Clostridium botulinum

Background

Microbiology

• Gram-positive anaerobic bacillus with a subterminal spore
• Diverse species whose defining trait is the production of botulinum toxin
• Subdivided into four groups based on biochemical tests
• These strains produce eight toxin types, A through H, that are identified by serology; some strains produce two different toxins

Pathophysiology

• Botulinum toxins are zinc-dependent metalloproteinases, and inhibit the release of acetylcholine from the presynaptic neuron

Clinical Presentation

• Typically involves symmetric descending paralysis, starting with cranial nerves and often involving respiratory muscles
• Afebrile with normal or slow heart rate despite hypotension, and sparing the sensory nerves
• This presentation contrasts with polio, which can be asymmetric and often has fever

Foodborne botulism

• Symptoms start 12 to 36 hours after ingestion
• Nausea, diarrhea, and dry mouth
  • Of note, diarrhea is not caused by the toxin but by other ingested contaminants

Wound botulism

• Incubation period of t to 14 days
• May have fever secondary to an infected wound, although the wound can rarely appear to be healing well
• Can produce abscesses

Infant botulism

• Classically after ingesting unpasteurized honey
• Feeding difficulties, hypotonia, drooling, and weak cry
• Descending paralysis, including upper airway obstruction that may require intubation
• Distinguishing features are lack of fever, normal CSF
• Typically worsens over 1 to 2 weeks, then stabilizes for 2 to 3 weeks, then recovers
• Relapses are possible

Adult intestinal toxemia

• Rare form of botulism associated with colonisation of the GI tract
• Onset is more gradual and disease less severe than foodborne botulism
• Risk factors are gastrointestinal surgery or illness, such as inflammatory bowel disease

Differential Diagnosis

• Myasthenia gravis: lacks autonomic features
• Lambert-Eaton myasthenic syndrome
• Guillain-Barré syndrome