Osong Public Health and Research Perspectives

Nan-Ok Kim

4 Articles

Genome Sequencing Analysis of Atypical Shigella flexneri Isolated in Korea: Nan-Ok Kim, Hae-young Na, Su-Mi Jung, Gyung Tae Chung, Hyo Sun Kawk, Sahyun Hong; Osong Public Health Res Perspect. 2017;8(1):78-85. Published online February 28, 2017; DOI: https://doi.org/10.24171/j.phrp.2017.8.1.11

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Abstract PDF Supplementary Material: Objectives
An atypical Shigella flexneri strain with a plural agglutination pattern [i.e., reacting not only with serum samples containing type antigen II but also with serum samples containing group antigens (3)4 and 7(8)] was selected for genome sequencing, with the aim of obtaining additional comparative information about such strains.
Methods
The genomic DNA of atypical S. flexneri strain NCCP 15744 was sequenced using an Ion Torrent PGM sequencing machine (Life Technologies, USA). The raw sequence data were preprocessed and reference-assembled in the CLC Assembly Cell software (version 4.0.6; CLC bio, USA).
Results
Ion Torrent sequencing produced 1,450,025 single reads with an average length of 144 bp, totaling ~209 Mbp. The NCCP 15744 genome is composed of one chromosome and four plasmids and contains a gtrX gene. Among the published genome sequences of S. flexneri strains, including 2457T, Sf301, and 2002017, strain NCCP 15744 showed high similarity with strain 2002017. The differences between NCCP 15744 and 2002017 are as follows: i) NCCP 15744 carries four plasmids whereas 2002017 carries five; ii) 19 genes (including CI, CII, and cro) were lost in the SHI-O genomic island of NCCP 15744 and six genes were gained as compared with strain 2002017.
Conclusion
Strain NCCP 15744 is genetically similar to 2002017, but these two strains have different multilocus sequence types and serotypes. The exact reason is unclear, but the 19 lost genes may be responsible for the atypical seroconversion of strain NCCP 15744.

Surveillance of Bacillus cereus Isolates in Korea from 2012 to 2014: Su-Mi Jung, Nan-Ok Kim, Injun Cha, Hae-young Na, Gyung Tae Chung, Hyo Sun Kawk, Sahyun Hong; Osong Public Health Res Perspect. 2017;8(1):71-77. Published online February 28, 2017; DOI: https://doi.org/10.24171/j.phrp.2017.8.1.10

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Abstract PDF: Objectives
To investigate the prevalence and toxin production characteristics of non-emetic and emetic Bacillus cereus strains isolated via the laboratory surveillance system in Korea.
Methods
A total of 667 B. cereus strains were collected by the Korea National Research Institute of Health laboratory surveillance system from 2012 to 2014. The collected strains were analyzed by geographical region, season, patient age, and patient sex. Additionally, the prevalence rates of enterotoxin and emetic toxin genes were evaluated.
Results
The isolation rate of B. cereus strains increased during the summer, but the isolation rate was evenly distributed among patient age groups. Emetic toxin was produced by 20.2% of the isolated strains. The prevalence rates of five enterotoxin genes (entFM, nheA, cytK2, hblC, and bceT) were 85.0, 78.6, 44.5, 36.6, and 29.7%, respectively, among non-emetic strains and 77.8, 59.3, 17.8, 11.9 and 12.6%, respectively, among emetic strains. Thus, the prevalence rates of all five enterotoxin genes were lower in emetic B. cereus.
Conclusion
The prevalence of enterotoxin genes differed between non-emetic and emetic B. cereus strains. Among emetic B. cereus strains, the prevalence rates of two enterotoxin genes (cytK2 and hblC) were lower than those among the non-emetic strains. In both the emetic and non-emetic strains isolated in Korea, nheA and entFM were the most prevalent enterotoxin genes.

Enteric Bacteria Isolated from Diarrheal Patients in Korea in 2014: Nan-Ok Kim, Su-Mi Jung, Hae-Young Na, Gyung Tae Chung, Cheon-Kwon Yoo, Won Keun Seong, Sahyun Hong; Osong Public Health Res Perspect. 2015;6(4):233-240. Published online August 31, 2015; DOI: https://doi.org/10.1016/j.phrp.2015.07.005

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Abstract PDF Supplementary Material: Objectives
The aim of this study was to characterize the pathogens responsible for causing diarrhea according to season, region of isolation, patient age, and sex as well as to provide useful data for the prevention of diarrheal disease.
Methods
Stool specimens from 14,886 patients with diarrhea were collected to identify pathogenic bacteria from January 2014 to December 2014 in Korea. A total of 3,526 pathogenic bacteria were isolated and analyzed according to season, region of isolation, and the age and sex of the patient.
Results
The breakdown of the isolated pathogenic bacteria were as follows: Salmonella spp. 476 (13.5%), pathogenic Escherichia coli 777 (22.0%), Vibrio parahaemolyticus 26 (0.74%), Shigella spp. 13 (0.37%), Campylobacter spp. 215 (6.10%), Clostridium perfringens 508 (14.4%), Staphylococcus aureus 1,144 (32.4%), Bacillus cereus 356 (10.1%), Listeria monocytogenes 1 (0.03%), and Yersinia enterocolitica 10 (0.3%). The isolation rate trend showed the highest ratio in the summer season from June to September for most of the pathogenic bacteria except the Gram-positive bacteria. The isolation rate of most of the pathogenic bacteria by patient age showed highest ratio in the 0–19 year age range. For isolation rate by region, 56.2% were isolated from cities and 43.8% were isolated from provinces.
Conclusion
Hygiene education should be addressed for diarrheal disease-susceptible groups, such as those younger than 10 years, aged 10–19 years, and older than 70 years, and monitoring for the pathogens is still required. In addition, an efficient laboratory surveillance system for infection control should be continued.

Enhanced Type III Secretion System Expression of Atypical Shigella flexneri II:(3)4,7(8): Sahyun Hong, Injun Cha, Nan-Ok Kim, Seong-Han Kim, Kyung-Tae Jung, Je-Hee Lee, Dong-Wook Kim, Mi-Sun Park, Yeon-Ho Kang; Osong Public Health Res Perspect. 2012;3(4):222-228. Published online December 31, 2012; DOI: https://doi.org/10.1016/j.phrp.2012.10.002

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Abstract PDF: Objectives
We aimed at evaluating the virulence of atypical Shigella flexneri II:(3)4,7(8) by DNA microarray and invasion assay.
Methods
We used a customized S. flexneri DNA microarray to analyze an atypical S. flexneri II:(3)4,7(8) gene expression profile and compared it with that of the S. flexneri 2b strain.
Results
Approximately one-quarter of the atypical S. flexneri II:(3)4,7(8) strain genes showed significantly altered expression profiles; 344 genes were more than two-fold upregulated, and 442 genes were more than 0.5-fold downregulated. The upregulated genes were divided into the category of 21 clusters of orthologous groups (COGs), and the “not in COGs” category included 170 genes. This category had virulence plasmid genes, including the ipa-mxi-spa genes required for invasion of colorectal epithelium (type III secretion system). Quantitative reverse-transcription polymerase chain reaction results also showed the same pattern in two more atypical S. flexneri II:(3)4,7(8) strains. Atypical S. flexneri II:(3)4,7(8) showed four times increased invasion activity in Caco-2 cells than that of typical strains.
Conclusion
Our results provide the intracellularly regulated genes that may be important for adaptation and growth strategies of this atypical S. flexneri.

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