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Orientia tsutsugamushi, an obligate intracellular organism, is the causative agent of scrub typhus. Multilocus sequence typing (MLST) is a genetic typing method that provides a unified bacterial isolate characterization approach. However, there are no comparative studies in South Korea on the genotypic properties of O. tsutsugamushi based on MLST. To conduct a comparative analysis with previous data collected from Thailand, Laos, and Japan, we investigated the genetic diversity of O. tsutsugamushi from 51 patients with scrub typhus in South Korea by using MLST. The MLST analysis revealed 10 new alleles in the housekeeping genes: gpsA, n = 2; mdh, n = 1; nrdB, n = 1; nuoF, n = 1; ppdK, n = 1; sucB, n = 2; and sucD, n = 2. These novel alleles led to the assignment of six new sequence types (STs) (ST93–98). The 51 samples corresponded to seven different STs (ST48 and ST93–98), with ST48 accounting for the largest proportion (49.0%) of O. tsutsugamushi STs in South Korea. Interestingly, O. tsutsugamushi from patients with scrub typhus in South Korea were clustered in two different clades, and the five Korean STs (ST48, ST93, ST94, ST95, and ST98) were close genetically to ST80, which was isolated from Laos. The remaining two STs (ST96 and ST97) were close genetically to ST49 (Ikeda, Japan). Overall, our results suggest that the relative genetic stability and the clonal populations of O. tsutsugamushi strains in South Korea have remained mostly conserved.
These authors contributed equally to this work.
Financial support: This work is funded by the Basic Science Research Programs (NRF-2018R1D1A3B07049557 and 2019R1A6A1A11052070) of the National Research Foundation of Korea, which are funded by the Ministry of Education and the Fund of Biomedical Research Institute, Jeonbuk National University Hospital.
Disclaimer: Study funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Authors’ addresses: Joo-Hee Hwang and Chang-Seop Lee, Department of Internal Medicine, Jeonbuk National University Medical School, Jeonju, Republic of Korea, and Research Institute of Clinical Medicine of Jeonbuk National University–Biomedical Research Institute of Jeonbuk National University Hospital, Jeonju, Republic of Korea, E-mails: firstname.lastname@example.org and email@example.com. Jeongsik Kim, Faculty of Science Education, Jeju National University, Jeju, Republic of Korea, and Interdisciplinary Graduate Program in Advanced Convergence Technology & Science, Jeju National University, Jeju, Republic of Korea, E-mail: firstname.lastname@example.org. In O. Sun, Department of Internal Medicine, Presbyterian Medical Center, Jeonju, Republic of Korea, E-mail: email@example.com. Tae Hee Lee, Department of Microbiology and Immunology, Jeonbuk National University Medical School, Jeonju, Republic of Korea, and Institute for Medical Science, Jeonbuk National University Medical School, Jeonju, Republic of Korea, E-mail: firstname.lastname@example.org. Kyung Min Chung, Research Institute of Clinical Medicine of Jeonbuk National University–Biomedical Research Institute of Jeonbuk National University Hospital, Jeonju, Republic of Korea, Department of Microbiology and Immunology, Jeonbuk National University Medical School, Jeonju, Republic of Korea, and Institute for Medical Science, Jeonbuk National University Medical School, Jeonju, Republic of Korea, E-mail: email@example.com.