Question

A housewife fixed lunch for herself and two others. The lunch consisted of home-canned gefilte fish (served cold with horseradish on toast) soft drinks and milk. She ate two portions of gefilte fish, her employee ate one portion and her daughter-in-law ate half a portion. Four hours later, she complained of headache, epigastric distress, hoarseness and slight dyspnea. The epigastric distress continued. She vomited repeatedly and experienced dryness of the mouth, weakness, constipation, and urinary retention. Examination by a physician revealed an anxious woman with labored respirations (26 per minute); a blood pressure of 80/58 mm Hg, and a pulse rate of 110 beats per minute. The pupils were equal in size but somewhat dilated; they were reactive to light. Extraocular eye movements were normal, and no facial weakness was noted. Her throat and mouth were dry, and her voice was hoarse. The chest was normal to auscultation and to percussion. The abdomen was soft and nontender, with decreased bowel sounds. Deep tendon reflexes were normal. Because of a history of mild hypertension, the findings of tachycardia and hypotension and the history of substernal distress suggested the possibility of a myocardial infarction. The patient was hospitalized. Lab findings included normal results for a complete blood cell count and urinalysis. Values of serum electrolytes, bilirubin, amylase, and protein determined on serum from blood drawn the morning after admission were all within normal limits. Chest and abdominal X-ray films were interpreted as normal. An EKG was unchanged from previous tracings. The patient was treated symptomatically with antacids, nasogastric suction, and intravenous administration of fluids. Three days later the patient had a cardiopulmonary arrest and was resuscitated. Spontaneous respiration did not occur, and breathing was maintained on a mechanical respirator. No apparent benefit resulted from 80,000 units of bivalent (types A & B) and 10,000 units of type E antitoxin, which were administered intravenously. The next day the patient died. Autopsy showed generalized ischemic changes in the central nervous system and moderate arteriosclerosis of the coronary arteries with slight hypertrophy of the left ventricle. The liver and the spleen were enlarged and hyperemic. The lungs showed pulmonary edema with focal acute bronchopneumonia. The other two patients survived the infection.

Answer 1

Type E botulism occurred in three patients, one of whom died. The most prominent feature in all three cases was severe gastrointestinal symptoms (vomiting and abdominal discomfort without diarrhea), which diverted attention from the less prominent and more slowly developing neurological signs. The botulinus toxin was traced after eating home-prepared gefilte fish is a dish made from a poached mixture of ground deboned fish such as carp,whitefish etc, from three patients at a common meal. Lethal quantities of type E botulinus toxin were found in extracts of leftover gefilte fish, and Clostridium botulinum type E was recovered from cultures of the food. The incriminated food, which was eaten cold.

Botulism

Clostridium botulinum is a bacterium that produces dangerous toxins (botulinum toxins) under low-oxygen conditions.
Botulinum toxins are one of the most lethal substances known.
Botulinum toxins block nerve functions and can lead to respiratory and muscular paralysis.
Human botulism may refer to foodborne botulism, infant botulism, wound botulism, and inhalation botulism or other types of intoxication.
Foodborne botulism, caused by consumption of improperly processed food, is a rare but potentially fatal disease if not diagnosed rapidly and treated with antitoxin.
Homemade canned, preserved or fermented foodstuffs are a common source of foodborne botulism and their preparation requires extra caution.
Foodborne botulism is a serious, potentially fatal disease. However, it is relatively rare. It is an intoxication usually caused by ingestion of potent neurotoxins, the botulinum toxins, formed in contaminated foods. Person to person transmission of botulism does not occur.Spores produced by the bacteria Clostridium botulinum are heat-resistant and exist widely in the environment, and in the absence of oxygen they germinate, grow and then excrete toxins. There are 7 distinct forms of botulinum toxin, types A–G. Four of these (types A, B, E and rarely F) cause human botulism. Types C, D and E cause illness in other mammals, birds and fish.Botulinum toxins are ingested through improperly processed food in which the bacteria or the spores survive, then grow and produce the toxins. Though mainly a foodborne intoxication, human botulism can also be caused by intestinal infection with C. botulinum in infants, wound infections, and by inhalation.

Symptoms of foodborne botulism

Botulinum toxins are neurotoxic and therefore affect the nervous system. Foodborne botulism is characterized by descending, flaccid paralysis that can cause respiratory failure. Early symptoms include marked fatigue, weakness and vertigo, usually followed by blurred vision, dry mouth and difficulty in swallowing and speaking. Vomiting, diarrhoea, constipation and abdominal swelling may also occur. The disease can progress to weakness in the neck and arms, after which the respiratory muscles and muscles of the lower body are affected. There is no fever and no loss of consciousness.The symptoms are not caused by the bacterium itself, but by the toxin produced by the bacterium. Symptoms usually appear within 12 to 36 hours (within a minimum and maximum range of 4 hours to 8 days) after exposure. Incidence of botulism is low, but the mortality rate is high if prompt diagnosis and appropriate, immediate treatment (early administration of antitoxin and intensive respiratory care) are not given. The disease can be fatal in 5 to 10% of cases

Exposure and transmission

Foodborne botulism

C. botulinum is an anaerobic bacterium, meaning it can only grow in the absence of oxygen. Foodborne botulism occurs when C. botulinum grows and produces toxins in food prior to consumption. C. botulinum produces spores and they exist widely in the environment including soil, river and sea water.The growth of the bacteria and the formation of toxin occur in products with low oxygen content and certain combinations of storage temperature and preservative parameters. This happens most often in lightly preserved foods and in inadequately processed, home-canned or home-bottled foods.C. botulinum will not grow in acidic conditions (pH less than 4.6), and therefore the toxin will not be formed in acidic foods (however, a low pH will not degrade any pre-formed toxin). Combinations of low storage temperature and salt contents and/or pH are also used to prevent the growth of the bacteria or the formation of the toxin.The botulinum toxin has been found in a variety of foods, including low-acid preserved vegetables, such as green beans, spinach, mushrooms, and beets; fish, including canned tuna, fermented, salted and smoked fish; and meat products, such as ham and sausage. The food implicated differs between countries and reflects local eating habits and food preservation procedures. Occasionally, commercially prepared foods are involved.Though spores of C. botulinum are heat-resistant, the toxin produced by bacteria growing out of the spores under anaerobic conditions is destroyed by boiling (for example, at internal temperature greater than 85 °C for 5 minutes or longer). Therefore, ready-to-eat foods in low oxygen-packaging are more frequently involved in cases of foodborne botulism.Food samples associated with suspect cases must be obtained immediately, stored in properly sealed containers, and sent to laboratories in order to identify the cause and to prevent further cases.

Diagnosis and treatment:

Diagnosis is usually based on clinical history and clinical examination followed by laboratory confirmation including demonstrating the presence of botulinum toxin in serum, stool or food, or a culture of C. botulinum from stool, wound or food. Misdiagnosis of botulism sometimes occurs as it is often confused with stroke, Guillain-Barré syndrome, or myasthenia gravis.Antitoxin should be administered as soon as possible after a clinical diagnosis. Early administration is effective in reducing mortality rates. Severe botulism cases require supportive treatment, especially mechanical ventilation, which may be required for weeks or even months. Antibiotics are not required (except in the case of wound botulism). A vaccine against botulism exists but it is rarely used as its effectiveness has not been fully evaluated and it has demonstrated negative side effects.

Prevention:

Prevention of foodborne botulism is based on good practice in food preparation particularly during heating/sterilization and hygiene. Foodborne botulism may be prevented by the inactivation of the bacterium and its spores in heat-sterilized (for example, retorted) or canned products or by inhibiting bacterial growth and toxin production in other products. The vegetative forms of bacteria can be destroyed by boiling but the spores can remain viable after boiling even for several hours. However, the spores can be killed by very high temperature treatments such as commercial canning.

Commercial heat pasteurization (including vacuum packed pasteurized products and hot smoked products) may not be sufficient to kill all spores and therefore the safety of these products must be based on preventing bacterial growth and toxin production. Refrigeration temperatures combined with salt content and/or acidic conditions will prevent the growth of the bacteria and formation of toxin.

The WHO Five Keys to Safer Food serve as the basis for educational programmes to train food handlers and educate the consumers. They are especially important in preventing food poisoning.

The Five Keys are:

1. Keep clean
2. Separate raw and cooked
3. Cook thoroughly
4. Keep food at safe temperatures
5. Use good water and raw materials.