Lecture+5+Shigella+and+Salmonella+FST104_color_

Lecture+5+Shigella+and+Salmonella+FST104_color_ - Shigella...

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FST 104 January 20, 2012 Shigella & Salmonella Shigella vs E. coli Closest known relative of E. coli Differs from E. coli 1. Shigella are strictly human parasites 2.Only humans (and primates) are carriers 3.All Shigella species are pathogenic EIEC is nearly identical to Shigella
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Shigellosis - Most common cause of bacterial dysentery worldwide SHIGELLA Named for Kiyoshi Shiga , who first described the bacterial origin of dysentery caused by S. dysenteriae in early 1900s 4 species (all pathogenic) S. dysenteriae (rare in the USA) S. flexneri S. boydii S. sonnei SHIGELLA The disease Infective dose: very low (10 – 200 cells) Incubation period: 3+ days Illness duration: usually 2-7 days, longer in the more susceptible individuals Diarrhea (often bloody), fever , cramps
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Shigella invades intestinal cells Produces a Type III secretion system to injects proteins into host cells Invasive Engulfed by colonic enterocytes and grows intracellularly Invades in a manner similar to EIEC & Salmonella SHIGELLA Shigella sonnei : ~85% infections caused by Shigella in the USA Developing countries: 20x greater amounts of infection S. dysenteriae is the most common Transmission Disease is always the result of poor sanitation especially water supplies Spread through fecal-oral route No food products harbor Shigella naturally
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Causes gastroenteritis lasting longer (~1 week) and sometimes a mild dysentery S. sonnei Problem in institutional settings: Day-care centers Classical bacterial dysentery S. dysenteriae
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Lecture+5+Shigella+and+Salmonella+FST104_color_ - Shigella...

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