• Journal of Dairy Science and Biotechnology
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• v.39 no.2
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• pp.51-62
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• 2021

Escherichia coli are the predominant facultative bacteria found in the gastrointestinal tract of animals and humans. Some strains of E. coli that acquire virulence factors and cause foodborne and waterborne diseases in humans are called pathogenic E. coli and can be divided into five pathotypes according to the virulence mechanism: EAEC, EHEC, EIEC, EPEC, and ETEC. Although selective media have been developed to detect E. coli, distinguishing pathogenic strains from non-pathogenic ones is difficult because of their similar biochemical properties. Therefore, it is very important to find a new and effective diagnostic method to identify pathogenic E. coli. With recent advances in molecular biology and whole genome sequencing, the use of polymerase chain reaction (PCR) is increasing rapidly. In this review paper, we provide an overview of pathogenic E. coli and present a review on PCR detection methods that can be used to diagnose pathogenic E. coli. In addition, the possibility of real-time PCR incorporating IAC is introduced. Consequently, this review paper will contribute to solving the current challenges related to the detection of pathogenic E. coli.

• Journal of Food Hygiene and Safety
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• v.28 no.3
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• pp.272-278
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• 2013

To evaluate the effect of surface contaminated with Escherichia coli O157:H7 (E. coli O157:H7) on the microbiological safety of lettuce, this study was conducted to investigate the attachment, biofilm producing, survival, and cross-contamination of E. coli O157:H7 on stainless steel and polyvinyl chloride (PVC). The attachment rate of E. coli O157:H7 on PVC was 10 times higher than that on stainless steel after exposure 1 h in cell suspension. However, there was not a difference between two types of surface after exposure for 6 h and 24h. The biofilm producing of E. coli O157:H7 was TSB > 10% lettuce extracts > 1% lettuce extracts > phosphate buffer. When two kinds of materials were stored at various conditions ($20^{\circ}C$ and $30^{\circ}C$, relative humidity (RH) 43%, 69%, and 100%), the numbers of E. coli O157:H7 at $30^{\circ}C$, RH 43% or RH 69% were reduced by 5.0 log CFU/coupon within 12 h regardless of material type. Conversely, the survival of E. coli O157:H7 at RH 100% was lasted more than 5 days. In addition, the reduction rate of E. coli O157:H7 was decreased in the presence of organic matter. The transfer efficiency of E. coli O157:H7 from the contaminated surface to lettuce was dependent upon the water amount of the surface of lettuce. Especially, the transfer rate of E. coli O157:H7 was increased by 10 times in the presence of water on the lettuce surface. From this study, the retention of E. coli O157:H7 on produce contact surfaces increase the risk cross-contamination of this pathogen to produce. Thus, it is important that the surface in post harvest facility is properly washed and sanitized after working for prevention of cross-contamination from surface.

• Korean journal of food and cookery science
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• v.13 no.2
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• pp.106-112
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• 1997

The effect of low concentrations of allspice (Pimenta dioica L.) in culture broth as an antibacterial agent against Escherichia coli 0157:H7 and Staphylococcus aureus 196E was tested at 35,5 and -20$^{\circ}C$. Tryptic soy broth (TSB) containing 0∼2% (w/v) of allspice was inoculated with 10$\^$5/∼10$\^$6/ cells/$m\ell$ of E. coli and S. aureus and incubated at each temperature. The growth of E. coli was not inhibited at 0.1∼1.0% allspice and growth occured at 2％ allspice but only after a prolonged lag period. Growth of S. aureus was inhibited with increasing concentration of allspice at 35$^{\circ}C$. Growth of S. aureus occured at the presence of 0.1∼0.3% allspice but the viability of S. aureus at 0.5∼2.0% allspice was decreased during storage at 35$^{\circ}C$. During refrigerated storage at 5$^{\circ}C$, inhibition of E. coli and S. aureus was increased with the progress of time and increasing spice concentration. During frozen storage at -20$^{\circ}C$, antibacterial activity of allspice against E. coli was increased with increasing storage time and spice concentration while that activity against S. aureus was effective during early period of storage. There was no major changes in population of S. aureus in TSB with different concentration of spice frozen at -20$^{\circ}C$. Viable counts of E. coli and S. aureus at 0.l％ of allspice was less than that of control during frozen storage.

• Applied Biological Chemistry
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• v.41 no.1
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• pp.23-30
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• 1998

The cryIB, truncated cryIB$[cryIB({\alpha})]$, cryIA(b), and cytA genes, encoding 135-, 89-, 131-, and 27-kDa proteins, respectively, from Bacillus thuringiensis were cloned into a shuttle vector pBES and expressed in E. coli and Bacillus species. The morphology and solubility in alkaline buffer of the insecticidal crystal proteins were investigated. Transformation of intact cells of E. coli and Bacillus species was achieved by electroporation. High field strength of 11.0 kV/cm and resistance of 129 ohms were required for efficient transformation of E. coli strains and 4.5 kV/cm and 48 ohms for Bacillus species. Strains of recombinant E. coli and Bacillus species produced the insecticidal crystal proteins and accumulated as the same bipyramidal and irregular structures as those of CryIB and IA(b) and CytA of B. thuringiensls, respectively. The insecticidal crystal proteins accumulated in recombinant E. coli wire smaller in size than those in recombinant Bacillus species. The solubility in alkaline buffer of the insecticidal crystal proteins of recombinant E. coli increased gradually as the pH increased, whereas in the case of Bacillus species the solubility increased gradually as the pH increased up to 9 and then the solubility increased greatly up to two times higher than that of E. coli proteins.

• Journal of Microbiology and Biotechnology
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• v.30 no.3
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• pp.333-340
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• 2020

Macrophages are the cells of the first-line defense system, which protect the body from foreign invaders such as bacteria. However, Gram-negative bacteria have always been the major challenge for macrophages due to the presence of lipopolysaccharides on their outer cell membrane. In the present study, we evaluated the effect of phloretin, a flavonoid commonly found in apple, on the protection of macrophages from Escherichia coli infection. RAW 264.7 cells infected with standard E. coli, or virulent E. coli K1 strain were treated with phloretin in a dose-dependent manner to examine its efficacy in protection of macrophages. Our results revealed that phloretin treatment reduced the production of nitric oxide (NO) and generation of reactive oxygen species along with reducing the secretion of proinflammatory cytokines induced by the E. coli and E. coli K1 strains in a concentration-dependent manner. Additionally, treatment of phloretin downregulated the expression of E. coli-induced major inflammatory markers i.e. cyclooxygenase-2 (COX-2) and hemeoxygenase-1 (HO-1), in a concentration dependent manner. Moreover, the TLR4-mediated NF-κB pathway was activated in E. coli-infected macrophages but was potentially downregulated by phloretin at the transcriptional and translational levels. Collectively, our data suggest that phloretin treatment protects macrophages from infection of virulent E. coli K1 strain by downregulating the TLR4-mediated signaling pathway and inhibiting NO and cytokine production, eventually protecting macrophages from E. coli-induced inflammation.

• Journal of Food Hygiene and Safety
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• v.13 no.4
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• pp.365-369
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• 1998

The in vitro effects of trisodium phosphate and cetylpyridinium chloride on E. coli 0157:H7 and L. monocytogenes were investigated. The trisodium phosphate and cetylpyridinium chloride was bactericidal toward E. coli 0157:H7 and L. monocytogenes. The killing effects of the $1{\times}10^{-2}\;M$ trisodium phosphate on E. coli 0157:H7 and L. monocytogenes were 30~40%, 40~50%, respectively. The killing effects of the $5{\times}10^{-7}\;M$ cetylpyridinium chloride on E. coli 0157:H7 and L. monocytogenes were 90~95%, 95~99%, respectively. The killing effects of the trisodium phosphate was $10^5$ times that of the cetylpyridinium chloride. Factors effecting the bactericidal action of trisodium phosphate and cetylpyridinium chloride were investigated and the action depended on temperature and pH.

• The Journal of the Korean Society for Microbiology
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• v.18 no.1
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• pp.53-58
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• 1983

Enterotoxigenic E. coli is one of causative agents of the infantile diarrhea and traveler's diarrhea. A modified infant mouse assay(IMA) was developed for the detection of heat stable enterotoxin (ST) of E. coli isolated from diarrheal and control infants and assay system was established with using enterotoxin producing reference strains. The supernatant of the 24 hour-shaking culture of E. coli in Casamino Acid Yeast Extract Salt Broth(CYES-2) was ingested orally into the 2-4 day old ICR mice. After the mice were kept at $25^{\circ}C$ for 4 hours, they were sacrificed and the gut weight body weight ratio(GW/BW) was taken as the index of fluid accumulation induced by heat stable enterotoxin of E. coli. The results obtained were as follows; 1. The GW/BW responses of IMA tested with enterotoxin reference strains of E. coli(E. coli O148H28:$ST^+LT^+$, E. coli $O78H^-:ST^+LT^+$, E. coli O15H11:$ST^-LT^+$, E. coli O1H7:$ST^-LT^-$) appeared ta be ST dose-dependent, and not LT-dependent. From the dose-response curve, $25{\mu}l$ of culture supernatant was determined as test amount of the IMA. 2. Frequency distribution of IMA result from 643 strain of E. coli showed normal distribution at low GW/BW ratio and dispersed pattern at high GW/BW ratio. The GW/BW ratios of $0.056{\pm}0.004(mean{\pm}SD)$ of normal distribution which distributed from 0.044 to 0.068(P<0.01) was considered as ST negative. Thus the GW/BW ratio above 0.069 could be regarded as ST positive.

• Microbiology and Biotechnology Letters
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• v.27 no.5
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• pp.419-425
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• 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.

• Microbiology and Biotechnology Letters
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• v.17 no.4
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• pp.379-384
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• 1989

Glutamine production from glutamate was carried out using glutamine synthetase from E. coli K-12 pgln 6 and baker's yeast, which supplies ATP into the reaction system through alcohol fermentation, simultaneously. With whole cells of E. coli K-12 pgln 6 as an enzyme source of glutamine synthetase, 11.8 g/ι of glutamine produced after 18-h incubation (60％ yield based on a substrate, glutamate). Using the partially purified glutamine synthetase, 19.8 git of glutamine was produced after 5-h incubation. This amount of glutamine was correspond to 90％ yield, based on substrate, glutamate.

• The Korean Journal of Rheology
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• v.8 no.3_4
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• pp.226-231
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• 1996

침강제에 의해 형성된 E. coli floc들의 강도를 측정하기 위해 floc 의 shear index를 측정하였다. 형성된 E. coli floc은 10/sec 같이 낮은 shear rate에서도 분쇄되거나 변형되었 다. 측정된 shear index의 감소에서 보듯이 E. coli floc의 강도는 염의 농도가 증가함에 EK 라 감소하였다. E. coli floc의 shear index는 NaCl의 농도가 0에서 100 mM로 증가함에 따 라 0.47에서 0.09로 줄었다. 발효배지의 조성에서 형성된 E. coli floc들은(shear index=0.18-0.24 with BPA-1000. 0.13-0.22 with BPA-1050 and 0.37-0.42 with BPA-5020) 염이 없을 때 형성된 floc에(shear index=0.47 with BPA-1000 and 0.46 with BPA-1050) 비 해 약하였다. 따라서 발효배지에서 형성된 floc은 생물공정 중 쉽게 shear에 의해 분쇄되거 나 변형될것이다.