botulism

Botulism

A disease caused by the ingestion of food containing the neurotoxin produced by Clostridium botulinum.

The organism that causes it is:

1.       Gram-negative, an anaerobic, spore-forming rod with oval to cylindrical, terminal to sub-terminal spores.

2.       On the basis of serological specificity, Seven types of toxins are: A, B, C, D, E, F, G

3.       A, B, E, F, G = disease in humans

4.       C = botulism in fowls, cattle etc.

5.       D = forage poisoning of cattle

6.       E is nonproteolytic,  A and G are proteolytic.

TOXIN:

·         Minimal dose (human lethal) = 1 ng/kg of body weight

·         Type A is more lethal than B or E.

·         The neurotoxins are formed within the organism and released upon autolysis.

·         Produced as a single polypeptide chain that is posttranslationally nicked to form a chain that is composed of three domains: binding, translocation and catalytic.

·         The toxins are not completely inactivated by the proteolytic enzymes of the stomach, and, indeed, those produced by non-proteolytic may be activated.

·, Unlike the Staphylococcal enterotoxins, the b.toxin are heat sensitive and may be destroyed by heating at 80C for 10 min.

·         The growth of C.botulinum in some foods such as meats a proteinaceous, low-acid vegetable results in foul rancid odor. Gas production is not always evident.

·         Toxin persists in food for long periods.

MODE OF ACTION OF NEUROTOXIN:

·         It is absorbed mostly in the small intestine and paralyzes the involuntary muscles of the body.

·         After toxin binds to nerve cell receptors, it is internalized into an endosome followed by proteolytic cleavage of protein components of synaptic vesicles that block neurotransmitter release.

·         The toxin binds to presynaptic terminal membranes at nerve-muscle junctions where the release of acetylcholine is blocked.

FOOD INVOLVED:

·         Inadequately processed home-canned foods

·         Low and medium acid canned foods. Such as tomatoes, apricots, pears, and peaches

·         Preserved meats and fishes

·         Spores of C.botulinum survive long storage period in raw and precooked frozen foods.

DISEASE:

·         Symptoms appear 12 to 36 hours.

·         Nausea, vomiting, fatigue, dizziness, headache, dryness of mouth, skin, throat, constipation, paralysis of muscles, respiratory failure and death.

·         Duration of illness: 1 to 10 days.

·         Treatment is the administration of antitoxin, artificial respiration, maintaining the fluid balance in the body.

INFANT BOTULISM:

·         In the adult form of botulism, preformed toxins are ingested.

·         In infant botulism, viable spores are ingested- upon germination in the GI tract, the toxin is synthesized.

·         Infant over 1 year of age tends not to be affected.

Symptoms: weakness, lack of sucking, loss of head control

Vehicle foods (do not undergo heat processing to destroy endospores)- syrup and honey.

PREVENTION: Use of approved heat processes canned foods.

·         Rejection of swollen spoiled canned foods.

·         Refusal even to taste doubtful food.

·         Boiling of suspected food for at least 15 mins.

·         Avoidance of raw or precooked foods.