Bacillus And Clostridium (Spore-Forming Rods) Flashcards
How is B.anthracis transmitted?
Endospores:
- Cutaneous
- Inhalation
- Ingestion
Where is B.anthracis found?
Herbivores (zoonotic):
- Sheep
- Goats
- Cattle
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?
- Unique protein capsule (polymer of gamma-D-glutamic acid): antiphagocytic.
- Non-motile
- 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.
- Protective antigen (PA)
- Edema factor (EF)
- Lethal factor (LF)
What can B.anthracis cause?
- Cutaneous (95%) –> painless black vesicles - fatal if left untreated.
- Pulmonary (woolsorter’s disease).
- GI: Abdominal pain, vomiting, and bloody diarrhea.
Does infection with B.anthracis result in permanent immunity, if the patient survives?
Yes
How do we identify B.anthracis?
- Gram stain
- Culture
- Serology
- PCR of nasal swab
How is B.cereus transmitted?
Via endospores.
What is the metabolism of B.cereus?
Aerobic
What is the virulence of B.cereus?
- No capsule
2. Motile
What are the toxins of B.cereus?
Enterotoxins:
- Heat labile –> Similar to E.coli or enterotoxin of cholera.
- Heat stable –> Syndrome similar to that of S.aureus food poisoning, but with limited diarrhea.
What can B.cereus cause?
Food poisoning:
- Nausea
- Vomiting
- Diarrhea
How do we identify B.cereus?
Culture specimen from suspected food source.
Where is C.botulinum found?
- Soil
- Stored vegetables - home-canned, zip-lock storage bags.
- Smoked fish
- Fresh honey –> infant botulism.
How is C.botulinum transmitted?
Via endospores.
What is the virulence of C.botulinum?
Motile: flagella –> H-antigen positive.
What are the exotoxins of C.botulinum?
- Neurotoxin –> Inhibits release of ACh from peripheral nerves.
- Toxin is NOT secreted - it is rather released upon the death of the bacterium.
What can C.botulinum cause?
- Food-borne botulism
- Infant botulism
- Wound botulism
What happens in food-borne botulism?
- Cranial nerve palsies
- Muscle weakness
- Respiratory paralysis
What happens in infant botulism?
- Constipation
2. Flaccid paralysis
What happens in wound botulism?
Similar to food-borne except absence of GI prodromal symptoms.
How do we identify C.botulinum?
- Gram stain
- Culture –> Requires anaerobic conditions
- 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?
Tetanus:
- Muscle spasms
- Lockjaw (trismus)
- Risus sardonicus
- Respiratory muscle paralysis
How can we identify C.tetani?
- Gram stain: gram (+) rods, often with an endospore at one end, giving them the appearance of a drumstick.
- Cultures: anaerobic conditions.
Where is C.perfringens found?
- Soil
2. GI tract of humans and mammals
How is C.perfringens transmitted?
Via endospores.
What is the virulence of C.perfringens?
Non-motile
What are the toxins of C.perfringens?
Alpha toxin: lecithinase + 11 other tissue destructive enzymes.
What can C.perfringens cause?
Gaseous gangrene.
- Cellulitis/ wound infection.
- Clostridial myonecrosis - fatal if untreated.
- Watery diarrhea - associated with food-borne ingestion.
How do we identify C.perfrigens?
- Gram stain
2. Anaerobic culture
Where is C.difficile found?
- 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?
Pseudomembranous enterocolitis.
Antibiotic associated diarrhea.
How do we identify C.difficile?
- Immunoassay for C.difficile toxin.
2. PCR for toxin A and B genes.
