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O157
Kinds of O157 Terms modified by 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] Sensitivity of Shiga toxin-producing Escherichia coli (STEC) strains for colicins under different experimental conditionsFEMS MICROBIOLOGY LETTERS, Issue 2 2001Bart J.A.M. Jordi Abstract Twenty Escherichia coli strains producing well-characterised colicins were tested for their inhibitory activity against five Shiga toxin-producing E. coli (STEC) strains using different media under aerobic and anaerobic conditions. The five STEC strains used were of serotype O26, O111, O128, O145 and O157:H7 which are frequently isolated serotypes associated with disease in humans. The main route of infection for humans is through the eating of badly cooked or handled beef. The major reservoir for STEC strains in cattle is the rumen. To mimic the situation in the rumen of cattle, overlay assays were also performed under anaerobic conditions in the presence of 30% rumen fluid. Colicins E1, E4, E8-J, K and S4 are most active against STEC strains under anaerobic conditions in the absence or presence of rumen fluid. These colicins will be used in future experiments with the aim to eradicate the presence of STEC in cattle. [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] Inducible stx2 phages are lysogenized in the enteroaggregative and other phenotypic Escherichia coli O86:HNM isolated from patientsFEMS MICROBIOLOGY LETTERS, Issue 1 2000Sunao Iyoda Abstract We characterized two Shiga toxin-producing Escherichia coli (STEC) O86:HNM isolates from a patient with hemolytic uremic syndrome (HUS) or bloody diarrhea. Both of them did not possess the eaeA gene. However, the isolate from a HUS patient carried genetic markers of enteroaggregative E. coli (EAEC) and showed aggregative adherence pattern to HEp-2 cells. The other isolate from bloody diarrhea, which was negative with EAEC markers, was diffusely adhered to HEp-2 cells. The stx2 gene in both E. coli O86:HNM strains was encoded in each infectious phage, which was partially homologous to that of strain EDL933, a STEC O157:H7. These results will help to explain the genotypic divergences of STEC. [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] Identification and characterization of antimicrobial peptide, defensin, in the taiga tick, Ixodes persulcatusINSECT MOLECULAR BIOLOGY, Issue 4 2009Y. Saito Abstract Ixodes persulcatus is the primary vector for human tick-borne diseases in Japan. A cDNA library was constructed from whole body homogenates of fed nymphs of I. persulcatus. From this library, one cDNA encoding defensin-like antimicrobial peptide was identified. The amino-acid sequence showed high similarity to those of the defensins of other ticks and arthropods. I. persulcatus defensin mRNA transcripts were detected at all life cycle stages of fed ticks and found to be predominantly expressed in the midguts of adult female ticks, but not in the salivary glands, a finding corroborated by Western blotting analysis. To investigate the function of I. persulcatus defensin, we examined its antibacterial activity by evaluation of growth of several bacterial strains in the presence of the synthetic peptide. The defensin from I. persulcatus markedly inhibited the growth of Gram-positive bacteria including Staphylococcus aureus, Bacillus subtilis and Corynebacterium renale, but not Gram-negative bacteria except Escherichia coli O157. In conclusion, these results suggest that I. persulcatus defensin may be playing a significant role in the defence against microbes from bloodmeals. [source] Evaluation of pre-heating and extraction solvents in antioxidant and antimicrobial activities of garlic, and their application in fresh pork pattiesINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 2 2010Sung Y. Park Summary The objectives of this study were to screen the optimum conditions for antioxidant and antimicrobial activities of garlic as affected by pre-heating and different extraction solvents, and to evaluate the antioxidant and antimicrobial effects of these extracts in ground meat during refrigerated storage. Methanol extracted garlic had a greater total phenolic content, 1,1-diphenyl-2-picrylhydrazyl (DPPH)-radical scavenging activity and reducing power than water extracted one (P < 0.05), whereas the latter had a greater yield and iron chelating ability than the former (P < 0.05). Moreover, water extract from fresh garlic (WEFG) and methanol extract from heated garlic (MEHG) produced an inhibition zone against Escherichia coli O157:H7 and Listeria monocytogenes. The addition of garlic extracts (WEFG, MEHG and their combinations WEFMEHG)) to pork patties decreased the pH, hunter a values (redness), thiobarbituric acid substances values and the number of total plate count and Enterobacteriaceae (P < 0.05), while the hunter b values (yellowness) increased (P < 0.05). Results of this study indicated that the use of the garlic extracts was able to control lipid oxidation and microbial growth in pork patties. [source] Effect of water activity on the inactivation kinetics of Escherichia coli O157:H7 by electron beam in ground beef, chicken breast meat, and trout filletsINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 4 2008Jennifer Leah Black Summary Water activity (aw) of ground beef, chicken breast meat, and trout fillets was modified to intermediate (aw 0.98,0.99) and lowest (aw 0.94,0.96) levels. The meat samples with modified and unaltered (native, aw 1.00) aw were inoculated with Escherichia coli O157:H7 and subjected to electron beam (e-beam). Survivor curves were plotted and the D10 -values were calculated. The D10 -values ranged from 0.22 kGy for trout at native aw to 0.33 kGy for beef at intermediate, and chicken and trout at lowest aw. Regardless of the species, aw reduction increased E. coli resistance to e-beam, suggesting that even small depletion of unbound water from food increases survival. The difference of the D10 -values between the samples at intermediate and lowest aw was insignificant. E-beam could be used before aw -reducing techniques are applied to food products. However, this would require stringent microbial control following e-beam processing. The ,tailing' of survivors was observed for some samples with reduced aw. [source] Haemolytic uraemic syndrome: prognostic factorsINTERNATIONAL JOURNAL OF LABORATORY HEMATOLOGY, Issue 1 2000D. A. Green Haemolytic uraemic syndrome (HUS) associated with Escherichia coli O157:H7 is the commonest cause of acute renal failure (ARF) in childhood. Production of verotoxin by the organism is pivotal in the pathogenesis of the disease. Verotoxin binds to a receptor on blood and endothelial cells, expressed as the P1 blood group antigen on red blood cells. A protective effect of the P1 phenotype has been proposed in this disease. This study investigates prognostic factors and the relationship between outcome and P1 phenotype in 27 cases of diarrhoea-associated HUS. A poor outcome as defined by the presence of chronic renal failure (CRF), hypertension or proteinuria on 6 month follow-up was associated with the age of the patient at presentation and with the following clinical markers: maximum WBC and duration of raised WBC, duration of anuria and duration of need for dialysis. None of these outcome measures or prognostic factors, and no extra-renal manifestations of the disease were associated with P1 phenotype. [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] Host range and lytic capability of four bacteriophages against bovine and clinical human isolates of Shiga toxin-producing Escherichia coli O157:H7JOURNAL OF APPLIED MICROBIOLOGY, Issue 2 2009Y.D. Niu Abstract Aims:, To evaluate host range and lytic capability of four bacteriophages (rV5, wV7, wV8 and wV11) against Escherichia coli O157:H7 (STEC O157:H7) from cattle and humans. Methods and Results:, Four hundred and twenty-two STEC O157:H7 isolates (297 bovine; 125 human) were obtained in Alberta, Canada. The four phages were serially diluted and incubated for 5 h with overnight cultures of STEC O157:H7 to estimate their multiplicity of infection (MOI). All bovine STEC O157:H7 were subjected to pulsed-field gel electrophoresis (PFGE) and phage typing (PT). Phage wV7 lysed all human and bovine isolates irrespective of PFGE genotype or PT phenotype and exhibited the lowest MOI (0·004,0·006, P < 0·0001) of all phages. Phages rV5 and wV11 exhibited a lower MOI (0·002,0·04, P < 0·0001) than did phage wV8 (25,29) and they had a narrower host range than wV7 or wV8. Phages rV5, wV11 and wV8 lysed 342 (81·0%), 321 (76·1%) and 407 (96·4%), respectively, of the 422 isolates. Susceptibility of bovine STEC O157:H7 to rV5, w11 and wV8 was influenced by PFGE genotype and/or PT phenotype. Conclusions:, Phages exhibited activity against the majority of bovine and human STEC O157:H7 isolates. PFGE genotype and/or PT phenotype of the host-target influenced their vulnerability to phage attack. Susceptibility of bovine STEC O157:H7 to phage may also differ among farms. Both lytic capability and host range should be considered in the selection of therapeutic phage for on-farm control of STEC O157:H7. Significance and Impact of the Study:, The present work indicates that a four-phage cocktail should be equally effective at mitigating STEC O157:H7 isolates both of bovine and of human origin. Given that some STEC O157:H7 exhibited resistance to some but not all phages, a phage cocktail is the logical approach to efficacious on-farm therapy. [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] Physicochemical properties of Shiga toxigenic Escherichia coliJOURNAL OF APPLIED MICROBIOLOGY, Issue 4 2005L. Rivas Abstract Aims:, To investigate the physicochemical surface properties, such as cellular surface charge, hydrophobicity and electron donor/acceptor potential of a selection of Shiga toxigenic Escherichia coli (STEC) isolates grown in broth and agar culture. Methods and Results:, Cellular surface charge was determined using zeta potential measurements. Hydrophobicity of the isolates was determined using bacterial adhesion to hydrocarbons assay, hydrophobic interaction chromatography and contact angle measurements. Microbial adhesion to solvents was used to determine the electron donor/acceptor characteristics. No differences of surface charge measurements were found between broth and agar grown cultures. Isolates belonging to serogroup O157 and serotypes O26:H11 and O111:H- were significantly (P < 0·05) less negatively charged than other STEC serotypes tested. All strains were hydrophilic with most methods and demonstrated a lower hydrophobicity in agar culture compared with broth culture. All strains demonstrated a strong microbial adhesion to chloroform indicating that STEC possess an electron donor and basic character. A relationship between serogroup O157 and other STEC serotypes was apparent using principal-component analysis (PCA). Conclusions:, Combining the results for physicochemical properties using PCA differentiated between strains belonging to the O157 serogroup and other STEC/non-STEC strains. PCA found similar results for broth and agar grown cultures. Significance and Impact of the Study:, Particular serotypes of STEC possess similar physicochemical properties which may play a role in their pathogenicity or potential attachment to various surfaces. [source] Land application of treated sewage sludge: quantifying pathogen risks from consumption of cropsJOURNAL OF APPLIED MICROBIOLOGY, Issue 2 2005P. Gale Abstract Aims:, To predict the number of humans in the UK infected through consumption of root crops grown on agricultural land to which treated sewage sludge has been applied in accordance with the current regulations and guidance (Safe Sludge Matrix). Methods and Results:, Quantitative risk assessments based on the source, pathway, receptor approach are developed for seven pathogens, namely salmonellas, Listeria monocytogenes, campylobacters, Escherichia coli O157, Cryptosporidium parvum, Giardia, and enteroviruses. Using laboratory data for pathogen destruction by mesophilic anaerobic digestion, and not extrapolating experimental data for pathogen decay in soil to the full 30-month harvest interval specified by the Matrix, predicts 50 Giardia infections per year, but less than one infection per year for the other six pathogens. Assuming linear decay in the soil, a 12-month harvest interval eliminates the risks from all seven pathogens; the highest predicted being one infection of C. parvum in the UK every 45 years. Computer simulations show that a protective effect from binding of pathogens to particulate matter could potentially exaggerate the observed rate of decay in experimental systems. Conclusions:, The results confirm, assuming pathogens behave according to our current understanding, that the risks to humans from consumption of vegetable crops are remote. Furthermore the harvest intervals stipulated by the Safe Sludge Matrix compensate for potential lapses in the operational efficiency of sludge treatment. Significance and Impact of the Study:, The models demonstrate the huge potential impact of decay in the soil over the 12/30-month intervals specified by the Matrix, although lack of knowledge on the exact nature of soil decay processes is a source of uncertainty. The models enable the sensitivity of the predicted risks to changes in the operational efficiency of sewage sludge treatment to be assessed. [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] Occurrence of sublethal injury after pulsed electric fields depending on the micro-organism, the treatment medium ph and the intensity of the treatment investigatedJOURNAL OF APPLIED MICROBIOLOGY, Issue 1 2005D. García Abstract Aims:, The objective was to investigate the occurrence of sublethal injury after pulsed electric field (PEF) depending on the treatment time, the electric field strength and the pH of the treatment media in two Gram-positive (Bacillus subtilis ssp. niger, Listeria monocytogenes) and six Gram-negative (Escherichia coli, Escherichia coli O157:H7, Pseudomonas aeruginosa, Salmonella serotype Senftenberg 775W, Salmonella serotype Typhimurium, Yersinia enterocolitica) bacterial strains. Methods and Results:, A characteristic behaviour was observed for the Gram-positive and Gram-negative bacteria studied. Whereas Gram-positive bacteria showed a higher PEF resistance at pH 7·0, the Gram-negative were more resistant at pH 4·0. In these conditions, in which bacteria showed their maximum resistance, a large proportion of sublethally injured cells were detected. In most cases, the longer the treatment time and the higher the electric field applied, the greater the proportion of sublethally injured cells that were detected. No sublethal injury was detected when Gram-positive bacteria were treated at pH 4·0 and Gram-negative at pH 7·0. Conclusions:, Sublethal injury was detected after PEF so, bacterial inactivation by PEF is not an ,all or nothing' event. Significance and Impact of the Study:, This work could be useful for improving food preservation by PEF. [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] | ||||||||||||||||||||||||||||||||||