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BotulismAutor: Marcelo Moraes Gazola, MD |
Botulism is a neurologic disease caused by the exotoxin that is produced by some clostridial species; especially Clostridium botulinum. The disease is characterized by the paralytic involvement of cranial nerves, followed by a caudal progression of the symptoms and leading to paralysis of the extremities.
It can be divided into five categories: food-born botulism, caused from the ingestion of food contaminated with the preformed toxin; wound botulism, caused from the production of toxin on a wound contaminated by the bacteria; infant botulism, caused by the production of botulinum toxin in vivo after colonization of an infant's intestine by C. botulinum; adult infant botulism for older children and adults, caused by the same mechanism of infant botulism; and unclassified cases, including persons over 12 months old who have clinical manifestations of botulism without any identifiable source of contamination.
Clostridium botulinum is a gram-positive, spore forming obligate anaerobe, found worldwide in soil, dust, marine sediments, and many fresh, cooked agricultural products. The spores of C. botulinum are very resistant and survive boiling for several hours, which enables the bacteria to survive attempts at food preservation. In contrast, botulinum toxin is heat labile and easily destroyed by heating at 80°C for 5-10 min.
Each strain of C. botulinum produces a antigenically distinct toxin, designated A trough H. All are neurotoxins, and human disease is caused by toxin types A, B, E, F, and G. Aside from C. botulinum, other clostridial species, such as C. butyricum and C. barati also produce botulinum toxin and, therefore can cause botulism.
Botulinum toxin is the most poisonous substance known. It enters the vascular system independently whether ingested, produced at a wound or at the intestines. After its hematogenous dissemination, the toxin reaches the peripheral cholinergic nerve terminals, where it binds irreversibly inhibiting acetylcholine release, resulting in hypotonia with a descending symmetric flaccid paralysis. The central nervous system is spared.
Human botulism occurs worldwide. The food-borne type can occur when a food to be preserved is contaminated with spores; or the preservation does not inactivate the spores, but rather kills other putrefactive bacteria that would have otherwise inhibited the growth of C. botulinum (also providing anaerobic ideal conditions for germination and toxin production); or food is not heated at a temperature that would destroy the neurotoxin it is eaten. The most common vehicle implicated with this kind of botulism in the United States is in home canned foods, such as peppers, olives, aspargus, and beans. The disease occurs generally when the food, usually with a putrefactive odor, is tasted to verify if it is rotten or not. Meat and meat products are more commonly responsible in Europe, and preserved fish is most frequent in Japan, Scandinavia, and Russia.
Wound botulism has been implicated in wounds contaminate with soil; in chronic drug abusers; and in cesarean delivery. It is a rare form of the disease with approximately only 100 cases reported worldwide. Most cases have occurred in young males, who are at the greatest risk of traumatic injury.
Infant botulism is another uncommon form of botulism, and it is often not recognized. It occurs after the colonization of the gastrointestinal system in children between 1 and 9 months old. Identified risk factors for the illness include the ingestion of honey and a slow intestinal transit time (less than one stool per day). Breast feeding appears to protect against the fulminant death from botulism. Under rare circumstances, such as altered intestinal anatomy, physiology, and microflora, older children and adults may develop the adult-infant form of botulism.
Food-born botulism: After the ingestion of contaminated food, the illness varies from mild, which needs no medical attention; to severe disease, which can result in death in less than 24 hours. The incubation period is usually 18 to 36 hours, but may range from a few hours to many days depending on the amount of toxin ingested. The shorter the incubation period, the more severe the clinical manifestations are. The onset of the symptoms is characterized by cranial nerve involvement, mainly in those innervating the bulbar musculature. This results in the appearance of diplopia, difficulty in close-range focusing, dysphonia, dysartria, and dysphagia. The weakness progresses rapidly to involve the neck, shoulder, thorax, abdomen, arms, and legs. Nausea, vomiting, and abdominal pain may appear before or after the onset of paralysis. The weakness is usually symmetric, but may be asymmetric as well. Autonomic involvement may cause dizziness, blurred vision, dry mouth, very dry and sore throat, ileus, and salivary retention. The tendon reflexes may be normal, but are usually diminished. The pupillary reflexes are depressed, and the pupils may be fixed and dilated. The patient is alert and conscious, and mentation is spared. The gag reflex is also diminished or abolished. Typically there is no fever, but the descending paralysis also attacks the respiratory muscles. This, along with bulbar paralysis and secondary infections, is the main cause of death together.
Wound botulism: This form of botulism appears after a wound is contaminated by the spores of C. botulinum, which is found in soil. The spores then germinate into vegetative forms that produce toxin. The period of incubation for this form of botulism is longer, ranging from 4 to 14 days, with a median average of 10 days. The clinical manifestations are identical to the food-borne botulism, with the exception of gastrointestinal symptoms. The illness occurs even after preventative antibiotics are administered.
Infant botulism: This usually differs in apparent initial symptoms of the illness, simply because infants cannot verbalize them. Almost invariably, the first indication of illness is constipation, defined as three or more days without defecation. Parents usually notice lethargy, listlessness, poor appetite, a weak cry, and diminished movements. Dysphagia may be seen as "drooling" from the mouth. Gag, suck, and corneal reflexes diminish as paralysis advances. Oculomotor palsies also occur. The pupillary reflex may be spared until the child is severely ill. Loss of head control is a prominent sign, and respiratory arrest may occur suddenly.
Adult-infant botulism: In this form of botulism the clinical manifestations are the same as mentioned above. The disease affects adults and children, who are older than 12 months old, by the C. botulinum colonization of the intestines. It is there that the disease-causing toxin is produced.
Botulism should be suspected in any mentally intact patient who has an afebrile, descending paralysis without sensory manifestations. In these cases analysis (searching for C. botulinum or its toxin) of serum, stool, gastric contents or vomit, food, and wounds is necessary.
The demonstration of the toxin in serum is definitive, but the test may be negative, particularly in infant or wound botulism. The demonstration of toxin or the organism in vomit, gastric fluid, or stool is strongly suggestive, because intestinal carriage is rare. Isolation of the organism from food without the toxin is insufficient for the diagnosis. Wound cultures showing the organism are suggestive. Cerebrospinal fluid examination is normal, unless dehydration or starvation are present. The electromyography may demonstrate a defect in neuromuscular transmission, and a typical finding is facilitation (potentiation) of the evoked muscle action potential at high frequency stimulation.
The differential diagnosis that should be elicited in food-born and wound botulism are: acute gastroenteritis, myasthenia gravis, Guillain-Barré syndrome, organophosphate poisoning, meningitis, encephalitis, psychiatric illness, cerebrovascular accident, poliomyelitis, hypothyroidism, hypocalcemia, hypermagnesemia, carbon monoxide poisoning, inflammatory myopathy, and aminoglycoside-induced paralysis.
On dealing with infant and adult-infant botulism it should be differentiated with: Guillain-Barré syndrome, myasthenia gravis, disorders of amino-acid metabolism, hypothyroidism, drug ingestion, brain stem poisoning, poliomyelitis, viral polyneuritis, Hirshprung disease, metabolic encephalopathy, dehydration, and sepsis.
Any patient suspected of having botulism should be hospitalized and monitored closely-both clinically and by spirometry, pulse oximetry, and measurement of arterial blood gases to prevent respiratory failure. Intubation and mechanical ventilation should be considered when vital capacity falls below 30% of prediction-especially when paralysis is progressing rapidly and hypercarbia is present.
In food-borne illness, trivalent antitoxin should be administered as soon as possible after material for laboratory analysis is obtained. Since the toxin may persist in the blood for extended periods, the antitoxin should be given irrespectively to the time of progression of the illness. One should not wait for laboratory confirmation before initiating treatment. After testing for horse serum hypersensitivity, two vials of trivalent antitoxin, containing 7500I of type A, 5500I of type B, and 8500I of type E should be administered; one intravenously, and another intramuscularly. This dose may be repeated 2 to 4 hours later. Hypersensitivity reactions may occur since the antitoxin is made of horse serum. Anaphylaxis and serum sickness are feared reactions, and allergic patients should be desensitized prior to the administration. If there is no ileus, cathartics and enemas should be given to eliminate toxin from the gut. Emetics and gastric lavage are also used if the ingestion of the contaminated food has been recent within a few hours. Other therapeutic considerations are the use of guanidine hydrochloride (15 to 50mg/kg daily), to enhance acetylcholine release, and antibiotics (penicillin), to eliminate the bacteria from the intestine.
In the infant botulism neither the antitoxin, nor antibiotics have shown to be beneficial. Supportive care is the basis for the treatment, along with nutrition maintenance and ventilatory support. The wound botulism requires the same treatment given to one that is food-borne. It is also necessary to make wound debridement, and to eradicate the C. botulinum in the wound by administering penicillin. It is not necessary to eradicate the bacteria from the gut, because no C. botulinum, in this instance, is infecting the gastrointestinal system.
In the absence of complications, the prognosis is a full and complete recovery. However, if complications appear, the prognosis is a little worse. The lethality rate is only 10% when intensive supporting measures are taken. The surviving patients usually have a complete recovery, and only some cases of adults have reported subsequent chronic weakness.
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4.BARTLETT, John G. Botulism. In: BENNET, J Claude & PLUM, Fred. Cecil Textbook of Medicine. 20th ed. W.B. Saunders Co., 1996.
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