Micro - enterics
Terms
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H. pylori:
bacterial characteristics -
*small G- spiral-shaped rods
*microaerophilic
*urease+ -
H. pylori:
virulence factors -
*urease action leads to the production of ammonia which creates an area of alkalinity
*flagella allow movement beneath mucus coat -
H. pylori:
disease states -
*asymptomatic carrier (50%)
*PUD
*correlation with gastric cancer -
H. pylori:
diagnosis -
*antrum biopsy and culture
*C-14 urease breath test -
E. coli:
general characteristics -
*facultative anaerobe
*G-
*rod
*lac+ - What causes pathogenesis in E. coli spp?
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*migration to a new area of the body
*plasmids, phages, or pathogenecity islands encoding factors -
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 -
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 -
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 -
EPEC:
Describe pathogenesis -
*Usually doesn't penetrate the epithelium
*causes denuding of brush border
*inflammatory response may cause ulceration -
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 - What characteristic differentiates EHEC from other strains of E. coli?
- 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 - What two factors contribute to the virulence of EHEC?
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*synthesis of Shiga toxin
*low infectious dose - Decribe the vibrio cholerae bacteria.
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*G- comma-shaped rod
*waterborne organism -
What is the infectious dose of V. cholerae?
What does this indicate? -
*high (10^8 - 10^10)
*very susceptible to low pH -
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 - What two things mediate pathogenesis with V. cholerae?
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*attachment pili
*toxin synthesis - What is the struucture of the cholera toxin?
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*one A subunit, 5 B subunits
*each A subunit consists of A-1 and A-2 - What is the mode of action for the cholera toxin?
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*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 - 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. -
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 -
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 -
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 -
Listeria monocytogenes:
prevention/tx. -
*no vaccine
*intrapartum antibiotics not shown to reduce vertical transmission -
Yersinia enterocolitica:
bacterial characteristics -
*G- rod
*found in humans, domesticated animals
*able to survive in contaminated water -
Yersinia enterocolitica:
Symptoms? Dose? -
*voluminous watery diarrhea
*mesenteric lymphadenitis mistaken for appy
*infectious dose ~10^6
*granuloma formation (rare)
*prevalent in peds -
Camplylobacter jejuni:
bacterial characteristics -
*G- curved rod
*microaerophilic -
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 -
Camplylobacter jejuni:
disease -
*bloody, pus-filled diarrhea
*bacteremia is rare, susceptible to macrophages
*assoc. w/Guillan-Barre syndrome -
Camplylobacter jejuni:
treatment -
*macrolides
*resistance to fluoroquinolones -
Shigella:
bacterial characteristics -
*G- rod
*lac-
*H2S-
*urea-
*indole- -
Shigella:
Spread -
*no non-primate reservoir
*fecal-oral transmission
*low infectious dose (10-100) -
Shigella:
symptoms -
*dysentary, small-volume bloody diarrhea
*due to immune response - What kind of toxin is the Shiga toxin? What does it do?
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*A+B toxin
*inhibits protein synthesis
*associated w/HUS -
Shigella:
treatment -
*rehydration
antibiotic resistance emerging -
Salmonella enteritidis:
bacterial characteristics -
*G- rod
*facultative anaerobe
*lac-
*produces lg amt of H2S on TSI -
Salmonella enteritidis:
What is its reservoir? What's the infectious does? -
*animal and human reservoir
*infectious dose ~10^6 -
Salmonella enteritidis:
What's its pathogenesis? Symptoms? Communicability? -
*invade GI mucosal epithelia
*rarely disseminates
*bloody, pus-filled diarrhea
*communicable throughout infxn - Describe the bacterial appearance of Salmonella Typhii. How does it stain? How does it culture?
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*G- rod
*lac-
*produces only a small ring of H2S on TSI slant -
T/F:
S. typhii has no animal reservoir while S. enteritidis does. - True.
- How is S. typhii transmitted? What is its infectious dose?
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*fecal-oral route, with or without a food intermediate
*dose = 10^5 - What are the steps involved in the pathogenesis of S. typhii?
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*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 - A chronic carrier state is possible with S. typhii. What organ is notorious for sequestering the bacteria?
- Gall bladder
- Is there a vaccine for S. typhii?
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There are 2:
1.live, attenuated PO (3 doses)
2.capsular IM (1 dose) - What is the disease course of S. typhii and what is its prognosis? What kind of drug resistance has been seen?
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*fever, malaise, and flu sx
*usually self-limited in 4-6 wks
*fluoroquinolone resistance is emerging
*resistance to chloramphenicol, SMZ-TMP, and doxycycline documented