Question

Clostridium botulinum

• Disease(s) information
• Number of cases and deaths per year information
• Taxonomy information
• Signs and symptoms information
• Identification information
• Prevention and treatment information

Answer 1

Answer :

Clostridium botulinum disease information :

Clostridium botulinum causes severe form of food poisoning. The word Botulism itself is derived from Latin "Botulus" which means sausages. The bacteria itself is non-invasive and virtually non-infectious. Its pathogenicity is due to the toxin it produces. All the effects of toxin collectively are called Botulism. It will include adult food-borne Botulism, Infant food-borne Botulism and wound infections. Wound-borne Botulism is very rare.

Number of cases and Deaths :

In US alone an average of 150 cases are reported each year. 60% of which are infant botulism, of the remaining 40%, Half are adults with wound infections and last 20% are food borne infections.
Among these cases mortality rate is 3%. of which for infants mortality is less than 1%.

Taxonomy :

Clostridium botulinum was first isolated by Van Ermengem in 1896 from Ham. Early classification in genus Bacillus was modified because it was found to an anaerobic bacteria. Bacillus was associated with aerobic bacteria.

Domain - Bacteria
Phylum - Firmicutes
Class - Clostridia
Order - Clostridiales
Family - Clostridiaceae
Genus - Clostridium
Species -  botulinum

Types of Clostridium botulinum known are - A, B , C, D, E, F, G and vary from region to region.

Signs and Symptoms of Botulism :

Foodborne botulism is due to ingestion of preformed toxin which is a neurotoxin (affects the nervous system).  The source of botulism is usually preserved food specially meat and meat products, fish and sea foods and sometimes vegetables.
Symptoms begin usually 12 - 36 hours after ingestion of food. Vomiting, thirst and constipation are followed by difficulty in swallowing and blurry vision with breathing difficulties. It leads to delirium and may result in coma if not intervened. The fatality of disease is due to respiratory failure and varies greatly from place to place. It may take upto 7 days of untreated Botulism to cause death.
Wound Botulism happens when wound is infected with this bacteria and toxin is produced at the site of infection. The gastrointestinal symptoms are missing but rest all neurological symptoms remain same as above.

Identification of Clostridium botulinum :

It is a gram positive, motile, strict anaerobe with endospores. They grow on ordinary lab media but under anaerobic growth conditions. They make transparent colonies with irregular fimbriate borders. They can grow at 35oC but also survive and sometimes grow at 1 - 5oC. They produce proteolytic enzymes and hence show digestion on milk agar / meat agar. They release ammonia and H2S thus giving a pungent smell. Clostridium can be diagnosed by isolating it from food or for faeces of the patient. Alternatively, presence of botulinum toxin can be demonstrated from food of faeces.

Prevention and treatment of Botulism :

As most cases of Botulism occur due to consumption of inadequately canned food or unhygienic conditions during food preservation. Prevention can be achieved if these two causes are eliminated. The vegetative cells of clostridium are destroyed by boiling but the spores survive. Spores can be destroyed only at very high temperature. Prevention can be achieved by giving unfavourable conditions in the food so that spores would not  germinate and hence no toxin is produced in the food. Consuming food from known brands and not buying from unknown people will also help.
Botulism in infants is caused by giving honey to infants less than 1 year old. Clostridium botulinum can easily contaminate honey from soil and as honey is taken untreated, they survive and release toxin in honey. Commercial honey producers screen for presence of Clostridium botulinum and take preventive measures to ensure that toxin is not present in the honey.

As bacteria may or may not be present in the contaminated food, the treatment is aimed at removing toxin from the system. Antibiotics will not help (except maybe in wound infections). Antitoxin is given as early as possible and will give relief soon. Till the effect of antitoxin takes hold, supportive treatment is provided depending on symptoms. Ventilators are required in severe cases as patients have breathing difficulties. In case of infants, immediate admission into PICU and strict case monitoring is required to get desired results.