Clostridium botulinum
From IDWiki
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 (acute inflammatory demyelinating polyneuropathy): asymmetric, ascending, and involves sensory nerves; or ataxia, in the Miller-Fisher variant that involves cranial nerves
- Tick paralysis: Dermacentor tick still attached
- Polio: febrile and asymmetric
- Others: diphtheria, organophosphate toxicity, brainstem stroke
Diagnosis
- Gold standard is the mouse bioassay
- A mouse is injected with a sample (serum, gastric secretions, stool, or food) and are monitored for paralysis
- Toxin type is determined by administering type-specific antitoxin and monitoring for improvement
- Anaerobic cultures of serum, stool, or food, though low sensitivity
- EMG may show small decrement in motor response or brief small abundant motor unit action potentials (BSAP)
Management
- Call the Botulism Reference Service for Canada (or equivalent): office (613) 957-0902; laboratory (613) 957-0885; after-hours (613) 296-1139
- Supportive care
- Intubation and ventilation if necessary
- Bowel routine including enemas if constipated but without severe ileus
- Antitoxin
- For infants up to 1 year old, BabyBIG (BIG-IV) 50 mg/kg
- Human-derived
- For children over 1 year and adults, heptavalent botulinum antitoxin (HBAT)
- Horse-derived
- Including antitoxins to toxin types A through G
- Risk of sensitization or anaphylaxis to horse proteins
- For infants up to 1 year old, BabyBIG (BIG-IV) 50 mg/kg
- Antibiotics
- May cause more toxin to be released from dying bacteria, so generally avoided
- Aminoglycosides and tetracyclines can worsen the paralysis of infant botulism
Prognosis
- Mortality with appropriate treatment is 5 to 8% in adults and 1% in infants
- Takes weeks to months to recover and may have weakness for more than one year