• Journal of Microbiology
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• v.43 no.2
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• pp.209-212
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• 2005

The purpose of this study was to develop species-specific PCR primers for use in the identification and detection of Actinobacillus actinomycetemcomitans. These primers target variable regions of the 168 ribosomal RNA coding gene (rDNA). We assessed the specificity of the primers against 9 A. actinomycetemcomitans strains and 11 strains (3 species) of the Haemophilus genus. Primer sensitivity was determined by testing serial dilutions of the purified genomic DNAs of A. actinomycetemcomitans ATCC$ 33384^$T Our obtained data revealed that we had obtained species-specific amplicons for all of the tested A. actinomycetemcomitans strains, and that none of these amplicons occurred in any of the other species. Our PCR protocol proved able to detect as little as 4 fg of A. actinomycetemcomitans chromosomal DNA. Our findings suggest that these PCR primers are incredibly sensitive, and should prove suitable for application in epidemiological studies, as well as the diagnosis and monitoring of periodontal pathogens after treatment for periodontitis.

• Environmental Engineering Research
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• v.14 no.2
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• pp.120-125
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• 2009

Water stress has become a major concern in agriculture. Korea suffers from limited agricultural water supply, and wastewater reuse has been recommended as an alternative solution.A study was performed to examine the effects of microorganism concentration in the ponded-water of a paddy rice field with reclaimed-water irrigation for evaluating the microbial risk to farmers and neighborhoodchildren.Most epidemiological studies were performed based on an upland field, and they may not directly applicable to paddy fields. Beta-Poisson model was used to estimate the microbial risk of pathogen ingestion. Their risk value increased significantly high level after irrigation and precipitation.It implies that agricultural activities such as plowing, and fertilizing, and precipitation need be practiced a few days after irrigation considering health risks. The results about field application of the microbial risk assessment using E. coli showed difference according to monitoring time and treatment plot. Result of the microbial risk assessment showed that risk values of ground-water and reclaimed secondary waste water irrigation were lower than directly use of wastewater treatment plants' effluent. This paper should be viewed as a first step in the application of quantitative microbial risk assessment of E. coli to wastewater reuse in a paddy rice farming.

• Journal of Radiation Industry
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• v.9 no.4
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• pp.181-185
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• 2015

Today the biosafety evaluation, a common problem of vital importance, is based on internationally proved test-systems, standards and techniques. The paradigm of biosafety includes multidisciplinary approach, a combination of physical, chemical and biological tests to monitor the environmental level of pollutants and needs to be improved by modern approaches. The genetic risk of environmental pollutions has long been studied by many researchers. In this study, used was the known sensitive plant test-system, clones of plant Tradescantia (spiderwort) able to detect gene mutations (frequency of mutational events and formation of micronuclei) in combination with chemical and, in some instances, with radiological measurements. In addition, male gametophyte generation of fruit trees was applied as bioindicators of genotoxicity. The obtained results did not show any significant increase along with wind direction. As for the male gametophyte assay, the fertility of the investigated fruit-trees near to NPP did not significantly differ from that of the control point. The influence of the NPP on the male generative system of the investigated taxa of fruit trees for the investigated year was not revealed. The system described needs to be expanded by species of interest (human) as there is a difficulty to transfer the revealed dose correlations to humans. The development of this idea includes various levels: population (epidemiological studies), individual, cellular, molecular (DNA), etc.

• Microbiology and Biotechnology Letters
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• v.48 no.4
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• pp.564-568
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• 2020

Although studies on Hepatitis A virus (HAV) were crucial in the establishment of the HAV infection prevention programs, no systematic investigation into HAV has been conducted since 1999. We retrospectively analyzed the data between January 2010 to December 2018 from all the patients who underwent HAV antibody tests at the Dankook University Hospital Health Care Center. Data were collected from 56,204 individuals. Overall, 34,834 (62.0%) individuals from this cohort were positive for HAV antibodies and the annual rate of anti-HAV antibody positivity was highest in 2010 (68.5%) and lowest in 2013 (54.8%). The average decline in the antibody positivity rate was 0.62% per year, showing a statistically significant difference (p < 0.001). In the over 40s age group, anti-HAV antibody positivity rates decreased from 89% in 2010 to 64% in 2018 (p < 0.001), with an annual decrease of 3.1%. In the over 30s age group, it decreased from 48.2% in 2010 to 34.7% in 2018 (p < 0.001), with an annual decrease of 1.82%. This study shows that the antibody positivity rate is decreasing across age groups but given that HAV infection poses more significant risks in older patients it is important to expand the evaluations of the current and future antibody positivity rates for HAV in various age groups.

• Journal of Environmental Health Sciences
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• v.45 no.5
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• pp.434-442
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• 2019

Objectives: This study was performed in order to report the epidemiological features of a food poisoning outbreak caused by multiple pathogens in a high school in Chungcheongnam-do Province, Korea in April 2019 and to suggest measures to prevent a similar incidence. Methods: A total of 39 patients with diarrhea were examined. Environmental samples were obtained from 6 food handlers, 4 food utensils, 72 preserved foods served during the food poisoning outbreak, 9 door handles, 10 drinking water samples from water dispensers, and 6 ground water samples from water taps. These analyzed to detect viruses and bacteria. Results: Among the 39 patients, 21 cases (53.8%) of enteroaggregative E. coli (EAEC), 7 cases of Staphylococcus aureus (17.9%), and 17 cases of norovirus (43.6%) were positive, and in 16 of the cases a co-infection with at least one other pathogen were observed. EAEC was assumed to be transmitted from contaminated drinking water because it was also detected in the water sample from a water dispenser in the dormitory. Staphylococcus aureus was isolated only in the fecal samples of patients, meaning it was not possible to trace its origin. The genotype of norovirus detected in the drinking water and ground water was consistent with that isolated from patients, and it was determined that the norovirus infection originated from the school's water environment. Conclusions: These findings indicate that a lack of environmental hygiene management related to school meals caused the food poisoning incident. In particular, a lack of management of drinking water, water supply, and personal hygiene should be pointed out. This should be urgently addressed and continuous monitoring should be carried out in the future. In addition, students and staff should be educated and trained to improve their personal hygiene.

• Parasites, Hosts and Diseases
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• v.59 no.5
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• pp.507-512
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• 2021

Since 1993, vivax malaria has been recognized as a public health burden in Korea. Despite of pan-governmental malaria-control efforts and the dramatic reduction in the burden of this disease over the last 10 years, vivax malaria has not been well controlled and has remained continuously endemic. We focused interviewed and examined the charts of 28 confirmed vivax malaria patients given malarial therapy for whom daily records were kept from Gimpo-si, Gyeonggi-do of Korea. Various epidemiological characteristics of vivax malaria, including the incubation period, medication used, and recurrence, and an evaluation of the parasitic characteristics from the focused interviews of patients from this region are described here. Most of the participants indicated the 3 most common symptoms of malaria (headache, chills and fever). Of the 28 cases, 2 experienced a second attack and there were 17 and 11 cases with short- and long-term incubation periods, respectively, yielding a short-term to long-term ratio of 1.5. Based on the parasitemia stages, most of the participants were tested at 5 to 7 days (11 cases) and 7 to 15 days (11 cases) after initial wave of asexual parasites. In conclusion, public health authorities should consider developing management measures to decrease the time lag for diagnosis and drafting unified and robust guidelines for drug use for malaria and drawing up unified and robust guidelines on the use of medication for malaria. It also suggests that routine monitoring, surveillance, and precise medical surveys in high-risk vivax malaria endemic areas are pivotal to controlling this persistent public disease and finally eliminating it from Korea.

• Korean Journal of Clinical Laboratory Science
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• v.50 no.4
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• pp.406-413
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• 2018

The emergence of carbapenem resistance among Pseudomonas aeruginosa has become an increasing problem worldwide. In particular, $metallo-{\beta}-lactamases$ (MBLs) are responsible for the high-level resistance to carbapenem. Sequence type 235 (ST235) has been found internationally in a multidrug-resistant clone and is involved in the dissemination of genes encoding IMP-6 and VIM-2. This study examined the prevalence of MBLs and the epidemiological relationship in carbapenem-resistant P. aeruginosa (CRPA) isolates obtained from a tertiary hospital in Daejeon, Korea, between March 2008 and June 2014. The antimicrobial susceptibilities were determined using the disk-diffusion method and PCR and DNA sequencing were used to identify the MBL genes. In addition, an epidemiological relationship was investigated by multilocus sequence typing (MLST). Among the 110 CRPA isolates, 32 isolates (29.1%) were MBL-producers; the major type was IMP-6 (29 isolates, 90.6%). VIM-2 was identified in 3 isolates (9.4%) of ST357. IMP-6-producing isolates were multidrug-resistant (MDR) and belonged to ST235. ST235 (55 isolates, 50.0%) was the clone most frequently detected and has gradually emerged during a seven-year period. To prevent the spread of MDR ST235 P. aeruginosa isolates, the current widespread use of carbapenems needs to be curtailed, and novel continuous monitoring strategies should be developed as soon as possible.

• Korean Journal of Clinical Laboratory Science
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• v.53 no.3
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• pp.217-224
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• 2021

Fluoroquinolone (FQ) resistant gram-negative pathogens have emerged worldwide, and the recent increase in FQ resistant Escherichia coli is of great concern in Korea. This study investigated FQ resistance determinants and the epidemiological relationship of 56 ciprofloxacin-resistant E. coli isolated from a tertiary hospital in Daejeon, South Korea from June to December 2018. Molecular epidemiology was investigated by multilocus sequence typing (MLST). Polymerase chain reaction (PCR) and sequence analysis were performed to identify chromosomal mutations in the quinolone resistance determining regions (QRDR) of gyrA, gyrB, parC, and parE and to describe the occurrence of the following plasmid-mediated quinolone resistance (PMQR) genes: aac(6)-Ib-cr, qepA, qnrA, qnrB, qnrC, qnrD, and qnrS. MLST analysis showed 12 sequence types (STs) and the most prevalent ST was ST131 (31/56, 55.4%), followed by ST1193 (13/56, 23.2%), and ST405 (3/56, 5.4%). In 56 ciprofloxacin-resistant E. coli isolates, Ser83→Leu and Asp87→Asn in gyrA and Ser80→Ile and Glu84→Val in parC (51.8%, 29/56) were the most frequent amino acid substitutions and aac(6)-Ib-cr (33.9%, 19/56) was the most common PMQR gene. These results of FQ resistance determinants were more frequently observed in ST131 compared with other clones. Continuous monitoring of the epidemiological characteristics of ciprofloxacin-resistant E. coli isolates and further investigation of FQ resistance determinants are necessary.

• Korean Journal of Clinical Laboratory Science
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• v.54 no.4
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• pp.265-272
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• 2022

The emergence and dissemination of carbapenemase-producing Enterobacteriaceae (CPE), particularly the Klebsiella pneumoniae carbapenemase-2 (KPC-2) producing Klebsiella pneumoniae, has been rapidly increasing worldwide and is becoming a serious public health threat. Since the epidemiology and characteristics of these KPC-2-producing K. pneumoniae vary according to the region and period under consideration, this study investigated the prevalence of carbapenemases and the epidemiological relationship of 78 carbapenem-resistant K. pneumoniae (CRKP) isolated from a tertiary hospital in Daejeon, from March 2017 to December 2020. The antimicrobial susceptibility tests were identified using the disk-diffusion method. PCR and DNA sequencing were used to determine the carbapenemase genes. In addition, molecular epidemiology was performed by multilocus sequence typing (MLST). Among the 78 CRKP isolates, 35 isolates (44.9%) were carbapenemase-producing K. pneumoniae (CPKP) and the major carbapenemase type was KPC-2 (30 isolates, 85.7%). The New Delhi metallo-enzyme-1 (NDM-1) and NDM-5 were identified in 4 isolates (11.4%) and 1 isolate (2.9%), respectively. Multilocus sequence typing (MLST) analysis showed 10 sequence types (STs) and the most prevalent ST was ST307 (51.4%, 18/35). All the ST307 isolates were KPC-2-producing K. pneumoniae and were multidrug-resistant (MDR). In addition, ST307 has gradually emerged during a four-year period. These findings indicate that continuous monitoring and proper infection control are needed to prevent the spread of KPC-2-producing K. pneumoniae ST307.

• BMB Reports
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• v.29 no.2
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• pp.105-110
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• 1996

Polyclonal antiserum R101 against aflatoxin $B_1$ ($AFB_1$) was raised in New Zealand white rabbits after injection of bovine serum albumin-$AFB_1$ conjugate. Competitive ELISA (enzyme linked immuno-sorbent assay) demonstrated that antiserum R101 has the highest binding for $AFB_1$ (50% inhibition at 170 fmol) and aflatoxicol II (50% inhibition at 112 fmol). It also reacts with other aflatoxins such as $AFB_2$, $AFG_1$, $AFG_2$, and aflatoxin metabolites ($AFM_1$, $AFM_2$, $AFP_1$, and $AFQ_1$), but it does not cross-react with $AFG_2a$. Using this antiserum, aflatoxins were quantitated in 100 urine samples of undergraduate students at the College of Pharmacy, Sung Kyun Kwan University, Republic of Korea. By ELISA, $AFB_1$ and its metabolites were detected in human urine samples (N=100, male=89, female=11, ages=20~31 yrs) with a range of 1.4~200.6 ng/kg/day (mean$\pm$SD=$18.11{\pm}33.01\;ng\;AFB_1/kg/day$ in males, $3.82{\pm}2.65\;ng/kg/day$ in females). Assuming that urinary excretion is about 7.6% of $AFB_1$ intake (Groopman et al., 1992), we estimated that Koreans were daily exposed to a total dietary $AFB_1$ of $240.20{\pm}438.67\;ng/kg/day$ in males and $50.35{\pm}29.88\;ng/kg/day$ in females, respectively. When the human monitoring data was applied to a linear regression model of Y=21.67X-10.04 {Y=liver cancer incidence per 100,000, X=Log $AFB_1$ intake (ng/kg/day), r=0.99} developed from previously reported epidemiological data, calculated liver cancer incidences attributed to $AFB_1$ exposure were 41.56/100,000 in males and 26.84/100,000 in females. The incidences were similarly correlated with liver cancer mortality rates of 43.43/100,000 in males and 11.23/100,000 in females in Korea. These results suggest that aflatoxin exposure may be an important risk factor for the high incidence of liver cancer in Korea.