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INTRODUCTION

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Botulism, recognized at least since the eighteenth century, is a neuroparalytic disease caused by botulinum toxin, one of the most toxic substances known. While initially thought to be caused only by the ingestion of botulinum toxin in contaminated food (food-borne botulism), three additional forms caused by in situ toxin production after germination of spores in either a wound or the intestine are now recognized worldwide: wound botulism, infant botulism, and adult intestinal colonization botulism. In addition to occurring in these recognized natural forms of the disease, botulism symptoms have been reported in patients receiving injections of botulinum toxin for cosmetic or therapeutic purposes (iatrogenic botulism). Moreover, botulism was reported after inhalation of botulinum toxin in a laboratory setting. All forms of botulism manifest as a relatively distinct clinical syndrome of symmetric cranial-nerve palsies followed by descending bilateral flaccid paralysis of voluntary muscles, which may progress to respiratory compromise and death. The mainstays of therapy are meticulous intensive care and treatment with antitoxin as soon as botulism is suspected and before other illnesses have been ruled out.

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ETIOLOGY AND PATHOGENESIS

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Seven serologically distinct confirmed serotypes of botulinum toxin (A through G) have been confirmed. Botulinum toxin is produced by four recognized species of clostridia: Clostridium botulinum, Clostridium argentinense, Clostridium baratii, and Clostridium butyricum. Certain strains may produce more than one serotype. All are anaerobic gram-positive organisms that form subterminal spores; C. botulinum and C. argentinense spores have been recovered from the environment. The spores survive environmental conditions and ordinary cooking procedures. Toxin production, however, requires a rare confluence of product storage conditions: an anaerobic environment, a pH of >4.6, low salt and sugar concentrations, and temperatures of >4°C. Although commonly ingested, spores do not normally germinate and produce toxin in the adult human intestine.

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Food-borne botulism is caused by consumption of foods contaminated with botulinum toxin; no confirmed host-specific factors are involved in the disease. Wound botulism is caused by contamination of wounds with C. botulinum spores, subsequent spore germination, and toxin production in the anaerobic milieu of an abscess or a wound. Infant botulism results from absorption of toxin produced in situ by toxigenic clostridia colonizing the intestine of children ≤1 year of age. Colonization is thought to occur because the normal bowel microbiota is not yet fully established; this theory is supported by studies in animals. Adult intestinal colonization botulism, a very rare form that is poorly understood, has a pathology similar to that of infant botulism but occurs in adults; typically, patients have some anatomic or functional bowel abnormality or have recently used antibiotics that may help toxigenic clostridia compete more successfully against the normal bowel microbiota. Despite antitoxin treatment, relapse due to intermittent intraluminal production of toxin may be observed in patients with adult intestinal colonization botulism.

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Regardless of how exposure occurs, botulinum neurotoxin enters the vascular system and is transported to peripheral cholinergic nerve ...

Evidence

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