• Food Science of Animal Resources
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• v.37 no.4
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• pp.579-592
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• 2017

This study assessed the quantitative microbial risk of non-enterohemorrhagic Escherichia coli (EHEC). For hazard identification, hazards of non-EHEC E. coli in natural and processed cheeses were identified by research papers. Regarding exposure assessment, non-EHEC E. coli cell counts in cheese were enumerated, and the developed predictive models were used to describe the fates of non-EHEC E. coli strains in cheese during distribution and storage. In addition, data on the amounts and frequency of cheese consumption were collected from the research report of the Ministry of Food and Drug Safety. For hazard characterization, a doseresponse model for non-EHEC E. coli was used. Using the collected data, simulation models were constructed, using software @RISK to calculate the risk of illness per person per day. Non-EHEC E. coli cells in natural- (n=90) and processed-cheese samples (n=308) from factories and markets were not detected. Thus, we estimated the initial levels of contamination by Uniform distribution ${\times}$ Beta distribution, and the levels were -2.35 and -2.73 Log CFU/g for natural and processed cheese, respectively. The proposed predictive models described properly the fates of non-EHEC E. coli during distribution and storage of cheese. For hazard characterization, we used the Beta-Poisson model (${\alpha}=2.21{\times}10^{-1}$, $N_{50}=6.85{\times}10^7$). The results of risk characterization for non-EHEC E. coli in natural and processed cheese were $1.36{\times}10^{-7}$ and $2.12{\times}10^{-10}$ (the mean probability of illness per person per day), respectively. These results indicate that the risk of non-EHEC E. coli foodborne illness can be considered low in present conditions.

• 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.

• Journal of Digital Convergence
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• v.14 no.4
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• pp.371-378
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• 2016

An aim of current study was to investigate the prevalence and the mechanism of quinolone-resistance in E. coli isolates obtained from chicken cecum in Korea. In addition, multilocus sequence typing (MLST) was also performed for the molecular characterization of E. coli isolates. In an antimicrobial susceptibility test by the disk diffusion method, the 63.5% (54/85) of E. coli isolates showed the resistance to quinolone group of antimicrobial agents. All of the 54 E. coli isolates showing resistant to quinolone group had sense mutations in gyrA gene and point mutations at the $57^{th}$, $80^{th}$, or $84^{th}$ residues in parC gene were detected in 90.7% of the isolates. Interestingly, E. coli ST was closely related to amino acid substitutions in parE gene. Our results indicated that the long-term use of antimicrobial agents in food-producing animals was strongly associated with a prevalence of antimicrobial resistance in commensal Enterobacteriaceae, suggesting the need for continuous surveillance and monitoring of antimicrobial resistant determinants in bacterial isolates from food animals.

• Applied Chemistry for Engineering
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• v.25 no.4
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• pp.386-391
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• 2014

Atmospheric-pressure nonthermal corona discharge plasma was applied to the sterilization of biologically contaminated scoria powder. Escherichia coli (E. coli) culture solution was uniformly sprayed throughout the scoria powder for artificial inoculation, which was well mixed to ensure uniformity of the batch. The effect of the key parameters such as discharge power, treatment time, type of gas and electrode distance on the sterilization efficiency was examined and discussed. The experimental results revealed that the plasma treatment was very effective for the sterilization of scoria powder; 5-min treatment at 15 W could sterilize more than 99.9% of E. coli inoculated into the scoria powder. Increasing the discharge power, treatment time or applied voltage led to an improvement in the sterilization efficiency. The effect of type of gas on the sterilization efficiency was in order of oxygen, synthetic air (20% oxygen) and nitrogen from high to low. The inactivation of E. coli under the influence of corona discharge plasma can be explained by cell membrane erosion or etching resulting from UV and reactive oxidizing species (oxygen radical, OH radical, ozone, etc.), and the destruction of E. coli cell membrane by the physical action of numerous corona streamers.

• Korean Journal of Veterinary Research
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• v.28 no.1
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• pp.59-65
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• 1988

This paper deals with the 0 groups of citrate utilizing variants of Escherichia coli ($Cit^+$ E. coli) isolated from cattle, the production of colicin, hemolysin, K99 antigen, heat stable enterotoxin, and the isolation of plasmid DNA. Among 42 $Cit^+$ E. coli, 12 strains were 020, 9 strains 08, 5 strains 045, 3 strains 0115, 1 strain 064, 1 strain 0139 and remaining strains(11) were untypable. Thirty-nine(81.3%) out of 48 $Cit^+$ E. coli were produced colicin and 13(27.0%) were produced hemolysin. Of 12 $Cit^+$ E. coli bearing K99 antigen, 6(50.0%) were produced heat stable enterotoxin. In gel electrophoresis for the isolation of plasmid DNA, the number of plasmids varied from 1 to 7 in 10 $Cit^+$ E. coli. It's molecular weight ranged from 2 to 50 Mdalton, and 50 Mdalton plasmid was commonly existed in all strains.

• 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.

• Korean Journal of Veterinary Service
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• v.15 no.2
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• pp.134-143
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• 1992

The present study was conducted to investigate the biochemical characteristics and anti-biotic resistance of Escherichia coli(E. coli) isolated from piglets with diarrhea in Kyongbuk province during the Period from February to November 1991. 368 E. coli strains were isolated from 382 piglets with diarrhea and the biochemical and cultural reaction were compared with the classification criteria of Edwards and Ewing. Tetracycline and sulfadimethoxine were found to be highly ineffective at in vitro inhibition of the E. coli of piglets origin. The majority of E. coli were susceptible to amikacin, chloramphenicol and gentamicine. 89 (89.0%) of 100 strains of E. coil were resistant to one or more drugs. The organisms resistant to 20 or 3 drugs were 54(60.6%) of 89 strains, whereas 16(17.9%) strains were found to be resistant to one drug. 55(61.8%) out of 89 drug resistance strains carried R factors($R^+$) which were transfer-able to the recipients by conjugation.

• Korean Journal of Microbiology
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• v.23 no.1
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• pp.49-55
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• 1985

The survival of Escherichia coli in river water was comparatively studied by laboratory and in sity study methods. The survival by two methods was evaluated as a function of E. coli strain, indigeneous predator, level of water pollution, and water temperature in different season. The survival rate of E. coli examined by laboratory method was lower than that by in situ method. That was found to be due to the fact that higher number of predator was maintained in labortory study than in in situ study. The survival rates of E. coli in gradually polluted river waters could be differentiated by in situ study, but not by laboratory study. Therefore, an in situ method rather than labortory method was thought to be a choice of study method for the survival of E. coli in river waters.

• 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.

• Journal of Microbiology and Biotechnology
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• v.9 no.6
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• pp.722-725
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• 1999

Filamentation-suppressed recombinant Escherichia coli strain harboring the Alcaligenes latus polyhydroxyalkanoate (PHA) biosynthesis genes and the E. coli ftsZ gene was constructed and cultivated for the production of poly(3-hydroxybutyrate) [P(3HB)] with high concentration and high content. By the pH-stat fed-batch culture of this recombinant E. coli strain XL1-Blue(pJC5), the final cell concentration and P(3HB) concentration obtained in 44.25h were 172.2g cell dry weight/l and 141.9g P(3HB)/l, respectively, resulting in productivity of 3.21g P(3HB)/l-h. More importantly, the P(3HB) content obtained was 82.4 wt %, which was significantly higher than that obtained with the recombinant E. coli harboring only the PHA biosynthesis genes.