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 higher than recommended doses of botulinum toxin (iatrogenic botulism) for therapeutic or cosmetic purposes. Moreover, botulism was once reported after possible inhalation of botulinum toxin in a laboratory setting. Botulism manifests as a clinical syndrome of bilateral cranial-nerve palsies that may progress to respiratory compromise, a descending bilateral flaccid paralysis of voluntary muscles, and even death. Patients exposed to the same contaminated food may have a varying constellation of cranial nerve palsies and varying illness severity. Cases are known to be misdiagnosed or suspected late in a hospital course. The mainstays of therapy are meticulous intensive care and treatment with antitoxin early in the clinical course while alternative diagnoses are still being worked up. Early suspicion of botulism and empirical treatment are critical to favorable clinical outcomes.
ETIOLOGY AND PATHOGENESIS
Seven serologically distinct serotypes of botulinum toxin (A through G) have been confirmed. Botulinum toxin is produced by four recognized species of clostridia: Clostridium botulinum and rare strains of Clostridium argentinense, Clostridium baratii, and Clostridium butyricum. All these species are anaerobic gram-positive spore-forming organisms. 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 >4.5, low salt and sugar concentrations, and temperatures of >3°C. Although commonly ingested, spores do not normally germinate and produce toxin in the adult human intestine.
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 toxin produced from germinating C. botulinum spores that contaminate an abscess or a wound. Infant botulism is caused by 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 rare form that is poorly understood, is believed to have 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. Relapse ...