• 한국지하수토양환경학회:학술대회논문집
• /
• 한국지하수토양환경학회 2004년도 임시총회 및 추계학술발표회
• /
• pp.312-316
• /
• 2004

Single-well tracer tests, especially push pull tracer tests, are more effective to estimate hydraulic parameters and microbial metabolic activities in terms of duration and cost compared to multi-well tracer tests. However, there are some drawbacks in accuracy, complicated data analysis and uniqueness. These shortages are thought to be derived from the applied conditions which affect mass recovery curve and breakthrough curve. Factors such as extraction rate, resting period, hydraulic conductivity and hydraulic gradient are considered as the major factors determining the mass recovery rate and shape of the breakthrough curve. The results of the sensitivity analysis are summarized as follows: 1) the significant change in concentration of breakthrough curve is obtained when the extraction rate increases. This effect would also be much higher if the hydraulic conductivity is lower; 2) the mass recovery rate decreases with the increase of resting time, and the difference of mass recovery rates for different resting times is inversely proportional to the hydraulic conductivity; 3) the sensitivity values decrease with time. The hydraulic conductivity affects not only the early period, but the later period of the breakthrough curves; 4) The influence of the hydraulic gradient on the breakthrough curves is greater at earlier stage than at later stage. The mass recovery rate is inversely proportional to the hydraulic gradient.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
• /
• 제49권4호
• /
• pp.198-207
• /
• 2023

Objectives: This study investigated causative strains and their antibiotic sensitivity in patients who were hospitalized for maxillofacial odontogenic infections at a tertiary center in South Korea over the past 10 years with the aim of providing guidelines for the selection of appropriate empirical antibiotics. Materials and Methods: Patients with head and neck fascial space abscesses due to odontogenic infections who underwent incision and drainage surgery with pus culture tests between 2013 and 2022 at the Department of Oral and Maxillofacial Surgery, Dankook University Hospital were included. The bacterial isolates and antibiotic sensitivity of each strain were analyzed for 2013-2022, 2013-2017, and 2018-2022. The affected fascial spaces were classified into primary, secondary, and deep neck spaces. Results: In the 192 patients included in this study, 302 strains were detected. Viridans streptococcus had the highest frequency (51.7%), followed by Prevotella spp. (16.9%), Staphylococcus spp. (5.6%), and Klebsiella pneumoniae (4.6%). The identification rate of viridans streptococcus significantly increased from 41.8% in 2013-2017 to 60.9% in 2018-2022. Viridans streptococcus showed an antibiotic sensitivity of 80.5% to ampicillin; the sensitivity to penicillin antibiotics decreased over the study period. Antibiotic susceptibility was approximately 94% for third-generation cephalosporins. K. pneumoniae, which was identified at a high percentage in patients with deep neck space infection, showed increasing antibiotic resistance to most antibiotics over the study period. Conclusion: Viridans streptococcus was identified in head and neck fascial space abscesses with the highest frequency. Empirical antibiotics should be effective against this strain; penicillin antibiotics are considered inappropriate. For effective treatment of deep neck space abscesses, bacterial culture and antibiotic sensitivity tests performed as soon as possible are essential.

• Tuberculosis and Respiratory Diseases
• /
• 제39권1호
• /
• pp.1-6
• /
• 1992

The diagnosis of tuberculosis is usually established using staining and culturing techniques. Fluorescent stains have improved the sensitivity of direct microscopy. Improved culture media coupled with radiometric means of detecting early mycobacterial growth have shortened the time needed for cultural diagnosis. Rapid immunodiagnostic techniques based on the detection of mycobacterial antigen or of antibodies to theses antigens have not, however, come into widespread clinical use. The DNA or RNA hybridization tests with labeled specific probes which have been described so far are not sensitive enough to be used for clinical speicimens without prior culturing. The advent of the polymerase chain reaction (PCR) has opened new possibilities for diagnosis of microbial infections. This technique has already been applied to a number of microorganisms. In the field of mycobacteria the PCR has been used to identify and to detect DNAs extracted from various mycobacteria. However, despite the extraordinary enthusiasm surrounding this technique and the considerable investiment, PCR has not emerged from the developmental "trenches" in the passed several years. It may be a considerable lenth of time before clinical microbiology laboratories become PCR playgrounds because many details remain to be worked out.

• Journal of Microbiology
• /
• 제44권1호
• /
• pp.72-76
• /
• 2006

Plasma-derived products are produced from plasma via fractionation and chromatography techniques, but can also be produced by other methods. In the performance of nucleic acid amplification tests (NAT) with plasma-derived products, it is necessary to include an internal control for the monitoring of all procedures. In order to avoid false negative results, we confirmed the usefulness of the bovine viral diarrhoea virus (BVDV) for use as an internal control in the detection of hepatitis C virus (HCV) RNA in plasma-derived products. These products, which were spiked with BVDV, were extracted and then NAT was performed. Specificity and sensitivity were determined via the adjustment of primer concentrations and annealing temperatures. BVDV detection allows for validation in the extraction, reverse transcription, and amplification techniques used for HCV detection in plasma-derived products.

• International Journal of Oral Biology
• /
• 제48권2호
• /
• pp.9-18
• /
• 2023

The rapid detection of bacteria in the oral cavity, its species identification, and bacterial count determination are important to diagnose oral diseases caused by pathogenic bacteria. The existing clinical microbial diagnosis methods are time-consuming as they involve observing patients' samples under a microscope or culturing and confirming bacteria using polymerase chain reaction (PCR) kits, making the process complex. Therefore, it is required to analyze the development status of substances and systems that can rapidly detect and analyze pathogenic microorganisms in the oral cavity. With research advancements, a close relationship between oral and systemic diseases has been identified, making it crucial to identify the changes in the oral cavity bacterial composition. Additionally, an early and accurate diagnosis is essential for better prognosis in periodontal disease. However, most periodontal disease-causing pathogens are anaerobic bacteria, which are difficult to identify using conventional bacterial culture methods. Further, the existing PCR method takes a long time to detect and involves complicated stages. Therefore, to address these challenges, the concept of point-of-care (PoC) has emerged, leading to the study and implementation of various chair-side test methods. This study aims to investigate the different PoC diagnostic methods introduced thus far for identifying pathogenic microorganisms in the oral cavity. These are classified into three categories: 1) microbiological tests, 2) microchemical tests, and 3) genetic tests. The microbiological tests are used to determine the presence or absence of representative causative bacteria of periodontal diseases, such as A. actinomycetemcomitans, P. gingivalis, P. intermedia, and T. denticola. However, the quantitative analysis remains impossible, and detecting pathogens other than the specific ones is challenging. The microchemical tests determine the activity of inflammation or disease by measuring the levels of biomarkers present in the oral cavity. Although this diagnostic method is based on increase in the specific biomarkers proportional to inflammation or disease progression in the oral cavity, its commercialization is limited due to low sensitivity and specificity. The genetic tests are based on the concept that differences in disease vulnerability and treatment response are caused by the patient's DNA predisposition. Specifically, the IL-1 gene is used in such tests. PoC diagnostic methods developed to date serve as supplementary diagnostic methods and tools for patient education, in addition to existing diagnostic methods, although they have limitations in diagnosing oral diseases alone. Research on various PoC test methods that can analyze and manage the oral cavity bacterial composition is expected to become more active, aligning with the shift from treatment-oriented to prevention-oriented approaches in healthcare.

• Tuberculosis and Respiratory Diseases
• /
• 제68권3호
• /
• pp.146-154
• /
• 2010

Background: The increasing incidence of multidrug-resistant tuberculosis (MDR-TB) and extensively drug-resistant tuberculosis (XDR-TB) has become a serious worldwide problem. However, there is insufficient data regarding the current status of MDR-TB and XDR-TB in Korea. This study examined the recent status of MDR- and XDR-TB using the data from 7 laboratories, in which almost all drug susceptibility tests (DST) for Mycobacterium tuberculosis were performed. Methods: The patients' identification data and DST results were collected from all 7 laboratories from 2001 to 2006 and the number of patients with MDR-TB and XDR-TB were calculated. Results: The number of DSTs was 140,638 for 6 years with an increasing incidence each year (p<0.001). The number of DST with MDR results was 18,510 and personal identifying information was obtained in 16,640 (89.9%) tests. The number of MDR-TB patients from 2001 to 2006 was 2,329, 2,496, 2,374, 2,300, 2,354, and 2,178, respectively, when counting the duplications in a year as one patient. The number of MDR-TB patients when counting the duplications in 6 years as one patient was 2,281, 1,977, 1,620, 1,446, 1,512, and 1,373, respectively. When the same method was adopted, the number of XDR-TB patients was 191, 238, 282, 260, 272, and 264, respectively, and 189, 150, 130, 90, 122, and 110 patients, respectively. Conclusion: Despite the national efforts to control TB, there are still a large number of MDR- and XDR-TB patients in Korea.

• 한국미생물·생명공학회지
• /
• 제50권1호
• /
• pp.147-156
• /
• 2022

Urinary tract infections (UTIs) are one of the most common infections in different age groups, including children. Bacteria are the main etiological agents of UTIs. The aim of the present study was to isolate, identify, and determine the antibiotic susceptibility of bacteria isolated from children with UTIs from Baghdad, Iraq. Three hundred and two urine samples were collected from children aged 6 months to 12 years. The samples were cultured on blood agar and MacConkey agar. The selected colonies were subjected to biochemical tests and antibiotic susceptibility analysis using the Vitek^® 2 Compact automated microbial identification system. In this sample, 299 bacteria were identified, of which, 267 were gram-negative bacteria, and 32 were gram-positive bacteria. Escherichia coli (56%) was the most commonly isolated gram-negative bacteria, followed by Pseudomonas aeruginosa (14%), Enterobacter spp. (10.48%), Klebsiella pneumoniae (9.36%), Proteus spp. (7.8%), Acinetobacter baumannii (1.5%), and Morganella morganii (0.37%). Enterococcus faecalis (62.5%) was the most commonly detected gram-positive bacteria, followed by Staphylococcus aureus (37.5%). E. coli and P. aeruginosa were the most antibiotic-resistant bacteria. Among the tested antibiotics, meropenem showed 100% sensitivity, followed by imipenem (97.4%), amikacin (91.8%), and tobramycin (83.5%). In contrast, the high frequencies of resistance were observed with cefixime (93.2%), cefotaxime (78.7%), and ceftriaxone/cefotaxime (71.2%). In conclusion, carbapenems and aminoglycosides are highly recommended for the empirical treatment of UTIs, while, Quinolones, penicillins, and cephalosporins are not suggested. Frequent antibiotics susceptibility testing are warranted to determine the resistance pattern of UTI bacteria.

• Journal of Periodontal and Implant Science
• /
• 제44권2호
• /
• pp.79-84
• /
• 2014

Purpose: While single-species biofilms have been studied extensively, we know notably little regarding multispecies biofilms and their interactions. The purpose of this study was to develop and evaluate an in vitro multispecies dental biofilm model that aimed to mimic the environment of chronic periodontitis. Methods: Streptococcus gordonii KN1, Fusobacterium nucleatum ATCC23726, Aggregatibacter actinomycetemcomitans ATCC33384, and Porphyromonas gingivalis ATCC33277 were used for this experiment. The biofilms were grown on 12-well plates with a round glass slip (12 mm in diameter) with a supply of fresh medium. Four different single-species biofilms and multispecies biofilms with the four bacterial strains listed above were prepared. The biofilms were examined with a confocal laser scanning microscope (CLSM) and scanning electron microscopy (SEM). The minimum inhibitory concentrations (MIC) for four different planktonic single-species and multispecies bacteria were determined. The MICs of doxycycline and chlorhexidine for four different single-species biofilms and a multispecies biofilm were also determined. Results: The CLSM and SEM examination revealed that the growth pattern of the multispecies biofilm was similar to those of single-species biofilms. However, the multispecies biofilm became thicker than the single-species biofilms, and networks between bacteria were formed. The MICs of doxycycline and chlorhexidine were higher in the biofilm state than in the planktonic bacteria. The MIC of doxycycline for the multispecies biofilm was higher than were those for the single-species biofilms of P. gingivalis, F. nucleatum, or A. actinomycetemcomitans. The MIC of chlorhexidine for the multispecies biofilm was higher than were those for the single-species biofilms of P. gingivalis or F. nucleatum. Conclusions: To mimic the natural dental biofilm, a multispecies biofilm composed of four bacterial species was grown. The 24-hour multispecies biofilm may be useful as a laboratory dental biofilm model system.

• 한국균학회지
• /
• 제43권4호
• /
• pp.260-266
• /
• 2015

국내에 분포하는 벼 키다리병균의 benomyl에 대한 저항성 정도를 조사하기 위하여 연도별로 균주를 수집하고, 병원성을 검정하였으며, 한천희석법을 사용하여 각 균주의 benomyl에 대한 MIC값과 $EC_{50}$값을 조사하였다. 그 결과, 2006년부터 2007년에 분리한 균주의 MIC값은 1.5625~3.125 ug/mL인 균주가 가장 높은 빈도로 분포하였고, 2013년부터 2014년 분리균의 MIC값은 25 ug/mL 이상의 농도에서 분포비율이 가장 높았다. 또한 2006년부터 2007년 분리균의 평균 $EC_{50}$값은 1.6397 ug/mL이었으며, 2013년부터 2014년 분리균은 2.4892 ug/mL로 조사되었다. 국내 벼 키다리병균의 benomyl에 대한 저항성 기준은 MIC값이 25ug/mL 이상이고, $EC_{50}$값이 2.4 ug/mL 이하일 때는 중도저항성으로, $EC_{50}$값이 2.4 ug/mL 이상일 때는 저항성으로 하는 것이 타당할 것으로 생각된다. 이 기준에 의한 저항성 균주의 비율은2006년부터 2007년에 12.5%에서 2013년부터 2014년에는 36.4%로 증가하였다. 한편, prochloraz와 benomyl에 모두 저항성을 보이는 균주가 20.3%인 것으로 나타나 벼 키다리병균의 다중저항성이 증가하는 것으로 조사되었다.

• Clinical and Experimental Pediatrics
• /
• 제49권7호
• /
• pp.777-783
• /
• 2006

목 적 : 최근 소아 요로감염의 가장 흔한 원인균인 E. coli에 대한 항생제 내성 문제가 점차 대두되고 있다. 본 연구에서는 소아 원외 요로감염 환아에서 분리된 E. coli에 대한 cefixime을 포함하여 흔히 사용되고 있는 경구용 항생제의 시험관 내 감수성 연구를 시행하여 적합한 치료 항생제 선택의 기초 자료를 얻고자 하였다. 방 법 : 2004년 10월부터 2005년 9월까지 연구 참여 병원 소아과 외래에서 요로감염으로 진단된 206명 환아의 요 배양검사에서 동정된 211개 균주 중 188개 E. coli를 대상으로 경구용 항생제(ampicillin, amoxillin, ampicillin-sulbactam, cefaclor, TMP-SMX, cefixime)에 대한 시험관 내 감수성 검사를 실시하였다. 결 과 : 분리된 E. coli 균주에 대한 항생제별 감수성 결과에서 내성률은 각각 ampicillin 81.4%, amoxicillin 85.6%, ampicillin-Sulbactam 77.2%, cefaclor 93.6%, TMP-SMX 50.5%, cefixime 13.3%이었다. ESBL 생성 E. coli는 7.0%이었다. 결 론 : Aminopenicillins계, cefaclor, sulfa약제들은 E. coli에 대한 내성률이 매우 높아 소아 요로감염의 일차 선택 항생제로 유용하지 못한 것으로 추정할 수 있었다. 그러나 cefixime과 같은 3세대 cephalosporin은 일차 치료 실패할 경우 이차 선택항생제로 유용할 수 있으며, 일차 선택 항생제로도 사용될 수 있을 것으로 추정되었다. E. coli의 항생제 내성 양상에 대한 광범위한 연구와 지속적 감시를 통하여 소아 원외 요로감염 치료에서 1차적으로 선택될 수 있는 경구용 항생제에 대한 지침 자료가 요구된다.