• Korean Journal of Veterinary Service
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• v.34 no.1
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• pp.37-43
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• 2011

This study was conducted to investigate the prevalence and genotypes of extended-spectrum ${\beta}$-lactamase (ESBL) in 377 Escherichia coli isolated from healthy and sick animals. Two isolates (0.5%), each of which were isolated from diseased swine and chicken, respectively, were confirmed as ESBL producing isolates by double disk synergy test, and showed a multidrug resistant phenotype. Minimum inhibitory concentration of cefotaxime for the two ESBL producing isolates were 3~4 times higher than those of ceftazidime, respectively. By PCR and sequencing, one isolate from swine have both $bla_{CTX-15}$ and $bla_{TEM-1}$, and one isolate from chicken have $bla_{CTX-15}$ and $bla_{TEM-116}$. Also, these genes were transferred to E. coli J53 by conjugation. These two isolates showed unrelated pulsed-field gel electrophoresis. To our knowledge, this is the first time that $bla_{TEM-116}$ gene was identified in E. coli isolated from animals in Korea. These results suggest more prudent use of third- generation cephalosporins, and surveillance and monitoring for ESBL producing E. coli in both animals and their environments should be necessary.

• Korean Journal of Plant Resources
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• v.33 no.6
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• pp.615-623
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• 2020

Brassica rapa is one of the most valuable vegetable crops worldwide. Cultivated varieties of B. rapa exhibit diverse developmental and morphological appearances, which includes important vegetables, oilseeds, and fodder crops. In this study, various phenotypes of recombinant inbred lines (RILs) of B. rapa were investigated, including their responses to five different pathogenic Botrytis cinerea isolates, responses to aphid and thrips during flowering stages, days to flowering, and plant heights. Responses of 113 RILs to five different B. cinerea isolates showed variations, suggesting that genetic factors controlling resistance or tolerance against each isolate were dependent on isolate/genotype pairs. Correlation analysis was performed to understand the nature of genetic factors and the relationship among these phenotypes. Although high levels of correlation were not detected between phenotypes assessed in this study, statistically significant correlation was detected for several combinations. Significant positive correlations were found for different B. cinerea isolates, supporting that certain levels of commonality could exist in genetic components controlling resistance against different B. cinerea isolates. Based on correlation analysis using numbers of insects counted on plants, it was speculated that genetic factors responsible for aphid tolerance or repellence might be also involved in the response against thrips. Relationship between vegetative growth and tolerance against B. cinereal or insects is rather more complicated. However, it was observed that shorter plants appeared to have a certain level of tolerance or repellence against both aphids and thrips. Data presented in this study could be used to assist further genetic studies and breeding efforts to obtain Botritis and insect resistance for B. rapa.

• Journal of the Korean Society of Safety
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• v.37 no.1
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• pp.12-19
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• 2022

Circuit breakers are a crucial factor in ensuring the safety of a Direct Current (DC) grid. One type of DC circuit breaker, the Z-source DC circuit breaker (ZCB), uses a thyristor, which is a type of semiconductor switch. In the event of a fault in the circuit, the ZCB isolates the fault by generating a zero crossing current in the thyristor. The thyristor quickly and actively isolates the fault while generating a zero crossing current, but thyristor switch cannot control turn-off and the allowable current is lower than the current of the mechanical switch. Therefore, it is best to use a mechanical switch with a high allowable current capacity that is capable of on/off control. Due to the slow reaction time of mechanical switches, they may not isolate the fault during the zero crossing current time interval created by the existing circuit. In this case, the zero crossing current time can be increased by using the property that hinders the rapid change in the current of the inductor. This paper will explore whether adding system inductance to increase the zero crossing current time interval is a solution to this problem. The simulation of changing inductor and capacitor (LC) of the circuit is repeated to find an optimal change in the zero crossing current time according to the LC change and provides an inductor and capacitor range optimized for a specific load. The inductor and capacitor range are expected to provide optimization information in the form LC values for future applications of ZCB's using a mechanical switch.

• 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 Korean Society of Environmental Engineers
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• v.28 no.7
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• pp.757-763
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• 2006

In our previous studies, we have isolated bacteria from BTEX-contaminated sediment, which utilized BTEX as a sole carbon source and $NO_3$-N as an electron acceptor. For the possibility of field application, we have applied co-culture of those isolates in the BTEX-contaminated soil and evaluated their biodegradation efficiencies. To investigate the relationship between the isolates and indigenous microorganism in soil, changes of microbial community structure in soil samples with respect to time were monitored. To examine this, soil samples were artificially contaminated with benzene, toluene, ethylbenzene and o-xylene. BTEX-degrading bacteria such as Pseudomonas stutzeri strain 15(DQ 202712), Klebsiells sp. strain 20(DQ 202715) and Citrobacter sp. strain A(DQ 202713) were injected into the soil samples in the ratio of 2:1:1. Our results showed that the highest BTEX biodegradation efficiency was achieved when both BTEX and $NO_3-N$ existed simultaneously. The change in soil microbial community structure was characterized by PCR-DGGE analysis comparing the relative DGGE band intensities. The band intensities of indigenous microorganisms in the soil were reduced by injecting co-culture of the three isolates. On the contrary, the relative band intensities of the isolates were increased. Among the three isolates, Pseudomonas stutzeri strain 15 rendered the highest band intensity. This indicates that the Pseudomonas stutzeri was the dominant microbial species found in the soil samples.

• 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.

• Korean Journal of Food Science and Technology
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• v.33 no.5
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• pp.582-588
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• 2001

To control the growth of Salmonella on raw chicken supplied in food service, they were isolated and analysed for their physiological characteristics. Total viable microbe counts under the skin of the chicken amounted to 10% of numbers on their skin. Fifty one of Salmonella were isolated and identified from 75 chicken carcass samples. About 70% of the isolates showed resistance to more than four antibiotics, which indicated very high resistance among the strains ever reported in Korea. Lactic acid and trisodium phosphate(TSP) as sanitizing agent were applied to the Salmonella spp. isolates by agar diffusion method. The resistance by isolates to those sanitizing agents was compared with type strains of S. typhimurium ATCC 14028, S. typhimurium ATCC 12023, S. heidelberg and S. enteritidis. The isolates showed similar or less resistance to the type strains as for the lactic acid. However, as for trisodium phosphate known recently as a good sanitizer, 50% of the isolates showed more resistant compared with the type strains. Also, the treatment time and regeneration medium affected significantly the resistance of the isolates, which indicates that more careful test might be needed for TSP's practical application to raw chicken. Therefore, From the results, it is suggested that antibiotic treatment during breeding broiler and contamination after slaughtering should be minimized along with careful use of sanitizing agent in order to ensure more safe raw chicken supply.

• Korean Journal Plant Pathology
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• v.1 no.1
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• pp.38-43
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• 1985

A bacterial brown stripe disease new to Korea was noted for the first time on rice seedlings grown in the nursery pots and in a field nursery. Artificial hypodermic injection and pricking inoculation with isolates obtained from lesions of naturally infected plants produced symptoms similar to those occurring under natural condition. Among eleven species of ten genera of gramineous plants Echinochloa crusgalli, Digitaria sanguinalis and Setaria viridis were the new hosts for the pathogen. On the basis of bacteriological and biochemical tests of isolates from infected rice seedlings, the causal bacterium is considered to be Pseudomonas avenae Manns.

• Korean Journal of Microbiology
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• v.12 no.1
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• pp.37-51
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• 1974

Three strains which accumulated large quantities of L-hlutamic acid as the chief product of metabolism in the presence of glucose and inorhanic ammonium salt under the aerobic condition sere newly isolated. These strains have the general characters as follows: Gram-positive, short fod-shaped, non-sporulating, non-motile, and facultative anaerobe. A change of cell shates was not almost observed in their life cycles and neither a phenomenon of cell-elongation nor a pleomorphism was recognized in any cases. Together with rigid stability in Gram-stain, these characters as above indicated evidences that newly isolates would belong to genus Brevibacterium clearly differentiated from genus Corynebacterium. At the same time the newly isolates, in addition to nutritional requirement of biotin and thiamine, showed the distinctive character of requirement of special amino acid such as histidine or cysteine for their considerable growth. These physiological characters including nitrates reduction, reaction on milk, and slow formation of acid from sugar also were useful in confirming that these bacteria would be Brevibacterium ammoniagenes.

• Journal of Environmental Health Sciences
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• v.29 no.4
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• pp.1-3
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• 2003

Jinyangho is a natural water supply source of tap water in west Gyeongnam area, but mass mortality of crusian carp occurred during the time of temperature rise in spring. Examinations on diseased fishes were able to isolate four bacteria isolates and then identified the bacteria as a member of Aeromonas sp. Challenge experiment with mirror carp (Gyrinus carpiospecilaris) was proved the virulence, the isolates were in turn believed as the causative agent of mass mortality in Jinyangho.