WEEK 11: CLOSTRIDIAL INFECTIONS Flashcards
Are vaccines often toxin based for C.perfringes?
- YES
What are some characteristics of genus Clostridium?
- Gram +ve rods
- Obligate anaerobes
- Form heat resistant endospores (heated=activated, - endo= within bacterial cell)
- Common inhabitants of the GI tract
- Important in agriculturs (soil maintenance–> break down organic matter) and industry (biofuels)
- Important human and animal pathogens (only under certain circumstances)
What are two ways to culture Clostridium if it is an anaerobe?
- Anaerobic jars
- Anaerobic chamber
When does clostridium form endospores?
- Under adverse environmental conditions (e.g. presence of O2) act as survival mechanism
What are the clostridium spores characterized based on?
- The position
- The size
- The shape
What type of spores do most clostridium have?
- OVOID subterminal spores (OST)
What kind of spores do C.tetani have?
- Round terminal spores (RT)
What does the exosporium that clostridium have allow them to be?
- Allow them to be sticky. So spores of epidemic strains are stickier.
What do the pathogenic Clostridia produce?
- Potent protein toxins
- E.g. C.perfringes–>gas gangrene
- C.tetani–> tetanus
- C.botulinum–> botulism
What are the neurotoxic Clostridia?
- C.tetani and C.botulinum (tetanus and botulism)
What are the enterotoxic Clostridia?
- C.perfringes
- C.difficile
What does Clostridium Tetani cause and what does this produce?
-Causes tetanus and produces the tetanus toxin (neurotoxin)
What is the pathogenesis of tetanus?
Entry of spore into DEEP wound (these cut off blood supply to tissue so it can be anaerobic)
Germination of spore in anaerobic environment
Production of toxin by growing bacteria which is released when they die
Toxin binds to nerve endings and it is TRANSLOCATED into nerve cells
This INHIBITS NT release –> blockage of the muscle relaxation pathway
What effects does tetanus lead to?
-Uncontrolled stimulation of muscles —>tension, cramping twisting of muscles, spasms and convulsions, rigid paralysis, death from spasms of the diaphragm and respiratory muscles
What is an effective preventive measure for tetanus?
Vaccination using the tetanus toxin
What does Clostridium botulinum cause?
- Causative agent of botulism
- Food-borne disease
- Commonly from contaminated canned foods that have been inadequately heated
What is the pathogenesis of Clostridium botulinum?
Spores germinate in food and toxin is produced during vegetative growth
Pre-formed toxin (BoNT) is INJESTED with food
Toxin localises in neuromuscular junction–> BLOCKS the release of NT
-C.botulinum produces a lot of gas when it grows (gas gangrene)
What does Clostridium botulinum result in?
- Uncontrolled relaxation of muscles
- Symptoms within 18-24 hours of ingesting toxin
- Blurred vision, difficulty speaking, muscle weakness, nausea, vomiting
- Flaccid paralysis
- death due to cardiac or respiratory failure
Is there a vaccine available for Clostridium botulinum?
NO
- But can treat it with antitoxin if administered quickly
What are the therapeutic uses of botulinum toxin?
- BoNT used to treat severe focal dystonias muscle spasms and facial tics
- BoNT used in cosmetic industry removal of wrinkles
- Very safe and effects last 1-4 months
Where is BoNT injected into for theraeutic use?
- Striated muscle –> leads to REVERSIBLE denervartion of NMJ
Can you get Igs against the toxin which reduce the effectiveness of it?
- YES
What is the location of C.perfringes?
- IN the gut of everyone
Can C.perfringes cause food poisoning?
- YES –> Present in meat that has been heated and cooled slowly
- Ingested in HUGE numbers
Does C.perfringes prodce an enterotoxin?
- YES
- Bacteiral cells sporulate in intestine
- Production of enterotoxin is associated with sporulation
How long does it take for the onset of symptoms in C.perfringes?
- 8-16 hours –> then watery diarrhoea, nausea, abdom cramps
Is treatment usually required for C.perfringes?
- NO but antibiotics can be prescribed
What does C.pefringes cause in humans?
- Food poisoning and gas gangrene
What does C.perfringes cause in animals?
- Enterotoxanaemic diseases
What toxin do ALL the strains of C.perfringes produce?
- Alpha toxin–> difficult to make vaccines
What are the predisposing factors that cause C.perfringes infections in animals (or make them susceptible) ?
- Antibiotics
- Feeding changes (changes in microbiome)
- Change of weather conditions (growing in field) –> will kill animals in 12-18 hours
Which toxins does the C.perfringes type C infection produce and which is the most important?
- Produces the alpha and beta toxin BUT the beta toxin is the most important in C.perfringes infection
What is the Beta toxin sensitive to?
- Trypsin
What does the beta toxin cause in humans?
-Enteritis necroticans (pig-bel) role of the trypsin inhibitor in sweet potatoes (inhibits the breakdown of the Beta toxin)
What is the pathogenesis of infection for C.perfringes type C?
beta toxin produced in the gut; gut trypsin degrades beta toxin. In type C infections:
- Low trypsinL Beta toxin remains active
- Intestinal necrosis
- Beta toxin and other toxins absorbed
- Toxins act on distant organs
What are the predisposing factors for the type D infection (c.perfringes)?
- Carbohydrates in diet (sudden changes)
- Bacterial contamination levels (farm)
- Immune status (against the ϵ toxin )