• 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.

• Korean Journal of Remote Sensing
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• v.32 no.5
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• pp.453-469
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• 2016

Many image fusion quality assessment techniques, which include Wald's, QNR and Khan's protocols, have been proposed. A total procedure for the quality assessment has been defined as the quality assessment protocol. In this paper, we compared the performance of the three protocols using KOMPSAT-2/3/3A satellite images, and tested the applicability to the fusion quality assessment of the KOMPSAT satellite images. In addition, we compared and analyzed the strengths and weaknesses of the three protocols. We carried out the qualitative and quantitative analysis of the protocols by applying five fusion methods to the KOMPSAT test images. Then we compared the quantitative and qualitative results of the protocols from the aspects of the spectral and spatial preservations. In the Wald's protocol, the results from the qualitative and quantitative analysis were almost matched. However, the Wald's protocol had the limitations 1) that it is timeconsuming due to downsampling process and 2) that the fusion quality assessment are performed by using downsampled fusion image. The QNR protocol had an advantage that it utilizes an original image without downsampling. However, it could not find the aliasing effect of the wavelet-fused images in the spectral preservation. It means that the spectral preservation assessment of the QNR protocol might not be perfect. In the Khan's protocol, the qualitative and quantitative analysis of the spectral preservation was not matched in the wavelet fusion. This is because the fusion results were changed in the downsampling process of the fused images. Nevertheless, the Khan's protocol were superior to Wald's and QNR protocols in the spatial preservation.

• Korean Journal of Veterinary Service
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• v.42 no.3
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• pp.153-159
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• 2019

The objective of this study was to identify mutations in the quinolone resistance determining region (QRDR) of the gyrA, gyrB, parC and parE genes, and the presence of plasmid-mediated quinolone resistance (PMQR) genes: qnrA, qnrB, qnrS, aac(6')-lb-cr and qepA in 40 nalidixic acid- resistant ($NA^R$) Salmonella isolates isolated from poultry slaughterhouse. The MIC of NA and ciprofloxacin for 40 $NA^R$ Salmonella isolates was $128{\sim}512{\mu}g/mL$ and < $0.125{\sim}0.25{\mu}g/mL$, respectively. The Salmonella isolates were resistant to NA (100%), gentamicin (5.0%) and ampicillin (2.5%). All $NA^R$ Salmonella isolates represented point mutation in codons Aspartic acid(Asp)-87 (90%) and Serine(Ser)-83 (10%) of QRDR of gyrA gene: $Asp87{\rightarrow}glycine$, $Ser83{\rightarrow}tyrosine$. No mutations were observed in QRDR of the gyrB, parC and parE gene. Moreover PMQR genes was not found in any of the tested isolates. Our findings showed that DNA gyrase is the primary target of quinolone resistance and a single mutation in codon Asp87 and Ser83 of the gyrA gene can confer resistance to NA and reduced susceptibility ciprofloxacin in Salmonella isolates.

• Biomedical Science Letters
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• v.26 no.2
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• pp.120-126
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• 2020

Fluoroquinolone (FQ) resistant uropathogenic Escherichia coli (UPEC) have become a major problem in urinary tract infections (UTIs). The purpose of this study was to compare the quinolone resistance-determining region (QRDR) and plasmid mediated quinolone resistance (PMQR) determinants of FQ resistant UPEC between 1989 and 2010-2014. A total of 681 strains of UPEC clinical isolates was collected from Korean healthcare facility in 1989 (123 strains) and in 2010-2014 (558 strains). The minimum inhibitory concentrations (MICs) of FQs were determined by agar dilution method. QRDRs (gyrA, gyrB, parC and parE) and PMQR determinants (qnrA, qnrB, qnrS, aac(6')-Ib-cr and qepA) were analyzed polymerase chain reaction and sequencing method. Among 681 isolates, FQ resistant UPEC were 3 strains (2.4%) in 1989 isolates and 220 strains (39.4%) in 2010-2014 isolates. The rate of the FQ resistant UPEC strains in 2010-2014 isolates was increased than that of in 1989 isolates. UPEC isolates from 1989 and 2010-2014 were shown to carry mutations in gyrA (Ser83 and Asp87), gyrB (Ser464 and Thr469), parC (Ser80 and Glu84) and parE (Glu460, Ser458, Ile464 and Leu445). The most common mutations of QRDRs in 1989 isolates were Ser83Leu and Asp87Gly in gyrA and Ser80Ile in parC (2 strains: 66.7%) while those in 2010-2014 isolates were Ser83Leu and Asp87Asn in gyrA and Ser80Il2 and Glu84Val in parC (88 strains: 40.0%). PMQR determinants were detected only in 2010-2014 UPEC strains (47 strains: 21.4%).

• JSTS:Journal of Semiconductor Technology and Science
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• v.12 no.1
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• pp.59-65
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• 2012

A study on the electrical characteristic analysis of solar cell diodes under experimental conditions of varying temperature and frequency has been conducted. From the current-voltage (I-V) measurements, at the room temperature, we obtained the ideality factor (n) for Space Charge Region (SCR) and Quasi-Neutral Region (QNR) of 3.02 and 1.76, respectively. Characteristics showed that the value of n (at SCR) decreases with rising temperature and n (at QNR) increases with the same conditions. These are due to not only the sharply increased SCR current flow but the activated carrier recombination in the bulk region caused by defects such as contamination, dangling bonds. In addition, from the I-V measurements implemented to confirm the junction uniformity of cells, the average current dispersion was 40.87% and 10.59% at the region of SCR and QNR, respectively. These phenomena were caused by the pyramidal textured junction structure formed to improve the light absorption on the device's front surface, and these affect to the total diode current flow. These defect and textured junction structure will be causes that solar cell diodes have non-ideal electrical characteristics compared with general p-n junction diodes. Also, through the capacitance-voltage (C-V) measurements under the frequency of 180 kHz, we confirmed that the value of built-in potential is 0.63 V.

• Korean Journal of Veterinary Service
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• v.43 no.2
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• pp.79-88
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• 2020

The aim of this study was to investigate the prevalence of CTX-M β-lactamase and plasmid-mediated quinolone resistance (PMQR) genes, and the pattern of antibiotic resistance in cefotaxime-resistant gramnegative bacteria. A total 126 gram-negative bacteria were isolated from hospitalized dogs and cats between 2018 and 2019. The most predominant isolates were E. coli (n=41), followed by Pseudomonas aeruginosa (n=25), Proteus mirabilis (n=14), Klebsiella pneumoniae (n=9), Sphingomonas paucimobilis (n=7), and Enterobacter cloacae and Serratia marcescens (respectively, n=5). Cefotaxime-resistant isolates were identified in 26.2% (33 isolates) of 126 gram-negative bacteria. CTX-M type β-lactamase were found in 15 isolates (10 E. coli, 1 Ent, cloacae and 4 K. pneumoniae, respectively). Among the CTX-M producing gram-negative bacteria, CTX-M-1 and CTX-M-9 were detected in 10 (66.7%) and 5 (33.3%) isolates, respectively. While, CTX-M-2 and CTX-M-8 were not found. PMQR genes were detected in 12 (36.4%) isolates (4 E. coli, 2 Ent, cloacae and 6 K. pneumoniae, respectively), and the predominant PMQR gene was aac(6')-lb-cr (n=9), followed by qnrB (n=8) and qnrS (n=1) alone or in combination. qnrA and qepA were not found. Additionally, 9 (60%) of 12 PMQR positive isolates were co-existence with CTX-M-1 or CTX-M-9. CTX-M or PMQR producing isolates showed highly resistance to penicillins (100%), cephalosporins (100~66.7%), monobactams (72.2%), and non-β-lactam antibiotics (94.4~61.1%) such as quinolones, trimethoprim/sulfamethoxazole, tetracycline and gentamicin. These findings showed CTX-M-1, CTX-M-9, aac(6')-lb-cr and qnrB were highly prevalent in cefotaxime-resistant Enterobacteriaceae isolates from companion animals in our region. Moreover, PMQR genes were closely associated with CTX-M type β-lactamase.

• Korean Journal of Clinical Laboratory Science
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• v.48 no.3
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• pp.210-216
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• 2016

Recently, there has been a considerable increase in the prevalence of CTX-M type extended-spectrum ${\beta}$-lactamase (ESBL)-producing E. coli isolates worldwide, including Korea. To investigate the ESBL genes in the E. coli strains isolated from a university hospital in the Chungcheong area, a study was conducted using PCR amplification and nucleotide sequence analysis of the amplified products to detect the plasmid mediated quinolone resistance (PMQR) genes in ESBL producing E. coli isolates. The number of CTX-M-14 producing isolates was 25 (16.0%) isolates, and of them, 9 (5.8%) isolates also produced CTX-M-15. All CTX-M type ESBL producing E. coli isolates showed resistance to cefotaxime. Twelve (48%) CTX-M type ESBL producing E. coli isolates contained the PMQR genes, 8 contained qnrS1, and 8 contained aac(6')-Ib-cr. Four isolates harbored both qnrS1 and aac(6')-Ib-cr genes. In our study, we confirmed that the plasmid mediated antimicrobial resistant determinants-the ESBL and PMQR genes-were distributed in the E. coli isolates. To prevent further spreading of the resistant genes among the E. coli isolates, consistent effort is required to investigate and monitor the resistant genes.

• Korean Journal of Veterinary Service
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• v.46 no.1
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• pp.35-45
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• 2023

Pathogenic Escherichia coli is the cause of a wide range of diseases in pigs, including diarrhea, edema disease, and septicemia. Diarrhea caused E. coli may result in significant economic losses, making pathogenic E. coli an important pathogen for the swine industry. This study investigated the prevalence of virulence factor genes, antimicrobial resistance phenotypes, and resistance genes in E. coli isolated from feces of piglets in Korea between 2017 and 2020. As a result, 119 pathogenic E. coli isolates were obtained from 601 fecal samples. The F4 adhesin gene and the STb enterotoxin gene were commonly present in E. coli isolated from diarrhea samples. The dominant virulotypes of isolates from diarrhea samples were STb, Stx2e, and F4:LT:STb. More than 80% of the screened isolates were resistant to ampicillin, sulfisoxazole, chloramphenicol, or tetracycline. To confirm the resistance mechanisms for β-lactam or quinolone, we investigated the genotypic factors of resistance. Each of the ceftiofur-resistant E. coli produced an extended-spectrum β-lactamase encoded by bla_CTX-M-14, bla_CTX-M-27, and bla_CTX-M-55. And all ciprofloxacin-resistant E. coli harbored mutations in quinoloneresistance-determining-regions. In addition, some of the ciprofloxacin-resistant E. coli contained the plasmid-mediated-quinolone-resistance genes such as qepA, qnrB1, or qnrD. This study has confirmed that the F4 fimbria and the STb enterotoxin are the most predominant in pathogenic E. coli isolated from piglets with diarrhea in Korea and there is a great need for responsible and prudent use of antimicrobials to treat colibacillosis.

• Korean Journal of Clinical Laboratory Science
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• v.50 no.4
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• pp.422-430
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• 2018

The inappropriate and widespread use of quinolones in humans and animals may cause accelerated emergence and spread of antimicrobial-resistant determinants. In this study, we investigated quinolone resistance mechanisms in a total of 65 nalidixic acid-resistant E. coli isolated from swine rectal swabs (N=40) and clinical specimens (N=25). Antimicrobial susceptibilities were determined by the disk diffusion method. PCR and DNA sequencing were performed for investigations of genes and mutations associated with quinolone resistance. In our study, 62 of 65 nalidixic acid-resistant E. coli harbored mutations in gyrA, parC, and/or parE genes; of the 65 isolates, 62 (95.4%) had mutations in the gyrA gene, 35 (53.8%) had mutations in the parC gene, 7 (10.8%) had mutations in the parE gene. The 35 isolates harbored mutations in two genes, gyrA and parC. Plasmid-mediated quinolone resistance (PMQR) determinants were investigated in the 65 isolates. Thirteen of 65 nalidixic acid-resistant E. coli contained the qnrS gene and 10 of those isolates had mutations in the gyrA, parC, and/or parE genes. We confirmed that an important mechanism of quinolone resistance in E. coli isolated from human and swine involves chromosomal mutations in the gyrA, parC, and/or parE genes with increasing use of quinolone for treatment or additives.

• Korean Journal of Clinical Laboratory Science
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• v.48 no.2
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• pp.118-123
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• 2016

Antimicrobial agents have been used in poultry for treatment of bacterial infections or additives over the past half century. However, increasing antimicrobial resistance has led to selective pressure for therapeutic use in humans and made treatment of bacterial infection more difficult. In this study, we examined the prevalence of plasmid mediated antimicrobial resistant determinants for resistance to ${\beta}-lactam$, quinolone, and aminoglycoside in Enterobacteriaceae isolates obtained from chickens in Gyeongsang provinces, and correlation between the resistant genes and antimicrobial resistance rate was also assessed. A total of 43 Enterobacteriaceae isolates were recovered from 40 chickens at Gyeongsang provinces in Korea. Antimicrobial susceptibility was determined by disk diffusion method. PCR and DNA sequencing were performed to characterize the antimicrobial resistant genes. Of the 43 Enterobacteriaceae isolates tested, 2 isolates harbored $bla_{CTX-M-14}$ gene, and 2 and 5 strains contained qnrS and aac(6')-Ib-cr genes, respectively. A total of 43 isolates displayed a relatively lower susceptible rate ranging between 0.0 and 23.3% to most of the antimicrobial agents, except cefepime, ceftazidime, and cefaclor. We confirmed that plasmid mediated antimicrobial resistant determinants were distributed in Enterobacteriaceae isolates from chickens. Investigation of the genes and monitoring of antimicrobial resistance rate is required to prevent further spreading of antimicrobial resistant genes among Enterobacteriaceae isolates.