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Lecture 06 - Enteric pathogens and toxins

Lecture 06 - Enteric pathogens and toxins - Lecture 06...

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Lecture 06 - Enteric pathogens and toxins MI-19a. List the bacteria associated with toxin-induced food-borne illness and differentiate between toxin production in vivo and ingestion of preformed toxin ???? MI-19f. Contrast the principles of treatment of these infections [[overall]] MI-19c. Explain how E. coli can be both normal enteric flora, yet also cause gastrointestinal disease Differences between E. coli 0157:H7 (EHEC) and E. Coli K12 K12 = normal flora 0157:H7 = harmful 0157:H7 has about 1400 genes not present in K12 o Enterohemorrhagic e colii o Has a lot of genes ! (4000 gene total in the E. coli) K12 has about 500 genes not present in 0157:H7 o The genes can be very different In shared genes, there are about 7.5x10 4 base pair differences 0157:H7 has a plasmid encoding virulence genes 0157:H7 has a lysogenic phage encoding a Shiga-like toxin Virulence loci of 0517:H7 A pathogenicity island encoding a mechanism for tight binding to the intestinal epithelium not present in non-pathogenic E coli A plasmid encoding a protease that degrades coagulation factor V, promoting hemorrhagic colitis A lysogenic phage encoding Shiga-like toxin that causes endothelial damage, promoting kidney failure The phage is integrated into the chromosome à causing the endothelial damage phage carry the gene for the shiga-like toxin this toxin is part of the hemolytic uric syndrome Patient has hemolytic (RBC gets trapped with the fibrin) Trapping of the toxin à renal failure MI-19d. Describe the epidemiology and pathology of enterotoxigenic E. coli Ribosome Inactivating Protein ( RIP ) Toxins Inactivate 28S ribosomal RNA Of the host cells Inhibit protein synthesis In host target cells Cleaves off the adenosine à inactiavte ribosome à shuts down protein synthesis RIP toxins of major medical significance: Ricin Shiga toxin family (shigella and e. coli) Clinical syndromes of RIPs Ricin Produced by the castor bean Castor bean grows as a weed (easy to purify this toxin) Usual route of intoxication is oral Produces liver damage Shiga-like toxins Absorbed from the GI tract during infection with Shigella and E. coli EHEC strains Produced by Shigella and E coli strains that are hemorragic Contributes to endothelial damage in the kidney
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