Mitochondrial Junction Region as Genotyping Marker for Cyclospora cayetanensis

Abstract

Cyclosporiasis is an infection caused by Cyclospora cayetanensis, which is acquired by consumption of contaminated fresh food or water. In the United States, cases of cyclosporiasis are often associated with foodborne outbreaks linked to imported fresh produce or travel to disease-endemic countries. Epidemiologic investigation has been the primary method for linking outbreak cases. A molecular typing marker that can identify genetically related samples would be helpful in tracking outbreaks. We evaluated the mitochondrial junction region as a potential genotyping marker. We tested stool samples from 134 laboratory-confirmed cases in the United States by using PCR and Sanger sequencing. All but 2 samples were successfully typed and divided into 14 sequence types. Typing results were identical among samples within each epidemiologically defined case cluster for 7 of 10 clusters. These findings suggest that this marker can distinguish between distinct case clusters and might be helpful during cyclosporiasis outbreak investigations.

Keywords: Cyclospora cayetanensis; United States; cyclosporiasis; enteric infections; epidemiology; food safety; food-borne infections; genotyping; genotyping marker; mitochondrial DNA; mitochondrial junction region; parasites; water-borne infections.

Figure

Relationships between detected Cyclospora mitochondrial junction (Cmt) types, United States. Fourteen unique Cmt types were detected. Cmt214.A (top left) was not detected in this study but was reported previously (GenBank accession no. MH430089.1); it represents the type with the largest number of 15-mer repeats (total 6) and is therefore included as reference for comparison. Three different 15-mer repeat sequences are known, and each Cmt type possesses 2–6 of these 15-mer repeats in various combinations. The sequence of each mt junction type can be elucidated from this figure starting with the first repeat, indicated by the red central asterisk, and then following the arrows to the end motif. A dashed line links the sequence to a pie chart that provides epidemiologic information. The size of the pie chart represents the number of times this particular Cmt type was detected. For instance, type 154.A was detected in 50 samples (as reflected by the scale) and represents the most common type. Red underlined letters indicate variable sites that exist in the end motif and 15-mer repeats.