Clostridium botulinum is a spore-forming, strictly anaerobic that means they live and grow in low oxygen environments, and gram-positive bacteria. The Clostridium botulinum bacteria remain dormant in the form of spores when conditions for survival are poor. The spore contains a small amount of all essential components of Clostridium botulinum, and has a thick protective coat that is responsible for the high resistance of spores to heat, radiation, chemicals, and dehydration. Spores are metabolically inactive. By forming spore, Clostridium botulinum is able to survive for many years. Both of bacteria and spores of Clostridium botulinum are found in the soil and marine sediments throughout the world, most commonly found in the form of spores. Though spores are harmless, upon exposure to suitable envionments, spores germinate into active Clostridium botulinum that can cause disease.
Diseases producing Clostridium botulinum:
Clostridium botulinum produces three clinical forms of botulism:
- Food borne botulism
- Infant botulism
- Wound botulism
Mode of transmission:
Spores of Clostridium botulinum contaminate vegetables, fruits, meats, and sea food from soil and marine sediments. When these foods are canned or vaccum- packed without adequate sterilization, spores of Clostridium botulinum survive within the canned food. The canning process remove the oxygen from jar, creating a low oxygen environment that allows the spores to germinate into active Clostridium botulinum. These active bacteria produce a most potent neurotoxin known as botulinum toxin within the canned food that causes food borne botulism.
Sometimes, ingestion of contaminated foods with spores of Clostridium botulinum may cause colonization of the spores in the large intestine of infant, germinate into active bacteria and produce botulinum toxin within intestine that cause infant botulism. Contaminated honey is one of the common cause of infant botulism.
Rarely, spores of Clostridium botulinum may contaminate a wound, germinate into active form under anaerobic condition, and produce botulinum toxin at the site of wound that producing wound botulism.
Common risk foods responsible for Clostridium botulinum infection:
The highest- risk foods are (a) home canned alkaline vegetables such as green beans, mushrooms, and peppers (b) smoked or pickled fish and (c) home-made cheese. Usually, low acidic foods (PH above 4.6) can support the spores to geminate into active Clostridium botulinum and toxin production.
How Clostridium botulinum produces botulism?
Botulinum toxin, whether ingested with contaminated food, or produced in the gastrointestinal tract or a wound, enters the blood circulation and is transported to peripheral nerve synapses, where it blocks the release of neurotransmitter acetylcholine. The neurotransmitter acetylcholine acts as a chemical messenger. Nerve cells of our body utilized this acetylcholine to communicate with each other, and also utilized to communicate with muscles. When the neurotransmitter acetylcholine is depleted, the nerve cells cannot send signal to muscles for contraction. As a result, flaccid type of paralysis is developed.
Usually symptoms of food borne botulism appear about 12 – 36 hours after ingestion of toxin and may progress for several days. The prominent symptoms are double vision, blurring of vision, dilated pupil, dropping of upper eyelid, nasal speech, difficulty in swallowing, and difficult and defective speech. Muscle weakness and paralysis starting from face, then involve neck, arms, chest, and legs. If the chest muscles and diaphragmatic muscles become paralyzed, breathing difficulty developed and the patient may dies from respiratory failure. Sometimes gastrointestinal symptoms such as abdominal pain, nausea, and vomiting may follow the onset of paralysis.
In infant botulism, symptoms appear about 3-30 days after ingestion of spores of Clostridium botulinum. The severity of symptoms ranges from mild illness to severe paralysis with respiratory failure.
In wound botulism, symptoms occur averaging about 10 days after exposure to Clostridium botulinum. Symptoms of wound botulism are same as food borne botulism except the gastrointestinal symptoms are lacing.
Laboratory diagnosis involves the following;
- Botulinum toxin in affected person’s serum can be demonstrated by mouse inoculation test.
- The demonstration of Clostridium botulinum or its toxin in uneaten food, gastric juice, vomitus, stool, or wound is suggestive of diagnosis.
Patients should be admitted to a hospital and monitored closely. Intravenous fluids or nasogastric feeding should be given if swallowing difficulty developed. Intubation and mechanical ventilation should be considered when respiratory paralysis developed. Antitoxin should be given as soon as possible, ideally within 24 hours of the onset of symptoms to arrest progression of disease. Administration of antitoxin should not be delayed for laboratory confirmation of diagnosis. In infant botulism, requires human botulism immunoglobulin. Neither antitoxin nor antibiotics have been shown to be beneficial in infant botulism.
A pentavalent vaccine is available to prevent the disease. Proper sterilization of all canned and vacuum-packed foods is essential. All home-canned foods must be adequately cooked to inactivate the toxin. The toxin of Clostridium botulinum is relatively heat-labile; it is inactivated by exposure to a temperature of 100oC for 10 minutes. Spores of Clostridium botulinum are highly resistant to heat but can be inactivated by exposure to high temperature (116-1210C) and pressure, as in pressure cookers or steam sterilizers used in accordance with the manufacturer’s instructions. The proteolytic enzymes of Clostridium botulinum form gas within the cans, which swells cans; so all swollen cans must be discarded.