Multicenter Study on the Molecular Epidemiology of Intestinal Protozoan Parasites in Korea

Abstract

Background: Intestinal protozoa are potential diarrhea-causing pathogens and monitored worldwide. The Korea Centers for Disease Control and Prevention has also been monitoring intestinal protozoa causing diarrhea for many years. Recently, the overall protozoa detection rate has decreased to less than 1%, but whether protozoa infection causing diarrhea has declined or is being underestimated has not been studied. This study aimed to investigate the molecular epidemiology of intestinal protozoan pathogens in stool samples collected from multiple Korean centers. Methods: Stool samples were collected from five university hospitals and a commercial laboratory. Direct smear and trichrome staining were performed on all samples. The presence of Cryptosporidium parvum, Giardia lamblia, Entamoeba histolytica, Cyclospora cayetanensis, Dientamoeba fragilis, and Blastocystis hominis were detected using Allplex™ Gastrointestinal Parasite Assays (Seegene Inc., Korea). Microsporidia species and Kudoa septempunctata were detected using PowerChek™ Microsporidia Multiplex and Kudoa Real-time PCR kits (Kogene Biotech, Korea), respectively. Results: The collected samples included 279 diarrheal and 51 non-diarrheal samples. Among the 279 diarrheal samples, nine samples [B. hominis (n=7), C. parvum (n=1), and Microporidia species (n=1)] were positive, but there were no positive samples for K. septempunctata. We could not detect any protozoa by direct smear and trichrome staining. Among the 51 nondiarrheal samples, 10 (19.6%) samples were positive for B. hominis, but no other protozoa were observed. Conclusion: This multicenter study showed that the detection rate of intestinal protozoa is currently low in diarrheal samples from Korea. However, B. hominis was frequently detected in non-diarrheal samples, indicating their low pathogenicity.