Clostridia Flashcards
What are the two pathogenic steps in establishing clostridia botulinum infections?
1) Toxins preformed in foods (botulin toxin)
2) Ingestion of microorganisms with adherence, colonization, and toxin formed in the gut (infant boluism)
What is the metabolic status of clostridium?
Obligate anaerobe
What is the morphology of clostridium?
gram positive rods with spores.
How does clostridium test for oxidase and catalase?
Negative for both–because they are OBLIGATE ANAEROBES
Which species of clostridium are noninvasive?
clostridium botulinum
clostridium tetani
clostridium difficile
Which species of clostridium are invasive?
Clostridium perfringens Clostridium septicum (in cancer)
What are the effects of botulism toxin?
flaccid paralysis
What are the effects of exotoxins A and B?
Diarrhea in pseudomembranous colitis from C. difficile
What are the effects of alpha toxin?
lecithinase, which lyses host cell membranes and causes gas gangrene from clostridium perfringens
Describe the morphology of Clostridium tetani
Gram + rod with a highly diagnostic “terminal spore”.
How is clostridium tetani contracted?
through spores in the soil
How many serological types of clostridium tetani are there?
One
How many subunits does the tetanus toxin have? What does it do?
2 subunits. Binds to the neurotransmitter synapses, preventing neurotransmitter release of GABA and glycine
What is the incubation period for tetanus?
4 days to weeks
What are the symptoms of tetanus? (fevers, senses)
No fever, no sensory deficit, violent muscle spasms leading to respiratory failure and arched back
How do you diagnose tetanus?
Mostly clinical symptoms and history because the organism is difficult to culture
What are the treatment options for tetanus?
anti-toxin penicillin wound debridement immunization respiratory support if needed
What is the dosage schedule of tetanus?
3 doses in the first six months
booster at 1 year
booster every 10 years
How would you treat a dirty wound with uncertain immunization?
anti-tetanus toxin
Complete immunization
What is the morphology of clostridium botulinum?
Gram + rod with subterminal oval spores
How would you get rid of botulism toxin?
heat labile–cook to inactivate the toxin
What are the three types of botulism?
Food botulism
Wound associated botulism- spore germination in wound
Infant botulism - Ingestion and colonization of GI tract
What are the different serotypes of botulism toxin?
A, B, and E are the most common
A-G toxins
What is the mechanism of action for botulism toxin?
absorption in intestine, carried to peripheral nerve synapses, and blockage of acetylcholine
What are the symptoms of botulism?
flaccid paralysis (symmetrical), no fever, normal mental status dysphagia dry throat diluted pupils NO SENSORY defect
What is the incubation period of botulism toxin?
18-36 hours
How do you diagnose botulism?
Clinical diagnosis
Detection of botulism toxin
Electromyography
Is a culture of clostridium botulinum from a patient sample sufficient for a diagnosis?
No. Need the presence of toxin.
How do you treat Clostridium botulism?
Lavage–emptying of stomach
Treatment with antitoxin, must be serotype specific
Supportive care
How can you prevent botulism?
Cooking food
What is a common source of contamination with infant botulism?
honey
What are the symptoms of infant botulism?
Constipation
Flaccidity
Cranial nerve deficit
What is the morphology of Clostridium difficile?
Gram + rod
What does exotoxin A bind to?
Enterotoxin that binds to the gut receptor
What does exotoxin B bind to?
ADP-ribosylates Rho, damaging the colonic mucosa and formation of pseudomembrane
What are the clinical symptoms of C difficile?
diarrhea with pseudomembrane visualized on colonoscopy
Diarrhea can be bloody sometimes
How do you diagnose C difficile?
History of antibiotic use (ampicillin, cephalosporin, clindamycin)
Eotoxin B detected in stool samples
Sigmoidoscopy to visualize stool samples
How can you treat C. difficile?
Stop the offending antibiotics
Treat with metronidazole, vancomycin, or fidaxomicin
What are the causes of clostridium perfringens?
Surgical disease
Food poisoning-self limiting
What are the symptoms of clostridium perfringens?
gas gangrene and tissue necrosis
Where can clostridium perfringens be found?
soil, but also human GI tract+vagina
What are the other species of clostridium that can also cause gas gangrene?
C septicum, C bifermentans and C ramosum, all anaerobes
What is the morphology of clostridium perfringens?
A gram + rod
What toxins does clostridium perfringens secrete?
lecithinase (alpha toxin)
collagenase
hyaluronidase (breaks down host matrix)
What are the growth byproducts of C perfringens?
h2 and co2 gases
What is unique about the growth of clostridium perfringens?
Rapid growth
Are a lot of spores needed for clostridium perfringens food poisoning?
Yes, 10^8
How does clostridium perfringens cause food poisoning?
After spores are ingested, the enterotoxin associated with the spore coat is released into the intestine
What are the symptoms of clostridium perfringens gas gangrene?
Depends on where the bug is located. If gas gangerene is in skin=cellulitis.
Necrotizing cellulitis, necrotizing fasciitis, myositis, myonecrosis
What are the symptoms of clostridium perfringens food poisoning?
Abdominal cramps and watery diarrhea, usually resolved by 24 hours. It is the 2nd or 3rd most common cause of food poisoning
How would you diagnose clostridium perfringens?
Crepitus, discoloration, and edema of the skin, which should be painful.
Gram stain of fluid
Culture of wound
X-ray for gas in tissues
If food poisoning, detect through ELISA enterotoxin in feces/food
How would you treat gas gangerene by C. Perfringens?
Surgical-wound debridement
Penicillin to kill remaining bacteria
Hyperbaric oxygen if available. Fatal if untreated
Why wouldn’t you want to culture a clostridium tetanus wound?
Because the culture would only be positive 39% of the time.
Which serotypes are most common in food botuulism?
A,B, and E. ABE likes to eat a lot which gives him food botulism. This is important because antitoxins are serotype specific
Which serotypes are common in infant botulism?
F, A, B.
Why wouldn’t you want to culture a clostridium tetanus wound?
Because the culture would only be positive 39% of the time.
Which serotypes are most common in food botuulism?
A,B, and E. ABE likes to eat a lot which gives him food botulism. This is important because antitoxins are serotype specific
Which serotypes are common in infant botulism?
F, A, B.
Which antibiotics are notorious for causing C. Diff infections?
Cephalosporins, fluoroquinolones, and Clindamycin
Which species of clostridium are non-motile?
Clostridium perfringens
