• Journal of Yeungnam Medical Science
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• v.6 no.2
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• pp.195-205
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• 1989

Development of drug resistance in tumors during treatment is a major factor limiting the clinical use of anticancer agents. When tumor cells acquire resistance to anticancer drug, they show cross-resistance to other antitumor agents. In the present study, SNU-1 cell was induced adriamycin $10^{-7}M$ drug resistance, SNU-1/ADR, in vitro culture system. We got the doubling time and number for viability test during 96 hours by MTT assay. To investigate the cross resistance of various anticancer drugs in human stomach cancer cell SNU-1 and SNU-1/ADR. We compared $IC_{50}$ (drug concentration of 50% reduction) and the relative resistance(RR). SNU-1/ADR was expressed multidrug resistant with vinblastine(RR ; 31.62), vincristine(RR ; 29.50), dactinomycin(RR ; 21.37), epirubicin(RR ; 17.78), daunorubicin(RR ; 14.12), adriamycin(RR ; 7.76), and etoposide(RR ; 4.46), and other drugs, 5-fluorouracil, cisplatin, cyclophosphamide, methotrexate, and aclarubicin, have not cross resistant with adriamycin. There was double minute chromosome in SNU-1/ADR by karyotyping although this change was not seen in SNU-1.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.7
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• pp.676-681
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• 2010

Antibiotic resistant bacteria were isolated from livestock wastes and the resistance patterns were investigated using various antibiotic agents. Also, a gamma ray was tested regarding the aspects of the effect on resistance pattern and the efficiency of disinfection. Among the isolates, Esherichia coli and Brevibacterium sp. showed the most serious resistance patterns. Esherichia coli had resistance against 9 agents whereas Brevibacterium sp. against 7 agents. It can be suggested from these results that the abuse of antibiotic agents will cause a serious mutation problem even to Esherichia coli which is ubiquitous in the ecosystem. Esherichia coli could be easily controlled but Brevibacterium sp. had a moderate resistance to the gamma ray under low doses. In the case of Brevibacterium sp, more than 2.0 kGy of a radiation dose will be required in order to achieve an enhanced efficiency of disinfection.

• Tuberculosis and Respiratory Diseases
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• v.66 no.3
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• pp.198-204
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• 2009

Background: First-line drugs, if sensitive, are the most potent drugs in the treatment of multidrug-resistant tuberculosis (MDR-TB). This study examined the frequency and risk factors associated with acquired drug resistance to first-line drugs during a standardized treatment using first-line drugs in patients with MDR-TB. Methods: This study included patients who were diagnosed with MDR-TB at the National Masan Tuberculosis Hospital between January 2004 and May 2008, treated with standardized first-line drugs, and for whom the preand post-treatment results of the drug susceptibility test were available. Their medical records were reviewed retrospectively. Results: Of 41 MDR-TB patients, 14 (34.1%) acquired additional resistance to ethambutol (EMB) or pyrazinamide (PZA). Of 11 patients initially resistant to isoniazid (INH) and rifampicin (RFP), 3 (27.3%) acquired additional resistance to both EMB and PZA, and 3 (27.3%) to PZA. Of 18 patients initially resistant to INH, RFP and EMB, 6 (33.3%) acquired additional resistance to PZA. Of 6 patients initially resistant to INH, RFP and PZA, 2 (33.3%) acquired additional resistance to EMB. Ten of the 41 MDR-TB patients (24.4%) changed from resistant to susceptible. No statistically significant risk factors associated with acquired resistance could be found. Conclusion: First-line drugs should be used cautiously in the treatment of MDR-TB in Korea considering the potential acquisition of drug resistance.

• Journal of Life Science
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• v.29 no.12
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• pp.1401-1407
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• 2019

To elucidate whether or not solvent-tolerant bacteria use anti-oxidative defense systems to defend themselves against toxic solvents, oxidative enzyme activity and total anti-oxidative capacity (T-AOC) were investigated in two tolerant strains of Pseudomonas sp. under toluene stress. The superoxide dismutase (SOD) activities of solvent tolerant BCNU 106 exhibited relatively increased levels at a toluene concentration of 100 mg/l, where those of solvent tolerant BCNU 171 increased at 200 mg/l. A greater than three-fold increase in catalase (CAT) levels was observed at concentrations of 200 and 300 mg/l in BCNU 106, and a two-fold increase was monitored at the same concentrations in BCNU 171. High glutathione S-transferase (GST) levels were also observed in the solvent tolerant bacteria. Higher levels of T-AOC was expressed in the solvent tolerant strains than in the ordinary non-tolerant KACC 10266. The highest plateau of SOD in BCNU 171 was observed at 1 hr of toluene exposure. CAT levels plateaued at 1 hr and 14 hr in BCNU 106 and reached the highest plateau at 3 hr in BCNU 171. The highest peak of T-AOC occurred at 9 hr in BCNU 106, and two high peaks occurred in BCNU 171, at 1 hr and at 9 hr of toluene exposure. The solvent-tolerant bacteria showed active antioxidant responses and could survive under harsh environments, including the presence of solvents, through means of antioxidant defense systems.

• The Journal of the Korean Society for Microbiology
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• v.13 no.1
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• pp.7-16
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• 1978

One hundred and three clinical isolates of enterococci were examined for susceptibility to 8 antibiotics, and transferability and transfer frequency of R plasmid. Ampicillin was the most active, followed in decreasing order by rifampin, amikacin and chloramphenicol, and tetracycline. High-level resistance(${\geq}2,000{\mu}g/ml$) to kanamycin, streptomycin, and gentamicin, known as the most active of the aminoglycosides to enterococcus, was present in 26.2%, 21.4%, and 18.3% of the isolates, respectively. In the drug susceptibility of the species, S. zymogenes was the most resistant and S. durans was the most sensitive to tested antibiotics. We could observed the transferability of enterococcal R plasmid in mixed culture: among the 28 strains which showed multiple drug resistance, 17 strains transferred all or part of their resistance with $2{\times}10^{-4}-2{\times}10^{-6}%$ of transfer frequency to a plasmid-free recipient, S. faecalis strain JH 2-2.

• Tuberculosis and Respiratory Diseases
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• v.38 no.2
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• pp.99-107
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• 1991

Drug resistance of M. tuberculosis has been investigated with isolates from patients screened out of the sample population of the nationwide tuberculosis prevalence surveys or from the routine cultures. The results showed a close inverse relationship between prevalence of drug resistance and efficiency of the past or current treatment regimens of NTP. Individual drug resistance also showed a close relationship with the extent of use of the relevant drugs. Drug resistance was found in 38.0% of M. tuberculosis isolates from patients found in 1965 survey and remained unchanged until it increased upto 48.0% in 1980 survey. The resistance prevalence, however, dropped to 30.8% in 1985 and further to 25.3% in 1990 survey. Such decrease was fairly well coincided with a continuous increase of the treatment efficiency (from 60% in 1984 to 77% in 1989) in 1980s. Initial drug resistance also showed a similar trend, namely 26.2% in 1965, 23.9% in 1970, 20.1% in 1975, 30.6% in 1980, 17.4% in 1985, and 15.0% in 1990. The similar figures were observed in M. tuberculosis isolates from patients diagnosed in the routine services. Higher prevalence of initial drug resistance was observed among urban patients than rural patients and among young patients than old patients. These findings signify that a continuous survey on drug resistance permits to monitor efficiency of treatment programme of the country.

• Pediatric Infection and Vaccine
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• v.22 no.3
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• pp.178-185
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• 2015

Purpose: We investigated trends in antibiotic pressure and the antibiotic susceptibility of gram negative bacteria isolated from Korean children over 10 consecutive years. Methods: From January 2004 to December 2013, the antibiotic susceptibility of Klebsiella pneumoniae, Escherichia coli, Pseudomonas aeruginosa, and Acinetobacter baumannii blood isolates obtained from children <18 years of age was determined according to the 2009 Clinical and Laboratory Standards Institute guidelines. Antibiotic consumption data were also analyzed. Results: The prevalence of K. pneumoniae, E. coli, P. aeruginosa, and A. baumannii bacteremia was 4.6, 3.5, 3.4, and 2.2 cases/1,000 blood cultures/year, respectively. In K. pneumoniae, resistance to the third and fourth cephalosporin did not increase significantly. However, carbapenem-resistant K. pneumoniae first appeared in 2010, and the resistance rate increased to 9% between 2012 and 2013. Resistance to 3rd and 4th cephalosporin increased from 10% to 50% in E. coli, and resistance to carbapenem rose abruptly from 11% to 71% in A. baumannii (P for trend <0.01). However, such an increase of resistance was not observed in P. aeruginosa. There is a positive correlation between the resistance rate of cefepime in E. coli and the consumption of cefepime (r=0.900, P=0.037). Conclusion: The significant burden of antibiotic consumption and the high prevalence of antibiotic resistance to gram negative pathogen isolated from bacteremic children were observed. Empirical antibiotics should be wisely selected, and continued efforts to decrease the overall antibiotic pressure are mandatory, especially in highly resistant situations.

• Pediatric Infection and Vaccine
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• v.27 no.3
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• pp.147-157
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• 2020

Purpose: We investigated the trend of antibiotic susceptibility of Haemophilus influenzae over 5 consecutive years. Methods: We analyzed the antibiotic susceptibility of H. influenzae isolated from children aged <18 years, who were admitted to the Asan Medical Center Children's Hospital from March 2014 to April 2019. Antibiotic susceptibility of H. influenzae was determined by the disk diffusion test according to the European Committee on Antimicrobial Susceptibility Testing guidelines. Results: Excluding duplicates, 69 isolates were obtained over the past 5 years. The median age of the patients was 5 years (range, 2.8-8.6 years). The antibiotic susceptibility patterns were as follows: ampicillin (AMP)-susceptible/amoxicillin-clavulanate (AMC)-susceptible (AS/ACS; n=15 [21.7%]), AMP-resistant/AMC-susceptible (AR/ACS; n=21 [30.4%]), and AMP-resistant/AMC-resistant (AR/ACR; n=33 [47.8%]). The prevalence of isolates with AR/ACR phenotype tended to increase from 42.1% in 2014-2015 to 54.5% in 2018-2019 (P=0.342). Compared to 2014-2015, the resistance rates to cefuroxime and ceftriaxone in 2018-2019 increased from 31.6% to 77.3% and from 0.0% to 59.1%, respectively (P=0.003 and P<0.001, respectively). Conclusions: Over the last 5 years, H. influenzae isolates with AR/ACR phenotype and ceftriaxone resistance were frequently observed at our institute. The incidence of resistance to cefuroxime and ceftriaxone has increased significantly.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.3 s.59
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• pp.105-115
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• 2006

지금까지 방사성 전자파 내성 시험과 ESD 내성 시험의 불확도에 대하여 IEC TC77B의 위원회안 진행문서를 중심으로 살펴보았다. 이 문서의 세부 내용에 대한 개정 작업이 진행 중이므로 최종 국제 규격은 수정되겠으나 전체적인 기조는 유지되리라 예상된다. 전자파 내성 시험 분야에서 불확도를 고려해야 하는 시기가 도래함에 따라 국내 전자파 적합성 시험 기관 및 산업체의 측정인(測定人)들이 한발 앞서 나가는데 본 내용이 도움이 되기를 바란다.

• ICROS
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• v.2 no.3
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• pp.25-41
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• 1996

본 고에서는 고장에 대한 내성을 갖는 로봇 시스템에 관련된 전반적인 연구분야에 대한 소개를 하였으며 구조적인 측면에 중점을 두어 기술되었으나, 고장에 내성을 갖는 위치/속도 센서, 힘/토크 센서 그리고 로봇 제어에 관련된 하드웨어와 소프트웨어 등과 같은 로봇 구성 요소들의 개발에 관한 연구, 고장이 발생하였을 경우에 수행중인 작업을 지속적으로 그리고 성공적으로 수행할 수 있도록 하는 고장회복을 위한 제어기법 등에 관한 구체적인 방법 등에 대하여 매우 활발한 연구가 필요된다. 마지막으로, 이러한 고장에 대한 내성을 갖는 로봇 매니퓰레이터의 개발에 관한 중요성이 인식되어 국내에서도 높은 관심과 더불어 활발한 연구가 진행되었으면 한다.