• Microbiology and Biotechnology Letters
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• v.48 no.2
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• pp.121-128
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• 2020

Diarrhea is a major public health concern associated with pathogenic Escherichia coli infections. Food-borne pathogenic E. coli can lead to large diarrheal outbreaks and hence, there is a need to estimate the frequency of pathogenic E. coli load in the various types of meat available in markets. In the present study, we classified and characterized diarrheagenic E. coli isolates collected from 399 raw meat samples from retail sources in Korea. Shiga toxin-producing E. coli (STEC) were detected in 11 (9.7%) samples, including nine strains (8.0%) in beef and two strains (1.8%) in chicken. The frequency of the detected virulence markers were as follows: astA, 28.3%; escV,18.6%; eaeA,17.7%; ent, 7.0%; EHEC-hly, 4.4%; stx1, 3.5%; and stx2, 3.5%. We did not observe any typical EPEC, EIEC, or ETEC virulence determinants in any of the samples. The STEC serotype O26 was detected in one sample, but no other serogroups (O91, O103, O128, O157, O145, O111, and O121) were found. Further research is needed to better understand the virulence mechanism of STEC serotypes, their ecology, and prevalence in animals, food, and the environment. These results will help improve risk assessment and predict the sources of food poisoning outbreaks.

• Journal of Biosystems Engineering
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• v.38 no.4
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• pp.335-340
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• 2013

Purpose: This study was performed to develop a lateral flow strip sensor for the detection of pathogenic Escherichia coli O157:H7 in various samples. Also, feasibility of using an image analysis method to improve the interpretation of the strip sensor was evaluated. Methods: The lateral flow strip sensor has been fabricated based on nitrocellulose lateral-flow membrane. Colloidal gold and E. coli O157:H7 antibodies were used as a tag and a receptor, respectively. Manually spotted E. coli O157:H7 antibody and anti-mouse antibody on nitrocellulose membrane were used as test and control dots, respectively. Feasibility of the lateral flow strip sensor to detect E. coli O157:H7 were evaluated with serially diluted E. coli O157:H7 cells in PBS or food samples. Test results of the lateral flow strip sensor were measured with an image analysis method. Results: The intensity of the test dot started to increase with higher concentration of the cells were introduced. The sensitivities of the sensor were both $10^4$ CFU/mL Escherichia coli O157:H7 spiked in PBS and in chicken meat extract, respectively. Conclusions: The lateral flow strip sensor and image analysis method could detect E. coli O157:H7 in 20 min, which is significantly quicker than conventional plate counting method.

• Korean Journal of Soil Science and Fertilizer
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• v.46 no.6
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• pp.647-651
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• 2013

Animal manure compost is a commonly used fertilizer in organic vegetable and fruit production in Korea. However, livestock manure compost produced from animal feces can contain a lot of the non-pathogenic and pathogenic bacteria. Of particular concern are bacteria causing human food-borne illness such as Escherichia coli O157:H7 and Listeria monocytogenes. The objective of this study was to investigate effect of temperature on survival of E. coli O157:H7 and L. monocytogenes in livestock manure compost. Commercial livestock manure compost (manure 60%, sawdust 40%) was inoculated with E. coli O157:H7 and L. monocytogenes. Compost was incubated at four different temperatures (10, 25, 35, and $55^{\circ}C$) for 20 weeks. Samples were taken every week during incubation depending on the given conditions. E. coli O157:H7 persisted for up to 1 day in livestock manure compost at $55^{\circ}C$, over 140 days at $10^{\circ}C$, 140 days at $25^{\circ}C$, and 120 days at $35^{\circ}C$, respectively. L. monocytogenes persisted for up to 1 day in livestock manure compost at $55^{\circ}C$ and 140 days at $10^{\circ}C$, 70 days at $25^{\circ}C$, and 40 days at $35^{\circ}C$, respectively. The results indicated that E. coli O157:H7 and L. monocytogenes persisted longer under low temperature condition. E. coli O157:H7 survived longer than L. monocytogenes at three different temperatures (10, 25, and $35^{\circ}C$). The results are being used to develop guidelines on the management of manure to reduce the risks of E. coli O157:H7 and L. monocytogenes transmission to foods produced in the presence of animal waste.

• Journal of Microbiology
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• v.37 no.3
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• pp.168-174
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• 1999

Escherichia coli O157 is an important pathogenic organism which causes diarrhea, haemorrhagic colitis, and haemolytic ureamic syndrome (HUS) in human. E. coli O157 KNIH317 was isolated form patients suffering with HUS in Korea. We designed a primer set for cloning shiga-like toxin (slt) gene. The amplified PCR product was used to Southern and colony hybridization as a probe. As a result, we cloned 4.5-kb KpnI fragment containing the slt gene encoding shiga-like toxin from chromosomal DNA of E. coli O157 KNIH317. This recombinant plasmid was named pOVT45. E. coli XL1-Blue harboring pOVT45 showed cytotoxicity in Vero cells. We sequenced the slt gene of this strain. The A-subunit gene of the slt was composed of 960 base pairs with ATG initiation codon and TAA terminationcodon. The B-subunit was composed of 270 base paris with ATG initiation codon and TGA termination codon. Nucleotide sequence comparison of the slt gene exhibited 100%, 98.4%, 93.7%, and 93.7% identity with that of shiga-like toxin type II (sltII) of E. coli bacteriophage 933W, variant slt of E. coli, slt of E. coli, and variant sltII of E. coli, respectively. From these results, it was concluded that the cloned slt gene belongs to SltII family and that the strain used in this study may be a lysogeny of E. coli bcteriphage 933W.

• Preventive Nutrition and Food Science
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• v.10 no.2
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• pp.130-133
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• 2005

The growth inhibitiory effect of chaff vinegar against various food-borne pathogenic bacteria was evaluated. Bacterial growth was evaluated in chaff vinegar at concentrations of 15, 30, 50, 65, 80, and $100\%$ using the paper disc diffusion method and 0.5, 1.0, 1.5, 1.8, 2.0, 2.2 and $2.5\%$ in broth. In the paper disc diffusion assay, chaff vinegar showed a clear zone on both the Gram-positive bacteria; Listeria monocytogenes, Staphylococcus aureus and Gram-negative bacteria; Escherichia coli O157:H7, Salmonella Typhimurium, and Vibrio parahaemolyticus. Chaff vinegar exhibited the greatest growth inhibition for V. parahaemolyticus. The bactericidal effect of chaff vinegar on the E. coli O157:H7 was tested at concentrations ranging from 0.5 to $2.5\%$ (v/v) in the LB broth media. Chaff vinegar retarded the lag phase time of the growth curve in proportion in a concentration-dependent manner. Chaff vinegar at $2.5\%$ completely inhibited the growth of E. coli O157:H7.

• Journal of Microbiology and Biotechnology
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• v.27 no.1
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• pp.67-71
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• 2017

This study examined the antimicrobial activity of flaxseed meal extract (FME) against Staphylococcus aureus and Escherichia coli O157:H7 inoculated on red mustard. With the treatment of 0.7% FME for 3 min, the reduction levels of S. aureus and E. coli O157:H7 populations were 1.23 and 1.83 log CFU/g, respectively. In addition, the combined treatment of 0.7% FME at $50^{\circ}C$ for 3 min reduced the populations of the pathogenic bacteria by 2.28 and 2.41 log CFU/g, respectively. The color and the vitamin C content were not significantly different between treatments. Thus, FME can be used as a novel antimicrobial agent in fresh-cut vegetables.

• Food Science of Animal Resources
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• v.18 no.1
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• pp.63-74
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• 1998

Recently the high outbreaks of intestinal disease caused by the consumption of frozen dairy foods containing pathogenic bacteria has generated considerable interest in the causative agent such as Listeria monocytogenes and E. coli O157:H7. This study was carried out to detect the above pathogens and compare the microbiological qualities of three commercial forzen yogurt products. The main results obtained were as follows. L. monocytogenes coliforms and E. coli O157:H7 were not detected in the total of seven frozen yogurt samples. For microbiological qualities the viable lactic counts of products manufactured by FA company were about 2.9$\times$108 -1.6$\times$109cfu/ml 1.7$\times$106 cfu/ml for FB's and 1.2$\times$106 cfu/ml for FC's The PH values of FA's FB's and FC's products was in the range of pH 4.1~5.3 and the values of FA's were 4.1~4.6 compared by the pH 5.2~5.3 of FB's and FC's products. During refrigeration of the test samples the survival rates of L. monocytogenes spiked into thawed frozen yogurt sample(FA's FB,s and FC's) were 0.55% 15.61% and 16.89% respectively. On the other hand E. coli O157:H7 and L. monocytogenes were 12.4% and 25.0% for FA's 10.8% and 20.8% for FB's and 10.26% and 22.7% for FC's under 37$^{\circ}C$ storage, As the results described above each frozen yogurt products were different in microbiological qualities. The survival rates of pathogens spiked into the samples increased with the pH of the products. This indicates that the pH or any other factors pre-sumable supressed the growth of E. coli O157:H7 and L. monocytogenes in frozen yogurt products.

• Journal of Food Hygiene and Safety
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• v.36 no.6
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• pp.481-487
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• 2021

The purpose of this study was to provide safety management information by analyzing the survival and growth-related properties of foodborne pathogens from Romaine lettuce. After cultivating E. coli O157:H7 for 72 h on Romain lettuce via spray inoculation, the bacteria population increased by 2.0 log CFU/g from the initial population, confirming the possibility of survival and multiplication of the pathogen thereon. The study also revealed that there is no significant difference in the cultivation of E.coli O157:H7 after 72 h from inoculation on damaged and undamaged lettuce leaves. As a result of investigating distribution of E.coli O157:H7 on damaged lettuce leaves, it was found that the bacteria is unlikely to adhere on the smooth surface of undamaged leaves and, thus, results in a low population density, whereas the bacteria cluster on the rough surface of damaged leaves and easily enter through the damaged tissues. Furthermore, after 24 h of cultivation of the pathogenic microbe in the extract with concentrations of 10-100%, utilization of the lettuce extract by the pathogen was found to be 8.9 log CFU/mL E. coli O157:H7, 8.6 log CFU/mL L. monocytogenes, and 8.8 log CFU/mL P. carotovorum. The increase in the population of both the pathogenic microbe and foodborne pathogen reached over 4 log CFU/mL, implying the microbe can utilize the lettuce extract as a source of nutrition. Compared to the initial inoculation concentration in 0.1% lettuce extract, the final concentration has increased up to 2.7 log CFU/mL E. coli O157:H7, 1.3 log CFU/mL L. monocytogenes, and 2.9 log CFU/mL P. carotovorum. Accordingly, the study confirms that the minimal growth concentration of the pathogenic microbe is lower than 0.1% and that the pathogen possibly survive and multiply inside the lettuce leaves given the lettuce extract with concentration of 0.1% is consistently supplied through the damaged tissues.

• Korean Journal of Food Science and Technology
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• v.36 no.3
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• pp.514-517
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• 2004

O157:H7, Salmonella typhimurium, Listeria monocytogenes were treated with aqueous chlorine dioxide to elucidate effect of aqueous chlorine dioxide treatment on major food-borne pathogenic bacteria. Survival plot of E.coli O157:H7 at 5 ppm chlorine dioxide showed typical first-order rate. After 5 min of treatment, cell number decreased by 1.5 log cycle. Survival plot slope gave D value of 3.37 min. S. typhimurium and L. monocytogenes showed biphasic curve. Aqueous chlorine dioxide treatment on S. typhimurium and L. monocytogenes resulted in bactericidal effect for 5 min, and thereafter no effect was observed under experimental conditions of this study. These results suggest concentration of chlorine dioxide is more important than treatment time, and 5 ppm chlorine dioxide treatment is not sufficient for sanitizing fresh vegetables.

• Journal of Microbiology and Biotechnology
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• v.18 no.7
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• pp.1278-1285
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• 2008

The intestinal epithelial cell (IEC) layer of the intestinal tract makes direct contact with a number of microbiota communities, including bacteria known to have deleterious health effects. IECs possess innate protective strategies against pathogenic challenge, which primarily involve the formation of a physicochemical barrier. Intestinal tract mucins are principal components of the mucus layer on epithelial surfaces, and perform a protective function against microbial damage. However, little is currently known regarding the interactions between probiotics/pathogens and epithelial cell mucins. The principal objective of this study was to determine the effects of Lactobacillus on the upregulation of MUC2 mucin and the subsequent inhibition of E. coli O157:H7 attachment to epithelial cells. In the current study, the attachment of E. coli O157:H7 to HT-29 intestinal epithelial cells was inhibited significantly by L. acidophilus A4 and its cell extracts. It is also important to note that the expression of MUC2 mucin was increased as the result of the addition of L. acidophilus A4 cell extracts (10.0 mg/ml), which also induced a significant reduction in the degree to which E. coli O157:H7 attached to epithelial cells. In addition, the mRNA levels of IL-8, IL-1$\beta$, and TNF-$\alpha$ in HT-29 cells were significantly induced by treatment with L. acidophilus A4 extracts. These results indicate that MUC2 mucin and cytokines are important regulatory factors in the immune systems of the gut, and that selected lactobacilli may be able to induce the upregulation of MUC2 mucin and specific cytokines, thereby inhibiting the attachment of E. coli O157:H7.