2. CLOSTRIDIUM-introduction
• Clostridia:
– are strictly anaerobic to aerotolerant sporeforming bacilli found in soil as
well as in normal intestinal flora of man and animals.
– There are both gram-positive and gram-negative species, although the
majority of isolates are gram-positive.
– Exotoxin(s) play an important role in disease pathogenesis.
– motile -- peritrichous flagella
(exception: C. perfringens—nonmotile)
– the sporangia– swollen
– typical clinical symptoms
4. C.botulinum
• Characteristics:
– Gram positive rod
– Subterminal endospore
– Noncapsule
– Obligate anaerobe
• Morphology:
– able to produce the neurotoxin during sporulation, which
can only happen in an anaerobic environment.
– is a lipase negative microorganism that grows
between pH of 4.8 and 7 and it can't use lactose as a
primary carbon source
– Spores of the organism are highly resistant to heat,
withstanding 100 °C for several hours.
5. TOXIN
• Virulence factor—botulinum toxin
– neurotoxin
– relatively heat-labile and resistant to protease
– types: A, B, C, D, E, F, G
– the most potent toxic material known
potassium cyanide(KCN)
mechanism of action
Toxin → gut → blood → cholinergic synapses → block the
release of exciting neurotransmitter, e.g., acetylcholine →
flaccid paralysis
10,000 times
6.
7. MECHANISM OF TOXIN.
• 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. Pathogenesis
• Disease—Botulism
– from Latin botulus, "sausage"
• There are three forms:
– adult botulism, caused by ingestion of preformed toxin in
food;
– infant botulism, in which the organism replicates and
secretes toxin in the intestinal tract;
– wound botulism, in which the organism replicates in the
wound and secretes toxin. Toxin binds to neuromuscular
junctions of parasympathetic nerves and interferes with
acetylcholine release, causing flaccid muscle paralysis.
10. CLNICAL MANIFESTATIONS
• Adult botulism:
flaccid paralysis: double vision, dysphagia, difficulty in
breathing & speaking ,rare gastrointestinal
symptoms .cause of death: respiratory failure
• Infant botulism:
– manifestation: constipation, poor feeding,
difficulty in sucking and swallowing, weak cry, loss
of head control.
Floppy baby
prevention: free of honey
13. Epidemiology
• U.S. incidence
– < 200 annual cases of all forms
– Approx 9 annual outbreaks of food-borne
• median of 24 cases
• Recent trend toward restaurant rather than home-preserved foods
• All ages and genders equally susceptible
• Mortality
– 25% prior to 1960
• 6% during 1990’sI
14. Epidemiology
• Incubation period
– Depends on inoculated dose
– Inhalational
• 12-18 hours in primate studies
• 72 hours in 3 known inhalational cases
• True incubation period is unknown
– Foodborne
• 6 hours to 8 days
– Wound
• 7.5 days (range 4-18 days) after injury
15. DIAGONOSIS
• Clinical diagnosis
• Diagnostic tests help confirm
– Toxin neutralization mouse bioassay
• Serum, stool, or suspect foods
– Infant botulism
• C botulinum organism or toxin in feces
– samples for diagnostic testing
• Serum, vomit, gastric aspirate, suspect food, stool
• Collect serum before antitoxin given
16. DIAGONOSIS
• Confirmation
– Takes 1-4 days
– Available only at CDC and state public health labs
• Mouse Bioassay
– Type-specific antitoxin protects vs. toxin in sample
– The assay can detect at minimal 0.03ng of toxin.
• Culture
– Fecal and gastric specimens cultured anaerobically
– Results in 7 to 10 days
• Unique features to help in diagnosis
– Disproportionate cranial nerve palsies
– More hyptonia in facial muscles than below neck
– Lack of sensory changes
17. 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
• 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%)
18. PREVENTION
• Natural disease
– Boil home-canned foods 10 minutes
– Follow USDA instructions on home-canning
– Restrict honey from < 1 year old
– Seek medical care for wounds
– Avoid injectable street drugs
• Vaccine
– Botulinum pentavalent toxoid
• Not available to general public
• In use for laboratory workers, military
• Protects vs. types A-E
• Long-lasting immunity
– Prohibits future therapeutic use of toxin
