• Biotechnology and Bioprocess Engineering:BBE
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• v.8 no.4
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• pp.227-232
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• 2003

A self-assembled monolayer of protein G was fabricated to develop an immunosensor based on surface plasmon resonance (SPR), thereby improving the performance of the antibodybased biosensor through immobilizing the antibody molecules (lgG). As such, 11-mercaptoundecanoic acid (11-MUA) was adsorbed on a gold (Au) support, while the non-reactive hydrophilic surface was changed through substituting the carboxylic acid group (-COOH) in the 11-MUA molecule using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrocholide (EDAC). The formation of the self-assembled protein G layer on the Au substrate and binding of the antibody and antigen were investigated using SPR spectroscopy, while the surface topographies of the fabricated thin films were analyzed using atomic force microscopy (AFM). A fabricated monoclonal antibody (Mab) layer was applied for detecting E. coli O157:H7. As a result, a linear relationship was achieved between the pathogen concentration and the SPR angle shift, plus the detection limit was enhanced up to 10$^2$ CFU/mL.

• Food Science and Biotechnology
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• v.15 no.4
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• pp.511-515
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• 2006

Antibiotic resistance of foodborne pathogens adapted to garlic (Allium sativum Linn.) was determined in order to understand the relationship between antibiotic resistance and garlic. The Gram (-) strains of Escherichia coli and Salmonella typhimurium and the Gram (+) strains of Bacillus cereus and Staphylococcus aureus were subcultured consecutively in a garlic broth, and the surviving colonies on the agar were selected as the adapted strains. Minimal inhibitory concentrations (MIC) for 15 antibiotics on the adapted strains were determined on Muller-Hinton Infusion agar. Adaptation to 1.3%(v/v) garlic juice increased MIC for vancomycin, aminoglycoside, and erythromycin on B. cereus, and for ampicillin and erythromycin on E. coli O157:H7. MIC of aminoglycosides, chloramphenicol, and vancomycin on the adapted S. aureus increased. The adapted S. typhimurium was more resistant to penicillin and vancomycin than the non-treated strain. The adapted S. typhimurium and S. aureus lost their antibiotic resistance in non-garlic stress conditions. However, the adapted B. cereus was still resistant to erythromycin and vancomycin, and the adapted E. coli was also resistant to erythromycin. Antibacterial garlic might increase the antibiotic resistance of E. coli, B. cereus, S. aureus, and S. typhimurium and this resistance can continue even without the stress of garlic. Therefore, garlic as a food seasoning could influence the resistance of such pathogens to these antibiotics temporarily or permanently.

• Journal of the Korean Society of Food Science and Nutrition
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• v.40 no.1
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• pp.123-127
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• 2011

This study was conducted to decrease the microbial hazard in kimchi saline water with microwave plasma sterilization system and to evaluate the inactivation of foodborne pathogens by the microwave plasma sterilization system as a non-thermal treatment. Contamination of coliform, Escherichia coli, and yeasts and molds were detected in the used saline water, and the microbial populations increased as the saline water was reused repeatedly. The $D_{10}$-values of E. coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes by the microwave plasma sterilization system were 0.48, 0.52, and 0.45 cycle, respectively. In addition, the microbial populations of coliform, E. coli, Salmonella spp., total aerobic bacteria, and yeasts and molds in the used kimchi saline water were significantly decreased by treating the saline water using the microwave plasma sterilization system. Therefore, these results suggest that microwave plasma sterilization system can be useful in improving the microbial safety of the used saline water.

• Journal of Food Hygiene and Safety
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• v.38 no.1
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• pp.31-36
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• 2023

This study was conducted to evaluate the efficacy of sodium hypochlorite in eliminating Escherichia coli strains from leafy green and stem vegetables, which are frequently sold at community service centers. A cocktail of non-pathogenic E. coli and enterohaemorrhagic E. coli (E. coli O157:H7) was used to artificially contaminate the vegetables (initial numbers of bacteria 7-8 log CFU/g). The contaminated vegetables were soaked in sodium hypochlorite for 5 min and then washed three times with running water. After the treatment, number of viable bacterial cells on the vegetables was estimated. Sodium hypochlorite treatment reduced the E. coli population by 1-2 log CFU/g on leafy green and stem vegetables, a significant reduction from the initial number. Further, sodium hypochlorite showed better antimicrobial efficacy for leaves with a larger surface area, less roughness, and softness. There was no significant difference in the antimicrobial effect between 100 and 200 mg/kg of sodium hypochlorite. Therefore, it is not necessary to increase sodium hypochlorite concentration than the level suggested in the school meal hygiene management guidelines. However, sodium hypochlorite treatment is not sufficient to achieve a safe level of microorganisms on leafy green and stem vegetables since they generally have a high abundance of microorganisms on their surface. Thus, an alternative cooking method for fresh leafy green and stem vegetables in summer should be developed to ensure they are safe for consumption.

• Journal of Microbiology and Biotechnology
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• v.31 no.5
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• pp.710-716
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• 2021

A risk analysis of Shiga toxin (Stx)-encoding bacteriophage was carried out by confirming the transduction phage to non-Stx-producing Escherichia coli (STEC) and subsequent expression of the Shiga toxin genes. The virulence factor stx1 was identified in five phages, and both stx1 and stx2 were found in four phages from a total of 19 phage isolates with seven non-O157 STEC strains. The four phages, designated as ϕNOEC41, ϕNOEC46, ϕNOEC47, and ϕNOEC49, belonged morphologically to the Myoviridae family. The stabilities of these phages to temperature, pH, ethanol, and NaClO were high with some variabilities among the phages. The infection of five non-STEC strains by nine Stx-encoding phages occurred at a rate of approximately 40%. Non-STEC strains were transduced by Stx-encoding phage to become lysogenic strains, and seven convertant strains had stx1 and/or stx2 genes. Only the stx1 gene was transferred to the receptor strains without any deletion. Gene expression of a convertant having both stx1 and stx2 genes was confirmed to be up to 32 times higher for Stx1 in 6% NaCl osmotic media and twice for Stx2 in 4% NaCl media, compared with expression in low-salt environments. Therefore, a new risk might arise from the transfer of pathogenic genes from Stx-encoding phages to otherwise harmless hosts. Without adequate sterilization of food exposed to various environments, there is a possibility that the toxicity of the phages might increase.

• Journal of Food Hygiene and Safety
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• v.17 no.1
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• pp.36-44
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• 2002

GC-l00X is non-corrosive alkaline ionic water (pH 12). It is composed of hydroxyl radicals and supplemented with xylitol. Its antimicrobial activity was examined against 6 major food-borne pathogens; Staphylococcus aureus FRI 913, Salmonella enterica serova Enteritidis ATCC 13076, S. enterica serova Typhimurium Korean isolate, Vibrio parahaemolyticus ATCC 17803, Escherichia coli O157:H7 ATCC 43894 and Pseudomonas aeruginosa KCTC 1637 at three different temperatures (4$^{\circ}C$, $25^{\circ}C$ and 36$^{\circ}C$) with or without an organic material (2% yeast extract), respectively. The antimicrobial activities showed over 4 log-reductions (1.0$\times$10$^4$CFU/ml reduction) against all pathogens reacted at 37$^{\circ}C$ for 3 hours in the absence of the organic material. The activities showed same results when GC-l00X was diluted with same volume of distilled water or standard hard water (CaCO$_3$300 ppm). Its antimicrobial activity was more effective and quicker in Gram-negative bacteria than Gram-positive bacteria. Its washing efficacy against E. coli O157:H7 exposed to the surfaces of tomatoes (grapes) was compared with that of the other sanitizers such as other kitchen synthetic detergent and 100-ppm chlorine water. For the toxicological evaluation of the sanitizers, viable counts of E. coli O157:H7 penetrated into the core of tomatoes after washing products were also compared. The result revealed that GC-100X stock solution and its 5% diluted solution had similar washing effects to 100-ppm chlorine water and more effective than the other kitchen synthetic detergent. This result indicated that GC- l00X had antimicrobial activity and no toxicological side effects, therefore, could be useful for a new sanitizer to use in flood safety and kitchen hygiene.

• Korean Journal of Food Science and Technology
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• v.52 no.1
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• pp.103-108
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• 2020

Shiga toxin-producing Escherichia coli (STEC) is an important pathogenic bacteria and can cause severe foodborne disease. For STEC detection, conventional culture methods have disadvantages in the fact that conventional culture takes a long time to detect and PCR can also detect dead bacteria. To overcome these problems, we suggest a bacteriophage amplification assay, which utilizes the ability of bacteriophages to infect living cells and their high specificity. We used a combination of six bacteriophages infecting E. coli to make the bacteriophage cocktail and added ferrous ammonium sulfate as a virucidal agent to remove free-bacteriophages. When cherry tomato and paprika were artificially inoculated with the cocktail at a final concentration of around 3 log CFU/mL and were enriched for at least 5 h in mTSB broth with Novobiocin, approximately 2-3 log PFU/mL were detected through the bacteriophage amplification assay. Therefore, bacteriophage amplification assay might be convenient and a useful method to detect STEC in a short period of time.

• Korean Journal of Food Science and Technology
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• v.53 no.6
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• pp.799-808
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• 2021

This study was performed to investigate the extent of microbial contamination, the presence of enterotoxin genes, and the antibiotic susceptibility of Bacillus cereus in 58 red pepper plants and 43 environmental samples (soil, irrigation water, and gloves) associated with the plant cultivation. The detected counts of total aerobic bacteria, coliform bacteria, Escherichia coli, Bacillus cereus, and Staphylococcus aureus were lower in these samples, as compared to the regulations of standards for foods; moreover, pathogens, such as E. coli, E. coli O157:H7, Listeria monocytogenes, and Salmonella spp., were not detected. Genes encoding hemolysin BL enterotoxins (hblA, hblC, and hblD) as well as non-hemolytic enterotoxins (nheA, nheB, and nheC) were detected in 23 B. cereus specimens that were isolated from the test samples and had β-hemolytic activity. Interestingly, B. cereus is resistant to β-lactam and susceptible to non-β-lactam antibiotics. However, in this case, the isolated B. cereus specimens exhibited a shift from resistant to intermediate in response to cefotaxime and from susceptible to intermediate in case of rifampin, trimethoprim-sulfamethoxazole, vancomycin, clindamycin, and erythromycin. Therefore, the levels of B. cereus should be monitored to detect changes in antibiotic susceptibility and guarantee their safety.

• Journal of the Korean Society of Food Culture
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• v.15 no.1
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• pp.9-15
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• 2000

This study was conducted to investigate the antimicrobial activity of grapefruit extracts and polylysine mixture against food-borne pathogens. The mixture was showed a potent and quick antibacterial activity for 5 major bacteria causing food poisoning i.e. Escherichia coli, Escherichia coli O-157, Salmonella typhi, Staphylococcus aureus, Vibrio cholerae. The antibacterial effect of the mixture on the ordinary bacteria inhibiting on the surface of lettuce was lasted even 6 hrs after the treatment, however the mixture was non-effective on the color, smell and taste of lettuce. The treatment with 10% mixture solution of the foods such as fish, meat, rice and bread suppressed the growth of the bacteria and kept the foods more freshly than the untreated foods.

• Korean Journal of Food Science and Technology
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• v.47 no.1
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• pp.81-86
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• 2015

Intense pulsed light (IPL), a nonthermal technology, has attracted increasing interest as a food processing technology. However, its efficacy in inactivating microorganisms has not been evaluated thoroughly. In this study, we investigated the influence of IPL treatment on the inactivation of Escherichia coli O157:H7 depending on light intensity, treatment time, and pulse number. Increased light intensity from 500 V to 1,000 V, raised the inactivation rate at room temperature. At 1000 V, the cell numbers were reduced by 7.1 log cycles within 120 s. In addition, increased pulse number or decreased distance between the light source and sample surface also led to an increase in the inactivation rate. IPL exposure caused a significant increase in the absorption at 260 nm of the suspending agent used in our experiments. This indicates that IPL-treated cells were damaged, consequently releasing intracellular materials. The growth of IPL-irradiated cells were delayed by about 5 h. The degree of damage to the cells after IPL treatment was confimed by transmission electron microscopy.