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Lec_6_Fungi - Escherichia coli cells ~0.5 x 1.0 micrometers...

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Escherichia coli cells: ~0.5 x 1.0 micrometers Typical rod-shaped bacteria: fecal indicator and pathogenic strains
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E. coli Genetics and Serology Genetics: Single, circular DNA molecule, ~4 x 10 6 base pairs Molecular weight of 4 x 10 9 Total length of about 1.4mm. Serology: E. coli can be subdivided by somatic (cell-wall) or O antigens and flagellar or H antigens. >160 recognized O types and 55 recognized H types over 8000 possible OH serotypes. also capsular (K) and fimbrial antigens.
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Virulence Properties of E. coli Enterotoxins: at least two types: Heat Stable (ST) and Heat Labile (LT) Verotoxins or Shiga-like toxins (interchangeable terms): Verotoxin term is based on the reactions of toxins on Vero cells VT1 (SLT I): similar to Siga-toxin (produced by some strains of Shigella dysenteriae) VT2 (SLT II) which is only about 50% realted Shiga toxin. Other Toxins: Cytolethal distending toxin (CLDT), VirCytotoxin, Cytotoxic necrotising factors (CNF), a possible Enteropathogenic E. coli EPEC) enterotoxin and a possible E. coli Sudden Infant Death Syndrome (SIDS)-toxin. Haemolysins: extracellular haemolysin known as alpha-haemolysin (many strains) cell-associated haemolysin, beta-haemolysin, (some strains) enterohaemolysin: extracellular; Enterohaemorrhagic E. coli (EHEC)
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Pathogenic E. coli Enteric Infections : Enteroadherent E. coli (EAEC) Enteroaggregative E. coli (EAggEC) Enterohaemorrhagic E. coli (EHEC) Enteroinvasive E.coli (EIEC) Enteropathogenic E. coli (EPEC) Enterotoxigenic E. coli (ETEC) Extraintestinal Infections: Uropathogenic E. coli (UPEC): urinary tract infections Neonatal Menigitis E. coli (NMEC).
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Virulence Properties of E. coli Fimbriae: CFAI/CFAII, Type 1 fimbriae, P fimbriae, S fimbriae most important: K88, K99 and CFA fimbriae associated with enterotoxigenic E. coli (ETEC). They have differing species specificities. The p-fimbriae: associated with urinary tract pathogens. E. coli also produce common fimbriae not associated with virulence. Adhesins: Intimin: non-fimbrial adhesin; causes the intimate association with target cells in enteropathogenic and enterohaemorrhagic E. coli . Associated with the 'attachment and effacement' phenomenon Causes destruction of the intestinal surface cells. Other outer membrane proteins can act as adhesins.
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Shigella spp.
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Shigella and Shigellosis Fecal-oral transmission person-to-person, fomites, food, water, ect. Waterborne and water-washed Reservoirs: humans and primates Infectious dose: low; as few as 10 cells to infect Incubation period: 1 to 7 days; typically, 1-3 days Duration of illness: untreated: severe symptoms for about two weeks Antibiotic treatment shortens illness and prevent spread to others
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Shigellosis - Epidemiology Four species of Shigella : flexneri, sonnei, dysenteriae, boydii Major public health problem in many developing countries causes about 5 to I0% of childhood diarrhoea up to 25% of all diarrhea-related deaths can be associated with Shigella
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