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Last Lecture on Microbes

4 Pages

Course Code
MICB 202

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Salmonella intracellular survival strategies • Enters cell by reorganizing actin after injecting virulence factor o Can lyse vacuole and survive in cytoplasm o Can prevent fusion of phagosome and lysosome, survives in the phagosome o If it does fuse with a lysosome, bacteria is acidified and oxidized and hydrolyzed and subject to antimicrobial peptides • Salmonella ingested, taken up by cells similar to phagocytosis o Ligand to surface receptor binding o Injects Src into cell, causing actin rearrangement and phagocytosis o Salmonella can penetrate mucuosal surface through M cells, then move into a variety of different lymphatic cells of peyer’s patches o Induces a severe inflammatory response (neutrophils enter and prostaglandins released, cAMP activation)  Efflux of electrolytes and water, causing diarrhea, vomiting, headaches, chills  But can also sometimes be asymptomatic o Salmonella protein SopB reprograms epithelial cells to become M cells (preferred targets) • Type III secretion systems: o Needle like structures spanning bacterial membranes that deliver virulence proteins into host cells o Many gram negatives have them (Eg. E. coli) o 2 types in salmonella  SPI-1 (injects Sop E2, SipA, SipC) • Gastroenteritis • Pro-inflammatory cytokine release • Macrophage apoptosis • Invasion of epithelial cells • SP1-1 injects bacterial proteins into host cells that cause actin rearrangement and ruffling which allows phagocytosis  SP2 • Systemic disease • Macrophage cytotoxicity—slow process • Induced inside host cells • Allow for survival and replication in mice macrophages • Used for intracellular survival since SPI-2 avoid lysosomal fusion within vacuole • Replicates inside this vacuole and then released from M cells to transfer to intestinal peuyer’s patches where it causes inflammation, diarrhea • Diagnosis and treatment o
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