• Title/Summary/Keyword: correlation coefficients.

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Study on the Chemical Management - 2. Comparison of Classification and Health Index of Chemicals Regulated by the Ministry of Environment and the Ministry of the Employment and Labor (화학물질 관리 연구-2. 환경부와 고용노동부의 관리 화학물질의 구분, 노출기준 및 독성 지표 등의 특성 비교)

  • Kim, Sunju;Yoon, Chungsik;Ham, Seunghon;Park, Jihoon;Kim, Songha;Kim, Yuna;Lee, Jieun;Lee, Sangah;Park, Donguk;Lee, Kwonseob;Ha, Kwonchul
    • Journal of Korean Society of Occupational and Environmental Hygiene
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    • v.25 no.1
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    • pp.58-71
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    • 2015
  • Objectives: The aims of this study were to investigate the classification system of chemical substances in the Occupational Safety and Health Act(OSHA) and Chemical Substances Control Act(CSCA) and to compare several health indices (i.e., Time Weighted Average (TWA), Lethal Dose ($LD_{50}$), and Lethal Concentration ($LC_{50}$) of chemical substances by categories in each law. Methods: The chemicals regulated by each law were classified by the specific categories provided in the respective law; seven categories for OSHA (chemicals with OELs, chemicals prohibited from manufacturing, etc., chemicals requiring approval, chemicals kept below permissible limits, chemicals requiring workplace monitoring, chemicals requiring special management, and chemicals requiring special heath diagnosis) and five categories from the CSCA(poisonous substances, permitted substances, restricted substances, prohibited substances, and substances requiring preparation for accidents). Information on physicochemical properties, health indices including CMR characteristics, $LD_{50}$ and $LD_{50}$ were searched from the homepages of the Korean Occupational and Safety Agency and the National Institute of Environmental Research, etc. Statistical analysis was conducted for comparison between TWA and health index for each category. Results: The number of chemicals based on CAS numbers was different from the numbers of series of chemicals listed in each law because of repeat listings due to different names (e.g., glycol monoethylether vs. 2-ethoxy ethanol) and grouping of different chemicals under the same serial number(i.e., five different benzidine-related chemicals were categorized under one serial number(06-4-13) as prohibited substances under the CSCA). A total of 722 chemicals and 995 chemicals were listed at the OSHA and its sub-regulations and CSCA and its sub-regulations, respectively. Among these, 36.8% based on OSHA chemicals and 26.7% based on CSCA chemicals were regulated simultaneously through both laws. The correlation coefficients between TWA and $LC_{50}$ and between TWA and $LD_{50}$, were 0.641 and 0.506, respectively. The geometric mean values of TWA calculated by each category in both laws have no tendency according to category. The patterns of cumulative graph for TWA, $LD_{50}$, $LC_{50}$ were similar to the chemicals regulated by OHSA and CCSA, but their median values were lower for CCSA regulated chemicals than OSHA regulated chemicals. The GM of carcinogenic chemicals under the OSHA was significantly lower than non-CMR chemicals($2.21mg/m^3$ vs $5.69mg/m^3$, p=0.006), while there was no significant difference in CSCA chemicals($0.85mg/m^3$ vs $1.04mg/m^3$, p=0.448). $LC_{50}$ showed no significant difference between carcinogens, mutagens, reproductive toxic chemicals and non-CMR chemicals in both laws' regulated chemicals, while there was a difference between carcinogens and non-CMR chemicals in $LD_{50}$ of the CSCA. Conclusions: This study found that there was no specific tendency or significant difference in health indicessuch TWA, $LD_{50}$ and $LC_{50}$ in subcategories of chemicals as classified by the Ministry of Labor and Employment and the Ministry of Environment. Considering the background and the purpose of each law, collaboration for harmonization in chemical categorizing and regulation is necessary.

Development and Validation of Analytical Method for Wogonin, Quercetin, and Quercetin-3-O-glucuronide in Extracts of Nelumbo nucifera, Morus alba L., and Raphanus sativus Mixture (연잎, 상엽, 건조 무 혼합 추출물의 지표성분 wogonin, quercetin 및 quercetin-3-O-glucuronide의 분석법 개발 및 검증)

  • Jang, Gill-Woong;Park, Eun-Young;Choi, Seung-Hyun;Choi, Sun-il;Cho, Bong-Yeon;Sim, Wan-Sup;Han, Xinggao;Cho, Hyun-Duk;Lee, Ok-Hwan
    • Journal of Food Hygiene and Safety
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    • v.33 no.4
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    • pp.289-295
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    • 2018
  • The aim of this study was to develop and validate an analytical method for determining the presence of wogonin, quercetin, and quercetin-3-O-glucuronide in extracts of Nelumbo nucifera, Morus alba L., and Raphanus sativus mixtures. We evaluated the specificity, linearity, precision, accuracy, limit of detection (LOD), and limit of quantification (LOQ) of analytical methods for wogonin, quercetin, and quercetin-3-O-glucuronide using high performance liquid chromatography. Our result showed that the correlation coefficients of the calibration curve for wogonin, quercetin, and quercetin-3-O-glucuronide were 0.9999. The LOD for wogonin, quercetin, and quercetin-3-O-glucuronide ranged from 0.09 to 0.16 and those for the LOQ ranged from 0.26 to $0.48{\mu}g/mL$. The inter-day and intra-day precision values of wogonin, quercetin, and quercetin-3-O-glucuronide ranged from 0.74 to 1.87 and from 0.28 to 1.12%, respectively. The inter-day and intra-day accuracies were 99.96~115.88% and 99.73~114.81%, respectively. Therefore, the analytical method was validated for the detection of wogonin, quercetin, and quercetin-3-O-glucuronide in extracts of Nelumbo nucifera, Morus alba L., and Raphanus sativus mixtures.

Establishment of analytical methods for HPHC list of mainstream cigarette smoke (담배 주류연 중 7개 그룹의 유해성분(HPHC) 분석법 확립 및 유효성 평가)

  • Park, Hyoung-Joon;Lee, Jin-Hee;Cho, So-Hyun;Heo, Seok;Yoon, Chang-yong;Baek, Sun-Young
    • Analytical Science and Technology
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    • v.28 no.6
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    • pp.385-397
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    • 2015
  • Harmful and potentially harmful constituents (HPHCs) are chemical compounds in tobacco smoke that cause harm to smokers and non-smokers. This study established and validated methods for the analysis of HPHCs from mainstream cigarette smoke. The analyzed HPHCs were categorized into seven groups: aromatic amines, volatile organic compounds (VOCs), heavy metals, tobacco specific nitrosamines (TSNAs), benzo[a]pyrene (B[a]P), ammonia, and carbonyl compounds. The methods were validated by specificity, linearity, limit of detection (LOD), accuracy, precision, and recovery. These validated methods were then applied to the reference cigarettes (1R5F, 3R4F). The correlation coefficients (r2) for the calibration curves of the seven groups were over 0.995. The LODs showed values of 0.01-0.04 ng/cig cig for aromatic amines, 0.01-0.16 μg/cig for VOCs, 0.01-1.27 ng/cig for heavy metals, 0.06-0.28 ng/cig for TSNAs, 0.04 ng/cig for benzo[a]pyrene, 0.08 μg/cig for ammonia, and 0.78-1.77 μg/cig for carbonyl compounds. The precisions obtained from the intra and inter-day batches were less than 15%. The accuracy and the recovery range were less than 15% and 79.2-117.5%, respectively. The proposed methods can therefore be applied for determining HPHCs in tobacco mainstream smoke.

The Partitioning Characteristics of Heavy Metals in Soils of Ulsan by Sequential Extraction Procedures (단계별추출법에 의한 울산지역 토양 중의 중금속 Partitioning 특성연구)

  • Lee, Byeong-Kyu;Koh, Il-Ha;Kim, Haeng-Ah
    • Journal of Korean Society of Environmental Engineers
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    • v.27 no.1
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    • pp.25-35
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    • 2005
  • This study analyzed total concentrations and existing forms of heavy metals in soils of Ulsan using a sequential extraction method. Soil samples were collected from 6 categorized areas including green, residential, heavy traffic, petrochemical industrial complex(IC), mechanical and shipbuilding IC, and non-ferrous metal IC areas. which represent different emission characteristics. The highest total concentrations of heavy metals by a sequential extraction analysis were observed in the soils collected from the non-ferrous metal IC area, followed by the mechanical and shipbuilding IC and heavy traffic areas. Dominant(> 50%) existing forms of Cd, Cr and Ni were residual forms followed by Fe and Mn oxides in almost areas. Residual fractions in the non-ferrous metal IC areas were relatively lower than those in other areas. However, the fractions of organic and sulphides in the IC areas were higher. The dominant farms of Cu were much different with the investigated areas. In most areas, the dominant forms of Pb and Zn were Fe and Mn oxides, followed by residual fraction for Pb. The exchangeable and carbonate fractions represent mobility of metallic elements in soils. They are also significantly affected by the environmental renditions, such as pHs of soil and rainfall. In this study the exchangeable and carbonate fractions were lower than other fractions. Because the total concentrations of heavy metals in the soils of the non-ferrous metal IC area were extremely high, however, the mobile fractions of heavy metals in the IC area would be significant. Thus a large amount of heavy metals can be released into plants, water bodies, and soils. Therefore, urgent measures, such as source control for soil remediation of heavy metals, in the non-ferrous metal IC areas are essentially required. Analysis results obtained from the sequential extraction and the aqua regia extraction showed a high correlation, whose determination coefficients(R2) of heavy metals except Cd approximately ranged from 0.7 to 0.9.

An Analysis on Characteristics of Turbulence Energy Dissipation Rate from Comparison of Wind Profiler and Rawinsonde (연직바람관측장비와 레윈존데의 비교를 통한 난류 에너지 감소률의 특성 분석)

  • Kang, Woo Kyeong;Moon, Yun Seob;Jung, Ok Jin
    • Journal of the Korean earth science society
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    • v.37 no.7
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    • pp.448-464
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    • 2016
  • The purpose of this study is to optimize the parameters related to consensus coherency within the PCL 1300, the operating program of wind profiler, from a validation of wind data between rawinsonde and wind profiler at Chupungryeong ($36^{\circ}13^{\prime}$, $127^{\circ}59^{\prime}$) site in Korea. It is then to analyze the diurnal and seasonal characteristics of the turbulence energy dissipation rate (${\varepsilon}$) in clear and rainy days from March 2009 to February 2010. In comparison of the wind data between wind profiler and rawinsonde during April 22-23, 2010, it was shown in a big error more than $10ms^{-1}$ over the height of 3,000 meters in the zonal (u) and meridional (v) wind components. When removing more than $10ms^{-1}$ in each wind speed difference of u an v components between the two instruments, the correlation coefficients of these wind components were 0.92 and 0.88, respectively, and the root mean square errors were 3.07 and $1.06ms^{-1}$. Based on these results, when the data processing time and the minimum available data within the PCL 1300 program were adjusted as 30 minutes and 60%, respectively, the bias errors were small. In addition, as a result of an analysis of sensitivity to consensus coherency of u and v components within the PCL1300 program, u components were underestimated in radial coherency, instantaneous and winbarbs coherency, whereas v components were overestimated. Finally by optimizing parameters of the PCL1300 program, the diurnal and seasonal means of ${\varepsilon}$ at each height were higher in rainy days than those in clear days because of increasing in the vertical wind speed due to upward and downward motions. The mean ${\varepsilon}$ for clear and rainy days in winter was lower than those of other seasons, due to stronger horizontal wind speed in winter than those in other seasons. Consequently, when the turbulence energy dissipation rates in the vertical wind speed of more than ${\pm}10cm\;s^{-1}$ were excluded for clear and rainy days, the mean ${\varepsilon}$ in rainy days was 6-7 times higher than that in clear days, but when considering them, it was 4-5 times higher.

A Study on the Functional Status in Life and Life Satisfaction for Elderly Residing at Home - Comparing Urban and Rural Elderly - (재택노인의 생활기능상태와 생활만족도에 관한 연구)

  • 이재면
    • Korean Journal of Health Education and Promotion
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    • v.12 no.2
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    • pp.109-119
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    • 1995
  • As the population of elderly in Korea is increasing rapidly since the 1990's and will more rapidly in the 21st Century, the demand of their health care would be a great burden to health care expenditure. Then it would be necessary to contemplate the functional status and life satisfaction for elderly to make them live more independently. The objectives of this study were find out the functional status in life and life satisfaction for the elderly aged 65 or over who had resided in urban area of two Gus in Pusan and rural area of two Myuns in Haman Gun in Kyeognam Province, and to provide basic data for planning systematic health care programme. The study period was two weeks from February 6 to February 18, 1995 and the subjects were 274 elderly of which 143 were urban residents, 131 were rural residents, and the study method was by structured questionnaire. The data were analyzed with SAS/PC/sup +/ programme using Chi-square test, t-test, ANOVA, Pearson's correlation coefficients, and multiple regression analysis. The results were as follows; 1. To see the pattern of living together, those living with partners were the most common, 39.1% ; 37.8% of urban elderly lived with married sons, 32.2% of them lived with partners, but 46.6% of rural elderly lived with partners, 16.8% of them lived with married sons, which showed difference between residence(p<0.005). 2. Elderly who had jobs were 64.1% in rural residents, and 7.7% in urban residents, which showed significant difference(p<0.05). 3. The score of cognitive function of total subjects was 24.7, that of urban elderly was 23.8, and that of rural elderly was 25.7, then it was higher in rural ones and low for old-elders and those who had no jobs. 4. The score of PADL was 26.8 for urban elderly, 30.1 for rural elderly, and that of IADL was 22.2 for urban elderly, 25.6 for rural elderly, which showed higher activities of daily living for rural elderly than urban elderly(p<0.001). 5. The score of domestic performance was 21.9 for urban elderly, and 30.5 for rural elderly, which showed higher score for rural elderly(p<0.001). 6. The score of life satisfaction was 20.7 for urban elderly, 29.8 for rural elderly, then it was higher for rural elderly(p<0.01). 7. As a result of ANOVA for functional status in living by general characteristics; the score of cognitive function differed by age, job; that of PADL differed by age, job, education, and the pattern of living together, that of IADL differed by age, job, and the pattern of living together. The score of domestic role performance differed by age, job, marital status, and the pattern of living together. 8. ANOVA for life satisfaction showed that the score of life satisfaction differed by job(p<0.001) and the pattern of living together(p<0.01). 9. The correlations between functional status in living and life satisfaction showed that the higher the score of cognitive function was(r=0.39), the higher the score of activities of daily living was(r=0.50), and the higher the score of domestic role performance was(r=0.41), the higher the score of life satisfaction. 10. Stepwise multiple regression analysis for life satisfaction pointed out that residence was responsible for 39.9% of the variance. cognitive function was for 5.3%, and domestic role performance was for 1.2%.

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Relationships between Insensible Perspiration and Thermo Physiological Factors during Wearing Seasonal Clothing Ensembles in Comfort (쾌적한 상태에서 계절별 의복을 착용하고 있는 동안 불감증설과 온열 생리 요소들 간의 관련성)

  • Lee, Joo-Young;Choi, Jeong-Wha;Park, Joon-Hee
    • Journal of the Korean Society of Clothing and Textiles
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    • v.31 no.12
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    • pp.1700-1709
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    • 2007
  • The purpose of this study was to examine the relationships between thermo-physiological factors and the insensible loss of body weight(IL) of resting women wearing seasonal comfortable clothing. Air temperature was maintained at a mean of 22.5, 24.7, and 16.8 for spring/fall, summer and winter, respectively. We selected a total of 26 clothing ensembles(8 ensembles for spring/fall, 7 ensembles for summer, and 11 ensembles for winter). The results showed that 1) IL was $19{\pm}5g{\cdot}m^{-2}{\cdot}hr$ for spring/fall environment, $21{\pm}5g{\cdot}m^{-2}{\cdot}hr$ for summer, $18{\pm}6{\cdot}m^{-2}{\cdot}hr$ for winter(p<.001). 2) Insensible water loss through respiratory passage(IWR) showed the reverse tendency to IL. IWR was $6{\pm}1g{\cdot}m^{-2}{\cdot}hr$ for winter and $5{\pm}1g{\cdot}m^{-2}{\cdot}hr$ for summer. This difference was significant(p<.001). 3) The proportion of IWR out of whole insensible water loss(IW), had a mean of the mean 28% for summer and 38% for winter(p<.001). 4) In comfort, the heat loss by IW out of heat production had a mean of 25% for spring/fall, 27% for summer, and 23% for winter. 5) There was a weak negative correlation between It and clothing insulation/body surface area covered by clothing. 6) There were significant correlations between IL and air temperature$(T_a)$, air humidity$(H_a)$, energy metabolism, ventilation, mean skin temperature $\={T}_{sk})$ and clothing microclimate humidity$(H_{clo})$. However, the coefficients were less than 0.5. In conclusion, there were weak relationships between the IL and thermo-physiological factors. However, when subjects rested in thermal comfort, the IL was maintained in a narrow range even though the clothing insulation and air temperature were diverse.

Ultrasensitive Enzymeimmunoassay for Testosterone in Human Saliva (사람 타액내 Testosterone의 초감도 효소면역측정법)

  • 윤용달;전은현;이창주;도병록;이준영
    • Development and Reproduction
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    • v.4 no.1
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    • pp.115-123
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    • 2000
  • A few enzymeimmunoassay (EfA) for testosterone (T) have been reported but was not suitable for all biological samples. The present study was designed to develop a rapid, ultrasensitive EIA and to apply this technique for study the physiological changes of T in biological samples. Saliva samples were collected at 06:00~09:00 hour during one menstrual cycle from 18 normally menstruating women and on 09:00~10:00 hour from 20 normal men. The present study shows an established EIA for testosterone, using horseradish peroxidase (HRP), which was covalently bonded to testosterone-3-carboxymethyloxime (T-3-CMO). One batch of T-antisera was also covalently linked to microcrystalline cellulose particles by a mixed anhydride method in order to facilitate separation of bound and free steroids. The established EIA was validated in terms of sensitivity, accuracy, specificity, precisions etc., comparing with conventional radioimmunoassay. The sensitivity of the established EIA was less than 25 pg/tube. The correlation coefficients between the expected T-values and observed T-values measured by EIA or RIA were r=0.985 and r=0.941 respectively. The cross reactivity of antiserum in EIA was a little higher than that of RIA, especially by 5 ${\alpha}$-DHT. The intra- and inter-assay precisions of the present EIA were similar to those of RIA. The present study also demonstrates that the normal T-values in saliva of Korean male & female samples are 265.65${\pm}$15.80 pmol/l and 109.74${\pm}$ 12.01 pmol/l, respectively. The present EIA seems to be established and suitable for use in the endocrinological studies. The advantages of this EIA system also might make the present T-EIA an ideal procedure for use in a routine assay of ordinary laboratory with a conventional spectrophotometer.

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An Observation Study on the Health Benefits of Fermented Milk in Relation to Gastrointestinal Diseases Prevention in Korean (유산균발효유(乳酸菌醱酵乳)의 음용(飮用)이 소화기질환(消化器疾患) 예방(豫防)에 미친 효과(效果)에 관한 조사연구(調査硏究))

  • Lee, Won-Chang;Yoon, Yoh-Chang
    • Journal of Dairy Science and Biotechnology
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    • v.14 no.1
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    • pp.57-69
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    • 1996
  • This study was desiged to carry out an observation study on the cognitive level of health benefitis of fermented milk and subsequntly, on prevention of gastrointestinal diseases for the consumers in Korea. Data used in this study were collected from two different source ; 1) 987 university students living in Seoul, were selected randomly and interviwed induvidual from May 25 to September 30 1994, to investigate the awareness status as a consomer of fermented milk, and 2) health benefits of fermented milk with respect to prevention gastric intestinal diseases such as typhoid fever, paratyphoid fever and bacillary dysentery in Korea with the raw data from the Yearbook of Health and Social Statistics by Ministry of Health and Social Affairs (1976${\sim}$1995) and Ministry of Agriculture, Forestry & Fisheries (1976${\sim}$1995), Republic of Korea. The results of this study were as follows : The effects of femented milk on health appeared to be attributed to taking care of an environment of the gastrointestinal tract regarding diarrhea, constipation and digestion, with showing 75.1% of male and 71.1% of female of university students in Seoul answered positively, The correlation coefficients of statistics between amounts of consumption per capita of fermented milk and incidence rates of gastrointestinal diseases during the period from 1975 to 1994 in the whole country was r = -0.308 (p<0.05). those of Seoul a major comsuming area of fermented milk in the country and Kangwon province, a minor consuming area were r = -0.704 (p<0.01) and r = +0.262 (n.s.), respectively. In conclusion, the results obtained in this study suggest that fermented milk exert its effect on gastrointestinal tract. Furthermore, the results warrant a futher study in the field of preventive medicine and health science with respect to efficacy of fermented milk consumption.

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Drug Resistance Patterns of the Bacterial Strains Isolated from Rural Areas and an Urban General Hospital (무의촌균주(無醫村菌株) 및 병원균주(病院菌株)의 항균제(抗菌劑) 내성(耐性) 양상(樣相)에 관(關)한 연구(硏究))

  • Rhee, Kwang-Ho;Kim, Ik-Sang;Shin, Hee-Sup;Cha, Chang-Yong;Lee, Seung-Hoon;Chang, Woo-Hyun;Lim, Jung-Kyoo
    • The Journal of the Korean Society for Microbiology
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    • v.15 no.1
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    • pp.19-32
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    • 1980
  • Besides the benefits of antimicrobial agents in the control of various infectious diseases, widespread and prolonged use of particular antimicrobial agents has brought about the increase of drug-resistant strains in a community and the profound changes in the pattern of infectious diseases. In Korea, there are some remote villages where no clinics and drug stores are available and the residents in those areas are assumed to have fewer chances to contact with antimicrobial agents. In the present study, the differences in susceptibilities to 14 antimicrobial agents between the isolates from rural areas(R) and Seoul National University Hospital(SNUH, H) were studied. The isolates and their numbers were Staphylococcus aureus, R;55, H;68), Enterococci(R;28, H;30), Escherichia coli(R;40, H;40), Enterobacter aerogenes(R;25, H;21) and Klebsiella pneunoniae(R;58, H;67). Minimal inhibitory concentrations(MIC's) of penicillin, ampicillin, carbenicillin, cephalexin, tetracycline, oxytetracyline, doxycycline, minocycline, gentamicin, kanamycin, streptomycin, erythromycin, troleandomycin and co-trimoxazole were determined by agar dilution method. I. Comparison of MIC's and resistant strain proportions between isolates from SNUH and rural areas. MIC's and/or resistant strain proportions of the isolates from SNUH were significantly higher than those of the isolates from rural areas in the cases of 1. S. aureus to doxycycline, streptomycin and kanamycin. 2. E. coli to penicillin, ampicillin, carbenicillin, tetracycline, oxytetracycline, doxycycline, minocycline, streptomycin, kanamycin, erythromycin and co-trimoxazole. 3. E. aerogences to carbenicillin, tetracycline, oxytetracycline, doxycycline, minocycline, streptomycin, kanamycin, genaamicin and co-trimoxazole. 4. K pneunoniae to penicillin, ampicillin, tetracycline, oxytetracycline, doxycycline, monocycline, streptomycin, kanamycine, gentamicin and co-trimoxazole. However, the mean MIC and resistant strain proportion of S. aureus to tetracycline were higher in isolates from rural areas than in those from SNUH and Enterococci showed no differences in susceptibilities to the antimicrobial agents between isolates from rural areas and from SNUH. Therefore, in general, differenes in susceptibility to these antimicrobial agents between the isolates from rural areas and SNUH were remarkably greater and broader in gram negative enteric bacteria. II. Multiple drug resistance pattern. Patterns and incidences of multiple drug resistance were studied with penicillin, ampicillin, tetracycline, cephalexin, gentamicin, streptomcin, kanamycin and co-trimoxazole in Enterococci, E. coli, E. aeroges and K. pneumoniae. There appeared significant differences in the incidence of multiply drug-resistant strains and multiple drug resistance patterns between the isolates from SNUH and rural areas in Enterococci, E. coli, E. aerogenes and K. pneumoniae. However, there was no difference in the incidence of multiply drug-resistant strains between isolates of S. aureus from SNUH and rural areas but the pattern of multiple resistance of the SNUH strains of S. aureus was diverse, while that of the rural strains was predominantly confined to penicillin-tetracycline combination. The incidence of multigly drug-resistant strains and diversity of their patterns were the highest in E. coli strains isolated from SNUH and there were no multiply drug resistant strrains in Enterococci and K. pneumoniae strains isolated from rural areas. The number of drug-resistance determinants was also different between the isolates from rural areas and SNUH. Most of the multiply drug-resistant strains of E. coli, E. aerogenes and K. pneumoniae isolated from SNUH were resistant to more than 3 kinds of antimicrobial agents, most frequently to ampicillin, tetracycline and streptomycin, while multiply drug-resistant strains from rural areas were resistant to 2 kinds of antimicrobial agents among ampicillin, tetracycline and streptomycin. With drug-resistant E. coli strains, resistance to tetracycline which was used most widely since 1951 was most frequently involved as a part of mutliple drug-resistance, followed by resistance to ampicillin and streptomycin. This strongly suggests that emergence of drug-restant strains in a community is directly dependent on the selective pressure exerted by the antimicrobial agent used. III. Cross resistance. Cross resistance of bacteria was studied among tetracycline penicillin, aminoglycoside and macrolide derivatives by analyzing correlation coefficients of sucseptibilities using the least square method. In this study, there were high correlations among the susceptibilities to related derivatives. It appears that the relatively low correlations in susceptibilities present in some cases are due to intrinsic resistance of E. aerogenes to penicillin, Enterococci to aminoglycoside and E. coli E. aerogenes and K. pneumoniae to macrolide derivatives.

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