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49 Cards in this Set
- Front
- Back
H. pylori:
bacterial characteristics |
*small G- spiral-shaped rods
*microaerophilic *urease+ |
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H. pylori:
virulence factors |
*urease action leads to the production of ammonia which creates an area of alkalinity
*flagella allow movement beneath mucus coat |
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H. pylori:
disease states |
*asymptomatic carrier (50%)
*PUD *correlation with gastric cancer |
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H. pylori:
diagnosis |
*antrum biopsy and culture
*C-14 urease breath test |
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E. coli:
general characteristics |
*facultative anaerobe
*G- *rod *lac+ |
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What causes pathogenesis in E. coli spp?
|
*migration to a new area of the body
*plasmids, phages, or pathogenecity islands encoding factors |
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Enterotoxigenic E. Coli:
Symptoms |
A cholera-like watery diarrhea
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ETEC:
Describe the 2 toxins |
*LT: heat labile; similar to cholera toxin but milder
*ST: heat stabile; causes increase in cGMP |
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ETEC:
What common disease does it cause? |
Traveller's diarrhea
|
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Enteroinvasive E. Coli:
Describe its mode of infection and symptoms. |
*invades intestinal epithelium similar to Shigella
*abd. cramping, blood and pus in stool |
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Enteropathogenic E. Coli:
What common disease state does it cause? |
Infant diarrhea
|
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EPEC:
Describe its mode of attachment |
*secretes Tir protein that inserts into epithelial cell membrane
*expresses intimin protein which binds Tir |
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EPEC:
Describe pathogenesis |
*Usually doesn't penetrate the epithelium
*causes denuding of brush border *inflammatory response may cause ulceration |
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What strain of EHEC causes disease?
Where is it typically found? |
*the O157:H7 serotype
*it is found in cattle, beef products, and fruit and veggies that have been fertilized with tainted manure |
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What characteristic differentiates EHEC from other strains of E. coli?
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Its inability to ferment sorbitol.
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Describe the symptoms caused by EHEC.
What other disease has it been associated with? |
*hemorrhagic colitis, bloody diarrhea, abd. cramping
*HUS - possibly because of specific LPS |
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What two factors contribute to the virulence of EHEC?
|
*synthesis of Shiga toxin
*low infectious dose |
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Decribe the vibrio cholerae bacteria.
|
*G- comma-shaped rod
*waterborne organism |
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What is the infectious dose of V. cholerae?
What does this indicate? |
*high (10^8 - 10^10)
*very susceptible to low pH |
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What are the symptoms of infection with V. cholerae?
What is the primary tx? Is there a vaccine? |
*sudden onset of voluminous "rice-water" diarrhea w/o abd pain
*rapid rehydration, preferably PO *a killed-cell vaccine is available |
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What two things mediate pathogenesis with V. cholerae?
|
*attachment pili
*toxin synthesis |
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What is the struucture of the cholera toxin?
|
*one A subunit, 5 B subunits
*each A subunit consists of A-1 and A-2 |
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What is the mode of action for the cholera toxin?
|
*B subunits bind GM1
*A-1 enters cell and ADP-ribosylates G-protein regulator of adenylate cyclase *increased cAMP *Na and Cl extruded into lumen *increased osmotic pressure drives cellular efflux of water |
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How is expression of the cholera toxin regulated?
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*Tox-R is regulatory
*triggered by drop in pH and rise in temp. |
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Listeria monocytogenes:
Bacterial characteristics? Where is it often found? |
*G+
*coccobacillus *catalase + *able to grow in high salt and low temp *found in contaminated dairy pdts and processed meats |
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Listeria monocytogenes:
pathogenesis |
*invades epithelium
*uses listeriolysin O to escape vacuole and replicate in cytoplasm *able to spread laterally like Shigella *tropism towards placental tissue |
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Listeria monocytogenes:
disease characteristics |
*self-ltd except in pregnant women, fetuses, neonates, and i-c pts
*SA, premature labor *early and late onset meningitis in neonates similar to GBS |
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Listeria monocytogenes:
prevention/tx. |
*no vaccine
*intrapartum antibiotics not shown to reduce vertical transmission |
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Yersinia enterocolitica:
bacterial characteristics |
*G- rod
*found in humans, domesticated animals *able to survive in contaminated water |
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Yersinia enterocolitica:
Symptoms? Dose? |
*voluminous watery diarrhea
*mesenteric lymphadenitis mistaken for appy *infectious dose ~10^6 *granuloma formation (rare) *prevalent in peds |
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Camplylobacter jejuni:
bacterial characteristics |
*G- curved rod
*microaerophilic |
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Camplylobacter jejuni:
How is it spread? What is the reservoir? What is the infectious dose? |
*assoc. w/livestock and feed animals
*often transmitted by contaminated poultry *no P-to-P spread *infectious dose ~500 |
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Camplylobacter jejuni:
disease |
*bloody, pus-filled diarrhea
*bacteremia is rare, susceptible to macrophages *assoc. w/Guillan-Barre syndrome |
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Camplylobacter jejuni:
treatment |
*macrolides
*resistance to fluoroquinolones |
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Shigella:
bacterial characteristics |
*G- rod
*lac- *H2S- *urea- *indole- |
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Shigella:
Spread |
*no non-primate reservoir
*fecal-oral transmission *low infectious dose (10-100) |
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Shigella:
symptoms |
*dysentary, small-volume bloody diarrhea
*due to immune response |
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What kind of toxin is the Shiga toxin? What does it do?
|
*A+B toxin
*inhibits protein synthesis *associated w/HUS |
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Shigella:
treatment |
*rehydration
antibiotic resistance emerging |
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Salmonella enteritidis:
bacterial characteristics |
*G- rod
*facultative anaerobe *lac- *produces lg amt of H2S on TSI |
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Salmonella enteritidis:
What is its reservoir? What's the infectious does? |
*animal and human reservoir
*infectious dose ~10^6 |
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Salmonella enteritidis:
What's its pathogenesis? Symptoms? Communicability? |
*invade GI mucosal epithelia
*rarely disseminates *bloody, pus-filled diarrhea *communicable throughout infxn |
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Describe the bacterial appearance of Salmonella Typhii. How does it stain? How does it culture?
|
*G- rod
*lac- *produces only a small ring of H2S on TSI slant |
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T/F:
S. typhii has no animal reservoir while S. enteritidis does. |
True.
|
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How is S. typhii transmitted? What is its infectious dose?
|
*fecal-oral route, with or without a food intermediate
*dose = 10^5 |
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What are the steps involved in the pathogenesis of S. typhii?
|
*binds M cells of GI epithelia
*endocytosed and transferred to Peyer's patch *replicates intracellularly *passes through basal lamina *taken up by macrophage and spread thru RES |
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A chronic carrier state is possible with S. typhii. What organ is notorious for sequestering the bacteria?
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Gall bladder
|
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Is there a vaccine for S. typhii?
|
There are 2:
1.live, attenuated PO (3 doses) 2.capsular IM (1 dose) |
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What is the disease course of S. typhii and what is its prognosis? What kind of drug resistance has been seen?
|
*fever, malaise, and flu sx
*usually self-limited in 4-6 wks *fluoroquinolone resistance is emerging *resistance to chloramphenicol, SMZ-TMP, and doxycycline documented |