Evaluation of the U.S. Food and Drug Administration validated method for detection of Cyclospora cayetanensis in high-risk fresh produce matrices and a method modification for a prepared dish

Abstract

The performance of the U.S. Food and Drug Administration (FDA) validated method for regulatory detection of Cyclospora cayetanensis in leafy greens and berries was evaluated in additional high-risk fresh produce items and in a dish prepared with these produce commodities. The method was robust and reproducible in basil, parsley, shredded carrots, shredded cabbage and carrot mix, and could detect as few as 5 oocysts in 25 g samples. Some differences in C. cayetanensis detection were found among the fresh produce analyzed. Significantly lower target gene copy numbers per reaction were obtained with shredded carrots, and shredded cabbage and carrot mix compared to leafy greens, which highlights the importance of evaluating the performance characteristics of validated methods in different food matrices. In the prepared dish, coleslaw with dressing, the method was optimized to detect 5 oocysts in a 25 g sample by using 1.0% Alconox^® in the washing solution instead of 0.1% as originally described. These data are important to assess the prevalence of C. cayetanensis in different produce items and to support outbreak investigations.

Keywords: Cyclospora cayetanensis; Fresh produce; Outbreaks; Prepared dish; Surveillance; qPCR.