• 대한의생명과학회지
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• 제8권3호
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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.

• Preventive Nutrition and Food Science
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• 제6권1호
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• pp.6-9
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• 2001

Minimal inhibitory concentrations (MIC) and antimicrobial effects of glycerol monolaurate (monolaurin) and organic acids, either alone or in combination, against Escherichia coli O157:H7 in tryptic soy broth were determined. MIC values of monolaurin(ML), acetic (AA), citric (CA), lactic (LA) and hydrochloric acid (HCl) were 300$\mu\textrm{g}$/mL (0.03%), 1250$\mu\textrm{g}$/mL(0.125%), 5000$\mu\textrm{g}$/mL(0.5%), 2500$\mu\textrm{g}$/mL(0.25%) and 2500$\mu\textrm{g}$/mL(0.25), respectively. When 150$\mu\textrm{g}$/mL of ML was combined with 50$\mu\textrm{g}$/mL AA, 250$\mu\textrm{g}$/mL HCl and 125$\mu\textrm{g}$/mL LA, the combined agents did not increase the inhibitory effect of the most active single compound alone. This result indicates that there was little interaction between ML and A, HCl and LA. However, the combination of 150$\mu\textrm{g}$/mL ML and 250$\mu\textrm{g}$/mL CA synergistically inhibited growth of E. coli O157:H7. The present study showed that the nature of combined antimicrobial response against E. coli O157:H7 was complex, but this information would be useful for determining interaction that could compromise effectiveness in food systems.

• 동아시아식생활학회지
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• 제22권1호
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• pp.109-119
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• 2012

본 연구에서는 오미자 에탄올 추출물의 천연 항균제로서의 이용 가능성을 살펴보기 위하여 식품 위해성 세균에 대한 항균활성을 측정하였다. Paper disc diffusion test와 최소저해 농도(MIC) 측정에서는 오미자 에탄올 추출물이 Listeria monocytogenes, Bacillus cereus, Escherichia coli O157:H7에 대해 큰 생육저해환과 낮은 MIC를 나타내었다. Time-kill assay에서는 L. monocytogenes의 생육이 오미자 에탄올 추출물에 의해 가장 저해되는 것으로 나타났다. 또한 오미자 에탄올 추출물을 처리한 E. coli, E. coli O157:H7, Staphylococcus aureus, Pseudomonas aeruginosa에서는 ${\beta}$-galactosidase와 o-nitrophenyl-${\beta}$-D-galactoside가 높은 반응을 나타냄으로써 오미자 에탄올 추출물로 인해 세포막 손상이 유발됨을 유추할 수 있었다. 또한 E. coli, E. coli O157:H7, P. aeruginosa, Salmonella Typhimurium 등 그람음성균에서는 오미자 에탄올 추출물의 처리 농도가 높을수록 세포구성물의 유출과 세포 외막의 투과성이 증가하는 현상이 나타났다. 시차주사현미경(SEM)과 투과전자현미경(TEM)을 이용하여 관찰한 세포구조에서도 오미자 에탄올 추출물 처리 시 세포막의 부분적인 파괴와 세포 팽윤이 일어난 것을 확인할 수 있었다. 따라서 이들 결과는 오미자 에탄올 추출물이 식품위해성 세균에 대해 높은 항균 활성을 가지고 있으며, 천연 항균소재로서의 이용 가능성이 있음을 보여주었다.

• 한국식품조리과학회지
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• 제24권4호
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• pp.445-451
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• 2008

This study compared the effects of chlorine dioxide and a commercial chlorine sanitizer for inhibiting foodborne pathogens, including Salmonella enterica serovar Typhimurium, Listeria monocytogenes, and Escherichia coli O157 : H7, on lettuce leaves. The lettuce samples were inoculated with each cocktail of the three strains, and were then treated with chemical sanitizers [distilled water, 100 ppm commercial chlorine and 50 ppm, 100 ppm, 200 ppm chlorine dioxide ($ClO_2$)] for 1 min, 5 min, and 10 min at room temperature($22{\pm}2^{\circ}C$). Following inoculation of the leaves, initial populations of E. coli O157:H7, L. monocytogenes, and S. Typhimurium were approximately 5.54, 4.47, and 5.12 log CFU/g, respectively these levels were not significantly reduced by the treatment with water,whereas the 100 ppm commercial chlorine sanitizer treatment and $ClO_2$ (at all tested concentrations) were effective at reducing levels of all three pathogens. The treatment of 200 ppm $ClO_2$ for 10 min was most effective at inhibiting the three pathogens, and reduction levels of E. coli O157 : H7, L. monocytogenes, and S. Typhimurium were 2.28, 1.95, 1.76 log, respectively. The inhibitory effect of $ClO_2$ increased with increasing treatment concentration of $ClO_2$, but there was no significant difference by the treatment times. When chemically injured cells of E. coli O157 : H7 and L. monocytogenes and S. Typhimurium were examined by SPRAB and selective overlay methods, respectively, it was observed that the commercial chlorine sanitizer generated greater numbers of injured L. monocytogenes than the $ClO_2$ treatment. From the overall results, $ClO_2$ was more effective at inhibiting pathogenic bacteria compared to the commercial chlorine sanitizer therefore, it has potential to be utilized as an alternative sanitizer to increase the microbial safety of fresh produce.

• 한국식품위생안전성학회지
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• 제30권1호
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• pp.92-97
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• 2015

본 연구에서는 포장방법 (진공, 일반)과 저장온도($4^{\circ}C$, $-20^{\circ}C$)를 달리한 육류 (소고기, 닭고기) 및 생선에 대해 저선량 감마선 반복조사를 적용하였을 때 나타나는 병원성 미생물 E. coli O157:H7 및 S. Typhimurium의 사멸효과를 확인하였다. 소고기와 닭고기의 경우 E. coli O157:H7은 최소 2 kGy 이상의 단일조사와 0.5 kGy 이상으로 반복조사 시 생육이 확인되지 않았고, S. Typhimurium은 최소 2 kGy 이상의 단일조사와 1 kGy 이상으로 반복조사 시 생육이 확인되지 않았다. 생선의 경우 최소 0.5 kGy 이상의 단일 및 반복조사 시 E. coli O157:H7 와 S. Typhimurium의 생육이 확인되지 않았다. 육류보다 생선이 낮은 선량으로 미생물을 사멸시킬 수 있었으며, 전반적으로 포장 방법에 따른 조사선량의 차이는 없었으나 저장온도의 경우 냉장보다 냉동의 경우가 좀 더 높은 조사선량을 요구하는 것으로 확인되었다.

• 한국식품영양과학회지
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• 제45권4호
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• pp.577-584
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• 2016

다양한 환경에서 분리된 시가독소 생산성 대장균(Shiga toxin-producing E. coli, STEC, n=18)을 초산혼합용액(AAS;400 mM, pH 3.2, $30^{\circ}C$)에 노출한 후 산 저항성을 측정하였다. 또한, 선정된 4종류의 non-O157:H7 STEC균을 사과주스, 파인애플주스, 오렌지주스, 딸기주스(pH 3.8)에 정봉하여 $4^{\circ}C$와 $20^{\circ}C$에서 24시간 산 적응시킨 후 위합성용액(SGF, pH 1.5)에서 2시간 동안 생존능력을 평가하였다. Non-O157:H7 STEC를 AAS에 노출했을 때 O111 혈청형의 STEC는 평균 0.12 log CFU/mL 감소하여 다른 혈청형에 비하여 가장 강한 산 저항성을 나타냈고 O157:H7 STEC와 유의적 차이가 없었으며(P>0.05), O26 혈청형의 STEC는 가장 민감한 것으로 나타났다. 반면, AAS에 glutamic acid를 첨가하였을 경우 모든 STEC는 혈청형과 관계없이 초산에 매우 강한 저항성을 나타내었다(P>0.05). SGF에서 생존능력을 측정한 결과, 06E0218(O157:H7)은 다른 non-O157:H7 STEC 균들보다 생존능력이 낮았고 03-4669(O145:NM)가 가장 강한 생존능력을 나타내었다. 한편, 과일주스 중에서는 파인애플주스에 산 적응된 STEC가 SGF에 가장 강한 생존능력을 나타내었다. $4^{\circ}C$의 과일주스에 STEC를 산 적응시켰을 경우 $20^{\circ}C$보다 SGF에 대한 생존능력이 현저하게 높았다(P<0.05). 따라서 과일주스에 의한 non-O157:H7 STEC의 산 적응력 증가는 위장관 내 생존율 및 식중독 발생을 높일 수 있으므로 이에 대한 적절한 연구와 안전관리 옵션을 제공할 필요가 있을 것으로 판단된다.

• 한국식품위생안전성학회지
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• 제12권3호
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• pp.188-194
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• 1997

The growth inhibition effect of Orally administrated yogurt ACE and Metchnikoffupon E. coli O157:H7 and S. typhimurium inoculated into gastric lumen of rabbits was in vestigated. The rabbits challenged with each 1 $m\ell$ of suspension containing 108 CFU/$m\ell$ of the pathogens were divided into 4 groups by the interval of yogurt administration: A group; preadministrated 7 days before inoculation of the pathogens and fed daily; B group; administrated daily after inocjlation of the pathogens, C group; administrated every 3 days after inoculation of the pathogens; Control group, not fed after inoculation of the pathogens. Each 3 $m\ell$ of yogurt containing 109 CFU/$m\ell$ was orally administrated into rabbits. All yogurt administrated groups (A, B, c) chowed growth ingibition effect on E. coli O157:H7 in one day after inoculation of the pathogen by the level of 0.8~1.0 log CFU/g, compared with the result differences between the control group and the yogurt administrated groups. In the control group after 5 days of inoculation, the number of colonized pathogens was 105~106 CFU/g, whereas 103~104 CFU/g was detected in the yogurt administrated groups. After 10 days of inoculation, the viable pathogen number per gram (g) of the rabbit feces was 103 CFU/g in the control group, whereas the number below 101 CFU/g was detected in the group A, and 102 CFU/g in the control group, B and C. The growth inhibition effect of yogurt administration on E. coli O157:H7 was highly increased in the order of A, B, and C group. The same effect on S. typhimurium was observed at the level of 2 log CFU/g in the Metchnikoff yogurt administrated groups, compared with the control group result in one day after inoculation of the pathogen. In 7 days after inoculation of the pathogen, the viable number was increasingly decreased, and finally after 15 days no viable cell of S. typhimurium was discharged into the fecal samples in the group A, and the mean level of 10* CFU/g was detected in the group B, but there was no growth inhibition effect in the group C. The growth inhibition effect on S. typhimurium was observed at the same level of viable cell number between the yogurt ACE administrated groups and the control group in 5 days after inoculation. But, after 10 days of inoclation the viable cell number was started to decrease, and the viable cell of S. typhimurium was not discharged from rabbit intestinal contents after 15 days of inoculation in the yogurt ACE administrated groups. In such a case that yogurt was administrated in order to prevent the pathogens, pre-administration on a daily basis one week before inoculation of the pathogens exerted considerable effect in growth inhibition. In comparison with two kinds of yogurt tested in this study, the growth inhibition effect on two kinds of pathogens was observed more highly in the Metchnikoff administated group than the ACE administrated group.

• Food Science and Biotechnology
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• 제17권3호
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• pp.679-682
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• 2008

A lactic acid bacterium producing an antimicrobial substance against Escherichia coli O157:H7 was isolated from raw milk and identified as Lactobacillus amylovorus ME-1. In addition to E. coli O157 :H7, the antimicrobial substance also inhibited the growth of Bacillus cereus, Listeria monocytogenes, Pseudomonas aeruginosa, Salmonella typhimurium, Staphylococcus aureus, Streptococcus agalactiae, Streptococcus pyrogenes, and Yersinia enterocolitica. The antimicrobial substance was stable at pH 2-12 and $121^{\circ}C$ for 15 min and insensitive to proteinase K, protease, amylase, and catalase. Purification of the antimicrobial substance was conducted through methanol and acetonitrile/ethylacetate extraction, ultrafiltration with a 500 Da cutoff, thin layer chromatography (TLC) with silicagel 60, and high performance liquid chromatography (HPLC) with a $C_{18}$ reverse phase column. The ${\lambda}_{max}$ of the purified antimicrobial substance was determined as 192 nm by ultra violet (UV) scanning, while the molecular weight was estimated as 453 Da based on the mass spectrum. Accordingly, the current results suggest that the antimicrobial substance from the L. amylovorus ME-1 was not a bacteriocin, but rather a new non-proteinaceous substance distinct from acidophilin, acidolin, diacetyl, and reuterin.

• 한국식품과학회지
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• 제53권6호
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• pp.819-822
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• 2021

To enhance phage endolysin-mediated cell wall disruption of Escherichia coli O157:H7, the cells were co-treated with aromatic compounds, namely thymol or eugenol, found in essential oils and endolysin LysECP26. Interestingly, the minimal inhibitory concentrations of LysECP26 was four times lower when used in combination with either of the two compounds than when it was used alone. This synergistic activity was also confirmed by viable cell counting. Within 1 h of LysECP26 and eugenol or thymol co-treatment to the cells, there was a 2.3 or 3.8 log CFU/mL reductions, respectively. Additionally, field emission scanning electron microscopy showed cell wall disruption and severe morphological alterations of the cells in case of the combination treatments. Therefore, endolysin and thymol or eugenol co-treatment can help in developing efficient bio-control strategies against gram-negative pathogen E. coli O157:H7.

• 한국환경농학회지
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• 제38권4호
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• pp.254-261
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• 2019

농업용수는 채소류의 식중독세균 오염의 주요 경로 중 하나임에도 불구하고 우리나라에서는 농업용수의 미생물학적 안전성 대한 기초 자료가 부족한 실정이다. 본 연구에서는 전라북도에서 2018년 4월, 7월, 10월에 31지점에서 수집한 지표수 시료와 2018년 4월 7월에 20지점에서 수집한 지하수 시료의 위생지표세균 밀도를 조사하였다. 지표수에서는 평균적으로 대장균군이 2.7±0.55 log CFU/100 mL, 분원성대장균군 1.9±0.71 log CFU/100 mL, 대장균 1.4±0.58 log CFU/100 mL로 나타났고, 7월에 가장 높은 밀도를 보였다. 지하수의 경우 평균적으로 대장균군이 1.9±0.58 log CFU/100 mL, 분원성대장균군 1.4±0.37 log CFU/100 mL, 대장균 1.0±0.33 log CFU/100 mL로 나타났고 조사시기 간의 유의한 차이가 나타나지 않았다. 총질소량(T-N), 질산성질소(NO₃-N) 등 유기물 함량이 높은 용수에서 E. coli O157:H7의 생존이 연장되는 것으로 나타났다. 물에서의 E. coli O157:H7 감소율은 25℃>35℃>5℃>15℃ 순으로 높게 나타났다. 이러한 결과는 전북 지역 농업용수의 미생물학적 오염도와 수질과 온도가 E. coli O157:H7의 생존에 미치는 영향을 보여준다. 이러한 결과는 농업용수의 미생물학적 오염도를 예측하고 미생물 제어 기술 개발의 기초자료로서 활용될 수 있다.