• Tuberculosis and Respiratory Diseases
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• v.47 no.2
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• pp.184-194
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• 1999

Backgrounds : The advent of penicillin has led to the marked reduction in the mortality from pneumococcal bacteremia, however, the mortality is still relatively high in this post-antibiotic era. Actually the prevalence of infection due to penicillin-resistant penumococci is increasing worldwide, and it is especially high in Korea due to irrelevant use of antibiotics. So, the high mortality of pneumococcal sepsis might be related to the emergence of penicillin-resistant strains, however, many other antibiotics, which eradicate pneumococci effectively, are available in these days. This has led us to suspect the role of penicillin-resistance in the high mortality rate. In this study, we evaluated the effect of penicillin resistance on the mortality of patients with penumococcal bacte remia. Methods: The study population consisted of 50 adult patients with penumococcal bacteremia who were admitted between Jan, 1990 and July, 1997. Medical records were analyzed retrospectively. Results: Most of the patients (96%) had underlying diseases. The most common local disease associated with pneumococcal bacteremia was pneumonia (42%), which was followed by spontaneous bacterial peritonitis (14%), cholangitis (10%), meningitis (8%), liver abscess (4%), pharyngotonsillitis (4%), sinusitis (2%) and cellulitis (2%). While the overall case-fatality rate in this study was 24%, it was higher when peumococcal bacteremia was associated with pneumonia (42%) or meningitis (50%). The rate of penicillin resistance was 40%, which was increased rapidly from 1991. The rate of penicillin resistance was significantly higher in patients with the history of recent antibiotics use and hospitalization within 3 months respectively. The clinical manifestations, that is, age, severity of underlying diseases, nosocomial infection, associated local diseases, and the presence of shock or acute renal failure were not statistically different between the patients with penicillin-resistant and -sensitive pneumococcal bacteremia. The mortality of patients infected with penicillin-resistant pneumococci was not statistically different from those with penicillin-sensitive pneumococcal bacteremia. Conclusion: Penicillin resistance is not associated with high mortality in adult patients with pneumococcal bacteremia. As the overall mortality is high, active penumococcal vaccination is recommended in patients with high risk of infection.

• Korean Journal of Clinical Laboratory Science
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• v.48 no.2
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• pp.74-81
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• 2016

Ureaplasma species can normally colonize in the bodies of healthy individuals. Their colonization is associated with various diseases including non-gonococcal urethritis, chorioamnionitis, neonatal meningitis, and prematurity. In 2012, the sum of the resistant and intermediate resistant rates of Ureaplasma spp. to ofloxacin and ciprofloxacin was 66.08% and 92.69%, respectively. DNA point mutations in the genes encoding DNA gyrase (topoisomerase II) and topoisomerase IV are commonly responsible for fluoroquinolone resistance. Each enzyme is composed of two subunits encoded by gyrA and gyrB genes for DNA gyrase and parC and parE genes for topoisomerase IV. In the current study, these genes were sequenced in order to determine the role of amino acid substitutions in Ureaplasma spp. clinical isolates. From December 2012 to May 2013, we examined mutation patterns of the quinolone resistance-determining region (QRDR) in Ureaplasma spp. DNA sequences in the QRDR region of Ureaplasma clinical isolates were compared with those of reference strains including U. urealyticum serovar 8 (ATCC 27618) and U. parvum serovar 3 (ATCC 27815). Mutations were detected in all ofloxacin- and ciprofloxacin-resistant isolates, however no mutations were detected in drug-susceptible isolates. Most of the mutations related to fluoroquinolone resistance occurred in the parC gene, causing amino acid substitutions. Newly found amino acid substitutions in this study were Asn481Ser in GyrB; Phe149Leu, Asp150Met, Asp151Ile, and Ser152Val in ParC; and Pro446Ser and Arg448Lys in ParE. Continuous monitoring and accumulation of mutation data in fluoroquinolone-resistant Ureaplasma clinical isolates are essential to determining the tendency and to understanding the mechanisms underlying antimicrobial resistance.

• Pediatric Infection and Vaccine
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• v.16 no.2
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• pp.150-161
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• 2009

Purpose : Staphylococcus aureus causes a variety of infections, ranging from benign skin infections to fatal invasive infections. Recently, methicillin-resistant S. aureus (MRSA) infections have emerged in patients who do not have established risk factors. This study was conducted to characterize S. aureus infections in children with an emphasis on communityassociated MRSA infections at a tertiary care pediatric facility during a 3-year period. Methods : Four hundred twenty-nine cases of S. aureus infections diagnosed at the Seoul National University Children's Hospital between January 2004 and December 2006 were retrospectively reviewed. The cases were classified as hospitalonset (HO) or community-onset (CO), healthcare-associated (HA), or community-associated (CA) infections. Results : Among the 206 cases <1 year of age, 72%, 7%, and 21% were HO-HA, CO-HA, and CA infections, respectively, as compared to 48%, 28%, and 24% among the 223 cases >1 year of age. The proportion of CO-HA infections among HA infections (8.6% vs. 37.1%, P<0.001) and the proportion of HA infections among the CO infections (24.5% vs. 54.3%, P <0.001) were greater in older children than in infants. Overall, 57% of the isolates were methicillin-resistant. Twenty-nine (30%) of 96 CA strains were MRSA, and the most common site of CA-MRSA infection was the skin and soft tissues (26 cases). Conclusion : The methicillin resistance rate of S. aureus from CA infections was high and CA-MRSA was most often associated with skin and soft tissue infections.

• Journal of the Korean Chemical Society
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• v.54 no.1
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• pp.77-87
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• 2010

Hospital-acquired methicillin-resistant Staphylococcus aureus (MRSA) has been an increasing problem worldwide since the initial reports over 40 years ago. To examine new drug leads with potential antibacterial activities, Various N'-[(-3-substituted-4-oxo-1,3-thiazolidin-2-ylidene]-4-hydroxy benzohydrazide (4a-4.i) and N'-[-(3,4-disubstituted)-1,3-thiazolidin-2ylidene)]-4-hydroxybenzohydrazide from (5.a-5.i) to (10.a-10.i) were synthesized using appropriate synthetic route. The entire test compounds (4.a-4.i) and from (5.a-5.i) to (10.a-10.i) were assayed in vitro against s. aureus strain. The minimum inhibitory concentration (MIC) was determined for test compounds and for reference standards. The test compounds showed significant antibacterial activity against the strains used, when tested in vitro. In general, p-hydroxybenzohydrazide ring and substituted thiazoline ring are essential for antimicrobial activity. Among the compounds tested, compounds 6.f, 7.g, 9.f and 10.f, 10 i were found to be most potent. The test compounds were found nontoxic upto the dose level of 2000 ${\mu}g$/mL. The intact compounds were then subjected for 3D-QSAR studies. 3D-QSAR study based on the principal of alignment of pharmacophoric features by Schrodinger PHASE module. The 3D-QSAR study allowed us to confirm the preferential binding mode of p-hydroxybenzohydrazide inside the active site.

• Journal of Life Science
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• v.22 no.7
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• pp.987-990
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• 2012

Mungbean sprout rot is one of the most serious problems of the commercial mungbean sprout industry. In this study, 70 strains of mungbean sprout rot pathogens were isolated from rotten sprouts at different time intervals. The pathogenicity of the isolated pathogens was tested. The highly pathogenic strain (YV-St-033) was identified as Pseudomonas sp. by 16S rRNA gene sequencing. In phylogenetic analysis, the YV-St-033 strain was grouped with P. mosselii, P. putita, P. fluorescens, P. entomophila, and P. lecoglossicida. The results of the 16S rRNA gene sequence analysis revealed that the YV-St-033 strain shared the highest sequence identity (more than 99%) with the P. mosselii R10 strain. The mungbean lines of Yeungnam University germplasm were screened against the YV-St-033 strain. Based on the growth rate of the sprouts after 3 days of inoculation with the pathogen, the YV148 line was highly resistant to the pathogen. The remaining lines were either partially or fully infected. The highly resistant line YV 148 is suitable for future breeding programs due to their thin sprouts and fast growing nature.

• Journal of Life Science
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• v.28 no.3
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• pp.357-360
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• 2018

This study developed a method to minimize rice damages and enhance timely control by accurately classifying Whitebacked Planthopper (WBPH). The body size of the 1st-3rd instar was 1.5-2 mm, and the body size of the 4-5 instar was 2.5-3.5 mm. In the third instar, the ratio of the front wing bud and the back wing-bud was 1:1. The fourth instar occupied 3/4 of the front wing-bud, and the 5th instar showed that the front wing-bud covers the back wing-bud. It was confirmed that the 1st instar does not have a sensory plate, the 2nd instar has 2-3, the 3rd instar has 4-5, the 4th instar has 6-9, the 5th instar has 10-15, and the adult instar has 15-20 sensory plates. The female spawning organs were reddish when the spawning horn was inserted. WBPH showed that the larvae of 2-3 larvae most actively feed on rice, and the damaged area was the stem of rice near the ground. In addition, a partial black wound was observed after the feeding. WBPH-susceptible 'Chucheong' was yellowish, and early growth was slower than that of 'Cheongcheong', which was resistant; moreover, a difference between susceptibility and resistance was observed. The identification of the number of such wounds in the bioassay will be a better basis for understanding the difference in susceptibility between WBPH strains and cultivars. These results will be used as basic data for cultivating the WBPH-resistant varieties of rice.

• Korean Journal of Clinical Laboratory Science
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• v.47 no.2
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• pp.65-70
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• 2015

Antimicrobial agents or additives have commonly been used in domestic animals for the prevention and treatment of bacterial diseases. Unfortunately, this has resulted in the overgrowth of bacteria that is resistant to antimicrobial agents used by humans, and these might get disseminated to humans via the food. In this study, we investigated the prevalence of integrons, and characterized gene cassette arrays in Proteus mirabilis isolates obtained from chickens in Chungcheong province of Korea. Additionally, the correlation between gene cassette arrays and antimicrobial resistance rate was studied. A total of 26 Proteus mirabilis isolates were recovered from chickens in Chungcheong province in Korea. Antimicrobial susceptibility was determined by disk diffusion method. PCR and DNA sequencing were performed to characterize the gene cassette arrays. In addition, we employed repetitive extragenic palindromic sequence-based PCR (REP-PCR) method for clonality analysis of P. mirabilis strains. Of the 26 P. mirabilis isolates tested, 14 (53.8%) isolates carried class 1 integrons, while class 2 and class 3 integrons were not detected in our study. The class 1 integrons harbored genes encoding resistance to aminoglycosides (aacCA5, aadA2, aadA5 and aadA7), trimethoprim (dfrA17, and dfrA32), lincosamides (linF) and erythromycin (ereA). In particular, the presence of class 1 integron had a significant correlatation to a high resistance rate of aminoglycoside and trimethoprim. We confirmed that class 1 integrons are widely disseminated in P. mirabilis isolates from chickens, contributing to the resistance to diverse antimicrobial agents in Korea. To prevent further spreading of antimicrobial resistant genes among P. mirabilis isolates, constant monitoring and clinical policing will become necessary.

• Korean journal of applied entomology
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• v.22 no.2 s.55
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• pp.98-105
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• 1983

The rapid increase in cases of insect resistance to insecticides indicates that the contribution of present chemical control practices inevitably leads to exhaustion of available insecticide resources against key insect species. Now the problem of insecticide resistance exists worldwide among insects and mites affecting field crops and animals including human beings, ranging from minimal or absent in some developing countries, where use of insecticides has been low, to extremely severe in many developed countries. Since the occurrence of insect resistance to insecticides was firstly recognized in 1908, the increase in recent decades has been almost linear and now the number of species of insects and acarines in which resistant strains have evolved have been increased to a total of 432. Of these, $261(60\%)$ are agricultural importance and $171(40\%)$ of medical/veterinary importance. The phenomenon of insecticide resistance is asserting itself as the greatest challenge to effective chemical control of many important insect pests. Resistance of insects to insecticides has a history of nearly 80 years, but its greatest increase and its strongest impact have occurred during the last 40 years following the discovery and extensive use of synthetic organic insecticides and acaricides. The impact of resistance should be considered not only in terms of greater cost of pest control due to increased dosages and number of applications but also in terms of the ecological disruption of pest-beneficial species density relationships, the loss of investment in the development of the insecticides concerned, and socio-economic disruption in agricultural communities. Despite its grave economic consequences, the phenomenon of insecticide resistance has received surprisingly little attention in Korea. Since the study of insecticides started firstly in 1963, many entomologists have been concerned with this study. According to their results, some of the rice pests and some of the mites on orchard trees, for example, have developed worrisome level of resistance in several areas of this peninsula. With many arthropods, considerable advances in the developed countries have been made in the study of the biochemical and physiological mechanisms of resistance. Progress involves the biochemical characteristics of specific defense mechanisms, their genetics, interactions, and their quantitative and qualitative contribution to resistance. But their studies arc still inadequately known and relatively little have been contributed in terms of unique schemes of population management in achieving satisfactory pest control. It is apparent that there is no easy solution to resistance as a general phenomenon. For future challenging to effective control of insect pests which are resistant to the insecticides concerned, new insecticide groups with distinctly novel mode of action are urgently needed. It is clear, however, that a great understanding of the factors which govern the intensity of selection of field population for resistance could lead to far more permanently successive use of chemicals within the framework of integrated pest management than heretofore practiced.

• Microbiology and Biotechnology Letters
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• v.43 no.2
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• pp.126-133
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• 2015

Ten types of farm-made brewing vinegars were collected and four high acetic acid-producing strains (CV1, CV3, CV5, and CV6) were isolated. Among them strain CV1, exhibiting highly alcohol-resistant and acetic acid-producing properties, was selected and its taxonomic properties were investigated by phenotypic (particularly chemotaxonomic) characterization and phylogenetic inference based on 16S rRNA gene sequence analysis. On SM broth agar, cells of strain CV1 were gram-stainingnegative and formed pale white colonies with smooth to rough surfaces. Strain CV1 produced acetate from ethanol and was resistant to up to 8% (v/v) ethanol in LM broth. Strain CV1 had a G+C content of 61.0 mol%, contained meso-DAP as the cell wall amino acid, and possessed Q-10 as the major ubiquinone. A comparison of 16S rRNA gene sequences showed that strain CV1 was most closely related to Gluconacetobacter saccharivorans (≥99.0% identity). In liquid media, the optimum growth conditions for acetic acid production were 30℃ and pH >3.0 and strain CV1 produced 9.3% and 8.4% acetic acids from 10% and 9% alcohol concentrations, respectively.

• Journal of Microbiology and Biotechnology
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• v.22 no.11
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• pp.1532-1539
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• 2012

The ${\alpha}$-galactosidase-coding gene agaAJB13 was cloned from Sphingomonas sp. JB13 showing 16S rDNA (1,343 bp) identities of ${\leq}97.2%$ with other identified Sphingomonas strains. agaAJB13 (2,217 bp; 64.9% GC content) encodes a 738-residue polypeptide (AgaAJB13) with a calculated mass of 82.3 kDa. AgaAJB13 showed the highest identity of 61.4% with the putative glycosyl hydrolase family 36 ${\alpha}$-galactosidase from Granulicella mallensis MP5ACTX8 (EFI56085). AgaAJB13 also showed <37% identities with reported protease-resistant or Sphingomonas ${\alpha}$-galactosidases. A sequence analysis revealed different catalytic motifs between reported Sphingomonas ${\alpha}$-galactosidases (KXD and RXXXD) and AgaAJB13 (KWD and SDXXDXXXR). Recombinant AgaAJB13 (rAgaAJB13) was expressed in Escherichia coli BL21 (DE3). The purified rAgaAJB13 was characterized using p-nitrophenyl-${\alpha}$-D-galactopyranoside as the substrate and showed an apparent optimum at pH 5.0 and $60^{\circ}C$ and strong resistance to trypsin and proteinase K digestion. Compared with reported proteaseresistant ${\alpha}$-galactosidases showing thermolability at $50^{\circ}C$ or $60^{\circ}C$ and specific activities of <71 U/mg with or without protease treatments, rAgaAJB13 exhibited a better thermal stability (half-life of >60 min at $60^{\circ}C$) and higher specific activities (225.0-256.5 U/mg). These sequence and enzymatic properties suggest AgaAJB13 is the first identified and characterized Sphingomonas ${\alpha}$-galactosidase, and shows novel protease resistance with a potential value for basic research and industrial applications.