infectious diseases
Botulism
Introduction
Botulism is poisoning that is due toClostridium botulinumtoxin and that affects the peripheral nerves. Botulism may occur without infection if toxin is ingested, injected, or inhaled. Symptoms are symmetric cranial nerve palsies accompanied by a symmetric descending weakness and flaccid paralysis without sensory deficits. Diagnosis is clinical and by laboratory identification of toxin. Treatment is with support and antitoxin. (See also Overview of Anaerobic Bacteria and is one of several species of clostridia that cause human disease. Botulism is a rare, life-threatening disorder that occurs when botulinum toxin spreads hematogenously and interferes irreversibly with release of acetylcholine at peripheral nerve endings in the Disorders of Neuromuscular Transmission manifesting as weakness. Botulism is a medical emergency and sometimes a public health emergency. C. botulinumelaborates 8 types of antigenically distinct neurotoxins (types A through G and F/A Hybrid). Five of the toxins affect humans: types A, B, E, and rarely F and F/A Hybrid (formerly labeled H). Botulinum toxins are highly poisonous proteins resistant to degradation by gastric acidity and proteolytic enzymes. Type F/A Hybrid is the most potent toxin known. About 50% of food-borne outbreaks in the United States are caused by type A toxin, followed by types B and E. Type A toxin occurs predominantly west of the Mississippi River, type B in the eastern states, and type E in Alaska and the Great Lakes area (type E is frequently associated with ingestion of fish and fish products). Botulism can occur when neurotoxin is elaborated in vivo byC. botulinumor when preformed neurotoxin is acquired in an external source. In vivo elaboration causes the following forms: Wound botulism Infant Botulism (the most common form) Adult enteric botulism (rare) Inwound botulism,neurotoxin is elaborated in infected tissue. Ininfant botulismand inadult enteric botulism,spores are ingested, and neurotoxin is elaborated in the gastrointestinal tract. Predisposing factors for enteric botulism in children ≥ 1 year of age and in adults include previous bowel or gastric surgery, anatomic bowel abnormalities, Crohn disease, inflammatory bowel disease, antimicrobial therapy, and immunosuppressive medications. Acquisition of preformed neurotoxin causes the following forms: Food-borne botulism Iatrogenic botulism Inhalation botulism Infood-borne botulism,neurotoxin produced in contaminated food is eaten. Iniatrogenic botulism,type A or B toxin is injected therapeutically to relieve excess muscle activity; rarely, botulism has occurred after cosmetic injections (with botulinum toxin). Ininhalation botulism,toxins becomes aerosolized either accidentally or when intentionally used as a bioweapon; aerosolized toxins do not occur in nature. C. botulinumspores are highly heat-resistant and may survive boiling for several hours at 100°C. However, exposure to moist heat at 120°C for 30 minutes kills the spores. Toxins, on the other hand, are readily destroyed by heat, and cooking food at 80°C for 30 minutes safeguards against botulism.C. botulinumcan produce type E toxin at temperatures as low as 3°C (ie, inside a refrigerator—for example, in vacuum-packed smoked fish). C. botulinumcan produce type E toxin at temperatures as low as 3°C, so if food is contaminated, refrigeration is not protective. 