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Chapter 20 Lecture 3 Bacterial Diseases of the Nervous System (Botulism…
Chapter 20 Lecture 3
Bacterial Diseases of the Nervous System
Botulism
Botulism not often considered an infection
Botulism is an intoxication caused by Clostridium botulinum that will adversely affect the synapses of the PNS. It has three manifestations:
Signs and symptoms
Foodborne botulism
Weak and dizzy one to two days following consumption
Blurred vision with fixed dilated pupils, dry mouth, constipation, N/V and abdominal pain
Progressive paralysis on both sides of the body and pt will remain mentally alert throughout illness
Slow recovery from growth of new nerve cell endings (could take years) if death occurs it is because of the paralysis of the diaphragm
Infant botulism
Results from the ingestion of endospores not ingested foods where the bacterium actually grows in intestinal tract and then will secrete a toxin
Nonspecific symptoms- crying, constipation, and a failure to thrive
Wound Botulism
Growth of bacterium in dead tissue after the introduction of endospores into the wound
S/S are similar to that of the foodborne disease but incubation period is longer – 4days
Pathogen and virulence factors
Clostridium botulinum is the causative agent
Gram-positive, endospore-forming bacillus
Common worldwide in soil and water
Its endospores survives improper canning of non-acidic foods like meats, eggs, mushrooms, beans, corn, beets, peas and some cheese
Different strains produce one of seven neurotoxins
Epidemiology
~60 cases of foodborne and wound botulism per year in the United States
Infant botulism most common form in the United States.
Pathogenesis of botulism
Each of the many ends of a motor neuron forms a synapse with a muscle cell (this is called the neuromuscular junction.
Remember that at the end of a synapse the two cells to not actually touch they have the synaptic cleft between them
The neuron stores acetylcholine in vesicles near it membrane
Ach is used to communicate between neurons and muscle cells.
Botulism will disrupt this communication by blocking the release of Ach by the motor neurons
When it blocks the Ach, it cannot communicate and the muscle does not contract, and you get a flaccid paralysis
It is permanent, and is irreversible
Remember– the blocked motor neuron axon can grow new branches
Diagnosis, treatment, and prevention
Symptoms are diagnostic
Can culture from food, feces, or from pts wounds
Four approaches to treatment
Maintain open and functional airways
Wash intestinal tract to remove Clostridium
Administer botulism immune globulin
Treat with antimicrobial drugs
Prevented by destroying endospores in contaminated food
Infants under 1 year old should not consume honey
Tetanus
A disease caused by a neurotoxin made by the species Clostridium
Signs and symptoms
Tightening of the jaw & neck muscles (lockjaw) and profuse sweating may occur, drooling, & grouchiness
Spasms and contractions may spread to other muscles especially back muscles
VIOLENT Spasms and contraction to other muscles becoming so severe that the arms and fists curl tightly , the feet curl down, and the body assumes a stiff backward arch as the heels and back of the head bend toward one another.
Irregular heartbeat and blood pressure, if toxins spread to neurons that control glands
Unrelenting contractions of the diaphragm result in a final inhalation and then pts can die because they cannot exhale
Pathogen and virulence factors
Clostridium tetani is causative agent produces a terminal endospore, giving the cell a lollipop appearance
Found in soil, dust, and the intestines of humans and animals
Produce neurotoxin called tetanospasmin when they die. It affects motor control by blocking the release of inhibitory neurotransmitters in the CNS
Pathogenesis
Can acquire through ANY break in skin or mucous membrane
NOT LIKE stepping on a rusty nail can be as simple as a wooden splinter or an accidental staple in the finger
Distance of infection from CNS determines incubation period
Epidemiology
Mortality rate is ~50% if left untreated
Incidence has decreased worldwide
Most cases occur where immunization or adequate medical care is unavailable
Diagnosis, treatment, and prevention
Diagnosis is based on characteristic muscle contraction (too late to save the pt)
Treatment involves several steps
Thorough wound cleaning to remove all endospores
Passive immunotherapy where antibodies are directed against tetanospasmin are injected
Administration of antimicrobials
Active immunization
Vaccine is available against tetanus. The number of cases have declined as a result of using tetanus toxoid, which is inactivated tetanuspasmin
CDC urges five doses beginning at 2 months of age and then a booster every ten years for life