Microbiology, Epidemiology, and Pathogenesis 
Botulism is a paralytic disease caused by neurotoxins elaborated by Clostridium botulinum, an anaerobic spore-forming gram-positive bacterium, as well as a few other toxigenic Clostridium spp.
- Botulism is caused by the toxin's inhibition of acetylcholine release at the neuromuscular junction through an enzymatic mechanism.
- - C. botulinum toxin types A, B, E, and (rarely) F cause human disease, with toxin type A causing the most severe syndrome.
- Toxin type E is associated with foods of aquatic origin.
- Transmission is usually due to consumption of foods contaminated with botulinum toxin, but contamination of wounds with spores also can result in disease.
- Most U.S. food-borne cases (average, 20 cases per year) are associated with home-canned food.
- Infant botulism results from toxigenic clostridial colonization of the intestine of children <1 year of age and is the most common form of the disease in the United States, with ∼80-100 cases reported annually.
- Toxin is heat-labile, and spores are heat-resistant; these properties underscore the importance of properly heating foods.
- Botulinum toxin is among the most toxic substances known and thus is of concern as a potential weapon of bioterrorism.
Botulism occurs naturally as four syndromes: (1) food-borne illness; (2) wound infection; (3) infant botulism; and (4) adult intestinal toxemia, which is similar to infant botulism. The disease manifests as bilateral cranial-nerve palsies (diplopia, dysarthria, dysphonia, ptosis, facial paralysis, and/or impaired gag reflex) that may progress to respiratory compromise, bilateral descending flaccid paralysis of voluntary muscles, and even death. Constipation due to paralytic ileus is often noted, and fever is usually absent.
- Food-borne botulism occurs 8-36 h (or up to 10 days, depending on the dose) after ingestion of food contaminated with toxin and ranges in severity from mild to fatal (within 24 h). Nausea, vomiting, and abdominal pain may precede or follow the onset of paralysis.
- Wound botulism occurs when spores contaminate wounds and germinate, with an incubation period of 4-17 days.
- In infant botulism and adult intestinal toxemia, spores germinate in the intestine and produce toxin, which is absorbed and causes illness. This form in infants has been associated with contaminated honey; thus, honey should not be fed to children <12 months of age. Adult pts typically have some anatomic or functional bowel abnormality or have a bowel microbiota disrupted by recent antibiotic use.
The clinical symptoms suggest the diagnosis. The definitive test is the demonstration of the toxin in clinical specimens (serum, stool, gastric aspirates, wound material) and food samples.
- This test may yield a negative result even if the pt has botulism, particularly if specimens are collected >7 days after symptom onset; additional tests (e.g., culture of stool or wound material for toxigenic clostridia) may be necessary.
- The temporal occurrence of two or more cases with botulism-compatible symptoms is essentially pathognomonic, as other botulism-like illnesses do not typically occur in clusters.
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Botulism
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