Biotoxins
Common Characteristics
- Are by-products of bacteria or naturally occurring chemicals
- Do not replicate within the host
- Are not communicable
- LD50 is quite low
- Can produce significant life-threatening disease when delivered as an aerosol
Clostridium botulinum Neurotoxin
- Three naturally occurring forms are recognized: food-borne, wound, and infant
- Inhalation botulism could occur if toxin is intentionally delivered as an aerosol
- The neurotoxin binds presynaptically to the cholinergic nerves blocking the release of acetylcholine producing severe neuromuscular paralysis
- Early symptoms include ocular paresis, rotatory nystagmus, dilated pupils, dysarthria, ataxia, and generalized weakness
- Clinical pearl: A young person presenting with difficulty swallowing and speaking who has not suffered a cerebral vascular accident is most likely to have botulism
- Electromyography may help to establish the diagnosis and a rabbit bioassay is available for confirmation
- The antitoxin is active against serotypes A, B, and E
- Treatment must be initiated when disease is suspected, without waiting for laboratory confirmation
- Trivalent antitoxin will prevent progression but will not reverse paralysis once it occurs
- Antibiotics are not indicated for inhalational botulism
Ricin
- A toxin that is derived from the castor bean, Ricinis communis
- Following inhalation, symptoms occur after 8 hours producing a necrotizing pnuemonitis and pulmonary edema
- After parenteral administration:
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- Local pain
- Fifteen to 24 hours later, nausea, vomiting, fever, and localized lymphadenopathy proximal to the injection
- After 48 hours, a sepsis-like syndrome occurs with hypotension, leukocytosis, DIC, multi-organ system
- Diagnosis may be confirmed by an ELISA assay
- Treatment is supportive:
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- A formalin-treated toxoid has had preclinical testing and may be available through the CDC as an Investigational New Drug
Staphylococcal Enterotoxin B (SEB)
- A superantigen that stimulates the major histocompatibility complex, producing a multi-system disease resembling sepsis:
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- Examples include toxic shock syndrome and staphylococcal food poisoning
- SEB is considered an incapacitating agent, although it can be lethal to some exposed victims
- After aerosolized exposure, respiratory symptoms predominate:
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- Within 10 hours, non-productive cough, dyspnea, orthopnea occur
- Headache, chest pain, myalgias, nausea, and vomiting can also occur
- An elevated white blood cell count, hypoxia, and a chest x-ray consistent with pulmonary edema may be seen
- Most symptoms resolve within 24 to 36 hours, but exertional dyspnea may persist for 10 days
- The SEB toxin may be detected on nasal swabs early in the course of the illness
- For rapid detection, a PCR amplification is available from the CDC
- Treatment is supportive:
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- Since sepsis and pneumonia are in the differential diagnosis, antibiotics should be administered pending confirmatory tests
Trichothecene Mycotoxin (T-2)
- A mycotoxin that inhibits DNA and protein synthesis and, to a lesser extent, RNA synthesis
- Trichothecene occurs naturally in nature and can be manufactured in large quantities
- The toxin is rapidly taken up across the pulmonary and gastrointestinal mucosa and more slowly through the skin
- Skin exposure causes burning, blistering, petechiae, and ecchymoses
- Ocular exposure can cause burning and corneal opacification
- Respiratory exposure causes cough, pleuritic chest pain, dyspnea, and hemoptysis
- Gastrointestinal symptoms include hematemesis, abdominal pain, and bloody diarrhea
- Diagnosis can be suspected when exposure to a yellow oily liquid occurs, followed by the constellation of symptoms described
- Environmental or biological samples can be used for confirmation using gas chromatography-mass spectrometry
- Emergency measures include immediate skin decontamination with soap and water and isolation of contaminated clothes
- Treatment is supportive
B. Zane Horowitz, MD, FMACT
Oregon Poison Center
Oregon Health Sciences University
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