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Year 1 Microbiology > GI bacteria I > Flashcards

GI bacteria I Flashcards

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1
Q

Which host defenses can trigger expression of bacterial virulence factors?

A

Mucous, bile

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2
Q

What is characteristic of GI distress 1-8 hours after ingestion?

A

Preformed toxin

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3
Q

What is characteristic of GI distress 8-16 hours after ingestion?

A

Production of toxin after ingestion

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4
Q

What is characteristic of GI distress 16+ hours after ingestion?

A

Adherence, growth, and virulence factor production

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5
Q

What pathogens infect with a preformed toxin 1-8 hours after ingestion?

A
  1. Staphylococcus aureus 2. Bacillus cereus (emetic) 3. Clostridium botulinum
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6
Q

What pathogens produce toxin 8-16 hours after ingestion?

A
  1. Bacillus cereus (diarrheal) 2. Clostridium perfringens 3. Clostridium botulinum
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7
Q

What pathogens adhere, grow, and produce virulence factors 16+ hours after ingestion?

A
  1. Shigella spp. 2. Listeria monocytogenes 3. EHEC 4. EPEC 5. ETEC 6. EIEC 7. Campylobacter spp. 8. Vibrio spp.
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8
Q

Is fever associated with bacterial food poisoning?

A

No

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9
Q

What are the four bacterial causes of food poisoning?

A
  1. Staphylococcus aureus 2. Clostridium botulinum 3. Clostridium perfringens 4. Bacillus cereus
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10
Q

What are the characteristics of staphylococcus aureus?

A
  1. Gram positive cocci in clusters 2. Non spore forming
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11
Q

What is the disease progression of staphylococcos aureus food poisoning?

A
  1. Ingestion of preformed toxin 2. Severe vomiting, diarrhea, constipation and abdominal pain 1-8 hours after ingestion
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12
Q

What is the pathogenesis of staphylococcus aureus food poisoning?

A

Heat stable toxin

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13
Q

What are the characteristics of clostridium botulinum?

A
  1. Gram positive rod 2. Spore forming
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14
Q

Does staphylococcus aureus produce spores?

A

No

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15
Q

Does clostridium botulinum produce spores?

A

Yes

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16
Q

What is the disease progression of clostridium botulinum food poisoning?

A
  1. Mediated by botulinum toxin 2. Early - vomiting, diarrhea, abdominal pain 1-8 after ingestion 3. Late - flaccid paralysis, progressive muscle weakness and respiratory arrest
17
Q

What is the pathogenesis of clostridium botulinum food poisoning?

A
  1. Ingestion of preformed toxin 2. Large number of spores germinate in intestine and produce toxin 3. Toxin acts at NMJ, blocks Ach release at synapses
18
Q

What are the characteristics of clostridium perfringens?

A
  1. Gram positive rod 2. Spore forming
19
Q

What is the disease progression for clostridium perfringens food poisoning?

A
  1. C. perfringens enterotoxin 2. Diarrhea and abdominal pain 8-16h after ingestion 3. Lasts for 24 hours
20
Q

Does clostridium perfringens produce spores?

A

Yes

21
Q

What are the characteristics of bacillus cereus?

A
  1. Gram positive 2. Spore forming
22
Q

What is the disease progression for the emetic form of bacillus cereus food poisoning?

A
  1. Vomiting, nausea, abdominal cramps 1-8 hours after ingestion of preformed heat stable enterotoxin 2. Associated with improper storage of cooked rice
23
Q

What is the disease progression for the diarrheal form of bacillus cereus food poisoning?

A
  1. Diarrhea, nausea, abdominal pain 8-16 hours after ingestion of contaminated food 2. Production of heat labile enterotoxin in intestine
24
Q

What are the characteristics of helicobacter pylori?

A
  1. Gram negative curved rod 2. Microaerophilic (5% oxygen)
25
Q

What is the pathogenesis of helicobacter pylori?

A
  1. Penetrates mucosa of stomach, attracted to hemin and urea 2. Produces urease which breaks down urea into NH3 and CO2 to increase pH
26
Q

What is the treatment for H. pylori?

A
  1. Antibiotics 2. Proton pump inhibitor to control acid / further mucosal damage
27
Q

What are the characteristics of listeria monocytogenes?

A
  1. Gram positive short rods sometimes in pairs 2. Facultative anaerobe
28
Q

What are the key survival traits of listeria monocytogenes?

A
  1. Wide growth range (cryophilic) 2. Resistant to high salt concentrations 3. Wide pH range
29
Q

What is the epidemiology of listeria monocytogenes?

A
  1. Contamination common in ready to eat meats 2. High risk of infection in elderly, immunocompromised
30
Q

What is the clinical manifestation of listeria monocytogenes in immunocompromised individuals?

A
  1. Bacteremia 2. Meningitis and encephalitis
31
Q

If a pregnant patient has a fever with no obvious focus, what pathogen should be included in the differential?

A

Listeria monocytogenes

32
Q

What is the clinical manifestation of neonatal listeria monocytogenes infection?

A
  1. Granulomatosis infantiseptica - pyogenic granulomas distributed over the whole body 2. Early onset in utero - premature birth, abortion3. Late onset - 2-3 weeks after birth
33
Q

What is the pathogenesis of listeria monocytogenes?

A
  1. Adherence via internalin A (IntA) 2. Internalized into a vacuole 3. Acidification of vacuole / phagosome 4. Listeriolysin produced in response to acidification of phagosome
34
Q

How does listeria monocytogenes adhere to the GI tract?

A

Internalin A

35
Q

What is activated by the acidification of the internalized vacuole in listeria monocytogenes infection?

A

Listeriolysin

36
Q

What is the role of listeriolysin in listeria monocytogenes infection?

A

Disrupts vacuole membrane to allow for escape into the cytosol

37
Q

What is the pathogenesis of listeria monocytogenes?

A
  1. Replication in host cell cytosol 2. ActA mediated polymerization to induce motility 3. Disseminated infection to liver, spleen, CNS
38
Q

What is the diagnosis for listeria monocytogenes?

A

Culture of CSF and blood for 1. Cold enrichment selection 2. Weak B hemolysis on blood agar 3. Motility test

39
Q

What is the treatment for listeria monocytogenes?

A

Beta lactam or trimethoprim-sulfamethoxazole

Year 1 Microbiology (42 decks)

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