• Korean Journal of Clinical Laboratory Science
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• v.48 no.2
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• pp.82-87
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• 2016

Enterotoxigenic Bacteroides fragilis (ETBF) produces enterotoxins known to be a virulence factor. Three isotypes of the B. fragilis toxin (BFT) gene have been identified: bft-1, bft-2, and bft-3. We investigated the presence of bft isotypes in clinical B. fragilis isolates and the antimicrobial resistance of BFT-negative and BFT-positive isolates. Overall, 537 B. fragilis isolates were collected from extraintestinal specimens over 8 years (2006~2013) from a university hospital in Korea. Samples were analyzed by multiplex PCR to identify the bft gene isotypes. Additionally, the antimicrobial susceptibility of 107 B. fragilis isolates (74 BFT-negative and 33 BFT-positive) was examined by the CLSI agar dilution method. PCR revealed a total bft gene detection rate of 30%, while 33% and 29% of blood and other extraintestinal isolates contained the gene, respectively. Among ETBF isolates, the most common isotype was bft-1 gene, followed by bft-2 and bft-3 (bft-1 77%, bft-2 14%, bft-3 9%). Resistance rates (%) for BFT-negative and positive isolates differed in response to various antimicrobial agents, with 3%, 5%, 1% and 38% of BFT-negative isolates and 3%, 6%, 3% an 42% of BFT-positive isolates being resistant to piperacillin-tazobactam, cefoxitin, imipenem, and clindamycin, respectively. Interestingly, neither BFT-negative nor positive isolates showed antimicrobial resistance to chloramphenicol and metronidazole. Overall, the proportion of ETBF from blood was similar to that of other extraintestinal sites and the bft-1 gene was the predominant isotype. Higher antimicrobial resistance rates were found in BFT-positive isolates than BFT-negative isolates, but these differences were not statistically significant.

• Research in Plant Disease
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• v.14 no.3
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• pp.143-152
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• 2008

Mixed-planting of two rice cultivars, HP ('Hopyeongbyeo') and NP ('Nampyeongbyeo'), having a dissimilar susceptibility to rice blast was practiced for chemical-free control of rice blast in the field. The HP/NP combination was selected for applying under mechanized agricultural conditions. Because they have similar genetic characteristics such as seed germination and heading time, culm length, rice quality and size of rice grains except susceptibility to blast. Incidence of panicle blast was reduced 50.4 % compare with supposed blast incidence by HP/NP mixed-planting when the seeds of two cultivars were combined 1 to 1 as weight. Supposed blast incidence was estimated from reduction of rice blast caused by addition of a resistant cultivar NP. Race diversity of Magnaporthe oryzae was examined for correlation with control effect of HP/NP mixed-planting on rice blast. The population of dominant race KJ-101 was diminished and replaced with various co-existing races and eleven new races were appeared in mixed-planting plot. Total number of race isolated from mixed-planting plot was not largely different from mono-culture. However, detection frequency of the new race was increased and variation of the population size of each race was decreased in mixed-planting plots. It was shown that a biased community with a dominant race (KJ-101 or KI-181) was altered to a balanced one of coexisting races. From these results, it was supposed that the balanced diversity among co-existing races within a community might be correlated to control effect by HP/NP mixed-planting on rice blast. Further more, it should be studied that genetic characteristics of the individual race including a virulence on cv. HP and NP was examined for verifying a correlation of mixed-planting effect and race diversity.

• Korean Journal of Microbiology
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• v.48 no.3
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• pp.180-186
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• 2012

Pseudomonas aeruginosa, a Gram-negative bacterium, is an ubiquitous and opportunistic human pathogen, which expresses many virulence factors through quorum sensing (QS) regulation. QscR, one of the QS signal receptors of P. aeruginosa, has unique features that make it possible to distinguish QscR from other QS receptors. In the present study, we focused on amino acid residues responsible for such a broad signal specificity of QscR. Thus we constructed mutant QscRs: $QscR_{T72I}$, $QscR_{R132M}$, and $QscR_{T140I}$ by substituting $72^{nd}$ threonine, $132^{nd}$ arginine, and $140^{th}$ threonine residues with isoleucine, methionine, and isoleucine, respectively by site-directed mutagenesis. When we examined the activity of these mutant QscRs, $QscR_{R132M}$ failed to respond to N-3-oxododecanoyl homoserine lactone (3OC12-HSL), but $QscR_{T72I}$ and $QscR_{T140I}$ remained the ability to respond to 3OC12-HSL despite much reduction of the sensitivity. When we treated a variety of acyl-HSLs with different structure, $QscR_{T72I}$ and $QscR_{T140I}$ showed better responsiveness to N-decanoyl HSL (C10-HSL) or N-dodecanoyl HSL (C12-HSL) that has no oxo-moiety at $3^{rd}$ carbon of acyl group than to 3OC12-HSL, and $QscR_{R132M}$ showed no responsiveness to any acyl-HSLs tested here. In addition, $QscR_{T72I}$ and $QscR_{T140I}$ were inhibited by 5f, a QscR inhibitor as similarly as wild type QscR was. These results suggest that while the $130^{th}$ arginine is crucial in both activity and acyl-HSL binding of QscR, the $72^{nd}$ and $140^{th}$ threonines are important in the activity, but they are little responsible for the discrimination of acyl-HSLs or competitive inhibitor.

• Korean Journal of Food Science and Technology
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• v.39 no.6
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• pp.669-675
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• 2007

The present study was conducted to explore the anti-inflammatory action of $2-hydroxyethyl-{\beta}-undecenate$ (HPS) purified from Cumin (Cuminum cymium L.) seed against periodontitis. From the study in which human leukocyte was employed to detect the inhibiting effects of 5-lipokygenase and cyclooxygenase, enzymes generating carriers of infection like $LTB_4$ and PGs, as well as of collagenase and elastase, organ-destroying enzymes, following conclusions could be drawn: HPS was found to inhibit leukotrien $B_4$ biosynthesis by stimulating more than 97% of human polymorphonuclear leukocyte (PMNL) with addition of $5\;{\times}\;10^{-2}\;M$ when $IC_{50}$ was set at $2\;{\times}\;10^{-4}\;M$. Ninety-two percent of enzyme activation turned out to be inhibited when $5\;{\times}\;10^{-2}\;M$ was added in a test to prove inhibiting effects of HPS against activation of PMNL 5-lipoxygenase from homogeneous humans and purified 5-lipoxygenase on the market. Besides, $IC_{50}$ for enzyme activation was valued at $2.5\;{\times}\;10^{-4}\;M$, while the value of $IC_{50}$ for purified 5-lipoxygenase was $2.3\;{\times}\;10^{-4}\;M$. The $IC_{50}$ values of COX-activated leukocyte and purified collagenase were $5.1\;{\times}\;10^{-4}\;M$ and $2.3\;{\times}\;10^{-4}\;M$, respectively. Moreover, the value of $IC_{50}$ for activation of leukocyte collagenase was $2\;{\times}\;10^{-3}\;M$, whereas that for purified collagenase was $5\;{\times}\;10^{-2}\;M$. In case of leukocyte elastase, addition of $5\;{\times}\;10^{-2}\;M$ inhibited its activation by 66%. In case of purified one, however, activation of enzyme was inhibited by 25% with addition of $5\;{\times}\;10^{-2}\;M$. Furthermore, the $IC_{50}$ value for activation of leukocyte elastase was revealed to be $7.5\;{\times}\;10^{-3}\;M$. From the virulence test with human gingiva cell, it was shown that, on the second day of cultivation, 47.83% of the cell had been activated when HPS was added by $5\;{\times}\;10^{-2}\;M$. Even the addition of HPS by $1\;{\times}\;10^{-2}\;M$ featured 68.53% of cell activation, suggesting relatively strong toxicity of the substance against gingiva cell.

• Journal of Veterinary Clinics
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• v.28 no.3
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• pp.297-302
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• 2011

Avian pathogenic Escherichia coli (APEC) causes a number of extraintestinal diseases in poultry. A virulence factor, P-fimbriae is firmly associated with the diseases. In this study, to develop an effective vaccine for the prevention of APEC, recombinant attenuatted Salmonella Typhimurium vaccines expressing PapA and PapG of P-fimbriae were evaluated whether these induced protective immune responses in murine models. Female BALB/c mice were primed and boosted orally at 7 and 10 weeks of age. In all immunized mice, the antigen-specific serum IgG levels were remained higher than those in the control mice from the fourth week post inoculation till the end of this study. In addition, antigen-specific serum IgG levels in the prime-booster immunized mice were enhanced as compared to the single immunized mice among each immunized group. The antigen-specific mucosal IgA levels in the mice immunized with each strain also induced higher than those in control mice. In addition, serum IgG and fecal IgA levels in mice administered with the combination of both strains were highly induced compared to those in mice immunized with each strain alone. These results indicated that PapA and PapG worked together for inducing high immune responses. To partly discern the nature of immunity induced by the strains, we quantified serum IgG subtypes IgG1 and IgG2a specific to antigens. The PapA and PapG strains biased the immunity to the Th1-type, as determined by the IgG2a/IgG1 ratio. On the other hand, the immunization with the both strains in combination produced mixed Th1- and Th2-type immune responses. These indicated that immunization with the combination of PapA and PapG could elicit both humoral and cell-mediated immunities.

• Korean Journal of Food Science and Technology
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• v.37 no.1
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• pp.134-141
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• 2005

To characterize genotypic and phenotypic traits of Staphylococcus aureus isolates (n = 86) from lettuces and raw milk, major virulence-associated genes and antibiotic susceptibility were detected using PCR-based methods and disk diffusion method, respectively. All isolates possessed coagulase gene and showed five polymorphism types [500 bp (2.4%), 580 bp (17.4%), 660 bp (61.6%), 740 bp (17.4%), and 820 bp (1.2%)] due to variable numbers of tandem repeats present within the gene. Two or three different loci of hemolysin gene family were dominant in isolates, 47 of which (55%) possessed combination of hla/hld/hlg-2 genes as the most prevalent types. Among enterotoxin-encoding genes, sea was detected from 32 isolates (37%), sed from 1 isolate (1%), and sea and sed genes were co-detected from 4 isolates (5%), whereas seb, sec, and tsst-1 genes were not detected. All isolates were susceptible to ciprofloxacin, trimethoprim/sulfamethoxazole, oxacillin, and vancomycin, 85 isolates (99%) to penicillin G, 54 isolates (63%) to chloramphenicol, 51 isolates (59%) to erythromycin, and 7 isolates (8%) to clindamycin. Among resistant isolates, seven displayed multiantibiotic-resistance against two different antibiotics.

• Journal of Korean Society of Forest Science
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• v.94 no.6
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• pp.402-409
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• 2005

This study was undertaken to compare and estimate the severity of pitch canker of individual trees of Pinus rigida and Pinus rigida ${\times}$ P. taeda in two seed orchards in Jeju island, in which the orchards have been damaged by the pitch canker for seven years. Wind-pollinated two-year-old seedlings of P. rigida and P. rigida ${\times}$ P. taeda, in which the seedlings of P. rigida ${\times}$ P. taeda were from seeds of phenotypically selected, uninfected(but untested) trees, were inoculated with the pathogenic fungus, Fusarium circinatum, isolated from P. rigida and P. thunbergii. The virulence of the isolates was also identified. Statistically significant difference was found in 'stem cankers'(SC; ${\chi}^2=7.76$, P=0.05) among 4 plantations of P. rigida ${\times}$ P. taeda of two seed orchards. P. rigida was higher in 'top kill' (TK) and 'branch tip symptoms' (BT) than those of P. rigida ${\times}$ P. taeda. In artificial inoculation tests, mortality of the seedlings from the resistant candidates was 14% higher than that of the seedlings from the susceptible candidates. This result may becaused by unknown pollen trees and/or candidate tree selection based only on phenotype. Two of five fungal isolates, C-6-L(9) and C-6-L(19), showed significantly higher mortality (68% and 60%, respectively) than others, suggesting that these isolates can be used as virulent isolates for a mass artificial inoculation. Resistance candidate seedlings that were selected from this study can be utilized as useful materials for fundamental studies of genetics and biochemistry to breed resistance varieties to pitch canker.

• Tuberculosis and Respiratory Diseases
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• v.44 no.3
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• pp.470-478
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• 1997

Background : Phagocytosis is probably the first step for mycobacteria to be virulent in host because virulent strains are more readily phagocytosed by macrophage than attenuated strains. According to the traditional concept, multi-drug resistant strains have been regarded as less virulent. However, this concept has been challenged, since recent studies(reported) showed that the degree of virulence and drug-resistance is not related. The purpose of this study is to evaluate whether the phagocytic activity of M.tuberculosis by peripheral blood mononuclear cells(PBMC) is different according to drug-resistance or host factor. To evaluate this, we estimated the difference of phagocytic activity of drug-resistant and drug-sensitive M.tuberculosis and also estimated the phagocytic activity of PBMC from intractable tuberculosis patients and healthy controls. Methods : PBMC from ten intractable tuberculosis patients and twelve healthy control, and three different strains of heat-killed M.tuberculosis, ie, ADS(all drug sensitive), MDR(multi-drug resistant), and ADR(all drug resistant) were used. After incubation of various strains of M.tuberculosis with PBMC, the phagocytic activity was evaluated by estimating proportion of PBMC which have phagocytosed M.tuberculosis. Results : Drug-resistant strains of M.tuberculosis were phagocytosed easily than drug sensitive strains(Percentage of PBMC phagocytosed M.tuberculosis in healthy control : ADS : $32.3{\pm}2.9%$, ADR : $49.6{\pm}3.4%$, p = 0.0022, Percentage of PBMC phagocytosed M.tuberculosis in intractable tuberculosis patients : ADS : $34.9{\pm}3.6%$, ADR : $50.7{\pm}4.5%$, p = 0.0069). However, there was no difference in phagocytic activity of PBMC from healthy control and intractable tuberculosis patients. Conclusion : Drug-resistant strains of M.tuberculosis were phagocytosed easily than drug sensitive strains and host factors does not seems to influence the phagocytosis of M.tuberculosis.

• Journal of Food Hygiene and Safety
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• v.32 no.2
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• pp.147-153
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• 2017

The purpose of this study was to isolate Escherichia coli from flies and to assess pathogenic genes and antibiotic resistance of the isolates. A total of 188 flies were captured in agricultural environment including fruits farms (n = 19), fermented soybean farms (n = 9), municipal waste (n = 46), livestock farms (n = 66), slaughterhouses (n = 38), and manure ground (n = 10). E. coli isolates of captured flies were tested for pathogenic gene and antibiotic resistance using PCR methods and VITEK2 systems. As a result, E. coli from 63% (119/188) of the captured flies has been detected, and the detection rate of E. coli was the highest (89%, 31/34) in flies captured at particular slaughterhouse. Of the 34 isolates, 94% (32/34) were pathogenic gene (ST gene) positive. Twenty-six percent (31/119) of the E. coli isolates were observed being resistant to one or more antibiotics. Markedly, one of E. coli isolates from Livestock farms was resistant to 7 antibiotics including ampicillin, ampicillin/sulbactam, cefazolin, cefotaxime, gentamicin, levofloxacin, and trimethoprim/sulfamethoxazole. In addition, it was ESBL positive. The results of the present study may suggest a risk of transmission of pathogenic and antimicrobial resistant bacteria from flies to livestock environment Therefore, it may need to prevent introducing flies into the agricultural production environment for safe food production.

• Journal of the Korean Society of Food Science and Nutrition
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• v.44 no.12
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• pp.1895-1904
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• 2015

Foodborne illness associated with food service establishments is an important food safety issue in Korea. In this study, foodborne pathogens (Bacillus cereus, Clostridium perfringens, Escherichia coli, pathogenic Escherichia coli, Listeria monocytogenes, Salmonella spp., Staphylococcus aureus, and Vibrio parahaemolyticus) and hygiene indicator organisms [total viable cell counts (TVC), coliforms] were analyzed for food and environmental samples from foodservice establishments at schools in Gyeonggi province. Virulence factors and antimicrobial resistance of detected foodborne pathogens were also characterized. A total of 179 samples, including food (n=66), utensil (n=68), and environmental samples (n=45), were collected from eight food service establishments at schools in Gyeonggi province. Average contamination levels of TVC for foods (including raw materials) and environmental samples were 4.7 and 4.0 log CFU/g, respectively. Average contamination levels of coliforms were 2.7 and 4.0 log CFU/g for foods and environmental swab samples, respectively. B. cereus contamination was detected in food samples with an average of 2.1 log CFU/g. E. coli was detected only in raw materials, and S. aureus was positive in raw materials as well as environmental swab samples. Other foodborne pathogens were not detected in all samples. The entire B. cereus isolates possessed at least one of the diarrheal toxin genes (hblACD, nheABC, entFM, and cytK enterotoxin gene). However, ces gene encoding emetic toxin was not detected in B. cereus isolates. S. aureus isolates (n=16) contained at least one or more of the tested enterotoxin genes, except for tst gene. For E. coli and S. aureus, 92.7% and 37.5% of the isolates were susceptible against 16 and 19 antimicrobials, respectively. The analyzed microbial hazards could provide useful information for quantitative microbial risk assessment and food safety management system to control foodborne illness outbreaks in food service establishments.