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27 Cards in this Set
- Front
- Back
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GI host defenses
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stomach acid
intestinal motility resident intestinal flora innate and adaptive immunity |
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inflammatory diarrhea
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pathogens elicit an immune response
blood and pus in the stool low volume diarrhea |
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Bacteria that cause inflammatory diarrhea by INVADING host cells
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Salmonella
Shigella Campylobacter |
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Bacteria that cause inflammatory diarrhea by colonizing the large intestine and secreting CYTOTOXINS that provoke inflammation
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Clostridium difficile
Entero-hemorrhagic E. coli |
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secretory diarrhea
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high volume diarrhea
NO blood nor pus little cramping, little nausea |
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Bacteria that cause secretory diarrhea via enterotoxins
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Vibrio cholerae
Entero-toxigenic E. coli |
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Enteroinvasive (enteric) pathogens
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Invade host cells
facultative intracellular pathogens Salmonella enterica Shigella Yersinia enterocolitica Campylobacter jejuni Listeria monocytogenes Enter-invasive E. coli |
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Entertoxigenic (enteric) pathogens
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Do NOT invade
Colonize and secrete an enterotoxin Vibrio cholerae (cholera toxin) Clostridium difficile (A toxin and B toxin) ETEC (LT toxin) |
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Enteropathogenic (enteric) pathogens
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Do NOT invade
Bacteria colonize and destroy epithelium Enteropathogenic E. coli Enterhemorrhagic E. coli Helicobacter pylori |
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diarrhea caused by enteroinvasive pathogens
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severe painful cramps
stools contain blood and pus |
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Zipper mechanism of invading non-phagocytic cells
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receptor-mediated endocytosis
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Trigger mechanism of invading non-phagocytic cells
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Bacteria injects effector proteins into the host cell that induces cytoskeletal rearrangement that lead to the endocytosis of the bacterium
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Type 3 secretion system
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used by: Salmonella, Shigella, Yersinia, EPEC and EHEC.
Bacteria injectes proteins directly into host cells |
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Typhoid fever
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Salmonella enterica serovar Typhi
Invasive - invades gut epithelial cells and M cells using type 3 secretion system. "Invades" phagocytes (able to survive inside them by preventing phagosome-lysosome fusion) Can downregulate the expression of MHC II on DCs Encapsulated - able to evade recognition by immune cells Disseminates via the RES system to the liver and spleen Colonizes the biliary duct and is passed in feces (can establish a chronic carrier state) Treated with long-term antibiotics 2 vaccines available |
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Non-typhoid Salmonella disease
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Zoonotic
Serotypes(vars): Enteritidis, Typhimurium, Cholerasuis Large infectious dose (100,000,000) Symptoms: intestinal inflammation, cramping, diarrhea, fever Septicemia is rare (does not disseminate) Invades M cells Highly resistant to killing by macrophages - prevents phagosome-lysosome fusion No capsule |
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Shigellosis
(Shigella sonnei, flexneri and dysenteriae) |
Bacilliary dysentery
Low infectious dose (10) fecal-oral transmission incubation period: 1-7 days Shigella invades M cells and spreads to neighboring cells using actin-based motility Symptoms range from mild to dysentery (abd pain, cramping, fever, water, bloody, low volume stools with pus, nausea and vomiting Rare - HUS (hemolytic uremic syndrome) Treat with rehydration and antibiotics Secretes Shiga toxin - inhibits host cell protein synthesis |
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Campylobacter jejuni
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gram-negative, curved rod, microaerophlic, motile, selective growth on charcoal
Most common bacterial cause of diarrhea in the US Low infectious dose (500) Symptoms: inflammatory diarrhea (sometime bloody), with cramps and fever Lasts ~1 weeks Secretes a genotoxin - a cytolethal distending toxin that arrests the host cell cycle and causes cell death |
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Listeria monocytogenes
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gram-postive bacillus
host range: humans, mammals, birds, fish, crustaceans Uses actin-based motility to spread from cell to cell. Grows well at 4 degrees Celsius (fridge temp) Associated with soft cheeses and processed meats Symptoms: fever, myalgia, vomiting (diarrhea not common) Pregnant women, fetuses and neonates: Pregnant women experiences mild flu-like symptoms. Can experience miscarriage, stillbirth and pre-term labor Symptoms in neonates are similar to GBS: meningiits and encephalitis |
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Vibrio cholerae
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gram-negative, comma shaped rod
polar flagellum that gives it darting mobility found in aquatic environments high infectious dose (100,000,000) Low infectious does when in the hyperinfectious state (when the bacteria exit the infected person they are "primed" to infect incubation period: 1-3 days "rice water stool" - 10-15L/day hypovolemia, hypokalemia secretes cholera toxin |
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Cholera toxin
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Secreted by Vibrio cholerae
A-B toxin B subunits binds to GM1 ganglioside and leads to endocytosis of the toxin A subunit is activated inside the cell - cleaved into A1 and A2. A1 locks adenylate cyclase in the active stage - increasing intracellular cAMP. Increase cAMP increases ion secretion into the lumen. Water follows, causing diarrhea |
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Clostridium difficile
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gram-positive rod; obligate anaerobe
SPORES asymptomatically colonizes a small proportion of people can lead to pseudomembranous colitis and toxic megacolon Toxins A and B disrupt host cell actin which rounds out the cell, killing them. Infected cells secrete loads of cytokines and chemokine that recruit neutrophils. This increases the permeability of the colonic epithelium (diarrhea) |
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Enterotoxigenic E. coli
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difficult to distiguish from cholera (rice water stool)
lacks darting motility, however ST and/or LT toxins - LT is identical to the cholera toxin |
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Helicobacter pylori
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Flagellar motility is essential for colonization of the stomach - pushes its way through the mucus barrier
Produces urease that converts urea to NH3 and CO2, raising the pH Increased pH allows bacteria to replicate Produce mucinases that break down the mucus barrier - stomach acid and contents (like pepsin) damage exposed epithelial cells and induce inflammation Treat with PPIs, antibiotics adn bismuth subsalicylate |
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Diarrheagenic E. coli
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Gram-negative rod
ferments lactose Critical virulence factors are encodes on plasmids, lysogenic phage and/or pathogenicity islands |
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EIEC
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Resembles Shigellosis (dysentery), but does NOT produce a toxin
invades colonic cells and causes inflammatory diarrhea fecal oral transmission |
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EPEC
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"traveler's diarrhea"
Attaching and effacing lesions that damage the intestinal epithelium (pedestals) Uses Type 3 secretion system |
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EHEC
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Highly virulent
Reservoir: GI tract Symptoms - hemorrhagic colits with bloody diarrhea ex strain, O157:H7 Produces shiga or shiga-like toxin Uses Type 3 secretion system |
