• Korean Journal of Microbiology
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• v.50 no.3
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• pp.185-190
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• 2014

The aim of this study was to investigate the prevalence of quinolone resistant E. coli from raw bulk milk and to characterize the resistance determinants. In this study, the gyrA, gyrB, parC, and parE quinolone resistance determining regions (QRDR) were sequenced from quinolone resistant E. coli isolates. Also, the presence of plasmid-mediated quinolone resistance (PMQR) and the expression of efflux pump genes based on quantitative real-time PCR (qRT-PCR) were investigated. Of the 487 coliform bacteria, 9 strains showed nalidixic acid resistance, and 6 of the 9 nalidixic acid resistant isolates were also ciprofloxacin resistant. These 9 strains had a single mutation at codon 83 (S83L) in gyrA, 2 of them had double mutations at codon 83 and 87 (S83L and D87N) in gyrA and 3 of the 9 isolates had single mutations at codon 80 (S80I) in parC. None of the 9 isolates harbored PMQR determinants. Compared with wild-type E. coli ATCC 25922, an over-expression of the acrB gene (2.15-5.74 fold), encoding the pump component of the AcrAB-TolC efflux pump was observed in 4 of 6 ciprofloxacin resistant isolates. This study identified the quinolone resistance mechanism of E. coli isolated from raw milk samples in Gyeonggi-do.

• Journal of environmental and Sanitary engineering
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• v.23 no.2
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• pp.71-79
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• 2008

We examined 165 unchlorinated natural drinking water samples for the presence of E. coli group resistant to antimicrobial agent and chlorine in nothern Gyeongbuk area in 2007. Among 165 water samples, 21 samples(12.7%) were positive to total coliforms and Six genus, 16 strains of E. coli groups isolated from 16 samples showed resistance against more than one antimicrobial agent such as Ampicillin, Tetracycline and Chloroamphenicol. Among 16 strains, 14 strains resistant to Ampicillin, 9 strains resistant to Tetracycline and one strain resistant to Chloroampenicol. but all 16 strains did not contain any integron gene cassettes, which contribute to the spread of antimicrobial resistance alleles by lateral gene transfer of gene cassettes in a variety of enteric bacteria. The minimal inhibitory concentration(MIC) of 14 strains which showed resistant to Ampicillin was between $12{\mu}g/m{\ell}$ and $32{\mu}g/m{\ell}$, Nine strains resistant to Tetracycline showed between $32{\mu}g/m{\ell}$ and $128{\mu}g/m{\ell}$ and one strain resistant to Chloroampenicol showed $128{\mu}g/m{\ell}$. The chlorine sensitivity of 16 strains isolated from unchlorinated natural water sample did not show any difference among strains by the concentration of initial free chlorine and elapsed time after chlorine treatment. All 16 strains were killed after 1hr. exposure at $0.2mg/m{\ell}$ of free chlorine per liter or 30minutes exposure at $0.4mg/m{\ell}$ of free chlorine per liter.

• Journal of Life Science
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• v.26 no.2
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• pp.220-225
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• 2016

Coagulase-negative staphylococci (CNS) have recently become the bacteria most frequently found in clinical infections. The aim of this study was to investigate the prevalence, antimicrobial susceptibilities, and molecular characteristics of CNS isolates from dental clinic environments in Busan, Korea. One hundred and fifty-four samples were collected from 10 dental clinics and dental hospitals in Busan from December 2014 to January 2015. Species were identified by matrix-assisted laser desorption/ionization–time-of-flight. Antimicrobial susceptibility was determined by disk diffusion methods. A polymerase chain reaction was performed to detect mecA, mupA gene, and SCCmec types. Of the 154 samples, 10(6.5%) isolates were identified as CNS (5 Staphylococcus epidermidis, 2 Staphylococcus capitis, 2 Staphylococcus, and 1 Staphylococcus haemolyticus). Among the 10 isolates, 6 were resistant to penicillin, 5 were resistant to gentamicin, 3 were resistant to tetracycline, and 2 were resistant to cefoxitin and erythromycin. However, clindamycin, ciprofloxacin, teicoplanin, and trimethoprim-sulfamethoxazole resistant isolates were not present. Genes encoding mecA were detected in 4 (2 S. warneri and 2 S. haemolyticus) isolates, and mupA in 1 (S. epidermidis) isolate. One methicillin-resistant CNS (S. warneri) isolate was determined as being of the SCCmec type I. It is concluded that CNS resistant to various antimicrobial agents was widely distributed in dental clinic environments in Korea.

• Journal of fish pathology
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• v.34 no.1
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• pp.39-46
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• 2021

Tetracycline (TC) is one of the antibiotics used for treatment of bacterial infection in Korea. Inadequate usage and abuse cause the resistance to antibiotics, like Tetracycline, Erythromycin, and Fluoroquinolone. It can also affect severe economic loss in aquaculture field in Korea. We isolated 101 bacterial samples from diseased fish at aquaculture sites in Gyeonggi-do during 2015~2018. Minimum inhibitory concentration (MIC) method has been used to determine distribution and to identify bacterial isolates resistant to antibiotics including Oxytetracycline (OTC), Ampicillin (AMP), Clindamycin (CLI), Enrofloxacin (ENRO), Gentamycin (GEN). TC resistant isolates were confirmed antibiotic resistant genes by conventional PCR. Bacterial isolates were identified as Aeromonas spp. (43.5%), Pseudomonas spp. (4.0%) and Vibrio spp. (5.0%). It was confirmed that multi-resistant isolates (77.2%) were predominant over single-resistant one (22.8%). TC resistant genes like tet(A), tet(D), tet(E), tet(G), tet(M), and tet(S) were detected and tet(A) was the most prevalent. Aeromonas spp. is a dominant strain in bacterial infections in fishes of aquaculture sites, and further investigation on various antibiotic resistance genes will be needed for clear understanding of aquaculture sites in Gyeonggi-do.

• Food Science and Biotechnology
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• v.14 no.4
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• pp.503-508
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• 2005

Screening for antilisterial activity was performed in about three thousand isolates of lactic acid bacteria (LAB) from Chinese cabbage kimchi, and finally based on the relatively stronger antilisterial activities eight bacterial strains were selected. The bacteria were further characterized in terms of their tolerance to artificial gastric juice, pH 2.5, bile salts (0.3% oxgall), and to the different NaCl concentrations. Of the isolates, YK005 was especially investigated for its physiological characteristics due to its inhibitory activity against gram-positive Listeria monocytogenes as well as gram-negative Escherichia coli O157:H7, as they have been constantly reported to be resistant against bacteriocins produced by a number of LAB strains. YK005 was found to be rod-shaped, $3.8\;{\mu}m$ long ${\times}\;0.5\;{\mu}m$ wide, non-sporeforming, non-motile, catalase-negative, and produced gas from glucose (heterolactic). Based on the biochemical data obtained by API 50 CHL medium, the isolate was tentatively identified as Lactobacillus brevis. To validate the result obtained by the biochemical identification, rRNA-based PCR experiments using a pair of species-specific primers for L. brevis were conducted and a single band of 1400 bp was observed, which strongly indicated that YK005 belongs to L. brevis. The LAB isolates are potentially exploited as human probiotic organisms and are employed to control some food-borne pathogens like L. monocytogenes.

• Journal of Korean Academy of Nursing
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• v.19 no.3
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• pp.249-258
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• 1989

The purpose of study was to confirm theory about the effectiveness of routine mental care on the reduction of catheter-associated urinary tract infection. The study was carried out at a university hospital from September 1,1987 to April 17, 1989 : 32 Patients with a foley -catheter were studied. The study compared the urinary tract infection rate of an experimental group with that of a control group and tested the antibiotic susceptibility of the isolated bacteria. The experimental group(16 patients) was given daily meatal care with 10% Betadine for periods ranging from 4 to 21 days. The control group(16 patients) was not given that care. The results obtained were as follows : 1. The urinary tract infection rate of the experimental group was 50.0 %, and that of the control group 43.8%. There was no significant difference between the groups. 2. Organisms isolated in the control group were bacteria 100%, and in the experimental group bacteria 50% and fungus 50%. The most common organisms of the 15 strains isolated in the total group were Staphylococcus coagulase negative (3 patients), and E-coli (3 patients). 3. Most of bacteria isolated in this study were sensitive to Norfloxacillin, but resistant to Ampicillin, Chloramphenicol, Kanamycin, Tetracycline, and Erythromycin. Hence the importance of controling catheter-associated urinary tract infections. Findings suggest the need to search for other sources of infection, further experimentation controling various sources of urinary tract infection and larger group of subjects.

• Analytical Science and Technology
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• v.30 no.3
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• pp.113-121
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• 2017

Now a day's rise of new antibiotic resistant bacterial strains is a global threat. Ethnic people of India have been employing Aphanamixis polystachya (Wall.) R. Parker wood extract in healing cancerous wounds. The aim of this study was to evaluate the antimicrobial activity and to identify the medicinally potent chemicals in the essential oil extract of A. polystachya. The antibacterial properties of various organic extracts were evaluated against a range of bacteria (gram-positive and gram-negative bacteria) based on the disc diffusion method and GC-MS based analysis for finding active oil extract components. All extracts of A. polystachya leaves showed potential antibacterial activity, notably ethyl acetate, while petroleum ether extracts revealed highly sensitive activity against all tested bacteria (zones of inhibition ranging from 8.83 to 11.23 mm). In addition, the petroleum ether extract had the lowest MIC value (32 to $256{\mu}g/mL$) against E. coli, S. lutea, X. campestris, and B. subtilis bacteria. The major compounds detected in oil [${\beta}$-elemene (16.04 %), ${\beta}$-eudesmol (12.78 %), ${\beta}$-caryophyllene (19.37 %), ${\beta}$-selinene (11.32 %), elemol (5.76 %), and ${\alpha}$-humulene (5.68 %)] are expected to be responsible for the potent antimicrobial activity. The results of this study offer valuable insights into the potent role of A. polystachya essential oil extract in pharmaceutical and antibiotic research.

• Journal of Veterinary Clinics
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• v.28 no.4
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• pp.348-351
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• 2011

The purpose of this study was to determine the distribution of gram-negative bacteria isolated from companion animals with sepsis, and to investigate the antimicrobial susceptibility patterns of the isolates. Bacterial pathogens were isolated from specimens of dogs and cats submitted to National Veterinary Research and Quarantine Service between 2008 and 2009. A total of 44 gram-negative pathogens were isolated from necropsied organs. The most common isolates were E. coli (n = 33), K. pneumoniae (n = 4) and B. bronchiseptica (n = 4). Most of gram-negative isolates were susceptible to ceftiofur (68.2%), colistin (84.1%), florfenicol (84.1%) and spectinomycin (61.4%). Most of those were resistant to ampicillin (77.3%), erythromycin (86.4%), flumequine (65.9%), lincomycin (97.7%), oxytetracycline (61.4%), penicillin (100%), streptomycin (63.6%), spiramycin (97.7%), sulfamethoxazole (90.9%), tylosin (97.7%) and tiamulin (100%). In conclusion, colistin and florfenicol could be useful against sepsis due to gram-negative bacteria.

• Microbiology and Biotechnology Letters
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• v.29 no.1
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• pp.1-11
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• 2001

Lactic acid bacteria (LAB) are widely used for various food fermentation. With the recent advances in modern biotechnology, a variety of bio-products with the high economic values have been produced using microorganisms. For molecular cloning and expression studies on the gene of interest, E. coli has been widely used mainly because vector systems are fully developed. Most plasmid vectors currently used for E, coli carry antibiotic-resistant markers. As it is generally believed that the antibiotic resistance markers are potentially transferred to other bacteria, application of the plasmid vectors carrying antibiotic resistance genes as selection markers should be avoided, especially for human consump-tion. By contrast, as LAB have some desirable traits such that the they are GRAS(generally recognized as safe), able to secrete gene products out of cell, and their low protease activities, they are regarded as an ideal organism for the genetic manipulation, including cloning and expression of homologous and heterologous genes. However, the vec-tor systems established for LAB are stil insufficient to over-produce gene products, stably, limiting the use of these organisms for industrial applications. For a past decade, the two popular plasmid vectors, pAM$\beta$1 of Streptococcus faecalis and pGK12 theB. subtilis-E. coli shuttle vector derived from pWV01 of Lactococcus lactis ssp. cremoris wg 2, were most widely used to construct efficient chimeric vectors to be stably maintained in many industrial strains of LAB. Currently, non-antibiotic markers such as nisin resistance($Nis^{r}$ ) are explored for selecting recombi-nant clone. In addition, a gene encoding S-layer protein, slp/A, on bacterial cell wall was successfully recombined with the proper LAB vectors LAB vectors for excretion of the heterologous gene product from LAB Many food-grade host vec-tor systems were successfully developed, which allowed stable integration of multiple plasmid copies in the vec-mosome of LAB. More recently, an integration vector system based on the site-specific integration apparatus of temperate lactococcal bacteriophage, containing the integrase gene(int) and phage attachment site(attP), was pub-lished. In conclusion, when various vector system, which are maintain stably and expressed strongly in LAB, are developed, lost of such food products as enzymes, pharmaceuticals, bioactive food ingredients for human consump-tion would be produced at a full scale in LAB.

• Journal of Microbiology and Biotechnology
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• v.28 no.5
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• pp.671-678
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• 2018

Papiliocin, isolated from the swallowtail butterfly (Papilio xuthus), is an antimicrobial peptide with high selectivity against gram-negative bacteria. We previously showed that the N-terminal helix of papiliocin (PapN) plays a key role in the antibacterial and anti-inflammatory activity of papiliocin. In this study, we measured the selectivity of PapN against multidrug-resistant gram-negative bacteria, as well as its anti-inflammatory activity. Interactions between Trp2 of PapN and lipopolysaccharide (LPS), which is a major component of the outer membrane of gram-negative bacteria, were studied using the Trp fluorescence blue shift and quenching in LPS micelles. Furthermore, using circular dichroism, we investigated the interactions between PapN and LPS, showing that LPS plays critical roles in peptide folding. Our results demonstrated that Trp2 in PapN was buried deep in the negatively charged LPS, and Trp2 induced the ${\alpha}$-helical structure of PapN. Importantly, docking studies determined that predominant electrostatic interactions of positively charged arginine residues in PapN with phosphate head groups of LPS were key factors for binding. Similarly, hydrophobic interactions by aromatic residues of PapN with fatty acid chains in LPS were also significant for binding. These results may facilitate the development of peptide antibiotics with anti-inflammatory activity.