, Kim, , Byun, , Oh, , Liu, , Bae, , and Won: Epidemiology and Subtype Distribution of Blastocystis Among Asymptomatic Volunteers in South Korea: A Multicenter Study

Seong Hoon Kim1,2*Jung-Hyun Byun3*YeJin Oh4Changseung Liu5Mi Hyun Bae6Eun Jeong Won1,2,7*

1Department of Parasitology and Tropical Medicine, Chonnam National University Medical School, Hwasun, Korea
2Department of Biomedical Sciences, Graduate School of Chonnam National University, Hwasun, Korea
3Department of Laboratory Medicine, Gyeongsang National University Hospital, Gyeongsang National University College of Medicine, Jinju, Korea
4Department of Laboratory Medicine, Green Cross Laboratories (GC Labs), Yongin, Korea
5Department of Laboratory Medicine, Gangneung Asan Hospital, University of Ulsan College of Medicine, Gangneung, Korea
6Department of Laboratory Medicine, Hanyang University Guri Hospital, Hanyang University College of Medicine, Guri, Korea
7Department of Laboratory Medicine, Asan Medical Center, Seoul, Korea

*Corresponding author: E-mail: dana_clinic@naver.com


Background: Blastocystis is a genus of intestinal, anaerobic protozoan parasites that can be isolated from humans, animals, and the environment. We aimed to determine the distribution of Blastocystis and subtypes (STs) using stool samples obtained from healthy volunteers at collection centers in South Korea.

Methods: A total of 478 stool samples from volunteers were collected at five collection centers throughout South Korea. The presence of Blastocystis was determined using PCR based on the small subunit (SSU) rRNA gene, and Blastocystis STs were confirmed through sequencing of the SSU rRNA gene.

Results: Molecular analysis revealed the presence of Blastocystis in 27 (5.6%) of the enrolled participants. Two STs were identified: ST3 (66.7%) and ST1 (33.3%). The positive rates of Blastocystis varied by geographical region, ranging from 1.2%–12.0%. ST3 was the predominant subtype in all centers except one, where only ST1 was isolated. Phylogenic analysis showed clustering based on ST, but no significant differences were found among the regions. There was no association between Blastocystis colonization and either age or sex of the participants.

Conclusions: The results of this multicenter study demonstrated colonization by Blastocystis, mainly ST3, in the gastrointestinal tracts of asymptomatic individuals in South Korea.


Figures & Tables

Table 1. Distribution of Blastocystis subtypes among the healthy volunteers enrolled in this study

Collection center (Region)

Tested number

No. (%) of positive specimens




A (Jeollanam-do)


9 (9.0)

4 (44.4)

5 (55.6)

B (Gyeongsangnam-do)


12 (12.0)

2 (16.7)

10 (83.3)

C (Chungcheong-do & Seoul)


2 (2.0)

0 (0.0)

2 (100.0)

D (Seoul & Gyeonggi-do)


1 (1.2)

0 (0.0)

1 (100.0)

E (Gangwon-do)


3 (3.0)

3 (100.0)

0 (0.0)



27 (5.6)

9 (33.3)

18 (66.7)

Abbreviation: ST, subtype.