511,116 research outputs found
Desk studies on feasibility of horizontal standard rapid methods for detection of E. coli (including E. coli O157) and Salmonella
No full textThe emerging methods becoming available for the rapid detection and enumeration of E. coli (including E. coli O157) and Salmonella in sludges, soil and treated biowastes have been evaluated with a view to possible future standardisation. The main methods that are available for the detection and enumeration of E. coli (including E. coli O157) and Salmonella have been developed largely for analysis of food and water and can be broadly divided into four groups. Proprietary Quantitray® technology, equivalent to the 5-tube most probable number (MPN) technique, employing disposable plastic trays for enumeration of E. coli and Salmonella. Immunological, involving a short or overnight pre-enrichment of the target organism followed by specific detection of cellular antigen in either a lateral flow device or following immunomagnetic capture. Molecular, involving PCR amplification of target DNA sequences from low numbers of cells, or preferably following a short pre-enrichment of the organism to amplify numbers and demonstrate viability prior to molecular detection. Physico-chemical, involving techniques such as measurement of impedance changes during enrichment and growth in appropriate media. The merits of each are described, in relation to their suitability for use with sludge, soil and biowastes. Since the majority of agar and MPN broth techniques take between 24-96 hours for identification and enumeration, we define “rapid” as any technique that detects, and if possible, enumerates the target organism in under 24 hours.All of the methods described have strengths and weaknesses, dependent on not only the Regulators’ types of requirements for sludge, soil and biowaste analysis but also their sensitivity, specificity, speed and cost. It is unlikely therefore that there can be only one methodology applicable to both E. coli (and E. coli O157) and Salmonella detection. Nevertheless, it is considered feasible to formulate horizontal standards to cover rapid analysis of E. coli and Salmonella in sludge, soil, soil improvers, growing media, and biowaste. None of the methods have been extensively evaluated for sewage sludge, soils or biowastes. As such, there is an urgent need for their modification and evaluation as part of the next phase of the Project Horizonta
Preferential attachment of Escherichia coli to different particle size fractions of an agricultural grassland soil.
No full textThis study reports on the attachment preference of a faecally derived bacterium, Escherichia coli, to soil particles of defined size fractions. In a batch sorption experiment using a clay loam soil it was found that 35% of introduced E. coli cells were associated with soil particulates >2 μm diameter. Of this 35%, most of the E. coli (14%) were found to be associated with the size fraction 15-4 μm. This was attributed to the larger number of particles within this size range and its consequently greater surface area available for attachment. When results were normalised with respect to estimates of the surface area available for bacterial cell attachment to each size fraction, it was found that E. coli preferentially attached to those soil particles within the size range 30-16 μm. For soil particles > 2 μm, E. coli showed at least 3.9 times more preference to associate with the 30-16 μm than any other fraction. We report that E. coli can associate with different soil particle size fractions in varying proportions and that this is likely to impact on the hydrological transfer of cells through soil and have clear implications for our wider understanding of the attachment dynamics of faecally derived bacteria in soils of different compositions
Herd-level risk factors associated with the presence of Phage type 21/28 E. coli O157 on Scottish cattle farms
No full text<p>Background: E. coli O157 is a bacterial pathogen that is shed by cattle and can cause severe disease in humans. Phage type (PT) 21/28 is a subtype of E. coli O157 that is found across Scotland and is associated with particularly severe human morbidity.</p>
<p>Methods: A cross-sectional survey of Scottish cattle farms was conducted in the period Feb 2002-Feb 2004 to determine the prevalence of E. coli O157 in cattle herds. Data from 88 farms on which E. coli O157 was present were analysed using generalised linear mixed models to identify risk factors for the presence of PT 21/28 specifically.</p>
<p>Results: The analysis identified private water supply, and northerly farm location as risk factors for PT 21/28 presence. There was a significant association between the presence of PT 21/28 and an increased number of E. coli O157 positive pat samples from a farm, and PT 21/28 was significantly associated with larger E. coli O157 counts than non-PT 21/28 E. coli O157.</p>
<p>Conclusion: PT 21/28 has significant risk factors that distinguish it from other phage types of E. coli O157. This finding has implications for the control of E. coli O157 as a whole and suggests that control could be tailored to target the locally dominant PT.</p>
Phenotypic microarrays suggest Escherichia coli ST131 is not a metabolically distinct lineage of extra-intestinal pathogenic E. coli
No full textExtraintestinal pathogenic E. coli (ExPEC) are the major aetiological agent of urinary tract infections (UTIs) in humans. The emergence of the CTX-M producing clone E. coli ST131 represents a major challenge to public health worldwide. A recent study on the metabolic potential of E. coli isolates demonstrated an association between the E. coli ST131 clone and enhanced utilisation of a panel of metabolic substrates. The studies presented here investigated the metabolic potential of ST131 and other major ExPEC ST isolates using 120 API test reagents and found that ST131 isolates demonstrated a lower metabolic activity for 5 of 120 biochemical tests in comparison to non-ST131 ExPEC isolates. Furthermore, comparative phenotypic microarray analysis showed a lack of specific metabolic profile for ST131 isolates countering the suggestion that these bacteria are metabolically fitter and therefore more successful human pathogens
AgandCuloadedonTiO2/graphite as a catalyst for �Escherichia coli- contaminated water disinfection
No full textTiO2 film was synthesized by means of the chemical bath deposition (CBD) method from TiCl4
as a precursor and surfactant cetyl trimethyl ammonium bromide (CTAB) as a linking and assem-
bling agent of the titanium hydroxide network on a graphite substrate. Ag and Cu were loaded
on the TiO2 film by means of electrodeposition at various applied currents. Photoelectrochemical
testing on the composite of Ag–TiO2/G and Cu–TiO2/G was used to define the composite for
Escherichia coli-contaminated water disinfection. Disinfection efficiency and the rate of disinfection
of E. coli-contaminated water with Ag–TiO2/G as a catalyst was higher than that observed for
Cu–TiO2/G in all disinfection methods including photocatalysis (PC), electrocatalysis (EC), and
photoelectrocatalysis (PEC). The highest rate constant was achieved by the PEC method using
Ag–TiO2/G, k was 6.49 × 10−2
CFU mL−1
min−1
. Effective disinfection times of 24 h (EDT24)
and 48 h (EDT48) were achieved in all methods except the EC method using Cu–TiO2/G.
Keywords: Ag–TiO2/G, Cu–TiO2/G, Escherichia coli, disinfectio
Unusual observations during construction of a new cloning vector providing lon gene expression in Escherichia coli
No full textFriehs K, Bailey JE. Unusual observations during construction of a new cloning vector providing lon gene expression in Escherichia coli. Journal of Biotechnology. 1989;9(4):305-316.The plasmid pJMC40 containing the lon gene was transformed into E. coli HB101 leading to clones with either pJMC40 or a large plasmid designated pJMC40ins. pJMC40ins has a 1.3 kb DNA insert outside of the lon operon. Attempts to reduce the size of pJMC40 through circularization of a 6.7 kb EcoRI fragment containing the lon operon and larger parts of pBR322 failed. Circularization of an 8.0 kb EcoRI fragment of pJMC40ins, consisting of the 6.7 kb fragment and the 1.3 kb insert, produced a new plasmid which is useful as a small vector with a functional lon operon. The lon gene was cloned in vitro into the vector pUC18 setting it under the control of the lac promotor. Different attempts to transform this construct into E. coli failed. We suggest that the expression level of lon is very crucial for the viability of E. coli cells. Changes in regulation of lon expression expected to elevate La activity are lethal for E. coli
The virulence of E. coli 0157:H7 isolated from Irish sheep and pigs to humans
No full textEnd of Project ReportInvestigations were carried out at five sheep and five pig export abattoirs
situated in the Republic of Ireland to determine the prevalence of E. coli
O157:H7 in these animals at slaughter. This is the first study for the presence
of E. coli O157:H7 on sheep and pigs to be carried out in Ireland. Faeces and
pre- and post-chill carcass swabs were collected from pigs over a one year
period between January and December 2004. Samples were collected from
sheep over a 13-month period between February 2005 and February 2006.
The pig study recovered E. coli O157:H7 from 0.24 % (n=4) of 1680 porcine
samples while the sheep study isolated the pathogen from 2.1 % (n=33) of
1600 ovine samples. PCR analysis of E. coli O157:H7 isolates determined that
they carried the virulence genes vt1, vt2, eaeA and hlyA typically associated
with clinical illness in humans. The results presented indicate that Irish sheep
and pigs are reservoirs for E. coli O157:H7 which may be potentially harmful
to humans
Produção de poli(3-hidroxibutirato) por linhagens de Escherichia coli DH5a e JM101 recombinantes
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Engenharia de AlimentosPoli-hidroxialcanoatos (PHAs) são uma família de polímeros biodegradáveis que muitos micro-organismos são capazes de sintetizar, sendo os mesmos considerados uma alternativa futura aos plásticos convencionais. O Poli(3-hidroxibutirato) (P(3HB)) é o PHA mais estudado. Técnicas de engenharia genética vem sendo desenvolvidas em Escherichia coli, um micro-organismo naturalmente não produtor de PHAs, para se estabelecerem processos de produção microbiana através das técnicas de DNA recombinante. Porém, antes de se submeterem determinadas linhagens a essas técnicas, é necessário que estas estejam bem caracterizadas. Desta forma, estudaram-se linhagens de E. coli, JM101 e DH5a, com os genes para a biossíntese de P(3HB) de C. necator, utilizando glicose como fonte de carbono. Para a linhagem DH5a as velocidades específicas máximas de crescimento foram de 0,79 h-1, para a cepa selvagem, e 0,21 h-1 para a recombinante. Os fatores de conversão de substrato em células foram de 0,32 e 0,20 (g.g-1), os fatores de conversão de oxigênio em células foram de 3,94 e 1,65 (g.g-1) e as velocidades específicas de consumo de oxigênio para manutenção celular foram 52,59 e 25,72 (g.g-1.h-1) para E.coli DH5a selvagem e recombinante, respectivamente. Os níveis de acúmulo de P(3HB) em E. coli DH5a alcançaram valores em torno de 56 %, com produtividade máxima de 0,23 g.L-1.h-1. Para a linhagem JM101 as velocidades específicas máximas de crescimento foram de 0,91 h-1 para a cepa selvagem e 0,72 h-1 para a recombinante. E. coli JM101 apresentou duas fases distintas de consumo de açúcares redutores. Assim, os fatores de conversão de substrato em células observados na primeira fase foram de 7,55 e 1,32 (g.g-1) e na segunda fase foram de 0,069 e 0,072 (g.g-1), os fatores de conversão de oxigênio em células foram de 2,95 e 2,85 (g.g-1) e as velocidades específicas de consumo de oxigênio para manutenção celular foram 55,23 e 58,89 (g.g-1.h-1) para E.coli JM101 selvagem e recombinante, respectivamente. Os níveis de acúmulo de P(3HB) em E. coli JM101 alcançaram valores em torno de 34 %, com produtividade máxima de 0,10 g.L-1.h-1. Com a análise conjunta dos dados experimentais é possível concluir que a inserção do plasmídeo pBHR68 em E. coli JM101 e DH5a afetou o desempenho celular, visto a diferença dos parâmetros cinéticos de crescimento e de respiração microbiana das cepas antes e depois da transformação. Os resultados observados sugerem que E. coli DH5a recombinante é mais adequado para produção de P(3HB), em meio LB adicionado de glicose, que E. coli JM101 recombinante, devido ao maior percentual de acúmulo (56 %) e maior produtividade de polímero (0,23 g.L-1.h-1).Polyhydroxyalcanoates (PHAs) are a family of biodegradable polymers synthesized for several bacteria. These polymers are considered a future alternative for conventional plastics. Poly(3-hydroxybutyrate) is the most widely studied PHA. Techniques of genetic engineering has been developed in Escherichia coli, a naturally non-producing PHAs microorganism, to establish processes of microbial production of P(3HB) through the techniques of recombinant RNA. However, before submitting E. coli strains to these techniques, it is necessary to investigate the strains and culture strategies. The present work examines two different strains of E. coli, JM101 and DH5a, a control strain and a P(3HB)-synthesizing strain, with the genes for biosynthesis of P(3HB) from C. necator, using glucose as a carbon source. The strain E. coli DH5a had a maximum specific growth rate of 0.79 h-1 for the control strain, and 0.21 h-1 for the recombinant strain, the carbon yield were 0.32 and 0.20 (g.g-1), the oxygen yield were 3.94 and 1.65 (g.g-1) and the oxygen consumption for maintenance were 52.59 e 25.72 (g.g-1.h-1), for the control strain and the recombinant strain, respectively. The P(3HB) accumulation in E. coli DH5a reached values around 56 %, with productivity of 0.23 g.L-1.h-1. For the strain E. coli JM101 the maximum speed of growth were 0.91 h-1 for the control strain and 0.72 h-1 for the recombinant. E. coli grows in two distinct phases, the carbon yield in the first phase were 7.55 and 1.32 (g.g-1) and in the second phase were 0.069 and 0.072 (g.g-1), the yield factors of oxygen in cells were 2.95 e 2.85 (g.g-1) and the oxygen consumption for maintenance were 55.23 and 58.89 (g.g-1.h-1) for the control strain and the P(3HB)-synthesizing strain, respectively. The P(3HB) accumulation in E. coli JM101 reached values around 34 %, with productivity of 0,10 g.L-1h-1.With this information it is possible to conclude that the insertion of the plasmid pBHR68 in E. coli JM101 and DH5á affected the metabolic. This fact was confirmed by the difference in growth parameters and microbial respiration of the strains before and after the transformation
Concentrations of E. coli, ESBL producing E. coli and CPE in the Dutch-German Vechte catchment
No full textThe occurrence of fecal indicator bacteria (E. coli) and antibiotic resistant E. coli, namely ESBL-producing E. coli (ESBL-EC) and carbapenemase-producing E. coli (CP-EC) were measured in the Dutch-German transboundary catchment of the Vecht River over the course of one year. Bacterial concentrations were monitored in in wastewater treatment plant (WWTP) influents and effluents and in surface waters with and without WWTP influence
Pathogenic Potential to Humans of Bovine Escherichia coli O26, Scotland
No full textEscherichia coli O26 and O157 have similar overall prevalences in cattle in Scotland, but in humans, Shiga toxin–producing E. coli O26 infections are fewer and clinically less severe than E. coli O157 infections. To investigate this discrepancy, we genotyped E. coli O26 isolates from cattle and humans in Scotland and continental Europe. The genetic background of some strains from Scotland was closely related to that of strains causing severe infections in Europe. Nonmetric multidimensional scaling found an association between hemolytic uremic syndrome (HUS) and multilocus sequence type 21 strains and confirmed the role of stx<sub>2</sub> in severe human disease. Although the prevalences of E. coli O26 and O157 on cattle farms in Scotland are equivalent, prevalence of more virulent strains is low, reducing human infection risk. However, new data on E. coli O26–associated HUS in humans highlight the need for surveillance of non-O157 enterohemorrhagic E. coli and for understanding stx<sub>2</sub> phage acquisition
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