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43 Cards in this Set
- Front
- Back
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What kind of bacteria is C. difficile?
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-gram-positive rod
-obligate anaerobe -spore former |
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Name the two toxins produced by C. difficile and their effects.
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-Toxin A - increases membrane permeability and inflammation of intestinal mucosa
-Toxin B - cytotoxin that results in necrosis/epithelial cell destruction |
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Proliferation of C. difficile and its two toxins cause ___________________.
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Pseudomembranous colitis
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Symptoms of C. difficile
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-range: mild/watery diarrhea to bloody diarrhea to inflammation and ulceration
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The only lactase-negative E. coli
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EIEC (enteroinvasive E. coli - intracellular/invasive)
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EIEC is biochemically identical to ___________.
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Shigella
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Name the 4 types of shigella. Which is the most aggressive and contains the genes for the shiga toxin?
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-S. dysenteriae - most agressive, shiga toxin genes
-S. sonnei - most common in US -S. flexneri - most common in homosexuals -S. boydii - least common |
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How is shigellosis transmitted?
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Fecal-oral
High secondary attack rates in household members Low infectious dose |
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T/F Shigellosis is held in an animal host, cattle.
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False - human only, no animal reservoir
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Symptoms of shigellosis
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-Fever, malaise, anorexia, myalgia
-followed by small volume stools with blood and pus (colitis) |
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Dysentery is a clinical triad which consists of what symptoms?
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-cramps
-tenesmus -frequent, small-volume, bloody-mucoid stools |
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T/F Shigellosis produces short-lived immunity to homologous serotypes.
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True
Also - incidence peaks in first 5 years and declines after, suggesting immunity after repeated childhood exposures |
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How does shigella infect the colon?
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-Injection via T3SS into colonic epithelial cells and M cell
-lysis of vacuole it is in once in the cytoplasm -lateral spread to other cells -induces apoptosis -also infects and kills macrophages |
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4 main virulence factors of shigella
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-Shiga toxin
-T3SS -LPS -acid resistance |
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How is shigellosis treated? Prevented?
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-treatment: self-limited, antibiotics reduce severity, rehydration
-prevention - sanitation |
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Group of gram-negative, lactase-negative, flagellated rods that cause both gastroenteritis and systemic infection
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Salmonella enterica
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Strains of salmonella enterica that cause a multi-organ infection that begins in the intestine through food and water contaminated with human feces
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S. Typhi and S. Paratyphi
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Symptoms of typhoid fever
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-fever, toxic shock, headache, myalgia, hepatomegaly, splenomegaly
-no diarrhea |
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How do Typhoid causing strains of salmonella invade cells?
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-T3SS invasion into M cells
-engulfed by macrophages - seed the blood |
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The carrier state of typhoid fever includes colonization of what organ which re-seeds the intestine?
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Gallbladder
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Major virulence factors of typhoid types of salmonella
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-T3SS
-LPS -Flagella -Vi capsular antigen - prevents phagocytosis |
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S. typhimurium and S. enteritidis cause what symptoms?
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-24-48 hours post-ingestion:
-N/V -abdominal pain -diarrhea x 3-7 days -fever in about 1/2 of patients -no blood |
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Sources of salmonella include...
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-animals - poultry, bovine, reptiles
-meat and eggs -water |
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An invasive, gram-negative, vibrio-shaped microaerophilic bacteria that is a leading cause of diarrhea in the US
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Campylobacter jejuni
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The most common source of human infection with campylobacter jejuni is what?
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uncooked poultry
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Clinical symptoms of campylobacter jejuni
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-Diarrhea with blood and pus to severe dysentery
-lower abdominal pain and fever, usually starts1-7 days post ingestion -self-limited within 3-5 days (treat with antibiotics if necessary) |
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Campylobacter jejuni infection can have what sequelae?
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-Guillan-Barre syndrome
-antibodies formed to 019 LPS cross-react with myelin --> paralysis |
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A gram-negative curved rod with a polar flagellum associated with gastric ulcers and cancer
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H. pylori
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How does H. pylori survive in the stomach?
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Urease production -- generation of ammonia
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Strains of H. pylori with what genes predispose individuals to gastric adenocarcinoma?
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CagA (cytotoxin-associated gene)
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How is H. pylori transmitted?
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-Human to human
-Fecal-oral |
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How does H. pylori evade defenses?
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-LPS-Lewis antigen mimicry (LPS contains lewis blood group antigen - cloaks the bacteria)
-apoptosis of T cells |
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Besides CagA, how do H. pylori apoptose cells?
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Vacuolating toxin A (VacA) - generates intracellular vacuoles
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CagA is injected into cells by what?
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T4SS
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Symptoms of H. pylori infection include...
Diagnosis of H. pylori infection can be made how? |
-gastritis - burning pain, N/V
-ulcers -urease breath test; biopsy, CagA PCR |
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Bacterium responsible for the black plague
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Yersinia pestis
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Two other yersinia bacteria that cause gastroenteritis
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-Y. pseudotuberculosis
-Y. enterocolitica major symptoms: gastroenteritis, polyarthritis associated with diarrhea |
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Infections with Y. pseudotuberculosis and enterocolitica are common in what countries?
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Scandinavia, some European countries
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What cells are targeted by yersinia?
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-M cells in the Peyer's patches
-form microabcesses in the peyer's patches -prevent normal phagocytosis/avoid engulfment -migrate to the lymph nodes and travel to the liver and spleen |
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Which yersinia colonizes Peyer's patches (vs. widespread dissemination)?
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-Dissemination - Y. pseudotuberculosis
-Peyer's colonization - Y. enterocolitica |
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T/F Yersinia have the ability to sense their environment for changes in temperature and Ca2+ concentration and change virulence factors accordingly.
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True
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What is yersiniabactin?
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A siderophore - protein that traps iron - a potential virulence factor of yersinia acquired through a pathogenicity island
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Which yersinia produces a heat-stable toxin (Yst)?
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Y. enterocolitica (not produced in pseudotuberculosis)
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