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Microbiology > Bacillus And Clostridium (Spore-Forming Rods) > Flashcards

Bacillus And Clostridium (Spore-Forming Rods) Flashcards

0
Q

How is B.anthracis transmitted?

A

Endospores:

  1. Cutaneous
  2. Inhalation
  3. Ingestion
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1
Q

Where is B.anthracis found?

A

Herbivores (zoonotic):

  1. Sheep
  2. Goats
  3. Cattle
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2
Q

What is the metabolism of B.antracis?

A

Aerobic - but since it can grow without oxygen, it is classified as facultative anaerobic.

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3
Q

What is the virulence of B.anthracis?

A
  1. Unique protein capsule (polymer of gamma-D-glutamic acid): antiphagocytic.
  2. Non-motile
  3. Virulence depends on acquiring 2 plasmids. One carries the gene for the protein capsule; the other carries the gene for its exotoxin.
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4
Q

What are the toxins of B.anthracis?

A

Exotoxin: 3 proteins.

  1. Protective antigen (PA)
  2. Edema factor (EF)
  3. Lethal factor (LF)
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5
Q

What can B.anthracis cause?

A
  1. Cutaneous (95%) –> painless black vesicles - fatal if left untreated.
  2. Pulmonary (woolsorter’s disease).
  3. GI: Abdominal pain, vomiting, and bloody diarrhea.
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6
Q

Does infection with B.anthracis result in permanent immunity, if the patient survives?

A

Yes

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7
Q

How do we identify B.anthracis?

A
  1. Gram stain
  2. Culture
  3. Serology
  4. PCR of nasal swab
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8
Q

How is B.cereus transmitted?

A

Via endospores.

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9
Q

What is the metabolism of B.cereus?

A

Aerobic

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10
Q

What is the virulence of B.cereus?

A
  1. No capsule

2. Motile

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11
Q

What are the toxins of B.cereus?

A

Enterotoxins:

  1. Heat labile –> Similar to E.coli or enterotoxin of cholera.
  2. Heat stable –> Syndrome similar to that of S.aureus food poisoning, but with limited diarrhea.
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12
Q

What can B.cereus cause?

A

Food poisoning:

  1. Nausea
  2. Vomiting
  3. Diarrhea
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13
Q

How do we identify B.cereus?

A

Culture specimen from suspected food source.

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14
Q

Where is C.botulinum found?

A
  1. Soil
  2. Stored vegetables - home-canned, zip-lock storage bags.
  3. Smoked fish
  4. Fresh honey –> infant botulism.
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15
Q

How is C.botulinum transmitted?

A

Via endospores.

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16
Q

What is the virulence of C.botulinum?

A

Motile: flagella –> H-antigen positive.

17
Q

What are the exotoxins of C.botulinum?

A
  1. Neurotoxin –> Inhibits release of ACh from peripheral nerves.
  2. Toxin is NOT secreted - it is rather released upon the death of the bacterium.
18
Q

What can C.botulinum cause?

A
  1. Food-borne botulism
  2. Infant botulism
  3. Wound botulism
19
Q

What happens in food-borne botulism?

A
  1. Cranial nerve palsies
  2. Muscle weakness
  3. Respiratory paralysis
20
Q

What happens in infant botulism?

A
  1. Constipation

2. Flaccid paralysis

21
Q

What happens in wound botulism?

A

Similar to food-borne except absence of GI prodromal symptoms.

22
Q

How do we identify C.botulinum?

A
  1. Gram stain
  2. Culture –> Requires anaerobic conditions
  3. Patient’s serum injected into mice results in death
23
Q

Where is C.tetani found?

A

In the soil.

24
Q

How is C.tetani transmitted?

A

Endospores: introduced through wound.

25
Q

What is the virulence of C.tetani?

A

Motile: flagella (so H-antigen positive).

26
Q

What is the toxin of C.tetani?

A

Tetanospasmin: inhibits release of GABA and glycine (both inhibitory neurotransmitters) from nerve cells, resulting in sustained muscle contraction.

27
Q

What does C.tetani cause?

A

Tetanus:

  1. Muscle spasms
  2. Lockjaw (trismus)
  3. Risus sardonicus
  4. Respiratory muscle paralysis
28
Q

How can we identify C.tetani?

A
  1. Gram stain: gram (+) rods, often with an endospore at one end, giving them the appearance of a drumstick.
  2. Cultures: anaerobic conditions.
29
Q

Where is C.perfringens found?

A
  1. Soil

2. GI tract of humans and mammals

30
Q

How is C.perfringens transmitted?

A

Via endospores.

31
Q

What is the virulence of C.perfringens?

A

Non-motile

32
Q

What are the toxins of C.perfringens?

A

Alpha toxin: lecithinase + 11 other tissue destructive enzymes.

33
Q

What can C.perfringens cause?

A

Gaseous gangrene.

  1. Cellulitis/ wound infection.
  2. Clostridial myonecrosis - fatal if untreated.
  3. Watery diarrhea - associated with food-borne ingestion.
34
Q

How do we identify C.perfrigens?

A
  1. Gram stain

2. Anaerobic culture

35
Q

Where is C.difficile found?

A
  1. Intestinal tract

2. Endospores found in hospitals and nursing homes

36
Q

How is C.difficile transmitted?

A

Fecal-oral: ingestion of endospores.

37
Q

What is the virulence of C.difficile?

A

Motile: flagella (H-antigen positive)

38
Q

What are the toxins of C.difficile?

A

Toxin A –> diarrhea

Toxin B –> cytotoxic to colonic epithelial cells

39
Q

What can C.difficile cause?

A

Pseudomembranous enterocolitis.

Antibiotic associated diarrhea.

40
Q

How do we identify C.difficile?

A
  1. Immunoassay for C.difficile toxin.

2. PCR for toxin A and B genes.

Microbiology (46 decks)

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