• Journal of Dairy Science and Biotechnology
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• v.40 no.4
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• pp.151-162
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• 2022

Although many developed countries (USA, Canada, and several EU countries) allow raw milk cheese to be aged more than 60 days, these countries have strict standards for the aging conditions, such as temperature, of raw milk cheese. Spiking experiments were conducted with Camembert cheese made from raw milk, to assess the microbiological safety of raw milk cheese aged for more than 60 days. We spiked Escherichia coli O157:H7 into raw milk with different inoculation levels (high, medium, and low). Camembert cheese was prepared from the inoculated raw milk, then aged in an incubator for up to 9 weeks (63 days). There were no significant differences in pH and water activity (aW) between uninoculated cheese and cheese samples inoculated with E. coli O157:H7 (p<0.05). The pH and aWof the Camembert cheese decreased throughout the storage period. In conclusion, E. coli O157:H7 did not affect the pH and aW of the cheese samples. Cell counts were conducted every week using the agar-plating method. Inoculated cells were completely eliminated, especially in Camembert cheese, after 60 days, and the reduction rate of cells was much faster in Camembert cheese.

• Food Science and Biotechnology
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• v.17 no.1
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• pp.191-194
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• 2008

The antagonistic activity of probiotic strains (Bifidobacterium animalis BB-12, Bifidobacterium bifidum A, Bifidobacterium longum B6, Lactobacillus acidophilus ADH, Lactobacillus paracasei ATCC 25598, and Lactobacillus rhamnosus GG) against nalidixic acid resistant ($NA^R$) Escherichia coli O157:H7 MF1847, E. coli O157:H7 H2439, E. coli O157:H7 ATCC 43894, and E. coli O157:H7 C7927 was investigated using the agar-overlay, well diffusion, and broth culture tests. L. paracasei ATCC 25598 was the most effective probiotic strain in terms of in vitro antagonistic activity against $NA^R$ E. coli O157:H7, followed by L. rhamnosus GG, B. longum B6, and L. acidophilus ADH. The use of selected probiotic strains could be an effective pre-harvest intervention strategy to reduce the risk of $NA^R$ E. coli O157:H7 by maintaining a balanced microflora in animals and might provide many potential benefits in lieu of using antimicrobials.

• Preventive Nutrition and Food Science
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• v.5 no.3
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• pp.131-135
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• 2000

The inhibitory effect of various organic acids on the growth and survival of Escherichia coli O157:H7 in tryptic soy broth with 0.6% yeast extract at 37$^{\circ}C$ or 4$^{\circ}C$ was determined. Minimal inhibitory pHs of acetic acid, citric acid, fumaric acid, hydrochloric acid and lactic acid were 5.0, 4.0, 4.5, 4.0 and 4.5, respectively. Acetic acid (0.012 m) showed the strongest antimicrobial activity, based on the pH values or equivalent molar concentrations, followed by lactic acid (0.0006 M), fumaric acid (0.004M) and citirc acid (0.004 M), respectively, E. coli O157:H7 with an initial inoculum of {TEX}$10^{7}${/TEX} CFU/ml and {TEX}$10^{5}{/TEX} CFU/ml in tryptic soy broth supplemented with 0.6% yeast extract, acidified to target pH with citric, fumaric and lactic acids at 37$^{\circ}C$, was completely inactivated after 7 d and 5 d incubation, respectively, except for the acetic acid (9 d). The bactericidal effect decreased at the same pH when the incubation temperature a was reduced from 37$^{\circ}C$ to 4$^{\circ}C$. The pH values of 0.2% acetic (pH 5.1), 0.6% citric (pH 4.2) and 0.4% lactic acid (pH 4.3) in TSBYE were almost correspondent to the minimal inhibitory pH values on E. coli O157:H7 of acetic (pH 4.0), citric (pH 4.0) and lactic acids (pH 4.5).

• Biomedical Science Letters
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• v.8 no.3
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• pp.107-113
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• 2002

Enterohemorrhagic Escherichia coli (EHEC) strains of serotype O157:H7 have been shown to colonize the intestinal epithelial cell by the attaching and effacing (AE) mechanism. The AE lesion is mediated by an intimin, of which production and expression are controlled by a 3-Kb eaeA gene located EHEC chromosomal DNA. If the eaeA gene is mutated, EHEC O157:H7 strains lose capacity of adhesion to intestinal epithelial cells. In this study, a 891 bp of the 3'-end region of a gamma intimin was amplified by polymerase chain reaction (PCR). The PCR product was inserted into pSTBlue-1 cloning vector and transformed into DE3 (BL21) competent cell. After plasmid mini-preparation and restriction enzyme digestion of eaeA/891-pSTBlue-1 vector, target eaeA gene was re-inserted into pET-28a expression vector and was transformed. Then the expression of recombinant eaeA/891 (891 bp) gene was induced by isopropyl-$\beta$-D-thiogalactopyranoside (IPTG). The expression of the 40-KDa recombinant protein was identified in SDS-PAGE and confirmed by immunoblotting using the His.Tag$^{\circledR}$ and T$_{7}$.Tag$^{\circledR}$ monoclonal antibody. This recombinant protein expressed by eaeA gene could be applied in further studies on the mechanisms of E. coli O157:H7 infection and the development of recombinant vaccine.

• Korean Journal of Food Science and Technology
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• v.47 no.5
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• pp.593-598
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• 2015

This study determined the thermal resistance of Bacillus cereus, Escherichia coli O157:H7, and Listeria monocytogenes in multi-grain soymilk and proposes processing conditions that meet the national standard for retort food products in Korea. D and z values were calculated from thermal inactivation kinetic curves after heating at 55, 60, and $65^{\circ}C$. The D value for B. cereus at $55^{\circ}C$ was the highest (22.8 min), followed by that for E. coli O157:H7 (18.8 min) and L. monocytogenes (17.6 min). At $60-65^{\circ}C$, the order was L. monocytogenes ($D_{60-65^{\circ}C}=3.4-0.9min$), E. coli O157:H7 (3.0-0.3 min), and B. cereus (1.2-0.3 min). The z values for these species were 5.2, 5.5, and $7.7^{\circ}C$, respectively. The Korean national standard for retort food products was achieved by thermal processing at $124{\pm}2^{\circ}C$ for 0.3-2.2 min. This study provides useful data for ensuring both the microbiological safety and product quality of multi-grain soymilk products.

• Journal of Food Hygiene and Safety
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• v.32 no.1
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• pp.64-69
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• 2017

This study was conducted to investigate the effect of cold plasma combined with UV-C irradiation against Escherichia coli O157:H7, Salmonella enterica serovar Typhimurium, and Listeria monocytogenes on lettuce. E. coli O157:H7, S. Typhimurium, and L. monocytogenes, corresponding to approximately 5.82, 5.09, 5.65 log CFU/g, were inoculated on lettuce, respectively. Then, the lettuce was treated with cold plasma, UV-C and combination (cold plasma + UV-C), respectively. The treated lettuce was stored for 9 days at $4^{\circ}C$ for microbiological analysis and sensory evaluation. Cold plasma reduced the populations of E. coli O157:H7, S. Typhimurium, and L. monocytogenes by 0.26, 0.65, and 0.93 log CFU/g, respectively. Each microorganism were reduced by 0.87, 0.88, and 1.14 log CFU/g after UV-C treatment. And, the combined treatment that was treated by cold plasma after UV-C treatment reduced the populations of inoculated microorganisms by 1.44, 2.70, 1.62 log CFU/g, respectively. The all treatment significantly (p < 0.05) reduced the populations of all inoculated bacteria compared to untreated lettuce. UV-C combined with cold plasma was the most effective for reducing the pathogenic bacteria on lettuce, by showing log-reductions of ${\geq}2.0\;log\;CFU/g$. All treatment was not significantly different until 6 day storage compared to control group in terms of appearance, texture and overall acceptability. Therefore, the combined treatment will be an effective intervention method to control the bacteria on lettuce.

• Food Science of Animal Resources
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• v.29 no.3
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• pp.391-395
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• 2009

Gelidium corneum - gelatin (GCG) blend films containing fermented pollen extract (FPE) were prepared and used as a packaging material of pork loins. Water vapor permeability (WVP) of the film containing FPE was better than the control film, and the film's antimicrobial activity against Escherichia coli O157:H7 and Listeria monocytogenes increased with increasing FPE concentration. Addition of 0.15% FPE decreased the populations of Escherichia coli O157:H7 and Listeria monocytogenes by 2.98 and 3.68 Log CFU/g, respectively, compared to the control. Pork loin samples were inoculated with E. coli O157:H7 and L. monocytogenes and packed with the film. The samples packed with the GCG film containing 0.15% FPE had a decrease in the populations of E. coli O157:H7 and L. monocytogenes by 1.49 and 1.01 Log CFU/g after 4 d of storage, respectively, compared to the control. The results suggested that shelf life of the pork loins could be extended by packaging with the GCG film containing 0.15% FPE.

• KSBB Journal
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• v.17 no.6
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• pp.537-542
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• 2002

To screening of antimicrobial activity, 95% ethanol and hot water extracts of roots, fruits, leaves, radix and stems of 50 species of traditional herbal medicines were examined. For their growth inhibitory effects on two food-born microorganisms, S. aureus and E. coli O157:H7, by the paper disc diffusion method and the minimum inhibitory concentration(MIC) test. Moutan radicis Cortex and Achyranthis Radix showed the highest inhibitory activities on both S. aureus and E. coli O157:H7. The Inhibition zones of Moutan radicis Cortex on S. aureus and E. coii O157:H7 were 22 mm and 24 mm respectively, and the corresponding inhibition zone of Achyranthis Radix were 23 mm and 22 mm. The MIC or Achyranthis Radix on S. aureus was 156.25 $\mu$g/mL, and the MIC or Achyranthis Radix and Moutan radicis Cortexas on E. coli O157:H7 were 625 $\mu$g/mL and 312.5 $\mu$g/mL, respectively. Their antimicrobial activities in ethanolic extracts were significantly higher than in hot water extracts. In the various solvent fractions prepared from ethanol extract, the ethyl acetate fraction of Achyranthis Radix and the CHCl$_3$ fraction of Moutan radicis Cortexas showed strongest activity.

• Microbiology and Biotechnology Letters
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• v.29 no.3
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• pp.169-175
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• 2001

This study was conducted to investigate the effects of bifidobacteria on the growth and Caco-2 cell-adherence of Escherichia coli O157:H7 .Dur-ing momo-culture of E. coli O157:H7 and mixed culture with Bifidobacterium infantis K9, pH viable cell count, and ammonia concentration were measured Co-cultivation of E. coli O157:H7 with bifidobacteria. producing acidic metabolites rapidly decreased the viable cell count of E. coli O157:H7 In addition rapid decrease of ammo- nia concentration was observed during mixed culture after 8 hrs incubation compared to single culture of E. coli O157:H7 Therefore it is likely that bifidobacteria assimilate ammonia produced by E. coli O157:H7 P4 B, infantis K9 showed quite similar adherence on the Caco-2 cells in either case. On the other hand adherence of E. coli O157:H7 decreased from 2.6% to 1.86% when B infantis K9 was adhered to Caco-2 cell 2 hrs prior to the application of E. coli O157:H7 In conclusion in adherence of E coli O157:H7 to Caco -2 cell was inhibited by competition of its binding to the adherence site with bifidobacteria. In addition inhibitory effects of bifidobacteria on E coli O157:H7 appeared to be much higher with increae of the number of bifidobacteria and its ability of adherence to Caco-2 cells.

• Korean Journal of Food Science and Technology
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• v.43 no.5
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• pp.618-623
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• 2011

Escherichia coli O157:H7 has been considered as a significant food-borne pathogen since its role in causing hemorrhagic colitis and hemolytic uremic syndrome in humans was recognized. In this study, we developed an immunochromatography (ICG) assay for the detection of E. coli O157:H7. E. coli O157:H7 monoclonal antibody (EC MAb) and colloidal gold were conjugated and its specificity was determined by the ICG treated with EC MAb and antimouse IgG at test and control lines, respectively. The detection limit of the ICG was $1{\times}10^5$ CFU/mL, and no crossreactivity was observed to other E. coli strains and major food-borne pathogens. To determine the minimum enrichment time for the ICG, meats and sprouts were inoculated with $1{\times}10$ CFU/100 ${\mu}L$ of E. coli O157:H7. After enrichment time of 10 and 2 h for meats and sprouts, respectively, up to $1{\times}10$ CFU/100 ${\mu}L$ of E. coli O157:H7 could be detected by ICG.