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E. Coli O157 (e + coli_o157)
Selected AbstractsQuantification of Survival of Escherichia coli O157:H7 on Plants Affected by Contaminated Irrigation Water,ENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 6 2006A. M. Ibekwe Abstract Enterohemorrhagic E. coli O157: H7 (EHEC) is a major foodborne pathogen capable of causing diarrhea and vomiting, with further complications such as hemolytic-uremic syndrome (HUS). The aim of this study was to use the real-time PCR method to quantify the survival of Escherichia coli O157:H7/pGFP in phyllosphere (leaf surface), rhizosphere (volume of soil tightly held by plant roots), and non-rhizosphere soils (sand and clay) irrigated with contaminated water and compare the results obtained between real-time PCR method and conventional plate counts. The real-time PCR probe was designed to hybridize with the (eae) gene of E. coli O157:H7. The probe was incorporated into real-time PCR containing DNA extracted from the phyllosphere, rhizosphere, and non-rhizosphere soils irrigated with water artificially contaminated with E. coli O157:H7. The detection limit for E. coli O157:H7 quantification by real-time PCR was 2.3 × 103 in the rhizosphere and phyllosphere samples. E. coli O157:H7 survived longer in rhizosphere soil than the non-rhizosphere soil. The concentration of E. coli O157:H7/pGFP in rhizosphere soils was , 104 CFU/g in both soils at day 12 based on both plate count and real time PCR, with the clay soil significantly (P = 0.05) higher than the sandy soil. This data showed that E. coli O157H:7 can persist in the environment for more than 50 d, and this may pose some risk for both animal and human infection and provides a very significant pathway for pathogen recontamination in the environment. [source] Survival of Escherichia coli O157:H7 in private drinking water wells: influences of protozoan grazing and elevated copper concentrationsFEMS MICROBIOLOGY LETTERS, Issue 1 2002Rebekka R.E Artz Abstract The survival characteristics of Escherichia coli O157:H7 in private drinking water wells were investigated to assess the potential for human exposure. A non-toxigenic, chromosomally lux -marked strain of E. coli O157:H7 was inoculated into well water from four different sites in the North East of Scotland. These waters differed significantly in their heavy metal contents as well as nutrient and bacterial grazer concentrations. Grazing and other biological factors were studied using filtered (3 and 0.2 ,m) and autoclaved water. The survival of E. coli O157:H7 was primarily decreased by elevated copper concentrations. This hypothesis was supported by acute toxicity assay data. In addition, significant protozoan predation effects were observed in untreated water when compared with survival rates in filtered water. The combination of these two factors in particular determines the survival time of the pathogen in a private water well. It therefore appears that wells with higher water quality as assessed using the European Union Drinking Water Directive standards will also allow survival of E. coli O157:H7 for much longer periods. [source] A proteomic study of Escherichia coli O157:H7 NCTC 12900 cultivated in biofilm or in planktonic growth modeFEMS MICROBIOLOGY LETTERS, Issue 1 2002Frédéric Trémoulet Abstract Escherichia coli 0157:H7 biofilms were studied by a new method of cultivation in order to identify some of the proteins involved in the biofilm phenotype. A proteomic analysis of sessile or planktonic bacteria of the same age was carried out by two-dimensional electrophoresis, matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF-MS) and database searching. Comparison of two-dimensional gels showed clear differences between protein patterns of sessile and planktonic cells. Fourteen proteins increased in biofilms, whereas three decreased. From these 17 proteins, 10 were identified by MALDI-TOF-MS and could be classified into four categories according to their function: (1) general metabolism proteins (malate dehydrogenase, thiamine-phosphate pyrophosphorylase), (2) sugar and amino acid transporters (d -ribose-binding periplasmic protein, d -galactose-binding protein, YBEJ), (3) regulator proteins (DNA starvation protein and H-NS) and (4) three proteins with unknown function. The results of this study showed that E. coli O157:H7 modified the expression of several proteins involved in biofilm growth mode. [source] Modelling the vector pathway and infection of humans in an environmental outbreak of Escherichia coli O157FEMS MICROBIOLOGY LETTERS, Issue 1 2001Norval J.C. Strachan Abstract Quantifying the transfer of Escherichia coli O157 from the environment to humans is essential for understanding outbreaks, establishing the infectious dose of the organism and proposing safeguards. We modelled the pathogen loading shed onto a field by sheep immediately prior to a scout camp where 18 scouts and two adults were infected with E. coli O157. We estimated the dose ingested (4,24 organisms) which is in agreement with the low infective dose reported previously for this organism in food outbreaks. These data closely fit a surrogate Shigella dose,response model which can be used as a basis for risk assessment. [source] Bacterial silver resistance: molecular biology and uses and misuses of silver compoundsFEMS MICROBIOLOGY REVIEWS, Issue 2-3 2003Simon Silver Abstract Resistance to silver compounds as determined by bacterial plasmids and genes has been defined by molecular genetics. Silver resistance conferred by the Salmonella plasmid pMGH100 involves nine genes in three transcription units. A sensor/responder (SilRS) two-component transcriptional regulatory system governs synthesis of a periplasmic Ag(I)-binding protein (SilE) and two efflux pumps (a P-type ATPase (SilP) plus a three-protein chemiosmotic RND Ag(I)/H+ exchange system (SilCBA)). The same genes were identified on five of 19 additional IncH incompatibility class plasmids but thus far not on other plasmids. Of 70 random enteric isolates from a local hospital, isolates from catheters and other Ag-exposed sites, and total genomes of enteric bacteria, 10 have recognizable sil genes. The centrally located six genes are found and functional in the chromosome of Escherichia coli K-12, and also occur on the genome of E. coli O157:H7. The use of molecular epidemiological tools will establish the range and diversity of such resistance systems in clinical and non-clinical sources. Silver compounds are used widely as effective antimicrobial agents to combat pathogens (bacteria, viruses and eukaryotic microorganisms) in the clinic and for public health hygiene. Silver cations (Ag+) are microcidal at low concentrations and used to treat burns, wounds and ulcers. Ag is used to coat catheters to retard microbial biofilm development. Ag is used in hygiene products including face creams, ,alternative medicine' health supplements, supermarket products for washing vegetables, and water filtration cartridges. Ag is generally without adverse effects for humans, and argyria (irreversible discoloration of the skin resulting from subepithelial silver deposits) is rare and mostly of cosmetic concern. [source] Thrombotic thrombocytopenic purpura: Results of the patients with thrombotic microangiopathies across Japan by ADAMTS13 analysis during 1998,2008ISBT SCIENCE SERIES: THE INTERNATIONAL JOURNAL OF INTRACELLULAR TRANSPORT, Issue n2 2009Y. Fujimura Background, Thrombotic microangiopathies (TMAs) are pathological conditions, characterized by generalized microvascular occlusion by platelet thrombi, thrombocytopenia, and microangiopathic hemolytic anemia. Two typical phenotypes of TMAs are hemolytic-uremic syndrome (HUS) and thrombotic thrombocytopenic purpura (TTP). Severe deficiency of plasma ADAMTS13 activity (ADAMTS13:AC) is more specific for TTP but not for HUS. Materials & Methods, Since 1998, our laboratory has functioned as a nationwide referral center for TMAs by analyzing ADAMTS13. Of 1564 tested patients from 426 hospitals, 919 were positive for TMAs. Levels of ADAMTS13:AC and the ADAMTS13-neutralizing autoantibodies (ADAMTS13:INH) in these patients were determined by chromogenic act-ELISA and/or by classic von Willebrand factor multimer assay. Results, TMA patients consisted of two groups, those with severe (less than 3% of normal control) and those with non-severe deficiency of ADAMTS13:AC. Additionally, both groups were divided into congenital (n = 65) and acquired (n = 854) TMAs. Of the congenital TMA patients, 41 had ADAMTS13:AC deficiency due to gene mutations, while the remaining 24 had the disease of unknown etiology. The 854 patients with acquired TMAs could be largely grouped into three categories: idiopathic TTP (n = 284), idiopathic HUS (n = 106), and secondary TMAs (n = 464). The secondary TMAs were observed in heterogeneous patient groups and were associated with drugs, connective tissue diseases, malignancies, transplantation, pregnancy, E. coli O157:H7 infection, and other factors. All of the patients with acquired severe ADAMTS13:AC deficiency were positive for ADAMTS13:INH. Conclusion, Although TMAs are highly heterogeneous pathological conditions, one third of TMA patients have severe deficiency of ADAMTS13:AC. Platelet transfusions to such patients are contraindicated. Thus, rapid ADAMTS13:AC assays will be prerequisite in medical facilities where TMA patients are treated. [source] Microbiological analysis of composts produced on South Carolina poultry farmsJOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2010M.W. Shepherd Jr Abstract Aims:, The purpose of this study was to determine whether the methods used in compost operations of small and medium-sized poultry forms resulted in the production of an amendment free of foodborne pathogens. Methods and Results:, Nine compost heaps on five South Carolina poultry farms were surveyed at different stages of the composting process. Compost samples were analysed for coliforms and enriched for Escherichia coli O157:H7, Salmonella spp. and Listeria monocytogenes. The waste materials and composting practices differed among the surveyed farms. On two farms, new materials were added to heaps that had previously completed the active composting phase. Five compost heaps did not reach an internal temperature of 55°C, and c. 62% of all internal samples in the first composting phase contained moisture contents <40%. Escherichia coli was detected in 63% of the surface samples (n = 38) and 9·8% of the internal samples (n = 82) from the first composting phase, as compared with 16·7% of the surface samples (n = 12) and 0% internal samples (n = 24) from the second composting phase. Salmonella was detected in 26 and 6·1% of all surface and internal samples collected from heaps in the first composting phase, respectively, but was absent in all compost samples undergoing a second composting phase. The predominant Salmonella serotypes were Thompson, Montevideo and Anatum. Neither E. coli O157:H7 nor L. monocytogenes was detected in any of the samples. Conclusions:, Our results indicate that the conditions at the compost surface are suitable for pathogen survival, and the complete composting process can result in the elimination of pathogens in poultry wastes. Significance and Impact of the Study:, This research provides information regarding the effectiveness of the composting practices and microbiological quality of poultry compost produced by small- and medium-sized farms. Ensuring the safety of compost that may be applied to soils should be an integral part of preharvest food safety programme. [source] Detection of viable Escherichia coli O157:H7 by ethidium monoazide real-time PCRJOURNAL OF APPLIED MICROBIOLOGY, Issue 5 2009L. Wang Abstract Aims:, The aim of this study was to develop and optimize a novel method that combines ethidium bromide monoazide (EMA) staining with real-time PCR for the detection of viable Escherichia coli O157:H7 in ground beef. EMA can penetrate dead cells and bind to intracellular DNA, preventing its amplification via PCR. Methods and Results:, Samples were stained with EMA for 5 min, iced for 1 min and exposed to bright visible light for 10 min prior to DNA extraction, to allow EMA binding of the DNA from dead cells. DNA was then extracted and amplified by TaqMan® real-time PCR to detect only viable E. coli O157:H7 cells. The primers and TaqMan® probe used in this study target the uidA gene in E. coli O157:H7. An internal amplification control (IAC), consisting of 0·25 pg of plasmid pUC19, was added in each reaction to prevent the occurrence of false-negative results. Results showed a reproducible application of this technique to detect viable cells in both broth culture and ground beef. EMA, at a final concentration of 10 ,g ml,1, was demonstrated to effectively bind DNA from 108 CFU ml,1 dead cells, and the optimized method could detect as low as 104 CFU g,1 of viable E. coli O157:H7 cells in ground beef without interference from 108 CFU g,1 of dead cells. Conclusions:, EMA real-time PCR with IAC can effectively separate dead cells from viable E. coli O157:H7 and prevent amplification of DNA in the dead cells. Significance and Impact of the Study:, The EMA real-time PCR has the potential to be a highly sensitive quantitative detection technique to assess the contamination of viable E. coli O157:H7 in ground beef and other meat or food products. [source] Proposed mechanism of inactivating Escherichia coli O157:H7 by ultra-high pressure in combination with tert -butylhydroquinoneJOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2008A.S. Malone Abstract Aims:, Investigating mechanisms of lethality enhancement when Escherichia coli O157:H7, and selected E. coli mutants, were exposed to tert -butylhydroquinone (TBHQ) during ultra-high pressure (UHP) treatment. Methods and Results:,Escherichia coli O157:H7 EDL-933, and 14 E. coli K12 strains with mutations in selected genes, were treated with dimethyl sulfoxide solution of TBHQ (15,30 ppm), and processed with UHP (400 MPa, 23 ± 2°C for 5 min). Treatment of wild-type E. coli strains with UHP alone inactivated 2·4,3·7 log CFU ml,1, whereas presence of TBHQ increased UHP lethality by 1·1,6·2 log CFU ml,1; TBHQ without pressure was minimally lethal (0,0·6 log reduction). Response of E. coli K12 mutants to these treatments suggests that iron,sulfur cluster-containing proteins ([Fe,S]-proteins), particularly those related to the sulfur mobilization (SUF system), nitrate metabolism, and intracellular redox potential, are critical to the UHP,TBHQ synergy against E. coli. Mutations in genes maintaining redox homeostasis and anaerobic metabolism were associated with UHP,TBHQ resistance. Conclusions:, The redox cycling activity of cellular [Fe,S]-proteins may oxidize TBHQ, potentially leading to the generation of bactericidal reactive oxygen species. Significance and Impact of the Study:, A mechanism is proposed for the enhanced lethality of UHP by TBHQ against E. coli O157:H7. The results may benefit food processors using UHP,based preservation, and biologists interested in piezophilic micro-organisms. [source] Diversity of Escherichia coli O157 in a longitudinal farm study using multiple-locus variable-number tandem-repeat analysisJOURNAL OF APPLIED MICROBIOLOGY, Issue 5 2008A.M. Urdahl Abstract Aims:, To perform a longitudinal study of the diversity of Escherichia coli O157 from a ruminant pasture/stream environment using multiple-locus variable-number tandem-repeat analysis (MLVA). Methods and Results:, Samples of faecal droppings from grazing ruminants and from an adjacent stream were tested longitudinally for E. coli O157 by enrichment and immunomagnetic separation (IMS). Using MLVA, 24 different profiles were identified from a total of 231 E. coli O157 isolates, of which 80 were included in a similarity analysis. Four main clusters with several subclusters were observed. Although there was close contact between sheep and cattle during the study period, E. coli O157 was surprisingly not detected from cattle faeces. Conclusions:, The cluster analysis indicated both unrelated and closely related E. coli O157 strains. The choice of loci to target in MLVA is important for the subtyping result, as loci with high diversities are essential for discriminating between closely related isolates. Significance and Impact of the Study:, There is a lack of data available on the use of MLVA to describe E. coli O157 diversity and changes over time in the animal reservoirs and the environment. Such data are needed in order to further develop MLVA as a typing method. [source] Leaching of bioluminescent Escherichia coli O157:H7 from sheep and cattle faeces during simulated rainstorm eventsJOURNAL OF APPLIED MICROBIOLOGY, Issue 5 2008A.P. Williams Abstract Aims:, Development of a novel inoculation technique to improve the current methods of determining the leaching of Escherichia coli O157:H7 from faeces. Methods and Results:, Ruminant faeces were inoculated with a high [c. 107 colony forming units (CFU) g,1] or low (c. 104 CFU g,1) load of a lux- marked strain of E. coli O157:H7 via injection, and subjected to four simulated heavy rainfall events. The population density and metabolic activity of E. coli O157:H7 recovered within the leachate was determined following each simulated rain event and compared with the indigenous E. coli population. The concentration of E. coli O157:H7 in the leachates followed a similar trend to that of nonpathogenic E. coli. Significantly greater densities of generic and pathogenic E. coli were recovered in the leachates generated from sheep faeces compared with cattle faeces. Pathogen metabolic activity was also significantly greater in sheep faeces. Conclusions:, Our findings show that E. coli O157:H7 may readily leach from ruminant faeces during rain events. The bacterium leaches more freely from sheep faeces than from cattle faeces and displays greater metabolic activity within sheep leachate. Significance and Impact of the Study:, A novel inoculation technique was developed that allowed the determination of both population density and cellular activity of E. coli O157:H7 in leachate derived from faeces. [source] Prevalence and potential link between E. coli O157:H7 isolated from drinking water, meat and vegetables and stools of diarrhoeic confirmed and non-confirmed HIV/AIDS patients in the Amathole District , South AfricaJOURNAL OF APPLIED MICROBIOLOGY, Issue 2 2008B.O. Abong'o Abstract Aim:, The current study investigated the prevalence and molecular relatedness between Escherichia coli O157:H7 isolated from water, meat and meat products and vegetables and from stools of confirmed and non-confirmed Human Immune Virus/Acquired Immunodeficiency Syndrome (HIV/AIDS) patients with diarrhoea. Methods and Results:, Culture-based and polymerase chain reaction techniques were used to identify E. coli O157:H7. Thirty-five per cent of meat products, 25·5% of water, 21·7% of vegetables as well as 56·5% and 43·5% of stools of confirmed and non-confirmed HIV/AIDS patients, respectively, were presumptively positive with E. coli O157. Molecular results indicated that 10·3%, 8·6% and 7·8% of the vegetables, water and meat products examined carried E. coli O157:H7, which had homologous fliCH7, rfbEO157 and eaeA genetic loci to the genes of some E. coli O157:H7 isolated from 12·2% and 8·8% of the stools of confirmed and non-confirmed HIV/AIDS patients, respectively. Conclusions:, Water, meat and meat products and vegetables are potential sources of E. coli O157:H7 that are potentially capable of causing diarrhoea in humans especially HIV/AIDS patients. Significance and Impact of the Study:, Great care should be exercised to ensure that water and foods consumed by HIV/AIDS patients are safe, as contaminated water and foods can cause secondary infections in these patients. [source] Can the high levels of human verocytotoxigenic Escherichia coli O157 infection in rural areas of NE Scotland be explained by consumption of contaminated meat?JOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2007O. Solecki Abstract Aims:, To determine if contamination levels of Escherichia coli O157 and generic E. coli in retail-minced meat products are greater in rural shops compared with urban shops in Grampian, NE Scotland. We also investigated whether meat from supermarkets and meat from local butcher shops had a similar bacteriological quality. Methods and Results:, Minced beef and minced lamb were tested from November 2004 to August 2006. Escheichia coli O157 was found at low levels in four samples out of 530 tested samples (0·75%). Generic E. coli were present in 11% of the samples tested, of which 67% came from supermarkets. We observed no significant difference in the prevalence of generic E. coli between rural and urban areas. Conclusions:, Low levels of contamination with E. coli O157 and generic E. coli in retail meat suggest that meat is not a major route of infection in NE Scotland. Significance and Impact of the Study:, The study does not suggest that the high incidence of E. coli O157 human infection in the rural areas of Grampian is because of meat consumption , this provides further evidence of contact with animals or water being the routes of infection. Hence, risk mitigation should be focussed more on environmental pathways of infection. [source] Combined effect of mild heat and acetic acid treatment for inactivating Escherichia coli O157:H7, Listeria monocytogenes and Salmonella typhimurium in an asparagus pureeJOURNAL OF APPLIED MICROBIOLOGY, Issue 5 2006J.-H. Shin Abstract Aims:, This study was conducted to validate combined heat and acid treatments for inactivating Escherichia coli O157:H7, Listeria monocytogenes and Salmonella typhimurium in an acidified brine containing, or pickled, asparagus model food. Methods and Results:, A mixture of three strains of E. coli O157:H7, L. monocytogenes and S. typhimurium were inoculated onto pickled asparagus samples. Combinations of various concentrations of acetic acid [0%, 0·25%, 0·5%, 0·75%, 1%, 1·5% and 2% (v/v)] and various temperatures (40°C, 50°C, 60°C and 75°C) were investigated. Following treatment, asparagus samples were stored at room temperature and enumerated at 0, 0·5, 1, 2 and 3 days. Heat and acetic acid treatments were synergistic. The inhibitory effects of these combined treatments on the tested foodborne pathogens were also effective during storage. Loss of green colour in the pickled asparagus significantly increased with increasing concentrations of acetic acid. Conclusions:, Using a combination of mild heat and acetic acid treatments can successfully control E. coli O157:H7, L. monocytogenes and S. typhimurium in pickled asparagus, combinations of heat and acid are synergistic and effective treatments can be selected to reduce adverse effect on colour which occur during product storage. Significance and Impact of the Study:, Mild heating plus acetic acid treatment are synergistic, so combined treatments can be developed, which would lower the temperature and amount of acetic acid required for minimally processed vegetables while maintaining pathogen control. [source] Prevalence of enterohaemorrhagic Escherichia coli from serotype O157 and other attaching and effacing Escherichia coli on bovine carcasses in AlgeriaJOURNAL OF APPLIED MICROBIOLOGY, Issue 2 2006A. Chahed Abstract Aims:, Bovine meat is the principal source of human contamination of attaching and effacing Escherichia coli, including enterohaemorrhagic E. coli O157. The aim was to study the prevalence of these strains on bovine carcasses in Algeria. Methods and Results:, Two-hundred and thirty carcasses were swabbed and analysed by classical microbiological methods for total E. coli counts and for the presence of pathogenic E. coli. The E. coli counts were high, with a 75th percentile of 444·75 CFUs cm,2. For pathogenic E. coli, more than 7% of the tested carcasses were positive for E. coli O157. Eighteen E. coli O157 strains were isolated and typed by multiplex PCR. The main isolated pathotype (78%) was eae+ stx2+ ehxA+. In addition to E. coli O157, other attaching and effacing E. coli (AEEC) were also detected from carcasses by colony hybridization after pre-enrichment and plating on sorbitol MacConkey agar using eae, stx1 and stx2 probes. Thirty carcasses (13%) on the 230 analysed harboured at least one colony positive for one of the tested probes. These positive carcasses were different from those positive for E. coli O157. Sixty-six colonies (2·9%) positive by colony hybridization were isolated. The majority (60·6%) of the positive strains harboured an enteropathogenic E. coli -like pathotype (eae+ stx,). Only three enterohaemorrhagic E. coli (EHEC)-like (eae+ stx1+) colonies were isolated from the same carcass. These strains did not belong to classical EHEC serotypes. Conclusions:, In this study, the global hygiene of the slaughterhouse was low, as indicated by the high level of E. coli count. The prevalence of both E. coli O157 and other AEEC was also high, representing a real hazard for consumers. Significance and Impact of the Study:, This is the first study of this type in Algeria, which indicates that the general hygiene of the slaughterhouse must be improved. [source] Soil survival of Escherichia coli O157:H7 acquired by a child from garden soil recently fertilized with cattle manureJOURNAL OF APPLIED MICROBIOLOGY, Issue 2 2006A. Mukherjee Abstract Aims:, This investigation was conducted to determine the survival of a naturally occurring Escherichia coli O157:H7 in garden soil linked to a sporadic case of E. coli O157 infection in Minnesota. Methods and Results:, The presence and viability of E. coli O157:H7 was monitored in manure-contaminated garden soil for several weeks. Bacterial isolates were characterized using PCR and pulsed-field gel electrophoresis (PFGE). Isolates obtained from the patient and the garden plots during this investigation had indistinguishable PFGE patterns and had the same virulence factors (stx1, stx2, eaeA, ehxA). The E. coli O157:H7 levels obtained from the garden plots declined gradually for a period of 2 months, and on day 69 only one garden plot of four had detectable levels of pathogen. All plots were negative on day 92. The rate of decline in the soil samples stored at 4°C was faster compared with soil samples that remained in ambient conditions, and in refrigerated storage E. coli O157:H7 could not be detected after 10 days. Conclusions:,E. coli O157:H7 strains can survive on manure-amended soil for more than 2 months, and this survival could be reduced by low temperature. Significance and Impact of the Study:, This is one of the few reports that have investigated the survival of a proven virulent strain in naturally contaminated soil samples. This case stresses the importance of avoiding the use of raw cattle manure to amend soil for cultivation of foods, including soils in residential garden plots. [source] Antimicrobial activity of essential oils and structurally related synthetic food additives towards selected pathogenic and beneficial gut bacteriaJOURNAL OF APPLIED MICROBIOLOGY, Issue 2 2006W. Si Abstract Aims:, To assess the potential of essential oils and structurally related synthetic food additives in reducing bacterial pathogens in swine intestinal tract. Methods and Results:, The antimicrobial activity of essential oils/compounds was measured by determining the inhibition of bacterial growth. Among 66 essential oils/compounds that exhibited ,80% inhibition towards Salmonellatyphimurium DT104 and Escherichia coli O157:H7, nine were further studied. Most of the oils/compounds demonstrated high efficacy against S. typhimurium DT104, E. coli O157:H7, and E. coli with K88 pili with little inhibition towards lactobacilli and bifidobacteria. They were also tolerant to the low pH. When mixed with pig cecal digesta, these oils/compounds retained their efficacy against E. coli O157:H7. In addition, they significantly inhibited E. coli and coliform bacteria in the digesta, but had little effect on the total number of lactobacilli and anaerobic bacteria. Conclusions:, Some essential oils/compounds demonstrated good potential, including efficacy, tolerance to low pH, and selectivity towards bacterial pathogens, in reducing human and animal bacterial pathogens in swine intestinal tract. Significance and Impact of the Study:, This study has identified candidates of essential oils/compounds for in vivo studies to develop antibiotic substitutes for the reduction of human and animal bacterial pathogens in swine intestinal tract. [source] Synergistic effect of enterocin AS-48 in combination with outer membrane permeabilizing treatments against Escherichia coli O157:H7JOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2005S. Ananou Abstract Aims:, To determine the effects of outer membrane (OM) permeabilizing agents on the antimicrobial activity of enterocin AS-48 against Escherichia coli O157:H7 CECT 4783 strain in buffer and apple juice. Methods and Results:, We determined the influence of pH, EDTA, sodium tripolyphosphate (STPP) and heat on E. coli O157:H7 CECT 4783 sensitivity to enterocin AS-48 in buffer and in apple juice. Enterocin AS-48 was not active against intact cells of E. coli O157:H7 CECT 4783 at neutral pH. However, cells sublethally injured by OM permeabilizing agents (EDTA, STPP, pH 5, pH 8·6 and heat) became sensitive to AS-48, decreasing the amount of bacteriocin required for inhibition of E. coli O157:H7 CECT 4783. Conclusions:, The results presented indicate that enterocin AS-48 could potentially be applied with a considerably wider range of protective agents, such as OM permeabilizing agents, with increased efficacy in inhibiting E. coli O157:H7. Significance and Impact of the Study:, Results from this study support the potential use of enterocin AS-48 to control E. coli O157:H7 in combination with other hurdles. [source] Assessment of resistance to colicinogenic Escherichia coli by E. coli O157:H7 strainsJOURNAL OF APPLIED MICROBIOLOGY, Issue 1 2005G. P. Schamberger Abstract Aims:, To assess a collection of 96 Escherichia coli O157:H7 strains for their resistance potential against a set of colicinogenic E. coli developed as a probiotic for use in cattle. Methods and Results:,Escherichia coli O157:H7 strains were screened for colicin production, types of colicins produced, presence of colicin resistance and potential for resistance development. Thirteen of 14 previously characterized colicinogenic E. coli strains were able to inhibit 74 serotype O157:H7 strains. Thirteen E. coli O157:H7 strains were found to be colicinogenic and 11 had colicin D genes. PCR products for colicins B, E-type, Ia/Ib and M were also detected. During in vitro experiments, the ability to develop colicin resistance against single-colicin producing E. coli strains was observed, but rarely against multiple-colicinogenic strains. The ability of serotype O157:H7 strains to acquire colicin plasmids or resistance was not observed during a cattle experiment. Conclusions:,Escherichia coli O157:H7 has the potential to develop single-colicin resistance, but simultaneous resistance against multiple colicins appears to be unlikely. Colicin D is the predominant colicin produced by colicinogenic E. coli O157:H7 strains. Significance and Impact of the Study:, The potential for resistance development against colicin-based strategies for E. coli O157:H7 control may be very limited if more than one colicin type is used. [source] Intermittent and persistent shedding of Escherichia coli O157 in cohorts of naturally infected calvesJOURNAL OF APPLIED MICROBIOLOGY, Issue 5 2004S.E. Robinson Abstract Aims:, We conducted two short-term studies of cohorts of naturally infected calves to determine the prevalence and concentrations of Escherichia coli O157 shed in faeces. Methods and Results:, Two cohorts of calves were sampled; in the first study 14 calves were sampled up to five times a day for 5 days; in the second study a group of 16 separate calves were sampled once or twice a day for 15 days. All cattle within the two cohorts shed E. coli O157 at some point during the respective studies. In 18% of samples, E. coli O157 could only be isolated using immunomagnetic separation after an enrichment period, suggesting concentrations <250 CFU g,1. The highest concentrations recorded were 6·7 × 105 and 1·6 × 106 CFU g,1 for studies 1 and 2 respectively. Conclusions:, Persistent, high shedders (shedding >103 CFU g,1) were evident in both studies but, in the majority of calves, the pathogen was isolated intermittently. Significance and Impact of the Study:, The variable patterns of shedding have important implications for the design of appropriate sampling protocols and for gaining meaningful estimates of parameters used in mathematical models of transmission. [source] A comparison of two pre-enrichment media prior to immunomagnetic separation for the isolation of E. coli O157 from bovine faecesJOURNAL OF APPLIED MICROBIOLOGY, Issue 1 2003G. Foster Abstract Aims: To compare the sensitivity of two pre-enrichment broth media prior to immunomagnetic separation for the isolation of Escherichia coli O157 from cattle faeces. Methods and Results: One-gram portions of 721 cattle faeces collected from 43 farms were pre-enriched in buffered peptone water containing vancomycin, cefixime and cefsulodin (BPW-VCC) and buffered peptone water without additives (BPW-WOA), respectively. A total of 137 samples were positive for E. coli O157: 127 pre-enriched with BPW-WOA and 89 pre-enriched in BPW-VCC. Representative isolates were tested for phage type, verotoxin and eae (E. coli attaching and effacing) gene sequences, resulting in the recognition of eight different types. All the E. coli O157 types recognized were isolated by both methods except for three different strains, each of which were isolated only on a single occasion: two by BPW-WOA and another by BPW-VCC. Conclusions: The results clearly demonstrate, under the conditions of this study, that BPW without antibiotics was the superior pre-enrichment medium for the isolation of E. coli O157 from cattle faeces. Significance and Impact of the Study: The use of BPW-WOA in preference to BPW-VCC for the isolation of E. coli O157 from cattle faeces in future research and outbreak studies should lead to a higher number of positive isolates. [source] Effect of subtherapeutic concentrations of tylosin on the inhibitory stringency of a mixed anaerobe continuous-flow culture of chicken microflora against Escherichia coli O157:H7JOURNAL OF APPLIED MICROBIOLOGY, Issue 1 2003T.L. Poole Abstract Aims: The aim of this study was twofold: first to determine the effect of subtherapeutic concentrations of tylosin, a macrolide antibiotic used for growth promotion, on a mixed anaerobic continuous-flow fermentation culture of chicken gastrointestinal microorganisms (CCF) and secondly, to determine if these concentrations would allow persistence of Escherichia coli O157:H7 in CCF. Methods and Results: CCF was treated with tylosin at 10·0, 20·0 and 40·0 ,g ml,1. Tylosin treatment resulted in a significant (P < 0·0001) decrease in total volatile fatty acids (VFAs) from a mean concentration of 101 ± 10·8 ,mol ml,1 in control cultures to 32·0 ± 6·3 and 40·2 ± 9·6 ,mol ml,1 in 10 and 40 ,g ml,1 treated cultures, respectively. Untreated CCF challenged with E. coli O157:H7 cleared the challenge microorganism in 7 days at a rate of 0·96 log10 CFU ml,1 day,1. In contrast, E. coli O157:H7 persisted in all tylosin treated cultures. Conclusions: In the presence of tylosin, E. coli O157:H7 was able to persist in the CCF culture. The significant decrease in the production of VFAs may have been a contributing factor. Significance and Impact of the Study: The use of low-level, growth-promoting antimicrobials may compromise the ability of normal microflora that serve as a natural host defence against infection. [source] Prevalence of verotoxin-producing Escherichia coli (VTEC) and E. coli O157:H7 in French porkJOURNAL OF APPLIED MICROBIOLOGY, Issue 1 2002J. Bouvet Aims:,To determination the prevalence of VTEC in pork products and the surrounding environment of the pork plant (slaughterhouse and cutting plant), and characterization of the VTEC strains isolated (virulence genes and serotype). Methods and Results: ,Among the 2146 carcass and pork samples and 876 environmental samples (swabs of surfaces or materials), 328 (15%) and 170 (19%) were PCR-positive for stx genes respectively. VTEC strains were recovered from positive samples by colony hybridization or immunoconcentration, serotyped and genetically characterized. Strains of E. coli O157:H7 were not isolated from 3 uidA-positive samples detected by PCR. The VTEC isolates did not harbour eae, ehx and uidA genes. Conclusions: ,Pigs and pork meat may contain VTEC strains but characterization of the strains based on virulence factors showed that the potential danger of pork meat appears to be low since although all strains harboured a stx gene, they did not have other virulence genes. Significance and Impact of the Study:,General hygiene measures appear to be sufficient and specific hygiene measures for VTEC are not necessary at this time. The porcine VTEC strains isolated in our study probably do not present a hazard. [source] Comparison of the sensitivity of manual and automated immunomagnetic separation methods for detection of Shiga toxin-producing Escherichia coli O157:H7 in milkJOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2002R.D. Reinders Aim:,To determine the sensitivity of methods for detection of injured and uninjured Escherichia coli O157:H7 (E. coli O157) in raw and pasteurized milk. Methods and Results:,Raw milk, pasteurized milk with 1·5% fat content and pasteurized milk with 3·5% fat content were spiked with E. coli O157 at low levels. The samples were enriched in modified tryptone soya broth with novobiocin (mTSBn) at 37°C. Aliquots of the enriched culture were analysed either by manual immunomagnetic separation (MIMS) and culturing on sorbitol MacConkey agar with or without cefixime and potassium tellurite (SMACct or SMAC), or by automated immunomagnetic separation and integrated ELISA (EiaFossÔ). Uninjured E. coli O157 organisms were detected in milk by both methods at 1 cfu 10 ml,1 sample). Injured organisms were detected at levels of about 4 cfu 10 ml,1 sample. Direct enrichment in mTSBn (22 h incubation) showed better sensitivity for injured cells than enrichment in buffered peptone water (BPW, 22 h incubation), or in a two-step enrichment consisting of BPW (6 h, 37°C) and mTSBn (16 h, 37°C), successively. Conclusions:,The methods showed equal sensitivity in that they were both able to detect 1 cfu 10 ml,1 milk sample. Injured organisms can be detected and isolated at a level almost as low as this. A resuscitation step is not recommended for the detection and isolation of injured and non-injured E. coli O157 from milk. Significance and Impact of the Study:,Due to the dilution of contamination in the bulk tank, analysis of milk for the presence of E. coli O157 requires a very sensitive method. Both methods described here are useful for such analysis. [source] Comparison of ATP and in vivo bioluminescence for assessing the efficiency of immunomagnetic sorbents for live Escherichia coli O157:H7 cellsJOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2002W. Sun Aims:,To develop methods to assess the efficiency of immunomagnetic separation (IMS). Methods and Results:,The capturing efficiency of biosorbents for Escherichia coli O157:H7, constructed using streptavidin-coated magnetic beads and biotinylated antibodies, was tested using both in vivo and ATP bioluminescence. Both methods were suitable for the enumeration of bacteria captured by the biosorbents. The level of both ATP and in vivo bioluminescence depended on the media used, but was unaffected by the magnetic beads. The capture efficiency depended on time and sample volume, but did not depend on the length of spacer arm of the biotinylation agent. For cell concentrations of , 105 cfu ml,1, in a 1-ml sample volume, nearly 80,85% recovery of the pathogen was observed after 0·5 h of incubation. For an 11-ml sample containing 104 cfu ml,1, maximum recovery (50% of cells) was achieved only after 2 h incubation. Conclusions:,The detection limit of an ATP-based bioluminescent assay for E. coli O157:H7 was reduced by 1 log cycle after optimization of IMS. The bioluminescent methods could be used for screening and testing the affinity of antibodies or other affinity elements of biosorbents towards live bacterial cells. Significance and Impact of the Study:,Bioluminescent assays provide an easy way to optimize conditions for the capture of bacteria by biosorbents in real time. [source] Inactivation and injury of pressure-resistant strains of Escherichia coli O157 and Listeria monocytogenes in fruit juicesJOURNAL OF APPLIED MICROBIOLOGY, Issue 3 2001S.L. Jordan Aims:,To investigate methods for inactivating a pressure-resistant strain of Escherichia coli O157 in fruit juices. Methods and Results:,Cells of a pressure-resistant strain of E. coli O157 (C9490) were exposed to pressures of between, 0·1 and 500 MPa for 5 min in orange, apple or tomato juice. Treatment at 500 MPa achieved an immediate reduction of 5 log units in apple juice (pH 3·5) and tomato juice (pH 4·1), but only about a 1,2 log10 reduction in orange juice (pH 3·8). The greater level of inactivation in tomato juice than in orange juice of lower pH was due to the presence of low levels (0·7%) of salt in the tomato juice. With the type-strain of E. coli (ATCC 11775) and Listeria monocytogenes NCTC 11994, similar levels of inactivation were achieved at pressures 200 MPa lower. Following storage of pressure-treated orange juice at 4°C for 24 h or 25°C for 3 h, the level of inactivation of E. coli O157 strain C9490 increased to 4·4 or > 7 log10 units, respectively. Conclusions:,Treatment at 500 MPa may be insufficient to achieve a ,5D' reduction in counts of pressure-resistant strains of E. coli, but subsequent death during storage substantially increases process lethality. Significance and Impact of the Study:,Commercially-practicable pressure processes can be used to inactivate even the most pressure-and acid-resistant strains of E. coli O157, provided that processing and subsequent storage conditions are carefully optimized. [source] Cross-talk involving extracellular sensors and extracellular alarmones gives early warning to unstressed Escherichia coli of impending lethal chemical stress and leads to induction of tolerance responsesJOURNAL OF APPLIED MICROBIOLOGY, Issue 5 2001R.J. Rowbury 1. Summary, 678 2. Introduction 2.1. Chemical and biological stress agents affecting enterobacteria, 678 2.2. Sensing of chemical and biological stress stimuli, 678 2.3. Intracellular sensors detect intracellularly-produced chemical stressing agents, 679 2.4. Intracellular sensors and intracellular induction components could delay response induction by extracellular chemical or biological stress agents, 680 2.5. Extracellular sensors and EICs give early warning of stress, 681 2.6. Disadvantages of extracellular components being needed for stress response induction, 682 2.7. Extracellular sensors and EICs allow stressed cells to warn unstressed ones, 682 2.8. A second role for some extracellular stress sensors, 683 3. Responses switched on by extracellular sensors and EICs 3.1. Involvement of EICs and ESCs in acid tolerance induction at pH 5·0 and at other mildly acidic pH values, 683 3.2. Further evidence for the obligate involvement of extracellular sensors and EICs in acid tolerance induction at pH 5·0, 684 3.3. On the nature of the acid pH tolerance-inducing ESC and EIC, 686 3.4. The acid tolerance ECs and their relation to other extracellular response-inducing components, 686 3.5. Extracellular components are needed for other inducible acid tolerance responses, 687 3.6. Involvement of EICs and extracellular sensors in acid tolerance in E. coli O157, 687 3.7. EICs involved in acid tolerance induction are diffusible, 687 4. Acid sensitization at alkaline pH and the role of extracellular sensor and EIC(s), 688 5. Responses affecting tolerance to alkali 5.1. Alkali sensitization at acidic pH, 688 5.2. Induced alkali tolerance at pH 9·0 and role of extracellular components, 688 6. Inducible tolerance to alkylhydroperoxides, 689 7. Are extracellular sensors and extracellular induction components needed for all stress responses?, 689 8. Altered responsiveness of extracellular sensors depending on growth conditions, 691 9. Protection of living cells from chemical stress by dead cultures, 691 10. How can intracellular levels of stress be detected?, 692 11. Are Nikolaev's extracellular ,protectants' and similar components related to EICs?, 693 12. Conclusions, 693 13. References, 694 [source] Valuing food-borne risks using time-series data: The case of E. coli O157:H7 and BSE crises in JapanAGRIBUSINESS : AN INTERNATIONAL JOURNAL, Issue 2 2006Shunji Oniki This study evaluates changes in consumers' concerns on food safety after the outbreaks of E. coli O157 and bovine spongiform encephalopathy (BSE) in Japan using household consumption time-series data. A food demand system for Japanese households is estimated using the linear approximate almost-ideal demand system (AIDS) model to evaluate the willingness to accept (WTA) compensation for risk. The Kalman filtering method is applied to produce estimates without a priori assumption regarding timing of the changes. The WTA value rises immediately after a food safety crisis occurs and declines in a short time. However, it does not return to previous levels for an extended period. A possible explanation for remaining effects of a crisis might be that they are the results of habit formation and learning effects of consumption. [EconLit citations: D12, D18, Q13]. © 2006 Wiley Periodicals, Inc. Agribusiness 22: 219,232, 2006. [source] PATHOGEN DETECTION IN FOOD MICROBIOLOGY LABORATORIES: AN ANALYSIS OF QUALITATIVE PROFICIENCY TEST DATA, 1999,2007JOURNAL OF FOOD SAFETY, Issue 4 2009DANIEL C. EDSON ABSTRACT The objective of this study was to assess laboratories' ability to detect or rule out the presence of four common food pathogens: Escherichia coli O157:H7, Salmonella spp., Listeria monocytogenes and Campylobacter spp. To do this, qualitative proficiency test data provided by one proficiency test provider from 1999 to 2007 were examined. The annual and cumulative 9-year percentages of false-negative and false-positive responses were calculated. The cumulative 9-year false-negative rates were 7.8% for E. coli O157:H7, 5.9% for Salmonella spp., 7.2% for L. monocytogenes and 13.6% for Campylobacter spp. Atypical strains and low concentrations of bacteria were more likely to be missed, and the data showed no trend of improving performance over time. Percentages of false-positive results were below 5.0% for all four pathogens. PRACTICAL APPLICATIONS The results imply that food testing laboratories often fail to detect the presence of these four food pathogens in real food specimens. To improve pathogen detection, supervisors should ensure that testing personnel are adequately trained, that recommended procedures are followed correctly, that samples are properly prepared, that proper conditions (temperature, atmosphere and incubation time) are maintained for good bacterial growth and that recommended quality control procedures are followed. Supervisors should also always investigate reasons for unsatisfactory proficiency test results and take corrective action. Finally, more research is needed into testing practices and proficiency test performance in food testing laboratories. [source] LISTERIA MONOCYTOGENES AND ESCHERICHIA COLI O157:H7 INHIBITION IN VITRO BY LIPOSOME-ENCAPSULATED NISIN AND ETHYLENE DIAMINETETRAACETIC ACIDJOURNAL OF FOOD SAFETY, Issue 2 2008T. MATTHEW TAYLOR ABSTRACT Encapsulation technologies that effectively reduce antimicrobial interaction with food components or protect antimicrobial compounds from food processing measures have the potential to improve the microbiological safety of ready-to-eat foods. Recent application of liposomes for the preservation of cheese has spurred research into their utility in other food matrices. To ascertain the feasibility of encapsulated antimicrobial for the control of Listeria monocytogenes and Escherichia coli O157:H7 growth in a model system, nisin (5.0 and 10.0 µg/mL) and the chelator ethylene diaminetetraacetic acid were entrapped in phospholipid liposomes. While phosphatidylcholine (PC) liposomes did not produce significant inhibition of target pathogens, PC/phosphatidylglycerol 8/2 and 6/4 (mol%) produced significant inhibition of pathogens. Near-complete inhibition of E. coli O157:H7 with liposomal antimicrobials at concentrations below those reported necessary for unencapsulated antimicrobial and chelator suggests that liposomes may represent a powerful technology for the encapsulation of antimicrobials and the control of foodborne pathogens. PRACTICAL APPLICATIONS The activity of many antimicrobials is abolished in many food products for a variety of reasons. Interference and cross-reactions of the antimicrobial and various food constituents, such as protein and fat, are difficult to overcome and often require large amounts of antimicrobial in order to gain significant reductions in the pathogen load in a product. Loss of solubility of some antimicrobials based on pH or ionic strength will negatively affect the antimicrobial potential of a compound like nisin. Liposome encapsulation technologies, such as that reported here, may allow for the maintenance of antimicrobial activity by protecting the antimicrobial against cross-reactions with food components. Additionally, the liposome core represents a microenvironment which can be manipulated by the manufacturer in order to preserve optimal antimicrobial solubility and stability conditions until the time of release. [source] | |||||||||||||||||||||||||||||||