• 한국식품위생안전성학회지
• /
• 제12권3호
• /
• pp.200-204
• /
• 1997

Effects of benzoate (0~0.6 g/$\ell$ ) and sorbate (0~2.0 g/$\ell$) on the growth of Escherichia coli O157:H7 in tryptic soy broth at various pH levels (4~8) and temperatures (4$^{\circ}C$, 37$^{\circ}C$) were investigated. Benzoate and sorbate were inhibited the growth of E. coli O157:H7 up to 12 hours cultivation at 4$^{\circ}C$, and 2.0 g/$\ell$ sorbate was only inhibited during 48 hours cultivation at 37$^{\circ}C$. Among the pH levels tested, pH 4 showed significant inhibitory effect against the E. coli O157:H7 on 4$^{\circ}C$ and at 37$^{\circ}C$, respectively. When used in combination 0.2 g/$\ell$ benzoate and sorbate were completely inhibited the growth of E. coli O157:H7 on pH 4 and at 37$^{\circ}C$. While on pH 5 at 4$^{\circ}C$, all of the concentration tested did not exert any inhibitory effect. The combined effects were retarded more than single treatment of E. coli O157:H7.

• 한국축산식품학회지
• /
• 제31권2호
• /
• pp.158-165
• /
• 2011

A sensitive reverse transcriptase-PCR (RT-PCR) method to detect viable Escherichia coli O157:H7 in milk was established. The primer sets were designed based on the nucleotide sequences of the rfbE (per) and wbdN genes in the O157 antigen gene cluster of E. coli O157:H7. RT-PCR using five different primer sets yielded DNA with sizes of 655, 518, 450, and 149-bp, respectively. All five of the E. coli O157:H7 strains were detected by RT-PCR, but 11 other bacterial species were not. The sensitivity of RT-PCR was improved by adding yeast tRNA as a carrier to the crude RNA extract. The RT-PCR amplifying the 149-bp DNA fragment was the most sensitive for detecting E. coli O157:H7 and the most refractory to the bactericidal treatments. Heat treatment at $65^{\circ}C$ for 30 min was the least inhibitory of all bactericidal treatments. Treatment with RNase A strongly inhibited the RT-PCR of heated milk but not unheated milk. This study described RT-PCR methods that are specific and sensitive with a detection limit of 10 E. coli O157:H7 cells, and showed that pre-treating milk samples with RNase A improved the specificity to detect viable bacteria by RT-PCR.

• 대한수의학회지
• /
• 제36권2호
• /
• pp.371-378
• /
• 1996

Three and 2 strains of E coli O157 were isolated from fecal materials of cattle (390) and pigs (420) in Korea, respectively. One strain of O157:H7 isolated from cattle and 2 strains of O157:H7 isolated from pigs were identified as verotoxin-1 (VT-1) produing strains and 2 strains (O157:H7 and O157:H-) isolated from cattle were identified as verotoxin-2 (VT-2) producing strains by neutralization test on HeLa and Vero cells. Culture supernatants of the isolates were cytotoxic to HeLa and Vero cells. The levels of cytotoxin produced by isolates were $10^2{\sim}10^4$ cytotoxic dose($CD_{50}$)/ml. Also, VT-2-converting bacteriophage was isolated from KSC109 strain which had been isolated from cattle. Molecular weight of the phage DNA was determined as approximately 45 Kb in 0.8% agarose gel electrophoresis, and morphology of the phage stained with phosphotungstic acid was observed by transmissible electron microscopy.

• Journal of Microbiology and Biotechnology
• /
• 제20권1호
• /
• pp.5-14
• /
• 2010

Enterohemorrhagic Escherichia coli O157:H7 is a major foodborne pathogen causing severe disease in humans worldwide. Healthy cattle are a reservoir of E. coli O157:H7, and bovine food products and fresh produce contaminated with bovine waste are the most common sources for disease outbreaks in the United States. E. coli O157:H7 also survives well in the environment. The abilities to cause human disease, colonize the bovine gastrointestinal tract, and survive in the environment require that E. coli O157:H7 adapt to a wide variety of conditions. Three major virulence factors of E. coli O157:H7 have been identified including Shiga toxins, products of the pathogenicity island called the locus of enterocyte effacement, and products of the F-like plasmid pO157. Among these virulence factors, the role of pO157 is least understood. This review provides a board overview of E. coli O157:H7 with an emphasis on pO157.

• 한국식품위생안전성학회지
• /
• 제12권4호
• /
• pp.367-378
• /
• 1997

• 대한수의학회지
• /
• 제38권4호
• /
• pp.745-750
• /
• 1998

A sensitive and rapid enzyme immunoassay(EIA) to detect Escherichia coli O157 in ground beef was developed by using a sandwich type assay with polyclonal antibodies to E coli O157. E coli O157 in ground beef could be detected within 15hr, including incubation for 12hr in enrichment broth and 3hr in immunoassay. The EIA could detect $1.3{\times}10^5$ cells of E coli O157/g of ground beef without enrichment. The lowest limit of detection was 0.23 E coli O157 per g of meat after enrichment. Confirmation was required in the positive specimens in the EIA by culture method even though the negative specimens were not. These results suggested that the immunoassay could be a very efficient method for the screening E coli O157 in meat.

• Food Science and Biotechnology
• /
• 제18권2호
• /
• pp.343-349
• /
• 2009

Inhibitory effect of Escherichia coli O157 adhered to Caco-2 cells by the cells of Lactobacillus plantarum K11 and the cell-free culture supernatant (CFCS) and bacteriocin prepared from this strain was investigated. As the cell counts of viable L. plantarum K11 previously adhered to Caco-2 were increased, the rate of adhesion and adherent cell counts of E. coli O157 was lower. However, because the heated L. plantarum K11 rarely have the adhesion ability to Caco-2, the adhesion rate and adherent cell counts of E. coli O157 were high. In addition, the inhibitory effects of E. coli O157 adhesion by the CFCS and bacteriocin of L. plantarum K11 were dose-dependent manner. Therefore, the inhibition of adhesion of E. coli O157 to Caco-2 may result from the antimicrobial substances such as lactic acid and bacteriocin. Moreover the inhibitory activity of adhesion by the heated bacteriocin for 30 min at 100oC was similar to activity of non-treated bacteriocin, but the activity was disappeared by treatment with protease.

• 한국식품위생안전성학회지
• /
• 제32권4호
• /
• pp.336-340
• /
• 2017

본 연구는 정향추출물의 E. coli O157:H7에 대한 항균효과와 E. coli O157:H7 감염 마우스에 대한 치료효과를 평가하기 위해 수행되었다. 정향 메탄올 추출물(FSAE)을 이용하여 E. coli O157:H7에 대한 항균효과 확인 시험을 수행한 결과, 배양 후 24시간째에, FSAE를 첨가한 모든 군들에서 E. coli O157:H7의 생존율이 무투여 대조군에 비해 통계적으로 유의성 있게 감소하는 결과를 보여(0.269 mg/ml, p < 0.05; 0.538과 1.075 mg/ml, p < 0.001), FSAE가 E. coli O157:H7의 증식억제 효과가 뛰어난 것으로 확인되었다. 또한, E. coli O157:H7을 감염시킨 마우스에 FSAE를 경구로 투여한 결과, 투여 후 3일째에, FSAE를 1.075 (p < 0.05)와 2.15 mg/ml (p < 0.01)로 투여한 군들에서 대조군과 비교하여 분변내 E. coli O157:H7의 균수가 유의성 있게 감소하였으며, 투여 7일째에는, 모든 FSAE 투여군들에서 대조군과 비교하여 E. coli O157:H7의 균수가 통계적으로 유의성 있게 감소하였다(0.538 mg/ml, p < 0.05; 1.075와 2.15 mg/ml, p < 0.001). 이상의 연구결과로부터, FSAE를 E. coli O157:H7에 감염된 마우스에 경구로 투여할 경우, 감염증상을 완화 시킬 수 있을 것으로 기대된다.

• 한국미생물·생명공학회지
• /
• 제27권5호
• /
• pp.419-425
• /
• 1999

Prophylactic effects of Bifidobacterium longum HY8001, Korean isolate, against Escherichia coli O157:H7 and Salmonella typhimurium DT104 enteric infection were examined at four groups of specific pathogen free(SPF)-ICR mouse for each pathogen. B. longum HY8001+B. typhimurium DT104+B. longum HY8001(BL+ST+BL) group and B. longum HY8001+E. coli O157:H7+B. longum HY8001(BL+E+BL) group were fed with B. longum HY8001 before and after E. coli O157:H7 or s. typhimurium DT104 challenge, while B. longum HY8001+S. typhimurium DT104(BL+ST) and B. longum HY8001+e. coli O157:H7(BL+E) groups were fed with B. longum HY8001 only before E. coli O157:H7 or S. typhimurium DT104 challenge. E. coli O157:H7(E) and S. typhimurium DT104(ST) groups were challenged with each pathogen without B. longum HY8001 administration and control groups were administered with phosphate buffered solution(PBS). After the oral administration with B. longum HY8001(109cfu), th emice were challenged with E. coli O157:H7(2$\times$1010cfu) or S. typhimurium DT104(108cfu) and the mortality rate and the fecal shedding of challenged pathogen were also examined define the reactivity of the B. longum HY8001. Production of toxin neutralizing substance(s) of B. longum HY8001 was determined by cell cytotoxicity assay using Vero cells. Fecal shedding of th eS. typhimurium DT104 was significantly decreased in BL+ST+BL group fed with B. longum HY8--1 before and after challenge(p<0.05), while the fecal shedding s of S. typhimurium DT104 in BL+ST and St groups remained more than 106cfu. the protective effect of the B. longum HY8001 against E. coli O157:H7 was significantly high only in BL+E+BL group fed with b. longum Hy8001 before and after E. coli O157:H7 challenge from the result of fecal E. coli O157:H7 isolation rate, mortality rate, and intestinal contents culture to detect E. coli O157:H7. the mortality rate of the BL+e and E groups. The cytopathic effect (CPE) of the Vero cytotoxin (Shiga like toxin I & II) in Vero cell was neutralized in B. longum HY8001 culture supernatant added wells which indicate the presence of soluble Vero cytotxin neutralizing substance(s) in B. longum HY8001 culture suprnatant.

• Journal of Microbiology and Biotechnology
• /
• 제12권5호
• /
• pp.780-786
• /
• 2002

An immunosensor based on surface plasmon resonance (SPR) with a self-assembled protein G layer was developed for the detection of Escherichia coli O157:H7. A self-assembled protein C layer on a gold (Au) surface was fabricated by adsorbing the mixture of 11-mercaptoundecanoic acid (MUA) and hexanethiol at various molar ratios and by activating chemical binding between free amine (-$NH_2$) of protein G and 11-(MUA) using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDAC) in series. The formation of a self-assembled protein G layer on an Au substrate and the binding of the antibody and antigen in series were confirmed by SPR spectroscopy. The surface morphology analyses of the self-assembled protein G layer on the Au substrate, monoclonal antibody (Mab) against E. coli O157:H7 which was immobilized on protein G, and bound E. coli O157:H7 extracts on Immobilized Mab against E. coii O157:H7 were performed by atomic force microscopy (AFM). The detection limit of the SPR-based immunosensor for E. coli O157:H7 was found to be about $10^4$ cells/ml.