Clostridium Botulinum

MORPHOLOGY:
  • Clostridium botulinum, which causes a disease of Neuromuscular transmission called botulism
  • It is a rod-shaped microorganism.
  • Obligate anaerobe, meaning that oxygen is poisonous to the cells.
  • Tolerates traces of oxygen due to the enzyme called superoxide dismutase (SOD) which is an important antioxidant defense in nearly all cells exposed to oxygen.
  • Does not form endospores as a way to protect the viability of the organism, but rather as a mechanism to produce the neurotoxin.
  • Able to produce the neurotoxin during sporulation, which can only happen in an anaerobic environment.
PATHOGENESIS:
  • It is an intoxication resulting from the ingestion of food in which C botulinum has grown and produced toxin.
  • Clostridium botulinum comes under Category A bioterrorism agents
  • In a 6 months old baby, floppy infant syndrome is seen commonly due to infection with Clostridium botulism
  • The most common offenders are spiced, smoked, vacuum-packed, or canned alkaline foods that are eaten without cooking.
  • In such foods, spores of C botulinum germinate; under anaerobic conditions, vegetative forms grow and produce toxin.
  • The toxin acts by blocking release of acetylcholine at synapses (by Presynaptic block)and neuromuscular junctions.
  • Flaccid paralysis results. [reduced muscle tone]
  • The electromyogram strength tests are typical.
TOXINS:
  • Seven antigenic varieties of toxin (A–G) are known.
  • Preformed toxin is important in food poisoning due to Clostridium botulism
  • Types A, B, and E (and occasionally F) are the principal causes of human illness.
  • Poisoning can be prevented by an antitoxin
  • Types A and B have been associated with a variety of foods
  • Type E predominantly with fish products.
  • Type C(non-neurotoxin) produces limberneck in birds;
  • Type D causes botulism in mammals.
CLINICAL FINDINGS:
  • Symptoms begin 18–24 hours after ingestion of the toxic food, with visual disturbances (incoordination of eye muscles, double vision), inability to swallow, and speech difficulty;
  • Dysphagia, diplopia, dysarthria are seen
  • Signs of paralysis are progressive, and death occurs from respiratory paralysis or cardiac arrest.
  • Gastrointestinal symptoms are not regularly prominent.
  • There is no fever.
  • The patient remains fully conscious until shortly before death.
  • The infants in the first months of life develop poor feeding, weakness, and signs of paralysis ("floppy baby").
  • It is assumed that C botulinum spores are in the babies' food, yielding toxin production in the gut.
  • Honey has been implicated as a possible vehicle for the spores.
  • Sudden infant death syndrome (SIDS) following administration of honey is due to Clostridium botulinum
  • C botulinum and botulinum toxin are found in feces but not in serum.
  • Infant botulism may be one of the causes of sudden infant death syndrome.
LAB DIAGNOSIS
  • The antigenic type of toxin is identified by neutralization with specific antitoxin in mice.
  • C botulinum may be grown from food remains and tested for toxin production.
  • In infant botulism, C botulinum and toxin can be demonstrated in bowel contents but not in serum.
  • Toxin may be demonstrated by passive hemagglutination or radioimmunoassay.
Exam Question
  • Botulism is a disease of Neuromuscular transmission caused by the toxin of the bacterium clostridium botulinum
  • Among the toxin produced by clostridium botulinum, the non neurotoxic one is C2
  • Clostridium botulinum A, B, C and F cause human disease
  • The gene for botulinum toxin is encoded by a bacteriophage
  • Clostridium botulinum comes under Category A bioterrorism agents
  • Preformed toxin is important in food poisoning due to Clostridium botulism
  • In a 6 months old baby, floppy infant syndrome is seen commonly due to infection with Clostridium botulism
  • Clostridium botulinum toxin mode of action is by Presynaptic block
  • Causative organism of food poisoning due to home canned food is Clostridium botulinum
  • Sudden infant death syndrome (SIDS) following administration of honey is due to Clostridium botulinum
  • Dysphagia, diplopia, dysarthria are characteristic symptoms of food poisoning due to Clostridium botulinum
  • Clostridium botulinum poisoning can be prevented by an antitoxin
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