Botulism

Botulism is a life-threatening condition of neuroparalysis that is caused by a potent neurotoxin produced by the spore-forming bacteria Clostridium botulinum. Botulinum toxin blocks the release of acetylcholine from motor end plates into the synaptic cleft, irreversibly inhibiting neurotransmission. There are three main types of botulism: foodborne botulism, infant botulism, and wound botulism. Foodborne botulism results from the ingestion of a food product already contaminated with botulinum toxin (typically home-canned foods). Infant botulism represents the majority of cases and is caused by the ingestion of spores (commonly from honey or soil), which then germinate and produce neurotoxins within the intestinal tract. In wound botulism, which typically occurs in IV drug users, Clostridium botulinum spores germinate in contaminated wounds. All three types present with neuroparalysis, while foodborne and infant botulism are sometimes also associated with gastrointestinal symptoms (e.g., discomfort, nausea, constipation). Clinical suspicion of botulism may be confirmed by quickly identifying the toxin in bodily fluids (e.g., serum, vomit, gastric acid, stool) and/or food. Foodborne botulism is best treated with an antitoxin and medically-induced bowel emptying. Treatment of infant botulism consists of the administration of botulism immune globulin. Wound botulism requires surgical debridement in addition to antitoxin administration.

Pathogen

• Clostridium botulinum
  • Gram-positive rod
  • Spore-forming
  • Obligate anaerobe
  • Produces heat-labile neurotoxin

Pathophysiology

• Botulinum toxin
  • Irreversibly inhibits acetylcholine release from the motor end plates by interfering in the fusion of transmitter-containing vesicles with the presynaptic membrane
  • One of the most potent poisons. The lethal dose is estimated at 70 μg for adults when ingested orally.

Clinical features

• Neurological symptoms
  • Descending paralysis
    • Peripheral flaccid muscle paralysis that descends caudally
    • Typically begins in frequently used muscles
    • Pupils: accommodation paralysis, mydriasis, diplopia
    • Pharynx: dysarthria, dysphagia
  • Autonomic nervous system: xerostomia
  • Infants may present with ptosis, floppy movements, general weakness, and poor feeding (weak sucking)
• Gastrointestinal symptoms: gastrointestinal discomfort, nausea, and vomiting, later followed by constipation
  • Only present in 30% of cases of foodborne botulism
  • Constipation is often the first symptom of infant botulism.
  • Absent in wound botulism

Diagnostics

• Rapidly identify botulinum toxin in samples from serum, vomit, gastric acid, stool, or suspicious foods “

Treatment

• Secure airways
• See the corresponding section for specific treatment measures.

References:^{[1][2][3][4][5]}

• Transmission
  • Ingestion of the botulinum toxin
    • The anaerobic spores survive in canned foods (e.g., home-canned vegetables) and packed meat despite vacuum sealing.
    • Germination of the spores produces dangerous toxins (botulinum toxins = enterotoxins A-F) and gas → bulging cans
• Incubation period: 12–36 hours
• Specific treatment
  • Administer (horse-derived) heptavalent botulism antitoxin
  • Eradication of toxin through bowel emptying (induced by medication)
• Prevention
  • Sterilize food through autoclaving.
  • Food should be boiled twice before being canned to kill spores that may have germinated after the first round of boiling.

References:^[1][3]

• Transmission
  • Ingestion of spores
    • Spores may be present in honey or contaminated soils.
    • Germination of the spores in intestinal tract → synthesis of botulinum toxin
• Incubation period: days to 4 weeks
• Specific treatment
  • Administer IV human botulism immune globulin (BIG-IV)
• Prevention: avoid honey during the first year of life

References:^[3][4]

• Guillain-Barré syndrome: associated with ascending paralysis

References:^[6]

The differential diagnoses listed here are not exhaustive.