Lecture 4 Part 1: Clostridium, Bacteroides, and Other Anaerobes Flashcards
How many Clostridium species are prevalent in human disease?
four
Name the 4 Clostridium species prevalent in human disease?
- C. perfringens
- C. tetani
- C. botulinum
- C. difficile
Which disease is caused by Clostridium perfringens?
gas gangrene
Which disease is caused by Clostridium tetani?
tetanus
Which disease is caused by Clostridium botulinum?
botulism
Which diseases are caused by Clostridium difficile?
diarrhea and colitis
Do all 4 4 Clostridium species prevalent in human disease form spores?
YES, THEY ALL FORM SPORES
What are the four general properties of Clostridium species? (on slide it says some exceptions)
- presence of endospores so it can survive adverse environmental conditions
- strict anaerobic metabolism
- inability to reduce sulfate to sulfite
- Gram(+) cell wall
What type of metabolism do Clostridium species have?
strict anaerobic metabolism (they thrive in environments without oxygen)
can Clostridium species reduce sulfate to sulfite?
no, they have an inability to reduce sulfate to sulfite
Name 4 places where Clostridium species commonly found?
They are ubiquitous in
1. soil
2. water
3. sewage
4. endogenous flora (normal flora of the body)
In terms of virulence how does Clostridium induce damage?
through numerous toxins
What is the shape and Gram-staining characteristic of Clostridium perfringens?
large, rectangular Gram-positive rods
How many types of Clostridium perfringens are there, and what are they based on?
there are 5 types (A-E) based on toxin production.
Which type of Clostridium perfringens is most prevalent in human infections?
type A
What are the four lethal toxins of Clostridium perfringens?
- Alpha toxin
- Beta toxin
- Epsilon toxin
- Iota toxin
What is the function of Clostridium perfringens Alpha toxin?
It is a phospholipase C that causes hemolysis (destruction of red blood cells)
Which Clostridium perfringens toxin is a pore-forming toxin?
beta toxin
How is Epsilon toxin activated?
It is a protoxin that is activated by trypsin
What is the mechanism of the Iota toxin?
It is an A-B toxin
the B subunit forms pores
the A subunit binds G actin
What does Clostridium perfringens enterotoxin do?
It is a heat-labile toxin that causes fluid loss and also acts as a superantigen
What types of soft-tissue infections can Clostridium perfringens cause?
soft-tissue infections ranging from cellulitis to gas gangrene
What is gas gangrene and how is it caused by Clostridium perfringens?
Gas gangrene is a severe infection where rapidly dividing bacteria produce gas metabolites
What type of foodborne illness can Clostridium perfringens cause?
food poisoning
What is necrotizing enteritis and how is it related to Clostridium perfringens?
Necrotizing enteritis is a severe intestinal infection caused by Clostridium perfringens
What other serious conditions can Clostridium perfringens cause?
Endometritis and septicemia
What is the shape and Gram-staining characteristic of Clostridium tetani?
Large, motile, spore-forming Gram-positive rods.
How does Clostridium tetani respond to oxygen?
It has extreme oxygen sensitivity; the bacterium is easily killed by oxygen, but its spores can persist
class note: Clostridium tetani is challenge to culture. in normal conditions since its extremly sensitive to oxygen
What is the main virulence factor of Clostridium tetani?
Tetanospasmin (A-B toxin)
What is tetanospasmin and how is it encoded?
Tetanospasmin is an A-B toxin and a plasmid-encoded neurotoxin
When is tetanospasmin produced and released?
It is produced during the stationary phase and released on lysis
How does tetanospasmin affect the nervous system?
It invades the central nervous system (CNS), binds to motor neurons, and is transported retrogradely to the cell soma
What neurotransmitter release does tetanospasmin block?
it blocks the release of inhibitory neurotransmitters (GABA), leading to continuous excitatory neurotransmission
What is the function of tetanolysin?
Tetanolysin is a pore-forming toxin
What is the primary effect of the tetanus toxin?
Continuous excitatio
How does the tetanus toxin cause continuous excitation?
By blocking the release of inhibitory neurotransmitters
(GABA)
What are the basic characteristics of Clostridium botulinum?
Large, spore-forming, anaerobic rods
Where is Clostridium botulinum commonly found?
in soil and water
describe the spores of Clostridium botulinum
The spores of Clostridium botulinum are heat-resistant and can germinate in anaerobic (oxygen-free) conditions
What disease does Clostridium botulinum cause and what are its symptoms?
Botulism, which causes neurologic symptoms
What are the 4 different forms of botulism?
- Foodborne (canned foods)
- infant (powdered milk)
- wound (rare)
- inhalation (potential biological weapon)
How many subunits does the botulinum toxin have and what is their effect?
Seven distinct subunits that cause paralysis
What is the function of the B subunit of the botulinum toxin?
It binds to sialic acids and glycoproteins on motor neuron
What is the function of the A subunit of the botulinum toxin?
It is a zinc endopeptidase that inhibits the release of acetylcholine (ACh).
What is the primary effect of botulinum toxins?
They cause paralysis
How do botulinum toxins cause paralysis?
By blocking the release of acetylcholine (ACh) at the neuromuscular junction (NMJ)
Where does Clostridium difficile colonize in the human body?
large intestine
How is the virulence of Clostridium difficile kept in check?
By normal flora and dimeric IgA
What can cause Clostridium difficile to proliferate?
Broad-spectrum antibiotic treatment
What range of symptoms can Clostridium difficile cause?
Symptoms can range from relatively benign to severe diarrheal disease (pseudomembranous colitis)
Why is Clostridium difficile a major concern in hospital settings?
It produces highly resistant spores, making it a major source of nosocomial outbreaks
Why do relapses occur in Clostridium difficile infections?
Relapse due to presence of spores
What is the 3 functions of Enterotoxin (Toxin A) produced by Clostridium difficile?
It acts as a
1. neutrophil chemoattractant,
2. stimulates cytokine release
3. disrupts tight junctions
What is the function of Cytotoxin B (Toxin B) produced by Clostridium difficile?
It induces actin depolymerization
How does increased toxin production affect the virulence of Clostridium difficile?
Increased toxin production, often due to a mutated regulatory gene, leads to higher virulence.
How does increased toxin production affect Clostridium difficile’s virulence?
Virulence increases with increased toxin production
What causes increased toxin production in Clostridium difficile?
A mutated regulatory gene leads to increased toxin production
