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Hyuk Chu 6 Articles
Annual Fluctuation in Chigger Mite Populations and Orientia Tsutsugamushi Infections in Scrub Typhus Endemic Regions of South Korea
Seong Yoon Kim, Byoungchul Gill, Bong Gu Song, Hyuk Chu, Won Il Park, Hee Il Lee, E-hyun Shin, Shin-Hyeong Cho, Jong Yul Roh
Osong Public Health Res Perspect. 2019;10(6):351-358.   Published online December 31, 2019
DOI: https://doi.org/10.24171/j.phrp.2019.10.6.05
  • 3,124 View
  • 191 Download
  • 2 Citations
AbstractAbstract PDF
Objectives

Chigger mites are vectors for scrub typhus. This study evaluated the annual fluctuations in chigger mite populations and Orientia tsutsugamushi infections in South Korea.

Methods

During 2006 and 2007, chigger mites were collected monthly from wild rodents in 4 scrub typhus endemic regions of South Korea. The chigger mites were classified based on morphological characteristics, and analyzed using nested PCR for the detection of Orientia tsutsugamushi.

Results

During the surveillance period, the overall trapping rate for wild rodents was 10.8%. In total, 17,457 chigger mites (representing 5 genera and 15 species) were collected, and the average chigger index (representing the number of chigger mites per rodent), was 31.7. The monthly chigger index was consistently high (> 30) in Spring (March to April) and Autumn (October to November). The mite species included Leptotrombidium pallidum (43.5%), L. orientale (18.9%), L. scutellare (18.1%), L. palpale (10.6%), and L. zetum (3.6%). L. scutellare and L. palpale populations, were relatively higher in Autumn. Monthly O. tsutsugamushi infection rates in wild rodents (average: 4.8%) and chigger mites (average: 0.7%) peaked in Spring and Autumn.

Conclusion

The findings demonstrated a bimodal pattern of the incidence of O. tsutsugamushi infections. Higher infection rates were observed in both wild rodents and chigger mites, in Spring and Autumn. However, this did not reflect the unimodal incidence of scrub typhus in Autumn. Further studies are needed to identify factors, such as human behavior and harvesting in Autumn that may explain this discordance.

Lon Mutant of Brucella abortus Induces Tumor Necrosis Factor-Alpha in Murine J774.A1 Macrophage
Sungdo Park, Young-Sill Choi, Sang-Hee Park, Young-Rok Kim, Hyuk Chu, Kyu-Jam Hwang, Mi-Yeoun Park
Osong Public Health Res Perspect. 2013;4(6):301-307.   Published online December 31, 2013
DOI: https://doi.org/10.1016/j.phrp.2013.10.002
  • 1,533 View
  • 19 Download
  • 5 Citations
AbstractAbstract PDF
Objectives
The objective of this study was to isolate a Brucella lon mutant and to analyze the cytokine response of B. lon mutant during macrophage infection.
Methods
A wild-type Brucella abortus strain was mutagenized by Tn5 transposition. From the mouse macrophage J774.A1 cells, total RNA was isolated at 0 hours, 6 hours, 12 hours, and 24 hours after infection with Brucella. Using mouse cytokine microarrays, we measured transcriptional levels of the cytokine response, and validated our results with a reverse transcriptase-polymerase chain reaction (RT-PCR) assay to confirm the induction of cytokine messenger RNA (mRNA).
Results
In host J774.A1 macrophages, mRNA levels of T helper 1 (Th1)-type cytokines, including tumor necrosis factor-alpha (TNF-α), interferon-gamma (IFN-γ), interleukin-2 (IL-2), and IL-3, were significantly higher in the lon mutant compared to wild-type Brucella and the negative control. TNF-α levels in cell culture media were induced as high as 2 μg/mL after infection with the lon mutant, a greater than sixfold change.
Conclusion
In order to understand the role of the lon protein in virulence, we identified and characterized a novel B. lon mutant. We compared the immune response it generates to the wild-type Brucella response in a mouse macrophage cell line. We demonstrated that the B. lon mutants induce TNF-α expression from the host J774.A1 macrophage.
Evaluation and Selection of Multilocus Variable-Number Tandem-Repeat Analysis Primers for Genotyping Brucella abortus Biovar 1 Isolated from Human Patients
Subok Lee, Kyu-Jam Hwang, Mi-Yeoun Park, Seon-Do Hwang, Hee-Youl Chai, Hyuk Chu, Sang-Hee Park
Osong Public Health Res Perspect. 2013;4(5):265-270.   Published online October 31, 2013
DOI: https://doi.org/10.1016/j.phrp.2013.09.005
  • 1,442 View
  • 15 Download
  • 1 Citations
AbstractAbstract PDF
Objectives
Brucellosis is the most common bacterial zoonosis in the world. Multilocus variable-number tandem-repeat (VNTR) analysis (MLVA) is a molecular method for genotyping bacterial species. Brucella abortus biovar I was isolated from most of the brucellosis-suspected patients in Korea. This study was conducted to investigate the ability of various MLVA primers that are used for molecular typing B. abortus isolates and for analyzing their epidemiological data.
Methods
A total of 80 human isolates of B. abortus biovar I isolated from human patients and the reference strain were used for MLVA. Genetic diversity was determined by calculating the Simpson's diversity index (DI) of each VNTR locus. The Brucella strains were subcultured 30 times to determine the stability of each locus. The DNA of the strains cultivated in each passage was extracted and subjected to MLVA for further investigation.
Results
The 15 VNTR loci were selected based on high DI values. The DIs of the 15 VNTR loci showed considerable discrimination power ranging from 59% for Bruce 43 to 87% for Bruce 22. Bruce 09, Bruce 11, Bruce 16, Bruce 42, and Bruce 43 were confirmed to remain stable in vitro among the 15 VNTR loci selected.
Conclusion
The results of this study suggest that the five loci subsets may be a useful epidemiological tool for investigating B. abortus biovar 1 outbreak.
Epidemiological Characteristics of Serologically Confirmed Q Fever Cases in South Korea, 2006–2011
Wooseok Kwak, Hyuk Chu, Seondo Hwang, Ji-Hyuk Park, Kyu Jam Hwang, Jin Gwack, Young-Sil Choi, Seung-Ki Youn, Mi-Yeoun Park
Osong Public Health Res Perspect. 2013;4(1):34-38.   Published online February 28, 2013
DOI: https://doi.org/10.1016/j.phrp.2012.12.006
  • 1,762 View
  • 15 Download
  • 21 Citations
AbstractAbstract PDF
Objectives
Q fever has been reported worldwide; however, there was almost no official report of Q fever in Korea. In this study, we describe the current status of human Q fever occurrence in Korea.
Methods
Demographic data of Q fever patients were collected from the National Notifiable Diseases Surveillance System from 2006 to 2011. Case investigation reports from regional public health departments were used for additional information, like risk factors and clinical manifestation, of the patients since 2008.
Results
There were 65 serologically confirmed cases during the study period. The annual notification rate of Q fever was 0.22 cases per million persons. The majority of cases were men (87.7%), adults (98.5%), and urban inhabitants (67.7%). Relevant exposures to risk factors were identified in 45.7% of patients. The most common symptoms of acute Q fever were fever (89.3%), myalgia (67.9%) and asthenia (53.6%). Two cases with endocarditis were identified in chronic Q fever.
Conclusion
This study suggests that Q fever has a low endemicity in Korea. However, management and research at national level is required for prevention of a future epidemic.
Application of the Microagglutination Test for Serologic Diagnosis of Human Brucellosis
Sang-Hee Park, Yoo-Hoon Lee, Hyuk Chu, Seon-Do Hwang, Kyu-Jam Hwang, Hee-Yeol Choi, Mi-Yeoun Park
Osong Public Health Res Perspect. 2012;3(1):19-23.   Published online December 31, 2011
DOI: https://doi.org/10.1016/j.phrp.2012.01.003
  • 1,483 View
  • 14 Download
  • 13 Citations
AbstractAbstract PDF
Objectives
Brucellosis is one of the most common zoonoses in the world, and occurs mainly in farmers, slaughterhouse workers, and veterinarians via direct or indirect contact with infected animals or their products. The clinical symptoms of human brucellosis are nonspecific, such as fever, headache, chills, and sweating. Diagnosis and treatment of brucellosis requires laboratory tests. Although the serum tube agglutination test (SAT) is the standardized gold method, it is laborious, time consuming, and requires a number of reagents. A microagglutination test (MAT) variant of the SAT or enzyme-linked immunosorbent assay (ELISA) is recommended for serological diagnoses. For the simple and rapid diagnosis of brucellosis, the MAT was standardized using samples for the SAT to define positive and negative categories, and we then compared the sensitivity and specificity of the MAT and ELISA.
Methods
Thirty SAT-positive sera and 60 SAT-negative sera were used in this study. Antibody titers of ≥1:160 were considered positive readings in both the SAT and MAT. Brucella abortus antigens and Brucella-positive control antiserum were used in the SAT and MAT. ELISAs of IgM and IgG were performed according to the manufacturers’ instructions.
Results
The titers of the MAT differed according to antigen concentration. The optimal concentration of B abortus antigen was determined to compare the sensitivity and specificity between the MAT and SAT. The sensitivity and specificity of the MAT were 93.3% and 96.7%, respectively, for IgG with reference to ELISA, and 96.7% and 98.3%, respectively, for IgM.
Conclusions
The optimal concentration of antigen for the MAT was 1:10. The MAT is less time consuming and requires less antigen and serum than the SAT. The results of the MAT showed good agreement with those of ELISA. The results of this study suggest that the MAT could be useful for diagnosis of brucellosis.
Serological Detection of Lyme Borreliosis Agents in Patients From Korea, 2005–2009
Sang-Hee Park, Kyu-Jam Hwang, Hyuk Chu, Mi-Yeoun Park
Osong Public Health Res Perspect. 2011;2(1):29-33.   Published online June 30, 2011
DOI: https://doi.org/10.1016/j.phrp.2011.04.004
  • 1,382 View
  • 13 Download
  • 13 Citations
AbstractAbstract PDF
Objectives
Laboratory tests are now being used to identify seropositive cases in patients suspected of having a Lyme borreliosis (LB) infection. From 2005 to 2009, we analyzed the serological and epidemiological characteristics of 53 LB positive cases in Korea using immunoblot assay.
Methods
During the five-year study period, a total of 1897 serum samples from suspected LB cases were referred to us for further laboratory diagnosis. The bacterial strains Borrelia afzeli pKo, Borrelia garinii 935T and Borrelia burgdorferi B31 were used for indirect immunofluorescent antibody assay. Immunoblot assay was performed using the recomBlot Borrelia.
Results
Based on the information from the clinicians, the main symptoms of LB infection were rash and fever (66.0%), neurological symptoms (30.2%), and arthritis (5.7%). Of the 53 cases, 16 (30.2%) were infected abroad and the remaining 37 cases (69.8%) were suspected to have been infected in Korea. Immunoblot assays detected high levels of the antigens p41 (FlaB) of B. burgdorferi and OspC of B. garinii in infected samples.
Conclusions
The causative bacteria of LB were not isolated from humans yet but from vector ticks and rodents in Korea, and a few cases were reported with serological diagnosis. Our results suggest that LB is present in all areas of Korea and indicate that B. garinii and B. burgdorferi may be the predominant bacteria in patients with LB. However, further studies are needed to isolate and identify the causative bacteria for LB in patients.

PHRP : Osong Public Health and Research Perspectives