Botulism and Clostridia Species Review

Clostridia species and toxins

  • C. botulinum produces serotypes A through H
  • C. baratti → toxin F
  • C. batyricum → toxin E
  • C. argentinense → toxin G

Clostridia species review

  • Types
    • Type A = West of Mississippi (0-7 day incubation)
    • Typer B = East of Mississippi (0-5 day incubation)
      • A/B process meat/vegetables – smells putrified
    • E – ALASKA -> Raw fermented fish/animals (food looks and tastes NORMAL) (incubation 0-2 days)
    • Most cases A, B, E or F
  • All spores resistant to heat, pH >4.5, NaCl content < 3.5%, low nitrite content
  • Toxin is protected from gastric pH by complexing with hemagluttinins that protect it from proteolytic environment – then dissociates in alkaline intestine (or PPI/H2RA)
  • Toxin is heat labile
  • BoNT most potent toxin known (LD50 1 mcg). Inhaled botulinum toxin 100 times more potent than ingested.
  • Iatrogenic botulism- Synthetic pharm agents: Patients develop neutralizing antibodies from long term use
  • Wound botulism – black tar heroin “skin popping”

MOA/Clinical Manifestations

  • Dichain toxin binds to the peripheral cholinergic nerve terminal
  • Impairs transmission at ACh dependent synapses at PNS
  • Delayed onset (12-24 hours)- if rapid onset, consider (ciguatera, TTX)
  • NO CNS involvement (ddx Miller-fisher variant of myasthenia gravis)
  • 1st sx is GI distress – occurs within a few hours, but not bad enough to seek medical attention
  • Followed by neuro: horizontal diplopia, b/l symmetric descending flaccid paralysis), constipation 
  • 12 D’s = dry mouth, diplopia, dilated pupils, droopy eyes (ptosis), droopy face, diminished gag reflex, dysphagia, dysarthria, dysphonia, difficulty lifting head, descending paralysis, diaphragmatic paralysis.
  • ALASKA has 5 D’s: dilated pupils, diplopia, dry throat, dysphagia, n/v.
  • Infant Bot – ingestion of spores – germinate in GI. Also exposure to dust @ sites where soil is disrupted, farming, plant nursery or plumbing.Can cause SIADH
  • Almost always A or B
  • 1st sx – constipation, difficulty feeding/sucking, febile cry, diffusely decreased muscle tone
  • Rare in adults but can be if: GI pH increased


  • Edrophonium testing (inh ACh metabolism): Positive response = myasthenia gravis/ miller-fisher variant of Guillain Barre; negative response = botulism (since it prevents the release of ACh)
  • Electrophysiologic testing: in all forms of Botulism, sensory nerve potentials are normal
  • Labs: anaerobic culture and mouse bioassay for BoNT. Mouse lethality test is the gold standard (serum, stool or food sample): 2 sets of mice inj with sample from patient: one control and one pretreated with antitoxin
  • Negative inspiratory force (NIF) MOST reliable, rabidly obtainable for determining need for intubation: intubate if NIF < minus 30 cm H20
  • DDX: Tick paralysis, hypokalemia, elapid envenomation


  • Should be initiated based on clinical suspicion and NOT wait for testing
  • AC+Sorbitol (due to decreased GI motility)
  • H-BAT – heptavalent botulinum antitoxin (equine) A through G
    • Doesn’t reverse paralysis
    • Dose: 1 vial diluted 1:10 in NS over 60 min
    • Used for all adult forms of bot: wound, iatrogenic, intestinal toxemia. Can be used for infant if not responding to BIG or non A/B type
  • Botulism immune globulin (BabyBIG) A+B only.
    • Must use H-BAT in infants for non A/B
    • Single dose, no repeat dosing


For more chapters, visit the ABAT Study Guide homepage

Botulism and Clostridia Species Review