Flashcards in Bacillus And Clostridium (Spore-Forming Rods) Deck (41):
Where is B.anthracis found?
How is B.anthracis transmitted?
What is the metabolism of B.antracis?
Aerobic - but since it can grow without oxygen, it is classified as facultative anaerobic.
What is the virulence of B.anthracis?
1. Unique protein capsule (polymer of gamma-D-glutamic acid): antiphagocytic.
3. Virulence depends on acquiring 2 plasmids. One carries the gene for the protein capsule; the other carries the gene for its exotoxin.
What are the toxins of B.anthracis?
Exotoxin: 3 proteins.
1. Protective antigen (PA)
2. Edema factor (EF)
3. Lethal factor (LF)
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.
Does infection with B.anthracis result in permanent immunity, if the patient survives?
How do we identify B.anthracis?
1. Gram stain
4. PCR of nasal swab
How is B.cereus transmitted?
What is the metabolism of B.cereus?
What is the virulence of B.cereus?
1. No capsule
What are the toxins of B.cereus?
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.
What can B.cereus cause?
How do we identify B.cereus?
Culture specimen from suspected food source.
Where is C.botulinum found?
2. Stored vegetables - home-canned, zip-lock storage bags.
3. Smoked fish
4. Fresh honey --> infant botulism.
How is C.botulinum transmitted?
What is the virulence of C.botulinum?
Motile: flagella --> H-antigen positive.
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.
What can C.botulinum cause?
1. Food-borne botulism
2. Infant botulism
3. Wound botulism
What happens in food-borne botulism?
1. Cranial nerve palsies
2. Muscle weakness
3. Respiratory paralysis
What happens in infant botulism?
2. Flaccid paralysis
What happens in wound botulism?
Similar to food-borne except absence of GI prodromal symptoms.
How do we identify C.botulinum?
1. Gram stain
2. Culture --> Requires anaerobic conditions
3. Patient's serum injected into mice results in death
Where is C.tetani found?
In the soil.
How is C.tetani transmitted?
Endospores: introduced through wound.
What is the virulence of C.tetani?
Motile: flagella (so H-antigen positive).
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.
What does C.tetani cause?
1. Muscle spasms
2. Lockjaw (trismus)
3. Risus sardonicus
4. Respiratory muscle paralysis
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.
Where is C.perfringens found?
2. GI tract of humans and mammals
How is C.perfringens transmitted?
What is the virulence of C.perfringens?
What are the toxins of C.perfringens?
Alpha toxin: lecithinase + 11 other tissue destructive enzymes.
What can C.perfringens cause?
1. Cellulitis/ wound infection.
2. Clostridial myonecrosis - fatal if untreated.
3. Watery diarrhea - associated with food-borne ingestion.
How do we identify C.perfrigens?
1. Gram stain
2. Anaerobic culture
Where is C.difficile found?
1. Intestinal tract
2. Endospores found in hospitals and nursing homes
How is C.difficile transmitted?
Fecal-oral: ingestion of endospores.
What is the virulence of C.difficile?
Motile: flagella (H-antigen positive)
What are the toxins of C.difficile?
Toxin A --> diarrhea
Toxin B --> cytotoxic to colonic epithelial cells
What can C.difficile cause?
Antibiotic associated diarrhea.