of such tools for regulatory purposes.