传染病学英文版课件：ENVR 133 Bacterial Pathogens-Overview.ppt

ENVR 133 Bacterial Pathogens - Overview Some Important Enteric Bacterial Pathogens and Their SourcesBacterium/Group Animal Feces Non-fecal sourcesSalmonella spp. yes no (except S. typhi) no noCampylobacter spp. yes yesEscherichia coli yes noHelicobacter pylori unknown unknownAeromonas hydrophila yes yesYersinia enterocolitica yes yesListeria monocytogenesVibrio cholerae yes yes some other Vibrio sp. yes yes Shigella spp. no no Typical Procaryotic Cell Gram Negative Outer Cell Membrane and Lipopolysaccharide Structure Structure of a Gram-Negative Cell Wall PorinsPorins are structures in the outer membranes of Gram-negative bacteria They allow diffusion of low molecular weight compounds into the periplasmic space.Function as channels for small hydrophilic molecules. Porins are beta-barrel proteins in the outer membranes.Porins occur as trimers in the membrane.In E. coli, porins with different specificities exist, e.g.. maltoporin and phosphoporin. Shigellosis - IllnessPersistent diarrhea with frequent and painful passage of stools consisting mostly of blood, mucus and pusaccompanied by fever and stomach cramps. Blood and mucus in stools are likely signs of shigellosisShigella infect, invade cells lining the large intestine (colon)Cause breaks (ulcers) in mucous membrane lining of intestine Inflammation and tissue damageCauses painful straining to pass stools; can lead to rectal prolapseUlcers commonly in the rectumresults in increased production of mucusloss of blood and serum proteins into intestinal cavityCauses the symptoms of dysentery, which include blood and mucus in the stool (bloody diarrhea); fever is also common Shigella and ShigellosisFecal-oral transmissionperson-to-person, fomites, food, water, ect.Waterborne and water-washedReservoirs: humans and primatesInfectious dose: low; as few as 10 cells to infectIncubation period: 1 to 7 days; typically, 1-3 daysDuration of illness: untreated: severe symptoms for abo