LYCOS RETRIEVER 
Escherichia Coli
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Escherichia coli O157:H7 is not pathogenic in cattle and is shed in the feces of healthy cattle. Escherichia coli O157:H7 does not invade the gastrointestinal tract, and adherence to the mucosa does not appear to be a prerequisite for fecal shedding.37,43 Fecal shedding is transient in cattle, often lasting 1 to 3 months or less, but E coli O157:H7 can persist on individual farms for up to 2 years.44 Escherichia coli O157:H7 can be isolated from other sources on the farm, such as water, horses, sheep, milk filters, and stable flies. Fecal shedding is more prevalent in the United States and Canada during the summer months and is more prevalent in Britain in the spring and fall. Also, fecal shedding varies among different classes of animals. Weaned heifers between 3 months of age and breeding age are more likely to shed E coli O157:H7 in feces than adult cattle or younger calves.16,43 Increased fecal shedding is associated with weaning and with the first month of lactation in dairy herds,44 and culled dairy cattle have a higher prevalence than has been previously reported.45 Contaminated water troughs, particularly those that are allowed to develop sediments, provide an environment for survival, proliferation, and horizontal spread of E coli O157:H7. Feces and E coli O157:H7 contaminated water can contaminate pastures and crops where it can survive and serve as a source for contamination of feed.46 In addition, E coli O157:H7 proliferates to extremely high populations in moist silage.
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Escherichia coli serotypes are specific O-group/H-antigen combinations. The H antigens are the flagellar antigens, of which there are at least 56 types. Escherichia coli isolates may be nonmotile and nonflagellated and hence H negative (H). H typing is important for E coli associated with diarrheal disease for two reasons. First, a strain causing an outbreak or epidemic can be differentiated from the normal stool flora by its unique O:H antigenic makeup. Second, most ETEC belong to specific serotypes (Table 25-1); this relationship facilitates their identification even in isolated cases.
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Escherichia coli is a bacterium that is a common — but certainly not the most abundant — inhabitant of the human intestine. It ... lives in the intestine of many other animals, wild as well as domestic.
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Escherichia coli diarrheal disease is best controlled by preventing transmission and by stressing the importance of breast-feeding of infants, especially where ETEC is endemic. The best treatment is oral fluid and electrolyte replacement (intravenous in severe cases). Antibiotics are not recommended because this practice leads to an increased burden of antibiotic-resistant pathogenic E coli and of more life-threatening enteropathogens.
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The 4,639,221-base pair sequence of Escherichia coli K-12 is presented. Of 4288protein-coding genes annotated, 38percent have no attributed function. Comparison with five other sequenced microbes reveals ubiquitous as well as narrowly distributed gene families; many families of similar genes within E.coli are ... evident. The largest family of paralogous proteins contains 80 ABC transporters. The genome as a whole is strikingly organized with respect to the local direction of replication; guanines, oligonucleotides possibly related to replication and recombination, and most genes are so oriented. The genome also contains insertion sequence (IS) elements, phage remnants, and many other patches of unusual composition indicating genome plasticity through horizontal transfer.
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Today Escherichia coli is the best characterized micro-organism known to science. Many thousands of different and well-characterized mutants have been described. The genome of Escherichia coli consists of approximately 4.6 kb (kilobases) of circular double-stranded DNA and approximately 70 % of it has been sequenced. More than 1500 genes have been identified, and approximately 80 % of its biochemical reactions are known.
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Escherichia Coli