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The aim of this work was to determine the survival of spores and vegetative cells of enterotoxic strains of B. cereus in a medium (GM-milk) simulating human stomach environment after consumption of milk or dairy products. Gastric medium (GM-milk) was prepared by mixing equal volumes of a gastric electrolyte solution (4.8 g/l NaCl, 1.56 g/l NaHCO₃, 2.2 g/l KCl, 0.22 g/l CaCl₂, 500 U/l pepsin solution [Sigma-Aldrich Chemie GmbH, nr kat. P6887]) with UHT milk (0,5% fat content). The total count of B. cereus after 6-hours’ incubation in GM-milk (pH~2 and pH~4,5) was determined in a MYP [Merck nr kat. 1.05267.]. After incubating the spores or vegetative cells in a pH~4,5 medium, the count remained unchanged in 70% and 30% strains, decreased by about 1.0 log cfu/ml in 20% and 40% strains or decreased by about 2.0 log cfu/cm³ in 10% and 30% strains, respectively. After incubating the spores in a pH~2 medium, the count remained unchanged in 10% strains, decreased by about 1.0 log cfu/cm³ and 2.0 log cfu/cm3 in 40% and 50% of the strains, respectively. In the same medium no survival of any tested strains of vegetative cells in 1 ml was ascertained after 1 hour incubation. The study demonstrated that the survival of B. cereus depended on the pH of the medium simulating the stomach environment and the physiological state of the cells (spores or vegetative forms).
The aim of the study was to develop a sensitive and specific ELISA for the detection of LT enterotoxin in E. coli strains. The test was based on the antitoxic antibodies obtained from rabbits immunized with В subunit of cholera toxin (CT). The toxin was structurally closely related with LTB of E. coli. CTB was expressed in a V. cholerae strain harboring a plasmid with a ctxB gene. The toxin was isolated and purified from a growth medium by means of precipitation. A goat antirabbit IgG labeled with HRP antibodies was used as a conjugate. The developed test turned out to be highly specific and sensitive: it was possible to detect from 1.5 to 4.0 ng of LTB. One hundred strains of E. coli isolated from piglets were tested by the LT ELISA. It was found that 67 strains (85.9%) isolated from piglets with diarrhea were LT+ whereas only 2 strains (9.1%) from healthy piglets proved to be enterotoxigenic.
Analizowano 30 szczepów E. coli. Typowanie serologiczne wykonano metodą aglutynacji szkiełkowej i przy użyciu testów lateksowych. Na podstawie analizy 35 reakcji metabolicznych, wykazano różnice w aktywności bioche#micznej szczepów wobec 12 substratów. Nie stwierdzono zróżnicowania biochemicznej aktywności szczepów E. coli O157: H7. Wykazano przydat#ność podłoża SMAC oraz podłoży z odczynnikiem MUG do identyfikacji pałeczek okrężnicy należących do tego typu serologicznego.
E. coli are the predominant microorganisms in the human gastrointestinal tract. In most cases, they exist as harmless comensals, and some of them are beneficial to their host in balancing gut flora and absorption of nutrients. However, there are pathogenic strains that cause a broad range of diseases in humans and animals, from diarrhea to bloodstream infections. Among bacterial strains causing these symptoms, seven pathotypes are now recognized: enteropathogenic E. coli (EPEC), shiga toxin-producing E. coli (STEC), enterotoxigenic E. coli (ETEC), enteroinvasive E. coli (EIEC), enteroaggregative E. coli (EAEC), diffusely adherent E. coli (DAEC), and adherent-invasive E. coli (AIEC). Several different strains cause diverse diseases by means of virulence factors that facilitate their interactions with the host, including colonization of the intestinal epithelial surfaces, crossing of the mucosal barriers, invasion of the bloodstream and internal organs or producing toxins that affect various cellular processes. Pathogenic E. coli are commonly studied in humans, animals, food and the environment, in developed and developing countries. The presented paper reviews recent information concerning the pathogenic mechanisms of E. coli, the role of animals and food in the transmission chain and a short overview of epidemiological data.
Badaniami objęto lipopolisacharydy wyekstrahowane z dziewięciu klinicznych szczepów B. fragilis wyizolowanych w Polsce. Biologiczną aktywność preparatów LPS oznaczono przy użyciu fotometrycznego testu BET (poprzednio LAL). Aktywność lipopolisacharydów klinicznych szczepów B. fragilis porównano z aktywnością LPS referencyjnych szczepów B. fragilis i LPS E. coli 055:B5. Wśród lipopolisacharydów pałeczek gatunku B. fragilis największą aktywność w reakcji z odczynnikiem LAL wykazał LPS szczepu wyizolowanego z ropnia trzustki.
Clostridium perfringens is an obligatorily anaerobic, Gram-positive, rod-shaped pathogen, which has the ability to form oval endospores. The microorganism is widespread in environments such as water, soil, waste water, the intestinal tract of humans and animals, as well as in raw and processed food. C. perfringens demonstrates the ability to produce a number of toxins, including enterotoxin (CPE) and major lethal toxins (α, β, ε and ι), which is the basis for a division into five toxinotypes (A, B, C, D, E). It was shown that CPE is encoded by the cpe gene and produced by less than 5% of C. perfringens strains, mainly belonging to type A. Production of enterotoxin is inextricably linked with the process of forming endospores. Considerable evidence implicates CPE as a virulence factor responsible for diarrhea and cramping symptoms associated with C. perfringens type A food poisoning. It is proven that this food poisoning can be caused by strains with the cpe gene located in the bacterial chromosome or on large plasmids, in contrast to other CPE-mediated diseases such as antibiotic (AAD) and sporadic diarrhea (SD), which are associated with plasmid-borne cpe-positive C. perfringens strains. Food poisoning caused by enterotoxigenic strains of C. perfringens type A is one of the most common gastrointestinal diseases in developed countries and shows a positive correlation with the growing percentage of people eating meals in catering establishments.
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