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Flashcards in Bacillus And Clostridium (Spore-Forming Rods) Deck (41):
0

Where is B.anthracis found?

Herbivores (zoonotic):
1. Sheep
2. Goats
3. Cattle

1

How is B.anthracis transmitted?

Endospores:
1. Cutaneous
2. Inhalation
3. Ingestion

2

What is the metabolism of B.antracis?

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

3

What is the virulence of B.anthracis?

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.

4

What are the toxins of B.anthracis?

Exotoxin: 3 proteins.
1. Protective antigen (PA)
2. Edema factor (EF)
3. Lethal factor (LF)

5

What can B.anthracis cause?

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

6

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

Yes

7

How do we identify B.anthracis?

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

8

How is B.cereus transmitted?

Via endospores.

9

What is the metabolism of B.cereus?

Aerobic

10

What is the virulence of B.cereus?

1. No capsule
2. Motile

11

What are the toxins of B.cereus?

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.

12

What can B.cereus cause?

Food poisoning:
1. Nausea
2. Vomiting
3. Diarrhea

13

How do we identify B.cereus?

Culture specimen from suspected food source.

14

Where is C.botulinum found?

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

15

How is C.botulinum transmitted?

Via endospores.

16

What is the virulence of C.botulinum?

Motile: flagella --> H-antigen positive.

17

What are the exotoxins of C.botulinum?

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

What can C.botulinum cause?

1. Food-borne botulism
2. Infant botulism
3. Wound botulism

19

What happens in food-borne botulism?

1. Cranial nerve palsies
2. Muscle weakness
3. Respiratory paralysis

20

What happens in infant botulism?

1. Constipation
2. Flaccid paralysis

21

What happens in wound botulism?

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

22

How do we identify C.botulinum?

1. Gram stain
2. Culture --> Requires anaerobic conditions
3. Patient's serum injected into mice results in death

23

Where is C.tetani found?

In the soil.

24

How is C.tetani transmitted?

Endospores: introduced through wound.

25

What is the virulence of C.tetani?

Motile: flagella (so H-antigen positive).

26

What is the toxin of C.tetani?

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

27

What does C.tetani cause?

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

28

How can we identify C.tetani?

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

29

Where is C.perfringens found?

1. Soil
2. GI tract of humans and mammals

30

How is C.perfringens transmitted?

Via endospores.

31

What is the virulence of C.perfringens?

Non-motile

32

What are the toxins of C.perfringens?

Alpha toxin: lecithinase + 11 other tissue destructive enzymes.

33

What can C.perfringens cause?

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

34

How do we identify C.perfrigens?

1. Gram stain
2. Anaerobic culture

35

Where is C.difficile found?

1. Intestinal tract
2. Endospores found in hospitals and nursing homes

36

How is C.difficile transmitted?

Fecal-oral: ingestion of endospores.

37

What is the virulence of C.difficile?

Motile: flagella (H-antigen positive)

38

What are the toxins of C.difficile?

Toxin A --> diarrhea
Toxin B --> cytotoxic to colonic epithelial cells

39

What can C.difficile cause?

Pseudomembranous enterocolitis.
Antibiotic associated diarrhea.

40

How do we identify C.difficile?

1. Immunoassay for C.difficile toxin.
2. PCR for toxin A and B genes.