Clostridium botulinum

Study on Clostridium botulinum.

1. Clostridium botulinum By Md.Ashfaq Aziz Department of microbiology Primeasia university

2. INTRODUCTION Clostridium botulinum is a Gram-positive, rodshaped bacterium that produces several toxins. The best known are its neurotoxins, subdivided in types A-G, that cause the flaccid muscular paralysis seen in botulism. They are also the main paralytic agent in botox . C. Botulinum is an anaerobic spore-former, which produces oval, sub terminal endospores and is commonly found in soil.

3. Morphological Characteristic A gram-positive, anaerobic bacilli. Spore forming. Toxin forming. Heat sensitive. Prefers low acid environment. Cause Botulism disease.

4. Morphological Characteristic Bacteria are 0.5 to 2.0 mcm in width and 1.6 to 22.0 mcm in length Create spores that can remain dormant for 30 years or more Spores extremely resistant to environmental stressors, such as heat and UV light

5. Morphological Characteristic

6. Virulence Factor Neurotoxin: - Liberated during growth. - Seven types of toxins (A-G). - Antigenic (light and heavy chain). - Environmental survival. (Inactivated by heat 100ºC for 20min ). - Most potential biological warfare agents. - Lethal dose= 1-2 micro gram.

7. Virulence Factor Botulinum toxin: - Botulinum toxin is synthesized as a single polypeptide chain ( low potency). - The toxin is nicked by a bacterial protease (or by gastric proteases) to produce two chains :  a light chain (the A fragment)  a heavy chain (the B fragment) connected by a disulfide bond. - The A fragment of the nicked toxin, becomes the most potent toxin found in nature

8. Virulence Factor Mechanism of Botulinum toxin: – Absorbed from the gut. – Binds to receptors of presynaptic membranes of motor neurons of the peripheral nervous system and cranial nerves. – Proteolysis-by the light chain of botulinum toxin of the target SNARE proteins in the neurons inhibits the release of acetylcholine at the synapse, resulting in lack of muscle contraction and paralysis. – SNARE proteins are- synaptobrevin , SNAP 25, syntaxin . – Type A and E toxin cleaves-SNAP 25. – Type B toxin cleaves synaptobrevin .

9. Virulence Factor Mechanism of Botulinum toxin: Figure: Mechanism A Figure: Mechanism B

10. Pathogenesis • Transmitted in three ways: – Food or water toxin contamination. – Wound infected with C. Botulinum . – Ingestion of C. botulinum. • Most common contaminated food: Vacuum packed, or canned alkaline food. E.g. fish, green beans, any home-canned food. • Foods eaten without cooking

11. Pathogenesis of Infant Botulism • Cause : infection by C. botulinum. • Age: 5 - 20 weeks of age. • Characterized by constipation and weak sucking. • It cause “sudden infant death syndrome-SIDS”. • Found in the stool.

12. Symptoms • Appear in 18-24 hrs. • Include : -Blurry vision, double vision. -Thrombocytopenia. -Dry mouth. -Trouble swallowing. -Trouble breathing. -Muscle weakness. -Constipation. -Dropping eyelid. -Irritability. • Fever is not a symptom of botulism.

13. Signs of Food-borne and Wound Botulism • Ventilatory (respiratory) problems. • Eye muscle paresis/paralysis (extra ocular, eyelid). • Dry mucous membranes in mouth/throat. • Dilated, fixed pupils. • Ataxia. • Hypotension. • Nystagmus. • Decreased to absent deep tendon reflexes.

14. Diagnosis • Clinical diagnosis • Diagnostic tests help confirm – Toxin neutralization mouse bioassay • Serum, stool, or suspect foods – Infant botulism • C. botulinum organism or toxin in feces • Testing is done in Reference laboratories under Biosafety regulations

15. TREATMENT • Passive immunization - equine antitoxin – Antibodies to Types A, B and E toxins. – Binds and inactivates circulating toxin. – Stops further damage but doesn’t reverse. • Heptavalent antitoxin – Investigational. – Effective against all toxins.

16. TREATMENT • Antitoxin action – Food-borne botulism • Neutralizing antibody levels exceed toxin levels • Single dose adequate – Large exposure (e.g. biological weapon) • can confirm adequacy of neutralization – recheck toxin levels after treatment • Antitoxin adverse effects – Serum sickness (2-9%), anaphylaxis (2%)

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