• Botulism is a neuro paralytic intoxication caused by ingestion of preformed enterotoxin in food produced by Clostridium botulinum.
• Etiological agent for Botulism:
  • Clostridium botulinum is gram +ve, anaerobic, rod shaped, spore forming bacteria.
  • They produce 8-types of neurotoxins (A, B, C₁, C₂, D, E, F and G) in food.
  • Therefore, Clostridium botulinum strains are classified into 8-group on the basis of type of neurotoxin they produce.
  • Type A, B, E and F cause botulism in human being and type C and D cause botulism in other animals.
  • It usually produces gas in food. It may or may not be proteolytic.
  • Proteolytic strain produces various bad smelling compounds like H₂S in food.
  • But, in case of non-proteolytic strain, spoilage cannot be judged by smell of food.
  • Similarly, bad odor is not developed in low protein or non-protein food.
  • Various factors affect spore germination growth and toxin production by C. botulinum.
  • Moisture below 30% inhibit toxin production. Similarly, salt concentration of 8% or more prevent neurotoxin production in food.
  • Similarly, neurotoxin is not produced if pH of food is 4.5 or below.
  • Composition of food determine type of toxin produced. For.eg. food containing milk or casein give more toxic type of type A toxin.

Properties of botulinum toxin (Botox):

• Toxin is produced in food during growth and autolysis of bacteria.
• Proteolytic strain produce toxin in active form but some non-proteolytic strain produce toxin in inactive form.
• This inactive toxin become active in stomach by acid hydrolysis.
• Unlike enterotoxin of S. aureus, this neurotoxin is damaged by heating at 80^oC for 10 minutes.
• Botulinum toxin is most toxic chemical found in nature.

Pathogenesis of botulism:

• Botulism occur by ingestion of pre-formed neurotoxin on food.
• After ingestion it is absorbed by cell of upper intestinal tract, then enters into lymph then into blood.
• From blood, it reaches neuromuscular junction and binds to nerve ending. After binding it inhibit release of acetylcholine neurotransmitter that gives paralysis of muscle.
• If this paralysis extends to breathing muscle, death occurs by respiratory failure.

Infant botulism:

• In adult botulism is intoxication i.e. it is caused by ingestion of preformed neurotoxin of Clostridium botulinum in food.
• In adult, ingested Clostridium botulinum cannot multiply in intestinal tract.
• It is because Clostridium botulinum is highly acid sensitive and it is killed by stomach acidity.
• Furthermore, this bacteria is very less competitive and cannot compete with normal flora of intestinal tract.
• So, in case of adult botulism occurs only by ingestion of pre-formed neurotoxin, but not by ingestion of bacterial cell but in infant stomach is not acidic and intestinal normal flora are not fully developed.
• Therefore, ingested Clostridium botulinum multiply and produce endotoxin in intestinal tract of infant.
• So, botulism in infant is an example of food infection.

Symptoms of Botulism:

• Incubation period is 12-36hrs, but it may be shorter or longer.
• Earliest symptom includes acute digestive disturbance followed by vomiting, sometime diarrhea, fatigue and headache.
• After above symptoms typical neurological symptoms appear. They include double vision, difficulty in speaking and swallowing, mouth becomes dry and tongue swells.
• Paralysis of involuntary muscle occurs. Paralysis of respiratory muscle results in death.

Treatment of Botulism:

• Treatment of botulism can be separated into three processes:
• First treatment is removal of unabsorbed neurotoxin from intestinal tract. For.eg. by inducing vomiting.
• Second treatment involves neutralization of neurotoxin by ingestion of antibody (anti-toxin). It is the only one successful treatment of botulism.
• Third treatment involves curing of symptoms. For.eg. by artificial breathing.

Prevention and control of botulism:

• Preventing contamination of food:
  • For this purpose, food should be kept away from soil and dust because its natural habitat is soil.
• Preventing growth and toxin production in food:
  • It can be done by making the food aerobic by adding chemicals, heat treatment etc.
• Damaging neurotoxin in food:
  • It can be done by heating the food at 80^oC for 10 minutes just before eating.

Botulism: Food poisoning caused by Clostridium botulinum

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