• International Journal of Oral Biology
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• v.35 no.1
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• pp.7-12
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• 2010

The aims of this study were to investigate the nosocomial infection route of methicillin-resistant Staphylococcus aureus (MRSA) and explore preventative methods for this pathogen that involve blocking its dispersion. We cultured MRSA from nasal cavity swabs collected between June and July 2008 that we obtained from eight dental healthcare providers, 32 nurses and the sputum specimens of two patients from our hospital. In addition, we used VITEK 2 equipment to measure drug sensitivity, and we further performed biochemical testing and pulse-field gel electrophoresis (PFGE) to isolate MRSA colonies. The incidence of these bacteria on the nasal swabs was 25.0% from dental clinic healthcare providers, 13.6% from the internal medicine ward nurses and 30.0% from intensive care unit nurses. Moreover, MRSA was detectable in sputum specimens of ward patients. The antimicrobial agents resistance and partial PFGE types of MRSA showed a similar pattern. We suggest from these analyses that nasal cavity infection by MRSA could occur by cross contamination between healthcare providers and patients which underscores the importance of stringent MRSA management practices.

• Archives of Pharmacal Research
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• v.27 no.2
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• pp.246-253
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• 2004

The prevalence, genotype for antibiotic resistance and antibiotic susceptibility of vancomycin resistant enterococci (VRE) were determined. And molecular typings of the Enterococcus faecium isolates were analyzed. Prevalence of VRE in chickens, healthy children and intensive care unit (ICU) patients was 41.6％,7.9％, and 20.4％, respectively. Forty out of 54 isolates from chicken intestines, and 9 out of 11 from ICU patients were identified as Enterococcus faecium. Eleven out of 13 isolates from non-hospitalized young children were E. gallinarium. Twelve strains of E. faecalis were isolated from chicken intestines. The gene for the antibiotic resistance in E. faecium, and E. faecalis was vanA, while that in E. gallinarium was vanC1. E. faecium isolates were resistant to most of antibiotics except ampicillin and gentamicin. Molecular typing of the E. faecium strains obtained by pulse field gel electrophoresis and repetitive sequence-based PCR suggest that VRE transmit horizontally from poultry to humans, especially young children, via the food chains in Korea.

• International Journal of Oral Biology
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• v.35 no.4
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• pp.185-190
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• 2010

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most prevalent pathogens in hospitals. To investigate cross contamination by this bacterium in both dental and medical settings, the pathogens that cause acute pyogenic infection and one of the major microbes responsible for nosocomial infection were isolated from health care providers, nurses and patients. We used VITEK II to measure drug sensitivity, and we further performed biochemical testing, coagulase serotype testing and pulse-field gel electrophoresis (PFGE) for isolated MRSA colonies. The isolation rate of Staphylococcus aureus from nasal swabs was 75.0% from dental health care providers and 18.8% from the medical health care providers. A total of 10 MRSA strains were isolated from 40 health care providers and 2 patients and the prevalent coagulase serotype from patients and health care providers was VII. The antimicrobial drug resistance and partial PFGE types of the isolated MRSA strains showed a similar pattern. These results suggest that MRSA may be one of the principal causes of nosocomial infection in dental and medical hospitals.

• Journal of Microbiology
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• v.43 no.2
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• pp.172-178
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• 2005

To determine the prevalence and genotypes of $\beta$-lactamases among clones of a metagenomic library from the cold-seep sediments of Edison seamount (10,000 years old), we performed pulse-field gel electrophoresis, antibiotic susceptibility testing, pI determination, and DNA sequencing analysis. Among the 8,823 clones of the library, thirty clones produced $\beta$-lactamases and had high levels of genetic diversity. Consistent with minimum inhibitory concentration patterns, we found that five ($167\%$) of thirty clones produced an extended-spectrum $\beta$-lactamase. 837- and 259-bp fragments specific to bla$_{TEM}$ genes were amplified, as determined by banding patterns of PCR amplification with designed primers. TEM­1 was the most prevalent $\beta$-lactamase and conferred resistance to ampicillin, piperacillin, and cephalothin. TEM-116 had a spectrum that was extended to ceftazidime, cefotaxime, and aztreonam. The resistance levels conferred by the pre-antibiotic era alleles of TEM-type $\beta$-lactamases were essentially the same as the resistance levels conferred by the TEM-type alleles which had been isolated from clinically resistant strains of bacteria of the antibiotic era. Our first report on TEM-type $\beta$-lactamases of the pre-antibiotic era indicates that TEM-type $\beta$-lactamases paint a picture in which most of the diversity of the enzymes may not be the result of recent evolution, but that of ancient evolution.

• Proceedings of the Botanical Society of Korea Conference
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• 1999.07a
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• pp.11-15
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• 1999

In order to evlauate feasibility of the gene tagging by the maize transposable element Ac in heterologous plant systems, we have investigated physical distances and directions of transposition of the element in Arabidopsis thaliana and tobacco cultured cell line BY-2. We prepared a T-DNA construct that carried a non-autonomous derivative of Ac with a site for cleavage by endonuclease I-Scel (designated dAc-I-RS element). Another cleavage site was also introduced into the T-DNA region outside dAc-I-RS. A number of transgenic Arabidopsis plants were generated, each of which had a single copy of the T-DNA at a different chromosomal location. To examine the pattern of transposition, three out of these transgenic plants were crossed with the Arabidopsis plant that carried the gene for Ac transposase and progeny in which dAc-I-RS had been transposed were isolated. After digestion of the genomic DNA of these progeny with I-SceI, sizes of segment of DNA were determined byd pulse-field gel electrophoresis. We also performed linkage analysis for the transposed elements and sites of mutations near the elements. Our results with three transgenic lines showed that 50% of all transposition events had occurred within 1,700 kilo-base pairs (kb) on the same chromosome, with 35% within 200 kb, and that the elements transposed in both directions on the chromosome with roughly equal probability. The data thus indicate that the Ac-Ds system is most useful for tagging of genes that are present within 200 kb of the chromosomal site of Ac in Arabidopsis. In addition, determination of the precise localization of the transposed dAc-I-RS element should definitely assist in map-based cloning of genes around insertion sites. In the present paper, we report typical examples of such gene isolation studies.

• Proceedings of the Botanical Society of Korea Conference
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• 1985.08b
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• pp.51-57
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• 1985

In order to evlauate feasibility of the gene tagging by the maize transposable element Ac in heterologous plant systems, we have investigated physical distances and directions of transposition of the element in Arabidopsis thaliana and tobacco cultured cell line BY-2. We prepared a T-DNA construct that carried a non-autonomous derivative of Ac with a site for cleavage by endonuclease I-Scel (designated dAc-I-RS element). Another cleavage site was also introduced into the T-DNA region outside dAc-I-RS. A number of transgenic Arabidopsis plants were generated, each of which had a single copy of the T-DNA at a different chromosomal location. To examine the pattern of transposition, three out of these transgenic plants were crossed with the Arabidopsis plant that carried the gene for Ac transposase and progeny in which dAc-I-RS had been transposed were isolated. After digestion of the genomic DNA of these progeny with I-SceI, sizes of segment of DNA were determined byd pulse-field gel electrophoresis. We also performed linkage analysis for the transposed elements and sites of mutations near the elements. Our results with three transgenic lines showed that 50% of all transposition events had occurred within 1, 700 kilo-base pairs (kb) on the same chromosome, with 35% within 200 kb, and that the elements transposed in both directions on the chromosome with roughly equal probability. The data thus indicate that the Ac-Ds system is most useful for tagging of genes that are present within 200 kb of the chromosomal site of Ac in Arabidopsis. In addition, determination of the precise localization of the transposed dAc-I-RS element should definitely assist in map-based cloning of genes around insertion sites. In the present paper, we report typical examples of such gene isolation studies.

• Journal of Life Science
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• v.13 no.4
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• pp.522-528
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• 2003

The RAD4 gene of Saccharomyces cerevisiae is essential for the incision step of UV-induced excision repair. A yeast RAD4 gene has been previously isolated by functional complementation. In order to identify the RAD4 homologous gene from fungus Coprinus cinereus, we have constructed cosmid libraries from electrophoretically separated chromosomes of the C. cinereus. The 13 C. cinereus chromosomes were resolved by pulse-field gel electrophoresis, hybridized with S. cerevisiae RAD4 DNA, and then isolated homologous C. cinereus chromosome. The insert DNA of the RAD4 homolog was contained 3.2 kb. Here, we report the characterization of fungus C. cinereus homolog of yeast RAD4 gene. Southern blot analysis confirmed that C. cinereus contains the RAD4 homolog gene and this gene exists as a single copy in C. cinereus genome. When total RNA isolated from C. cinereus cells was hybridized with the 1.2 kb PvuII DNA fragment of the S. cerevisiae RAD4 gene, a 2.5 kb of transcript was detected. In order to investigation whether the increase of transcripts by DNA damaging agent, transcripts levels were examined after treating the cells. The level of transcript did not increase by untraviolet light (UV). This result indicated that the RAD4 homologous gene is not UV inducible gene. Gene deletion experiments indicate that the RAD4 homologous gene is essential for cell viability.

• Journal of Microbiology and Biotechnology
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• v.30 no.12
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• pp.1862-1869
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• 2020

The spread of plasmid-mediated colistin resistance has posed a serious threat to public health owing to its effects on the emergence of pandrug-resistant bacteria. In this study, we investigated the prevalence and characteristics of mcr-1-positive Escherichia coli isolated from retail meat samples in Korea. In total, 1,205 E. coli strains were isolated from 3,234 retail meat samples in Korea. All E. coli strains were subjected to antimicrobial susceptibility testing and were examined for the presence of mcr-1 gene. All mcr-1-positive E. coli (n = 10, 0.8%) from retail meat were subjected to pulse-field gel electrophoresis (PFGE) and whole-genome sequencing (WGS). The transferability of mcr-1 gene was determined by conjugation assays. The mcr-1-positive strains exhibited diverse clonal types. Our mcr-1 genes were located in plasmids belonged to the IncI2 (n = 1) and IncX4 (n = 8) types, which were reported to be prevalent in Asia and worldwide, respectively. Most mcr-1 genes from mcr-1-positive strains (9/10) were transferable to the recipient strain and the transfer frequencies ranged from 2.4 × 10-3 to 9.8 × 10-6. Our data suggest that the specific types of plasmid may play an important role in spreading plasmid-mediated colistin resistance in Korea. Furthermore, our findings suggest that the retail meat may be an important tool for disseminating plasmid-mediated colistin resistance.

• Journal of Life Science
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• v.14 no.6 s.67
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• pp.1023-1027
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• 2004

The RAD3 gene of Saccharomyces cerevisiae is essential for the incision step of UV-induced excision repair. An yeast RAD3 gene has been previously isolated by functional complementation. In order to identify the RAD3 homologous gene from fungus Coprinus cinereus, we have constructed cosmid libraries from electrophoretically separated chromosomes of the C. cinereus. The 13 C. cinereus chromosomes were resolved by pulse-field gel electrophoresis, hybridized with S. cerevisiae RAD3 DNA, and then isolated RAD3 homologous DNA from C. cinereus chromosome. The RAD3 homolog DNA was contained in 3.2 kb DNA fragment. Here, we report the results of characterization of a fungus C. cinereus homolog to the yeast RAD3 gene. Southern blot analysis confirmed that the C. cinereus chromosome contains the RAD3 homolog gene and this gene exists as a single copy in C. cinereus genome. When total RNA isolated from the C. cinereus cells were hybridized with the 3.4 kb PvuII DNA fragment of the S. cerevisiae RAD3 gene, transcripts size of 2.8 kb were detected. In order to investigate whether the increase of the amount of transcripts by DNA damaging agent, transcript levels were examined after treating agents to the cells. The level of transcripts were not increased by untraviolet light (UV). This result indicated that the RAD3 homologous gene is not UV inducible gene. Gene deletion experiments indicate that the HRD3 gene is essential for viability of the cells and DNA repair function. These observations suggest an evolutionary conservation of other protein components with which HRD3 interacts in mediating its DNA repair and viability functions.

• Journal of Microbiology and Biotechnology
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• v.15 no.4
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• pp.844-854
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• 2005

We constructed a defined physical and genetic map of H. pylori strain 51, previously isolated from a Korean patient with a duodenal ulcer, by combining a restriction analysis by pulse-field gel electrophoresis with the construction of a BAC library. A Notl-digest of H. pylori strain 51 genome yielded seven fragments, from which the genomic size was estimated to be 1,698$\pm$24 kb. The BAC library was constructed from 50 to 200 kb fragments of HindIII-digested genomic DNA. From 700 BAC clones, an ordered overlapping maxi-set of 82 BAC clones was assembled that covered the entire genome. The positions of 15 genes were localized in the strain 51 genome with 4-22 kb of resolution and were compared with their orthologues in strain 26695 and strain J99. The arrangement of the 15 genes was identical in strain 51 and strain J99, except for flaA and hpaA. The plasticity zone of strain 51, like that of strain J99, was located in the single region, and was shorter than those of strain 26695 and strain J99. The strain 51 plasticity zone consisted of ORFs common only to strain 51 and J99 or to strain 51 and 26695, as well as strain 51-specific ORFs. Three genetic translocations and/or inversions were found between orthologue ORFs in strain 51 and strain J99. These results show that the chromosomal organization of strain 51 differs from Western strains such as strain 26695 and strain J99.