• Journal of Plant Biotechnology
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• v.43 no.3
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• pp.317-331
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• 2016

Development of disease resistant plant is one of the important objectives in rice breeding programs because biotic stresses can adversely affect rice growth and yield losses. This study was conducted to identify lines with multiple-resistance genes to biotic stress among 173 hybrid rice breeding lines and germplasms using DNA-based markers. Our results showed that one hybrid rice line [IR98161-2-1-1-k1-3 (IR86409-3-1-1-1-1-1/IRBB66)] possessed 5 bacterial blight resistance genes (Xa4, xa5, Xa7, Xa13 and Xa21) while two hybrid rice lines [IR98161-2-1-1-k1-2 (IR86409-3-1-1-1-1-1/IRBB66) and 7292s (IR75589-31-27-8-33S(S1)/IR102758B)] possessed 3 bacterial blight resistance genes (Xa4, Xa7 and Xa21, and Xa3, Xa4 and xa5). Molecular survey on rice blast disease revealed that most of these lines had two different resistant genes. Only 11 lines possessed Pib, Pi-5, and Pi-ta. In addition, we further surveyed the distribution of insect resistant genes, such as Bph1, Bph18(t), and Wbph. Three hybrid breeding lines [IR98161-2-1-1-k1-3 (IR86409-3-1-1-1-1-1/IRBB66), IR98161-2-1-1-k1-2 (IR86409-3-1-1-1-1-1/IRBB66), and 7292s (IR75589-31-27-8-33S(S1) /IR102758B)] contained all three resistance genes. Finally, we obtained four hybrid rice breeding lines and germplasms [IR98161-2-1-1-k1-2 (IR86409-3-1-1-1-1-1/IRBB66), Damm-Noeub Khmau, 7290s, and 7292s (IR75589-31-27-8-33S(S1)/IR102758B)] possessing six-gene combination. They are expected to provide higher level of multiple resistance to biotic stress. This study is important for genotyping hybrid rice with resistance to diverse diseases and pests. Results obtained in this study suggest that identification of pyramided resistance genes is very important for screening hybrid rice breeding lines and germplasms accurately for disease and pest resistance. We will expand their cultivation safely through bioassays against diseases, pests, and disaster in its main export countries.

• Journal of Life Science
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• v.29 no.1
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• pp.84-89
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• 2019

Previous screening of novel antibacterial agents revealed that some bacterial isolates exhibited antibiotic activity against both gram-positive and gram-negative bacteria and that they showed antibacterial activity, even against methicillin-resistant Staphylococcus aureus (MRSA). Among these isolates, one bacterial strain, BCNU 1204, was identified as Pseudomonas aeruginosa using phenetic and phylogenetic analysis, based on 16S ribosomal RNA gene sequences. The maximum productivities of antimicrobial substances of BCNU 1204 were obtained after being cultured at $35^{\circ}C$ and pH 7.0 for 4 d in King's medium B (KMB). Dichloromethane (DCM) and ethylacetate (EA) extracts of P. aeruginosa BCNU 1204 exhibited strong antimicrobial activity, particularly against gram-positive bacteria. The EA extracts exhibited broad-spectrum activity against antibiotic resistant strains. Fraction 5-2, was obtained by recycling preparative liquid chromatography (LC) and preparative thin-layer chromatography (TLC) and was identified as phenazine-1-carboxylic acid belonging to phenazines using gas chromatography and mass spectrometry (GC/MS). Its minimum inhibitory concentration (MIC) values were $25{\mu}g/ml$, $50{\mu}g/ml$, ${\geq}25{\mu}g/ml$, and ${\geq}50{\mu}g/ml$ for MRSA CCARM 3089, 3090, 3091, and 3095 strains, respectively. P. aeruginosa BCNU 1204 may be a potential resource for the development of anti-MRSA antibiotics. Additional research is required to identify the active substance from P. aeruginosa BCNU 1204.

• Microbiology and Biotechnology Letters
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• v.41 no.1
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• pp.96-104
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• 2013

Staphylococcus aureus is a major human pathogen that produces a wide array of toxins, leading to a number of adverse symptoms. We examined 275 strains of Staphylococcus aureus isolated from various foods between 2006 and 2008 for antimicrobial susceptibility. At least 259 (94.2%) of the tested strains showed antibiotic resistant properties, and 106 (40.7%) of them showed multiple antibiotic resistance. Eleven of the tested strains were resistant to oxacillin and mec A-positive. Moreover, oxacillin-resistant strains were significantly more likely to be multi-drug resistant (p < 0.01). Of the 275 isolates tested, 24.4% were noted as being positive for slime production and 30.5% were positive for biofilm assay. Antibiotic resistance was not associated with a significantly higher prevalence of biofilm formation. Twenty strains were classified using the DiversiLab system. Most of the strains could be classified into 2 clusters and 4 unique types. All 10 mec A-positive strains (cluster I) were grouped together into the same sub-cluster. Cluster II (6 strains) was not found to be resistant to oxacillin in this study. Although the prevalence of methicillin-resistant S. aureus in food is currently low, the risk of its transmission through the food chain cannot be disregarded.

• Food Science and Preservation
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• v.23 no.1
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• pp.139-143
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• 2016

This study investigated the effect of electron beam (EB) treatment on the microbial reduction of dried laver (Porphyra tenera) and identified EB-resistant bacteria from the treated dried laver. After EB treatments of 4 kGy and 7 kGy, the numbers of total bacteria and EB-resistant bacteria were measured using tryptic soy agar and mannitol salt agar, respectively. The morphological and biochemical characteristics of each isolated EB-resistant bacteria were investigated and these bacteria were identified. Compared to the control ($1.5{\pm}0.2){\times}10^6CFU/g$, the total bacterial number was significantly decreased to ($5.4{\pm}0.5){\times}10^4CFU/g$ and ($1.1{\pm}0.6){\times}10^4CFU/g$ after EB treatments of 4 kGy and 7 kGy, respectively. With a higher EB dosage, the number of red colonies was almost same, whereas the number of yellow colonies was significantly decreased to ($3.3{\pm}1.2){\times}10^3CFU/g$ and 0 CFU/g for 4 kGy and 7 kGy, respectively. All red and yellow colonies were gram-positive cocci, catalase-positive, and resistant to 3% and 5% NaCl media. From the 16S rDNA sequence analysis, yellow and red colonies were identified as either Micrococcus flavus or M. luteus, with 99% similarity for the yellow colonies, and Deinococcus proteolyticus and D. piscis, with 99% and 97% similarity for the red colonies, respectively.

• Journal of Applied Biological Chemistry
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• v.59 no.4
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• pp.351-356
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• 2016

Bacterial blotch caused by Pseudomonas tolaasii is one of the major diseases of oyster mushroom, Pleurotus ostreatus. Application of bacteriophages is a very useful tool to decrease the density of pathogens and it has been successful to making disease-free cultivation area, known as phage therapy. Effect of phages on pathogen sterilization is very limited to the specific host strains. Minor variations of the host strains may cause changes in phage sensitivity. The phage-resistant strains of P. tolaasii were isolated and their pathogenic characters were investigated to improve the effectiveness of phage therapy. In the phylogenetic analysis, both phage-resistant strains and the corresponding host strains were identical based on the sequence comparison of 16S rRNA genes. The pathogenic characters, such as hemolytic activity and brown blotch formation, were measured on the phage-resistant strains and no correlation between phage-resistance and pathogenic characters was observed. Nevertheless, pathogenic characters were sometimes changed in the phage-resistant strains depending on the host strains. In order to make the phage therapy successful, the bacteriophages having a wide host range should be isolated.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.48 no.3
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• pp.139-141
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• 2003

Disease severity, percent ripened grains, and yield were investigated in the seven mixtures by using near-isogenic lines having different resistant gene(s) to bacterial blight(BB) of rice. The seven mixtures including the four pure stands were inoculated with a 1:1:1 mixture of races $K_1$, $K_2$, and $K_3$ of BB. Among the seven mixtures-ML01, ML02, ML03, MLl2, MLl3, ML23 and ML0123-, disease severiety, percent ripened grains, and yield of ML01 and ML12, respectively did not show significant difference with those of mean values of their components. But degree of disease severity of the other mixtures, respectively -ML02, ML03, MLl3, ML23, and ML0123-was less than the mean of their components. Percent ripened grains and yield of them were higher than those of mean of their components. ML03, MLl3, ML23 and ML0123 comprised of the equal amount of two or four components having different resistant gene, these mixtures appeared to be a desirable combination for delaying spread of the pathogen, stabilizing of the race structure of the pathogen population, and extending durability of a cultivar with monogenic resistance.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.12
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• pp.503-511
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• 2017

This study was conducted to evaluate the anti-inflammatory activity and clinical efficacy of a sample (A.C.C. extracts) obtained by distillation extraction of 14 herbal medicines including Phellodendron bark. To confirm this, the amount of nitric oxide (NO) produced by the cells in RAW 264.7 cells stimulated by lipopolysaccharide (LPS) and the changes in the production of inflammatory cytokines such as tumor necrosis factor (TNF)-${\alpha}$, interleukin(IL)-$1{\beta}$ and IL-6 were determined. The results showed that A.C.C. extracts strongly inhibited the production of NO and inflammatory cytokines increased by LPS without cytotoxicity. In addition, A.C.C. extracts showed strong bacterial reduction rates of 99.9% in Pseudomonas aeruginosa, Staphylococcus aureus, MRSA (Methicillin-resistant Staphylococcus aureus), Candida albicans and Streptococcus mutans. These findings indicate that A.C.C. extracts are effective ingredients with a strong antimicrobial effect together with an anti-inflammatory effect. In addition, when A.C.C. extracts were applied to infants and toddlers who were suffering from diaper rash, itching, and perspiration symptoms, symptoms of rash, atopy, rash, itching, and heat rash were improved. After the lapse of time, it was visually confirmed that it was considerably relaxed. These findings confirm that A.C.C. extracts comprise a clinically effective anti-inflammatory and anti-bacterial agent that alleviates symptoms such as diaper rash and fever and may therefore be an effective alternative to inflammatory diseases.

• Journal of Microbiology
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• v.44 no.4
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• pp.423-431
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• 2006

Among 53 Acinetobacter baumannii isolates collected in 2004, nine imipenem-resistant isolates were obtained from clinical specimens taken from patients hospitalized in Busan, Korea. Nine carbapenemase-producing isolates were further investigated in order to determine the mechanisms underlying resistance. These isolates were then analyzed via antibiotic susceptibility testing, microbiological tests of carbapenemase activity, pI determination, transconjugation test, enterobacterial repetitive consensus (ERIC)-PCR, and DNA sequencing. One outbreak involved seven cases of infection by A. baumannii producing OXA-23 ${\beta}-lactamase$, and was found to have been caused by a single ERIC-PCR clone. During the study period, the other outbreak involved two cases of infection by A. baumannii producing IMP-1 ${\beta}-lactamase$. The two clones, one from each of the outbreaks, were characterized via a modified cloverleaf synergy test and an EDTA-disk synergy test. The isoelectric focusing of the crude bacterial extracts detected nitrocefin-positive bands with pI values of 6.65 (OXA-23) and 9.0 (IMP-1). The PCR amplification and characterization of the amplicons via direct sequencing showed that the clonal isolates harbored $bla_{IMP-1}$ or $bla_{oxA-23}$ determinants. The two clones were characterized by a multidrug resistance phenotype that remained unaltered throughout the outbreak. This resistance encompassed penicillins, extended-spectrum cephalosporins, carbapenems, monobactams, and aminoglycosides. These results appear to show that the imipenem resistance observed among nine Korean A. baumannii isolates could be attributed to the spread of an IMP-lor OXA-23-producing clone. Our microbiological test of carbapenemase activity is a simple method for the screening of clinical isolates producing class D carbapenemase and/or class B $metallo-{\beta}-lactamase$, in order both to determine their clinical impact and to prevent further spread.

• Research in Plant Disease
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• v.28 no.3
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• pp.143-151
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• 2022

In order to investigate the cause of wilting symptoms in red pepper field of Korea, the frequency of occurrence of red peppers showing wilting symptoms was investigated in pepper cultivation fields in Goesan, Chungcheongbuk-do for 5 years from 2010 to 2014. There was a difference in the frequency of wilting symptoms depending on the year of investigation, but the frequency of occurrence increased as the investigation period passed from June and July to August. During this period, Ralstonia solanacearum causing the bacterial wilt was isolated at a rate four times higher than Phytophthora capsica causing the Phytophthora late blight. In wilted peppers collected in Goesan of Chungbuk and Andong of Gyeongbuk in 2013 and 2014, R. solanacearum and P. capsici were isolated from 20.3% and 3.8% of the total fields, respectively. In the year with a high rate of wilting symptoms, the average temperature was high, and the disease occurrence date of the bacterial wilt, estimated with disease forecasting model, was also fast. The inconsistency between the number of days at risk of Phytophthora late blight and the frequency of occurrence of wither symptoms is thought to be due to the generalization of the use of cultivars resistant to the Phytophthora late blight in the pepper field. In our study, the wilting symptoms were caused by the bacterial wilt caused by R. solanacearum rather than the Phytophthora late blight caused by P. capsica, which is possibly caused by increasing cultivation of pepper varieties resistant to the Phytophthora late blight in the field.

• The Journal of the Korean Society for Microbiology
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• v.15 no.1
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• pp.19-32
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• 1980

Besides the benefits of antimicrobial agents in the control of various infectious diseases, widespread and prolonged use of particular antimicrobial agents has brought about the increase of drug-resistant strains in a community and the profound changes in the pattern of infectious diseases. In Korea, there are some remote villages where no clinics and drug stores are available and the residents in those areas are assumed to have fewer chances to contact with antimicrobial agents. In the present study, the differences in susceptibilities to 14 antimicrobial agents between the isolates from rural areas(R) and Seoul National University Hospital(SNUH, H) were studied. The isolates and their numbers were Staphylococcus aureus, R;55, H;68), Enterococci(R;28, H;30), Escherichia coli(R;40, H;40), Enterobacter aerogenes(R;25, H;21) and Klebsiella pneunoniae(R;58, H;67). Minimal inhibitory concentrations(MIC's) of penicillin, ampicillin, carbenicillin, cephalexin, tetracycline, oxytetracyline, doxycycline, minocycline, gentamicin, kanamycin, streptomycin, erythromycin, troleandomycin and co-trimoxazole were determined by agar dilution method. I. Comparison of MIC's and resistant strain proportions between isolates from SNUH and rural areas. MIC's and/or resistant strain proportions of the isolates from SNUH were significantly higher than those of the isolates from rural areas in the cases of 1. S. aureus to doxycycline, streptomycin and kanamycin. 2. E. coli to penicillin, ampicillin, carbenicillin, tetracycline, oxytetracycline, doxycycline, minocycline, streptomycin, kanamycin, erythromycin and co-trimoxazole. 3. E. aerogences to carbenicillin, tetracycline, oxytetracycline, doxycycline, minocycline, streptomycin, kanamycin, genaamicin and co-trimoxazole. 4. K pneunoniae to penicillin, ampicillin, tetracycline, oxytetracycline, doxycycline, monocycline, streptomycin, kanamycine, gentamicin and co-trimoxazole. However, the mean MIC and resistant strain proportion of S. aureus to tetracycline were higher in isolates from rural areas than in those from SNUH and Enterococci showed no differences in susceptibilities to the antimicrobial agents between isolates from rural areas and from SNUH. Therefore, in general, differenes in susceptibility to these antimicrobial agents between the isolates from rural areas and SNUH were remarkably greater and broader in gram negative enteric bacteria. II. Multiple drug resistance pattern. Patterns and incidences of multiple drug resistance were studied with penicillin, ampicillin, tetracycline, cephalexin, gentamicin, streptomcin, kanamycin and co-trimoxazole in Enterococci, E. coli, E. aeroges and K. pneumoniae. There appeared significant differences in the incidence of multiply drug-resistant strains and multiple drug resistance patterns between the isolates from SNUH and rural areas in Enterococci, E. coli, E. aerogenes and K. pneumoniae. However, there was no difference in the incidence of multiply drug-resistant strains between isolates of S. aureus from SNUH and rural areas but the pattern of multiple resistance of the SNUH strains of S. aureus was diverse, while that of the rural strains was predominantly confined to penicillin-tetracycline combination. The incidence of multigly drug-resistant strains and diversity of their patterns were the highest in E. coli strains isolated from SNUH and there were no multiply drug resistant strrains in Enterococci and K. pneumoniae strains isolated from rural areas. The number of drug-resistance determinants was also different between the isolates from rural areas and SNUH. Most of the multiply drug-resistant strains of E. coli, E. aerogenes and K. pneumoniae isolated from SNUH were resistant to more than 3 kinds of antimicrobial agents, most frequently to ampicillin, tetracycline and streptomycin, while multiply drug-resistant strains from rural areas were resistant to 2 kinds of antimicrobial agents among ampicillin, tetracycline and streptomycin. With drug-resistant E. coli strains, resistance to tetracycline which was used most widely since 1951 was most frequently involved as a part of mutliple drug-resistance, followed by resistance to ampicillin and streptomycin. This strongly suggests that emergence of drug-restant strains in a community is directly dependent on the selective pressure exerted by the antimicrobial agent used. III. Cross resistance. Cross resistance of bacteria was studied among tetracycline penicillin, aminoglycoside and macrolide derivatives by analyzing correlation coefficients of sucseptibilities using the least square method. In this study, there were high correlations among the susceptibilities to related derivatives. It appears that the relatively low correlations in susceptibilities present in some cases are due to intrinsic resistance of E. aerogenes to penicillin, Enterococci to aminoglycoside and E. coli E. aerogenes and K. pneumoniae to macrolide derivatives.