Clostridium botulinum

Categorization
Cell Wall: Gram Positive Shape: Spore-forming Rod
Metabolism: Obligate Anaerobe
Transmission
  • Overview
    • The causes of botulism tend to be slightly different in adults and infants.
  • Adult Botulism
    • C. botulinum spores may contaminate meats and vegetables that undergo packaging in cans. Within the anaeorbic environment of the can the spores can germinate, grow, and elaborate the Botulinum Exotoxin. Thus disease in adults is caused by ingestion of the pre-formed botulinum exotoxin while the actual bacteria may be dead.
  • Infant Boutlism
    • Food contaminated with C. botulinum spores, especially honey products, is ingested by infants. The spores germinate inside the infant's GI system, grow, and elaborate botulinum exotoxin. Thus disease in infants is caused by growing bacteria within the GI system which are actively elaborating exotoxin.
Virulence Factors
  • Botulinum Exotoxin:
    • Botulinum exotoxin is a neurotoxin which irreversibly blocks release of acetylcholine (Ach) from peripheral nerves at the synapse. The ingested toxin is absorbed and enters the blood which delivers it to peripheral nerve synapses. The gene for the botulinum exotoxin is carried on a lysogenic phage and is thus transmitted by transduction.
Clinical Consequences
  • Adult Botulism
    • Characterized by a descending paralysis which begins with diplopia and dysphagia. Paralysis continues with general muscle weakness ultimately resulting in respiratory depression and death. Importantly, this paralysis is characterized by flaccidity, rather than the rigor associated with C. tetani.
  • Infant Botulism
    • Infants first develop constipation followed by dysphagia and a generalized muscle weakness.
Treatment
  • Adult botulism: Antitoxin, an antibody which binds the botulinum toxin
  • Infant botulism: Supportive therapy as infants usually recover spontaneously