• Food Science of Animal Resources
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• v.32 no.5
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• pp.545-552
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• 2012

This study evaluated the effects of NaCl on heat resistance and Caco-2 cell invasion of Listeria monocytogenes in broth media and sausage. A 10-strain mixture of L. monocytogenes was inoculated in tryptic soy broth containing 0.6% yeast extract (TSBYE), and sausage formulated with 0, 2, 4, and 6% NaCl. The medium was stored at 7, 15, 20, and $25^{\circ}C$ for 3-16 d, and medium samples were withdrawn at the appropriate time and challenged to 55, 60, and $63^{\circ}C$ to evaluate the thermal resistance of the pathogen. Sausage samples were stored at 7 and $25^{\circ}C$, and they were exposed to $63^{\circ}C$ to evaluate thermal resistance. NaCl-habituated L. monocytogenes strains NCCP10811 and NCCP10943 were examined for 12 antibiotics and Caco-2 cell invasion assay (only L. monocytogenes NCCP10943). Bacterial populations of L. monocytogenes generally increased (p<0.05) during the heat challenge as NaCl concentrations increased in both TSBYE and sausage samples. The antibiotic resistance of L. monocytogenes was not observed ($p{\geq}0.05$) when it was exposed to a single concentration of NaCl in TSBYE, but the pathogen obtained resistance to some antibiotics when exposed to a sequential increase of NaCl concentration. Invasion efficiency of L. monocytogenes NCCP10943 was not increased ($p{\geq}0.05$) with NaCl concentration increase. These results indicate that NaCl may increase the resistance of L. monocytogenes to heat and to some antibiotics, but may not increase Caco-2 cell invasion of L. monocytogenes.

• Korean Journal of Organic Agriculture
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• v.19 no.spc
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• pp.39-42
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• 2011

This experiment was conducted to evaluate the effect of two different organic acid products as antibiotic replacement in olive flounder paralichthys olivaceus. Fish averaging $3.5{\pm}0.05$ g($mean{\pm}SD$) were fed one of the ten semi-purified diets : Diet 1 ; Control, Diet 2 ; add antibiotics - 50mg OTC/kg body weight/day(OTC), Diet 3 ; Add organic acid bland A(OABA) - 4g/kg diet, Diet 4 ; add organic acid bland B(OABB) - 4g/kg diet for 10 weeks. Total gut microflora counts were significantly higher in the control group compared to the OTC and organic acid groups(P<0.05). Fish fed OABA, OABB and OTC had lower gut Vibrio counts compared to the control, but were not significantly different. Results from the challenge study indicate that mortality in the different treatment groups (50%) was significantly lower than those observed for the control group (100%). There were no differences in mortality between the OTC and organic acid groups. Overall findings from this study indicate that the organic acid blends A and B were as effective as oxytetracycline, an antibiotic, in regulating total gut bacterial numbers, Vibrio counts and providing protection against a pathogen such as Edwardsiella tarda.

• Journal of Microbiology and Biotechnology
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• v.29 no.7
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• pp.1124-1136
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• 2019

Salinity is one of the major abiotic stresses that cause reduction of plant growth and crop productivity. It has been reported that plant growth-promoting bacteria (PGPB) could confer abiotic stress tolerance to plants. In a previous study, we screened bacterial strains capable of enhancing plant health under abiotic stresses and identified these strains based on 16s rRNA sequencing analysis. In this study, we investigated the effects of two selected strains, Bacillus aryabhattai H19-1 and B. mesonae H20-5, on responses of tomato plants against salinity stress. As a result, they alleviated decrease in plant growth and chlorophyll content; only strain H19-1 increased carotenoid content compared to that in untreated plants under salinity stress. Strains H19-1 and H20-5 significantly decreased electrolyte leakage, whereas they increased $Ca^{2+}$ content compared to that in the untreated control. Our results also indicated that H20-5-treated plants accumulated significantly higher levels of proline, abscisic acid (ABA), and antioxidant enzyme activities compared to untreated and H19-1-treated plants during salinity stress. Moreover, strain H20-5 upregulated 9-cisepoxycarotenoid dioxygenase 1 (NCED1) and abscisic acid-response element-binding proteins 1 (AREB1) genes, otherwise strain H19-1 downregulated AREB1 in tomato plants after the salinity challenge. These findings demonstrated that strains H19-1 and H20-5 induced ABA-independent and -dependent salinity tolerance, respectively, in tomato plants, therefore these strains can be used as effective bio-fertilizers for sustainable agriculture.

• Journal of Ginseng Research
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• v.43 no.2
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• pp.218-225
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• 2019

Background: Streptococcus pneumoniae, more than 90 serotypes of which exist, is recognized as an etiologic agent of pneumonia, meningitis, and sepsis associated with significant morbidity and mortality worldwide. Immunization with a pneumococcal pep27 mutant (${{\Delta}}pep27$) has been shown to confer comprehensive, long-term protection against even nontypeable strains. However, ${{\Delta}}pep27$ is effective as a vaccine only after at least three rounds of immunization. Therefore, treatments capable of enhancing the efficiency of ${{\Delta}}pep27$ immunization should be identified without delay. Panax ginseng Mayer has already been shown to have pharmacological and antioxidant effects. Here, the ability of Korean Red Ginseng (KRG) to enhance the efficacy of ${{\Delta}}pep27$ immunization was investigated. Methods: Mice were treated with KRG and immunized with ${{\Delta}}pep27$ before infection with the pathogenic S. pneumoniae strain D39. Total reactive oxygen species production was measured using lung homogenates, and inducible nitric oxide (NO) synthase and antiapoptotic protein expression was determined by immunoblotting. The phagocytic activity of peritoneal macrophages was also tested after KRG treatment. Results: Compared with the other treatments, KRG significantly increased survival rate after lethal challenge and resulted in faster bacterial clearance via increased phagocytosis. Moreover, KRG enhanced ${{\Delta}}pep27$ vaccine efficacy by inhibiting reactive oxygen species production, reducing extracellular signal-regulated kinase apoptosis signaling and inflammation. Conclusion: Taken together, our results suggest that KRG reduces the time required for immunization with the ${{\Delta}}pep27$ vaccine by enhancing its efficacy.

• Journal of Microbiology and Biotechnology
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• v.32 no.6
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• pp.730-739
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• 2022

Methicillin-resistant Staphylococcus aureus (MRSA) causes severe infections and poses a global healthcare challenge. The utilization of novel molecules which confer synergistical effects to existing MRSA-directed antibiotics is one of the well-accepted strategies in lieu of de novo development of new antibiotics. Thymol is a key component of the essential oil of plants in the Thymus and Origanum genera. Despite the absence of antimicrobial potency, thymol is known to inhibit MRSA biofilm formation. However, the anti-MRSA activity of thymol analogs is not well characterized. Here, we assessed the antimicrobial activity of several thymol derivatives and found that 4-chloro-2-isopropyl-5-methylphenol (chlorothymol) has antimicrobial activity against MRSA and in addition it also prevents biofilm formation. Chlorothymol inhibited staphyloxanthin production, slowed MRSA motility, and altered bacterial cell density and size. This compound also showed a synergistic antimicrobial activity with oxacillin against highly resistant S. aureus clinical isolates and biofilms associated with these isolates. Our results demonstrate that chlorinated thymol derivatives should be considered as a new lead compound in anti-MRSA therapeutics.

• Journal of Veterinary Science
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• v.21 no.2
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• pp.20.1-20.13
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• 2020

Actinobacillus pleuropneumoniae (APP) causes a form of porcine pleuropneumonia that leads to significant economic losses in the swine industry worldwide. The apxIBD gene is responsible for the secretion of the ApxI and ApxII toxins and the pnp gene is responsible for the adaptation of bacteria to cold temperature and a virulence factor. The apxIBD and pnp genes were deleted successfully from APP serotype 1 and 5 by transconjugation and sucrose counter-selection. The APP1ΔapxIBDΔpnp and APP5ΔapxIBDΔpnp mutants lost hemolytic activity and could not secrete ApxI and ApxII toxins outside the bacteria because both mutants lost the ApxI- and ApxII-secreting proteins by deletion of the apxIBD gene. Besides, the growth of these mutants was defective at low temperatures resulting from the deletion of pnp. The APP1ΔapxIBDΔpnp and APP5ΔapxIBDΔpnp mutants were significantly attenuated compared with wild-type ones. However, mice vaccinated intraperitoneally with APP5ΔapxIBDΔpnp did not provide any protection when challenged with a 10-times 50% lethal dose of virulent homologous (APP5) and heterologous (APP1) bacterial strains, while mice vaccinated with APP1ΔapxIBDΔpnp offered 75% protection against a homologous challenge. The ΔapxIBDΔpnp mutants were significantly attenuated and gave different protection rate against homologous virulent wild-type APP challenging.

• Journal of Practical Agriculture & Fisheries Research
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• v.25 no.3
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• pp.14-18
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• 2023

White leg shrimps cultured in an inland private aquaculture farm with low salinity waters showed abnormal swimming behavior and appetite reduction in July 2022. Then, gradual mortality was observed in the aquaculture farm. During the diagnosis, bacterial strain KNUAF-SHP3 was isolated from the hepatopancreas of the dead shrimps. Based on the sequence of 16S rRNA gene, KNUAF-SHP3 was proved to be Shewanella sp., clustering into a group with S. algae MARS 14 and S. chilikensis JC5T. According to the result of experimental infection test, all shrimps challenged with high concentrations, 2.1×108 CFU/ml and 2.1×109 CFU/ml showed apparent disease symptoms and the cumulative mortality rates reached 100% in 7 days post challenge. These results emphasized that Shewanella isolate in this study can be a potential pathogen of white leg shrimp cultured in low salinity water.

• Journal of Veterinary Science
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• v.25 no.1
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• pp.4.1-4.14
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• 2024

Background: Lawsonia intracellularis is the causative agent of proliferative enteropathy and is associated with several outbreaks, causing substantial economic loss to the porcine industry. Objectives: In this study, we focused on demonstrating the protective effect in the mouse model through the immunological bases of two vaccine strains against porcine proliferative enteritis. Methods: We used live-attenuated Salmonella Typhimurium (ST) secreting two selected immunogenic LI antigens (Lawsonia autotransporter A epitopes and flagellin [FliC]-peptidoglycan-associated lipoprotein-FliC) as the vaccine carrier. The constructs were cloned into a Salmonella expression vector (pJHL65) and transformed into the ST strain (JOL912). The expression of immunogenic proteins within Salmonella was evaluated via immunoblotting. Results: Immunizing BALB/c mice orally and subcutaneously induced high levels of LI-specific systemic immunoglobulin G and mucosal secretory immunoglobulin A. In immunized mice, there was significant upregulation of interferon-γ and interleukin-4 cytokine mRNA and an increase in the subpopulations of cluster of differentiation (CD) 4⁺ and CD 8⁺ T lymphocytes upon splenocytes re-stimulation with LI antigens. We observed significant protection in C57BL/6 mice against challenge with 10^6.9 times the median tissue culture infectious dose of LI or 2 × 10⁹ colony-forming units of the virulent ST strain. Immunizing mice with either individual vaccine strains or co-mixture inhibited bacterial proliferation, with a marked reduction in the percentage of mice shedding Lawsonia in their feces. Conclusions: Salmonella-mediated LI gene delivery induces robust humoral and cellular immune reactions, leading to significant protection against LI and salmonellosis.

• Clinical and Experimental Vaccine Research
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• v.12 no.4
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• pp.304-312
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• 2023

Purpose: Due to the many problems with commercially available vaccines, the production of effective vaccines against brucellosis is a necessity. The aim of this study was to evaluate the immune responses caused by the chimeric protein consisting of trigger factor, Bp26, and Omp31 (TBO) along with aluminum hydroxide (AH/TBO) and selenium (Se/TBO) nanoparticles (NPs) as adjuvants in mouse model. Materials and Methods: Recombinant antigen expression was induced in Escherichia coli BL21 (DE3) bacteria using IPTG (isopropyl-d-1-thiogalactopyranoside). Purification and characterization of recombinant protein was conducted through NiFe₃O₄ NPs, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and Western blot. NP characteristics, including morphology and particle size, were measured in vitro. The recombinant TBO was loaded on to AH and Se NPs and were administered subcutaneously. After mice immunization, measurement of antibody titter and protection assay was performed. Results: The average sizes of AH and Se NPs were about 60 nm and 150 nm, respectively. The enzyme-linked immunosorbent assay results showed that the serum of mice immunized by subcutaneous injection with both nanovaccines produced significant immunoglobulin G (IgG) responses against the chimeric antigen. The results of TBO-specific IgG isotype (IgG2a/IgG1) analysis showed that both AH and Se NPs induced a type to T-helper immune response. In addition, the results of the challenge with the pathogenic strain of Brucella melitensis 16M showed that vaccinated mice with AH/TBO NPs indicated a higher reduction of bacterial culture than immunized mice with Se/TBO NPs and TBO alone. Conclusion: The results showed that AH NPs carrying chimeric antigen can be a promising vaccine candidate against brucellosis by producing protective immunity.

• Microbiology and Biotechnology Letters
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• v.41 no.3
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• pp.358-366
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• 2013

The aim of this study was to evaluate the antimicrobial activities of Glycyrrhiza uralensis and Glycyrrhiza glabra extracts with various countries of origin. Three samples of licorice with various origins (Korea, China, and Uzbekistan) were evaluated for their antimicrobial activities against six skin microflora. The bioassay applied for determining the antimicrobial effects included the disc diffusion assay, minimum inhibitory concentration, and challenge test. The ethyl acetate fractions of G. uralensis and G. glabra extracts showed significant antimicrobial activities against two gram-positive (Bacillus subtilis, Propionibacterium acnes) and two gram-negative (Escherichia coli, Pseudomonas aeruginosa) bacteria. These samples had much more intensive antimicrobial activities than synthetic preservatives on B. subtilis, P. acnes, and P. aeruginosa, especially. Korean licorice showed the highest antimicrobial activity amongst the samples tested. In view of the observed inhibitory features of these G. uralensis and G. glabra extracts, it is suggested that they could be used as natural antiseptics against bacterial contamination in cosmetics and foods, instead of the common synthetic preservatives currently employed.