Molecular detection and genotype analysis of Kudoa septempunctata from food poisoning outbreaks in Korea

Abstract

Concerns about foodborne illnesses caused by <i>Kudoa septempunctata</i> are steadily growing, but reports of <i>K. septempunctata</i> in clinical and food specimens related to food poisoning in Korea are limited. This study aimed to genetically identify <i>K. septempunctata</i> in patients with acute diarrhea and in clinical and food samples related to food poisoning caused by sashimi consumption. Both real-time and nested polymerase chain reaction assays were performed to detect <i>K. septempunctata</i> 18S and 28S rDNA genes in the stools of 348 patients with acute diarrhea, 11 samples (6 stool and 5 rectal swab samples) from patients with food poisoning, and 2 raw <i>Paralichthys olivaceus</i> samples collected from a restaurant where a food poisoning incident occurred. <i>K. septempunctata</i> was identified in 5 clinical specimens (4 stools and 1 rectal swab) and 1 <i>P. olivaceus</i> sashimi sample. All detected <i>K. septempunctata</i> were of genotype ST3. This is the first study to identify <i>K. septempunctata</i> in both patients and food samples with epidemiological relevance in Korea, providing evidence that it is a pathogen that causes food poisoning. Also, this is the first study to confirm the presence of <i>K. septempunctata</i> genes in rectal swabs. Despite continuing suspected occurrences of <i>Kudoa</i> foodborne outbreaks, the rate of identification of <i>K. septempunctata</i> is very low. One reason for this is the limitation in obtaining stool and vomit samples for the diagnosis of <i>Kudoa</i> infection. We strongly suggest the inclusion of rectal swabs among the diagnostic specimens for <i>Kudoa</i> food poisoning.