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Year 1 Microbiology > GI bacteria III > Flashcards

GI bacteria III Flashcards

1
Q

What are the characteristics of vibrio spp.?

A
  1. Gram negative 2. Facultative anaerobe 3. Comma shaped 4. Broad temperature and pH range 5. Require sodium for growth
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2
Q

Which cholera serotype is toxin-producing?

A

O1

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3
Q

What are the properties of the current cholera pandemic serotype (El Tor)?

A
  1. Less severe disease (1 symptomatic to 30-100 asymptomatic) 2. Duration of carriage longer than classic strain 3. Survives better in environment
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4
Q

What is the pathogenesis of vibrio cholerae?

A
  1. Toxin co-regulated pilus (TCP) mediates adherence to intestinal epithelial cells 2. Cholera toxin
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5
Q

What are the properties of the cholera toxin?

A
  1. AB toxin 2. Activates adenylate cyclase - increases cAMP production 3. No significant cell damage 4. Similar to ETEC LT toxin in structure and function 5. Encoded on a prophage
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6
Q

What are the symptoms of vibro parahaemolyticus?

A

Explosive watery diarrhea, nausea, vomiting, abdominal cramps, low grade fever

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7
Q

What is the virulence for vibrio parahaemolyticus?

A

Kanagawa hemolysin - induces chloride secretion thus watery diarrhea

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8
Q

Vibrio parahaemolyticus is associated with what food?

A

Raw shellfish

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9
Q

Yersinia enterocolitica is what kind of bacterium?

A

Gram negative coccobacilli

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10
Q

What is the pathogenesis of yersinia enterocolitica?

A
  1. Binds to and invades M cells in terminal ileum 2. T3SS and injection of Yops 3. Produces heat stable enterotoxin
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11
Q

What are the characteristics of clostridium difficile?

A
  1. Gram positive anaerobe 2. Spore forming (important part of life cycle) 3. Non-invasive 4. Inflammatory 5. Associated with CDAD, pseudomembrane colitis, and fulminant colitis with toxic megacolon
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12
Q

What is the pathogenesis of clostridium difficile?

A

AB toxin causes damage to mucosa and host cell cytoskeleton

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13
Q

What is the treatment for clostridium difficile?

A

Vancomycin or metronidazole

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14
Q

What should be considered in a patient who has diarrhea and is on short or long term BSAs?

A

Clostridium difficile

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15
Q

What are the characteristics of enterohemorrhagic E. coli (EHEC)?

A
  1. Gram negative 2. Facultative anaerobe 3. Animal reservoirs - cattle, ruminants 4. Generally non-invasive
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16
Q

What is the disease progression for enterohemorrhagic E. coli (EHEC)?

A
  1. Hemorrhagic colitis - bloody diarrhea 2. No fever 3. Abdominal tenderness 4. Hemolytic uremic syndrome (HUS) - anemia and kidney failure 5. Similar to EPEC
17
Q

What is the pathogenesis of enterohemorrhagic E. coli (EHEC)?

A
  1. Attaching and effacing lesion like EPEC 2. Shiga-like toxin (verotoxin) blocks translation by cleaving part of 60S ribosomal subunit
18
Q

How is hemolytic uremic syndrome (HUS) caused by the EHEC shiga-like toxin?

A
  1. Shiga-like toxin binds kidney receptor, is internalized 2. Kidney cell death and ischemic damage from thrombi lead to kidney failure
19
Q

What is the diagnosis for enterohemorrhagic E. coli (EHEC)?

A
  1. Bloody diarrhea WITHOUT fever 2. Culture 3. PCR for stx gene that encodes toxin
20
Q

Why is antibiotic therapy not indicated for enterohemorrhagic E. coli (EHEC)?

A
  1. Shiga toxin is coded on a lysogenic phage 2. When phage detects damage, replicates its genome
21
Q

What are the characteristics of shigella spp.?

A
  1. Gram negative rods 2. Facultative anaerobes 3. Intracellular pathogens 4. Very acid tolerant 5. Inflammatory 6. Dysentery
22
Q

What is the epidemiology of shigella spp.?

A
  1. Humans are only reservoir 2. Fecal-oral 3. Extremely low infectious dose (
23
Q

What are the clinical manifestations of shigellosis?

A
  1. 1-3 days post infection 2. Usually self limiting 2-5 days post infection 3. Generally strain specific
24
Q

What is the pathogenesis of shigella spp.?

A
  1. Acid resistant 2. Adhere selectively to and pass through M cells - T3SS 3. Phagocytosis by macrophages 4. Rapid escape from phagosome 5. Rapid induction of macrophage apoptosis
25
Q

How are shigella spp. taken up by the intestinal cell?

A
  1. T3SS 2. Injection of Ipa proteins 3. Cytoskeletal rearrangement
26
Q

How do shigella spp. spread to neighboring cells?

A
  1. Hijack host actin 2. Evasion of host defense
27
Q

How does the shiga toxin cause damage?

A
  1. Binds to host Gb3 receptor 2. Inhibits translation - cell damage - tissue damage 3. Glomerular endothelial cells are rich in Gb3 receptors
28
Q

What causes the diarrhea seen in shigella infection?

A

Severe inflammation

29
Q

Does shigella infection confer immunity?

30
Q

What are the properties of enteroinvasive E. coli?

A
  1. Same as shigella but NO shiga toxin 2. Can move around intracellularly but since there is not shiga toxin there is no chance of HUS 3. Appears to have acquired a pathogenicity island from shigella via horizontal gene transfer

Year 1 Microbiology (42 decks)

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