Escherichia coli O157:H7 is one of the major foodborne pathogenic bacterial that cause infectious diseases in humans.The previous found that a combination of kojic acid and tea polyphenols exhibited better activity ag...Escherichia coli O157:H7 is one of the major foodborne pathogenic bacterial that cause infectious diseases in humans.The previous found that a combination of kojic acid and tea polyphenols exhibited better activity against E.coli O157:H7 than using either alone.This study aimed to explore responses underlying the antibacterial mechanisms of kojic acid and tea polyphenols from the gene level.The functional enrichment analysis by comparing kojic acid and tea polyphenols individually or synergistically against E.coli O157:H7 found that acid resistance systems in kojic acid were activated,and the cell membrane and genomic DNA were destructed in the cells,resulting in“oxygen starvation”.The oxidative stress response triggered by tea polyphenols inhibited both sulfur uptake and the synthesis of ATP,which affected the bacteria's life metabolic process.Interestingly,we found that kojic acid combined with tea polyphenols hindered the uptake of iron that played an essential role in the synthesis of DNA,respiration,tricarboxylic acid cycle.The results suggested that the iron uptake pathways may represent a novel approach for kojic acid and tea polyphenols synergistically against E.coli O157:H7 and provided a theoretical basis for bacterial pathogen control in the food industry.展开更多
AIM: To prepare a kind of magnetic iron-dextran nanopartidesthat was coated with anti-E.coli O157:H7 IgG, analyze its application conditions, and try to use it to isolate E.coli O157:H7 from foods.METHODS: Magnetic ir...AIM: To prepare a kind of magnetic iron-dextran nanopartidesthat was coated with anti-E.coli O157:H7 IgG, analyze its application conditions, and try to use it to isolate E.coli O157:H7 from foods.METHODS: Magnetic iron-dextran nanoparticles were prepared by the reaction of a mixture of ferric and ferrous ions with dextran polymers under alkaline conditions. The particles were coated with antiserum against E. coli O157:H7 by the periodate oxidation-borohydride reduction procedure. The oxidation time, amount of antibody coating the particles, amount of nanoparticles, incubation time and isolation time were varied to determine their effects on recovery of the organisms. Finally, the optimumconditions for isolating E. coli O157:H7 from food samples were established.RESULTS: E.coli O157:H7 can be isolated from samples within 15 min with the sensitivity of 101 CFU/mL or even less. In the presence of 108 CFU/mL of other organisms,the sensitivity is 101-102 CFU/mL. Nonspecific binding of other bacteria to the particles was not observed. Two and a half hours of enrichment is enough for the particles to detect the target from the food samples inoculated with 1 CFU/g.CONCLUSION: Isolation of target bacteria by immunomagnetic nanoparticles is an efficient method with high sensitivity and specificity. The technique is so simple that it can be operated in lab and field even by untrained personnel.展开更多
Objective:To survey the prevalence severe diarrhea arising from these bacteria in children under 5 years old in Marvdasht.Methods:In this study faecal sample from 615 children aged <5years old who were hospitalized...Objective:To survey the prevalence severe diarrhea arising from these bacteria in children under 5 years old in Marvdasht.Methods:In this study faecal sample from 615 children aged <5years old who were hospitalized lor gastroenteritis in Fars hospitals in Iran were collected and then enriched in Escherichia coli(E.coli) broth and modified tryplone soy broth with novobiocin media,fermentation of sorbitol,lactose and β— glucoronidase activity of isolated strains was examined by CT—SMAC,VRBA and chromogenic media respectively.Then isolation of E.coli O157:H7 have been confirmed with the use of specific antisera and with multiplex PCR method presence of virulence genes including:xtx_1.stx_2,eae.A.hly has been analyzed.Results:E.coli O157:H7 was detected in 7(1.14%) stool specimens.A significanl difference was seen between detection rale of isolated bacteria from age groups 18-23 months and other age groups(P=0.004).Out of considered virulence genes.only 1 of the isolated strains(0.16%)he stx,and eaeA genes were seen and also all isolated hacleria had resistance to penicillin,ampicillin and erythromycin antibiotics.Conclusions:We found thai children < 2 years of age were at highest risk of infection with E.coli O157:H7.Regarding severity of E.coli O157:H7 pathogenesis,low infectious dose and lack of routine assay for detection ol these bacleria in clinical laboratory,further and completed studies on diagnosis and genolyping of this E.coli O157:H7 strain has been recommended.展开更多
This study investigated the intervention effects of Lactobacillus casei LC2W in murine(SPF C57BL/c)challenge infection models induced by Escherichia coli O157:H7.Mice were fed streptomycin with water for 3 days prior ...This study investigated the intervention effects of Lactobacillus casei LC2W in murine(SPF C57BL/c)challenge infection models induced by Escherichia coli O157:H7.Mice were fed streptomycin with water for 3 days prior to intragastric gavage by E.coli O157:H7(Control)or L.casei LC2W together with E.coli O157:H7(Intervention)to explore the role of L.casei LC2W by biochemical indicators,histological evaluation,expression of colonic pro-inflammatory and intestinal barrier factors related to enteritis.Results showed that the administration of L.casei LC2W was able to alleviate the symptoms of colitis induced by E.coli O157:H7,exhibiting lower weight loss as well as more intact colon tissue.Furthermore,L.casei LC2W could down-regulate the expression of pro-inflammatory cytokines(TNF-α,IL-6,and IL-1β)and protect the intestinal barrier function by improving the level of MUC2,ZO-1 and E-cadherin 1 compared to the control group.These results demonstrate that L.casei LC2W can reduce the severity of E.coli O157:H7 infection,and suggest L.casei LC2W may maintain the immune balance and intestinal barrier to reduce colitis.In addition,we found the effect of intervention is similar to that of prevention,which is better than that of treatment.展开更多
The antagonistic activity of Lactobacillus acidophilus KLDS1.0901, KLDS1.0902, KLDSI.1003 and NCFM against Escherichia coli O157 ： H7 were investigated in this study. The culture supematants of all the L. acidophilus...The antagonistic activity of Lactobacillus acidophilus KLDS1.0901, KLDS1.0902, KLDSI.1003 and NCFM against Escherichia coli O157 ： H7 were investigated in this study. The culture supematants of all the L. acidophilus stains showed high bacteriostatic activities against E. coli O 157 ： H7 and the bacteriostatic substances of their Cell-Free Supernatants （CFS） were preliminarily determined from organic acids. The bacteriostatic activity from CFS or viable L. acidophilus against E. coli O157 ： H7 was also assessed by using co-incubation methods, CFS had high bactericidal activity against E. coli O157 ： H7, no viable E. coli O157 ： H7 was detected when 5×10^7 CfU ofE. coli O157 ： H7 was added to 5 mL of CFS and incubated at 37℃ for 2 h. However, L. acidophilus themselves had no bacteriostatic activity after directly contacted with E. coli O157 ： H7. The inhibition E. coli O157 ： H7 adhesion and colonization of L. acidophilus were also investigated based on competition, exclusion and displacement assays. L. acidophilus KLDS1.0901, KLDSI.1003 and NCFM strains were effective to displace E. coli O157 ： H7 from a Caco-2 cell layer in competition and exclusion assays. However, in displacement assay, all of the strains showed no significant antagonistic activities. Meanwhile, the probiotic potential of L. acidophilus strains was investigated based on adhesion assay to Caco-2 cells and anti- inflammatory effects by IL-8 produced in Caco-2 cells. The adhesion ability and anti-inflammatory effects of L. acidophilus strains showed a strain-dependent manner. In general, L. acidophilus KLDS 1.0901 and NCFM showed better probiotic potential than KLDS1.0902 and KLDSI.1003. Thus, the use ofL. acidophilus KLDS1.0901 and NCFM to prevent or treat of diseases associated induced E. coli O157 ： H7 in vivo was suggested.展开更多
基金supported by National Natural Science Foundation of China(31972021)R&D Projects in Key Areas of Guangdong Province(2019B020212003)+4 种基金the Science and Technology Program of Guangzhou,China(202206010177)Guangdong key research and development program(2021B0202060001)Foshan and agricultural academy cooperation projectGuangdong Modern Agriculture project(2022KJ117)Aquatic Products Center Project of GAAS。
文摘Escherichia coli O157:H7 is one of the major foodborne pathogenic bacterial that cause infectious diseases in humans.The previous found that a combination of kojic acid and tea polyphenols exhibited better activity against E.coli O157:H7 than using either alone.This study aimed to explore responses underlying the antibacterial mechanisms of kojic acid and tea polyphenols from the gene level.The functional enrichment analysis by comparing kojic acid and tea polyphenols individually or synergistically against E.coli O157:H7 found that acid resistance systems in kojic acid were activated,and the cell membrane and genomic DNA were destructed in the cells,resulting in“oxygen starvation”.The oxidative stress response triggered by tea polyphenols inhibited both sulfur uptake and the synthesis of ATP,which affected the bacteria's life metabolic process.Interestingly,we found that kojic acid combined with tea polyphenols hindered the uptake of iron that played an essential role in the synthesis of DNA,respiration,tricarboxylic acid cycle.The results suggested that the iron uptake pathways may represent a novel approach for kojic acid and tea polyphenols synergistically against E.coli O157:H7 and provided a theoretical basis for bacterial pathogen control in the food industry.
基金Supported by the National High-technology Research and Development Program of China (863 Program), No. 2003AA302260
文摘AIM: To prepare a kind of magnetic iron-dextran nanopartidesthat was coated with anti-E.coli O157:H7 IgG, analyze its application conditions, and try to use it to isolate E.coli O157:H7 from foods.METHODS: Magnetic iron-dextran nanoparticles were prepared by the reaction of a mixture of ferric and ferrous ions with dextran polymers under alkaline conditions. The particles were coated with antiserum against E. coli O157:H7 by the periodate oxidation-borohydride reduction procedure. The oxidation time, amount of antibody coating the particles, amount of nanoparticles, incubation time and isolation time were varied to determine their effects on recovery of the organisms. Finally, the optimumconditions for isolating E. coli O157:H7 from food samples were established.RESULTS: E.coli O157:H7 can be isolated from samples within 15 min with the sensitivity of 101 CFU/mL or even less. In the presence of 108 CFU/mL of other organisms,the sensitivity is 101-102 CFU/mL. Nonspecific binding of other bacteria to the particles was not observed. Two and a half hours of enrichment is enough for the particles to detect the target from the food samples inoculated with 1 CFU/g.CONCLUSION: Isolation of target bacteria by immunomagnetic nanoparticles is an efficient method with high sensitivity and specificity. The technique is so simple that it can be operated in lab and field even by untrained personnel.
基金the Islamic Azad University, Jahrom branch,for their executive support of this project
文摘Objective:To survey the prevalence severe diarrhea arising from these bacteria in children under 5 years old in Marvdasht.Methods:In this study faecal sample from 615 children aged <5years old who were hospitalized lor gastroenteritis in Fars hospitals in Iran were collected and then enriched in Escherichia coli(E.coli) broth and modified tryplone soy broth with novobiocin media,fermentation of sorbitol,lactose and β— glucoronidase activity of isolated strains was examined by CT—SMAC,VRBA and chromogenic media respectively.Then isolation of E.coli O157:H7 have been confirmed with the use of specific antisera and with multiplex PCR method presence of virulence genes including:xtx_1.stx_2,eae.A.hly has been analyzed.Results:E.coli O157:H7 was detected in 7(1.14%) stool specimens.A significanl difference was seen between detection rale of isolated bacteria from age groups 18-23 months and other age groups(P=0.004).Out of considered virulence genes.only 1 of the isolated strains(0.16%)he stx,and eaeA genes were seen and also all isolated hacleria had resistance to penicillin,ampicillin and erythromycin antibiotics.Conclusions:We found thai children < 2 years of age were at highest risk of infection with E.coli O157:H7.Regarding severity of E.coli O157:H7 pathogenesis,low infectious dose and lack of routine assay for detection ol these bacleria in clinical laboratory,further and completed studies on diagnosis and genolyping of this E.coli O157:H7 strain has been recommended.
基金supported by the National Key Research and Development Program of China(No.2018YFD0501600)National Natural Science Foundation of China(No.31972056)Shanghai Agriculture Applied Technology Development Program,China(Grant No.2019-02-08-00-07-F01152).
文摘This study investigated the intervention effects of Lactobacillus casei LC2W in murine(SPF C57BL/c)challenge infection models induced by Escherichia coli O157:H7.Mice were fed streptomycin with water for 3 days prior to intragastric gavage by E.coli O157:H7(Control)or L.casei LC2W together with E.coli O157:H7(Intervention)to explore the role of L.casei LC2W by biochemical indicators,histological evaluation,expression of colonic pro-inflammatory and intestinal barrier factors related to enteritis.Results showed that the administration of L.casei LC2W was able to alleviate the symptoms of colitis induced by E.coli O157:H7,exhibiting lower weight loss as well as more intact colon tissue.Furthermore,L.casei LC2W could down-regulate the expression of pro-inflammatory cytokines(TNF-α,IL-6,and IL-1β)and protect the intestinal barrier function by improving the level of MUC2,ZO-1 and E-cadherin 1 compared to the control group.These results demonstrate that L.casei LC2W can reduce the severity of E.coli O157:H7 infection,and suggest L.casei LC2W may maintain the immune balance and intestinal barrier to reduce colitis.In addition,we found the effect of intervention is similar to that of prevention,which is better than that of treatment.
基金Supported by the Agro-scientific Research of China(201203009)the Ministry of Agriculture,China
文摘The antagonistic activity of Lactobacillus acidophilus KLDS1.0901, KLDS1.0902, KLDSI.1003 and NCFM against Escherichia coli O157 ： H7 were investigated in this study. The culture supematants of all the L. acidophilus stains showed high bacteriostatic activities against E. coli O 157 ： H7 and the bacteriostatic substances of their Cell-Free Supernatants （CFS） were preliminarily determined from organic acids. The bacteriostatic activity from CFS or viable L. acidophilus against E. coli O157 ： H7 was also assessed by using co-incubation methods, CFS had high bactericidal activity against E. coli O157 ： H7, no viable E. coli O157 ： H7 was detected when 5×10^7 CfU ofE. coli O157 ： H7 was added to 5 mL of CFS and incubated at 37℃ for 2 h. However, L. acidophilus themselves had no bacteriostatic activity after directly contacted with E. coli O157 ： H7. The inhibition E. coli O157 ： H7 adhesion and colonization of L. acidophilus were also investigated based on competition, exclusion and displacement assays. L. acidophilus KLDS1.0901, KLDSI.1003 and NCFM strains were effective to displace E. coli O157 ： H7 from a Caco-2 cell layer in competition and exclusion assays. However, in displacement assay, all of the strains showed no significant antagonistic activities. Meanwhile, the probiotic potential of L. acidophilus strains was investigated based on adhesion assay to Caco-2 cells and anti- inflammatory effects by IL-8 produced in Caco-2 cells. The adhesion ability and anti-inflammatory effects of L. acidophilus strains showed a strain-dependent manner. In general, L. acidophilus KLDS 1.0901 and NCFM showed better probiotic potential than KLDS1.0902 and KLDSI.1003. Thus, the use ofL. acidophilus KLDS1.0901 and NCFM to prevent or treat of diseases associated induced E. coli O157 ： H7 in vivo was suggested.
