Osong Public Health and Research Perspectives

Yeon-Ho Kang

6 Articles

Occurrence of Norovirus GII.4 Sydney Variant-related Outbreaks in Korea: Sunyoung Jung, Bo-Mi Hwang, Hyun Ju Jeong, Gyung Tae Chung, Cheon-Kwon Yoo, Yeon-Ho Kang, Deog-Yong Lee; Osong Public Health Res Perspect. 2015;6(5):322-326. Published online October 31, 2015; DOI: https://doi.org/10.1016/j.phrp.2015.10.004

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Abstract PDF: Human noroviruses are major causative agents of food and waterborne outbreaks of nonbacterial acute gastroenteritis. In this study, we report the epidemiological features of three outbreak cases of norovirus in Korea, and we describe the clinical symptoms and distribution of the causative genotypes. The incidence rates of the three outbreaks were 16.24% (326/2,007), 4.1% (27/656), and 16.8% (36/214), respectively. The patients in these three outbreaks were affected by acute gastroenteritis. These schools were provided unheated food from the same manufacturing company. Two genotypes (GII.3 and GII.4) of the norovirus were detected in these cases. Among them, major causative strains of GII.4 (Hu-jeju-47-2007KR-like) were identified in patients, food handlers, and groundwater from the manufacturing company of the unheated food. In the GII.4 (Hu-jeju-47-2007KR-like) strain of the norovirus, the nucleotide sequences were identical and identified as the GII.4 Sydney variant. Our data suggests that the combined epidemiological and laboratory results were closely related, and the causative pathogen was the GII.4 Sydney variant strain from contaminated groundwater.

Epidemics of Norovirus GII.4 Variant in Outbreak Cases in Korea, 2004–2012: Sunyoung Jung, Hyun Ju Jeong, Bo-Mi Hwang, Cheon-Kwon Yoo, Gyung Tae Chung, Hyesook Jeong, Yeon-Ho Kang, Deog-Yong Lee; Osong Public Health Res Perspect. 2015;6(5):318-321. Published online October 31, 2015; DOI: https://doi.org/10.1016/j.phrp.2015.10.002

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Abstract PDF: Norovirus GII.4 is recognized as a worldwide cause of nonbacterial outbreaks. In particular, the GII.4 variant occurs every 2–3 years according to antigenic variation. The aim of our study was to identify GII.4 variants in outbreaks in Korea during 2004–2012. Partial VP1 sequence of norovirus GII.4-related outbreaks during 2004–2012 was analyzed. The partial VP1 sequence was detected with reverse transcription-polymerase chain reaction, seminested polymerase chain reaction, and nucleotide sequence of 312-314 base pairs for phylogenetic comparison. Nine variants emerged in outbreaks, with the Sydney variant showing predominance recently. This predominance may persist for at least 3 years, although new variants may appear in Korea.

Possibility of CTX-M-14 Gene Transfer from Shigella sonnei to a Commensal Escherichia coli Strain of the Gastroenteritis Microbiome: Seung-Hak Cho, Soon Young Han, Yeon-Ho Kang; Osong Public Health Res Perspect. 2014;5(3):156-160. Published online June 30, 2014; DOI: https://doi.org/10.1016/j.phrp.2014.04.007

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Abstract PDF: Objectives
To investigated whether the CTX-M-14 gene could be transferred from a clinical Shigella sonnei strain to commensal Escherichia coli strain in the gastroenteritis microbiome.
Methods
E. coli strains were isolated from 30 stool samples of S. sonnei infected students in a gastroenteritis outbreak in 2004 and were characterized by antibiotic resistance analysis, in vitro conjugation and in vivo transfer of CTX-M-14 gene and molecular assays.
Results
One strain of Escherichia coli that had high levels of resistance to cefotaxime was isolated from a patient infected with S. sonnei. Isoelectric focusing showed that the E. coli and S. sonnei strains produced a β-lactamase with an isoelectric point of 8.1. Moreover, polymerase chain reaction analysis indicated that both strains possessed the same DNA sequences for CTX-M-14. The results of in vitro and in vivo conjugation showed that the efficiency of CTX-M-14 transfer from S. sonnei to E. coli was similar to CTX-M-14 transfer between E. coli strains.
Conclusion
The data suggest that the acquisition of the extended-spectrum β-lactamases gene by pathogenic bacteria in the human intestinal tract to commensal microbiome bacteria can cause serious infectious diseases.

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.

Comparison of Antimicrobial Resistance in Escherichia coli Strains Isolated From Healthy Poultry and Swine Farm Workers Using Antibiotics in Korea: Seung-Hak Cho, Yeong-Sik Lim, Yeon-Ho Kang; Osong Public Health Res Perspect. 2012;3(3):151-155. Published online June 30, 2012; DOI: https://doi.org/10.1016/j.phrp.2012.07.002

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Abstract PDF: Objectives
The aim of this study is to compare the antibiotic resistance of Escherichia coli isolates from faecal samples of workers who often use antibiotics.
Methods
A total of 163E coli strains isolated from faecal samples of livestock workers (poultry and swine farm workers) and restaurant workers in the same regions as a control group were analyzed by agar disc diffusion to determine their susceptibility patterns to 16 antimicrobial agents.
Results
Most of the tested isolates showed high antimicrobial resistance to ampicillin and tetracycline. The isolates showed higher resistance to cephalothin than other antibiotics among the cephems. Among the aminoglycosides, the resistance to gentamicin and tobramycin occurred at higher frequencies compared with resistance to amikacin and netilmicin. Our data indicated that faecal E coli isolates of livestock workers showed higher antibiotic resistances than nonlivestock workers (restaurant workers), especially cephalothin, gentamicin, and tobramycin (p < 0.05). Moreover, the rates of the livestock workers in the association of multidrug resistance were also higher than the rates of the restaurant workers.
Conclusion
This study implies that usage of antibiotics may contribute to the prevalence of antibiotic resistance in commensal E coli strains of humans.

Prevalence of Antibiotic Resistance in Escherichia coli Fecal Isolates From Healthy Persons and Patients With Diarrhea: Seung-Hak Cho, Yeong-Sik Lim, Mi-Sun Park, Seong-Han Kim, Yeon-Ho Kang; Osong Public Health Res Perspect. 2011;2(1):41-45. Published online June 30, 2011; DOI: https://doi.org/10.1016/j.phrp.2011.05.003

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Abstract PDF: Objectives
This study aimed to investigate the prevalence of antibiotic resistance in fecal Escherichia coli isolates from healthy persons and patients with diarrhea.
Methods
E. coli isolates (n = 428) were obtained from fecal samples of apparently healthy volunteers and hospitalized patients with diarrhea. Susceptibility patterns of isolates to 16 antimicrobial agents were determined by agar disc diffusion.
Results
Most E. coli isolates exhibited less than 10% resistance against imipenem, cefotetan, aztreonam, cefepime, cefoxitin, amikacin and netilamicin, although greater than 65% were resistant to ampicillin and tetracycline. No significant difference in resistance rates for all tested antibiotics was found between isolates from the healthy-and diarrheal-patient groups, including for multi-drug resistance (p = 0.22). The highest number of resistant antibiotics was 12 antibiotics. No significant differences in antibiotic resistance were found among the sex and age strata for isolates from healthy individuals. However, antibiotic resistance rates to cefoxitin, cefotaxime, amikacin, and netilamicin were significantly higher in the isolates of men than those of women (p < 0.05) in isolates from patients with diarrhea. Furthermore, isolates from patients with diarrhea older than 40-years of age showed higher resistance to cefepime and aztreonam (p < 0.05).
Conclusion
High resistance to the antibiotics most frequently prescribed for diarrhea was found in isolates from patients with diarrhea and apparently healthy individuals without any significant difference.

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