Pathophysiology, clinical presentation, and management of botulism
Clostridium botulinum is a large, gram-positive, strictly anaerobic bacillus that primarily exists as a spore until environmental conditions suitable for germination arise. C botulinum spores are found throughout the world in soil samples and marine sediments.
The species is divided into 4 genetically diverse groups that share the common ability to produce botulinum toxin. Seven serologically distinct neurotoxins are produced by C botulinum, designated letters A to G. Human disease is attributed to toxin types A, B, E, and, less commonly, F.
Clinical botulism results from the entry of botulinum toxin into the systemic circulation and subsequent inhibition of acetylcholine release from the presynaptic nerve terminal. The toxin enters the circulation through the mucosa (foodborne and inhalational) or via a break in the skin (wound and iatrogenic). In infants, absorption occurs due to absence of competing normal flora.
Once absorbed into the bloodstream, the toxin is carried to the synapses of peripheral and cranial nerves. As a result, stimulation of the presynaptic cell fails to produce transmitter release, resulting in motor paralysis or autonomic dysfunction when parasympathetic nerve terminals or autonomic ganglia are involved.
Ingestion of food contaminated with botulinum toxin
Wound contamination by Clostridium botulinum spores
Inhalation of aerosolised botulinum toxin does not occur in nature and suggests an act of bioterrorism
Symptoms of botulism as a consequence of toxin use for cosmetic or therapeutic purposes
Results from exposure in the first year of life to contaminated soil, dust, or food sources
Early signs: Oculobulbar weakness, impaired accommodation, ptosis, hypoglossal weakness
Late signs: Descending symmetrical paralysis, diminished deep tendon reflexes, respiratory dysfunction, pupillary dilation (<50% of cases)
Conventional diagnosis of botulism relies on the demonstration of toxin in serum, gastric secretions, stool, or food samples.
Supportive care is the mainstay of botulism therapy. Patients with suspected or confirmed botulism should undergo serial vital capacity assessments in the intensive care unit. In addition, patients should be assessed for the adequacy of gag and cough reflexes, control of oropharyngeal secretions, oxygen saturation, and inspiratory force. Mechanical ventilation should be considered for any patient with upper airway compromise (due to pharyngeal muscle paralysis) or a decline in vital capacity.
Swift administration of botulism antitoxin is essential in the management of botulism cases. In the UK, antitoxin is available from local designated centres (www.toxbase.org), otherwise accessed outside working hours by telephoning the duty doctor at Public Health England. Detailed instructions on administration are provided with each dose.
| Type | Source/Transmission | Incubation Period | Unique Features |
|---|---|---|---|
| Foodborne | Preformed toxin in contaminated food | 2-36 hours | Gastrointestinal symptoms early in illness |
| Wound | Spore contamination of wounds | 4-14 days | No GI symptoms; requires wound debridement |
| Infant | Spore ingestion and colonization | Variable | Constipation initial symptom; requires BabyBIG |
| Inhalational | Aerosolized toxin (bioterrorism) | 12 hours-5 days | Rare; considered bioterrorism event |
| Iatrogenic | Medical/cosmetic toxin use | Variable | Related to therapeutic botulinum toxin |