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Gram positive endospore forming rods. Clostridium botulinum —anaerobic—adult and infant botulism Clostridium perfringens —anaerobic—diarrhea Bacillus cereus —facultatively anaerobic—gastroenteritis (diarrhea and vomiting). Why do bacteria form endospores. Survival of the bacterial species

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gram positive endospore forming rods

Gram positive endospore forming rods

Clostridium botulinum—anaerobic—adult and infant botulism

Clostridium perfringens—anaerobic—diarrhea

Bacillus cereus—facultatively anaerobic—gastroenteritis (diarrhea and vomiting)

why do bacteria form endospores
Why do bacteria form endospores
  • Survival of the bacterial species
  • Endospores carry the genomic information of the vegetative cell
vegetative cells vs endospores
Vegetative cells vs. endospores
  • Vegetative cells are metabolically active

(taking in nutrients, converting nutrients into energy and biomass, expelling wastes, growing and dividing)

Endospores are dormant—metabolically inactive (but contains the genetic material of the vegetative cell)

why are endospores dormant
Why are endospores dormant?
  • Filled with SASPS (small acid soluble proteins that protect DNA)
  • Has low water activity
  • Has relatively few metabolic enzymes
  • Surrounded by a tough keratin-like coat
how does being dormant benefit an endospore
How does being dormant benefit an endospore
  • Can survive the following conditions


high heat

UV irradiation

low pH

high osmolarity

low temperature

Conditions that most vegetative cells cannot survive

life cycle of an endospore
Life cycle of an endospore
  • Vegetative cell (unpleasant conditions)
  • Veg. cell replicates DNA, forms a septum 1/3 of the length of the cell and pumps DNA into the region
  • Endospore develops at that site and is finally surrounded by a tough keratin like coat
  • Veg cell dies releasing the mature endospore
  • Free mature endospore (pleasant conditions)
  • Endospore germinates to become a vegetative cell
clostridium botulinum
Clostridium botulinum
  • Causes botulism (food posioning)
  • Causes infant botulism from honey
  • Abundant in soil throughout the world

Type AC. botulinum—found in neutral/alkaline soil west of the Mississippi River

Type BC. botulinum—found in eastern part of the country

Type CC. botulinum—found in wet soils (can effect fish)

botulism cases are rare
Botulism cases are rare
  • Foodborn botulism—50 cases per annumusually due to home canning of food (Type A and Type B) or preserved fish (Type E)
  • Infant botulism—100 cases per annumusually due to spores present in honey that is introduced to formula
foodborn botulism toxin formed in food
Foodborn botulism—toxin formed in food
  • Canning—endospores are not eradicated if the temperature is not sufficiently high
  • Spores are present in a nutrient rich environment that is also anaerobic
  • The spores germinate and become vegetative bacteria
  • The vegetative bacteria produce botulism toxin—a potent neurotoxin
botulism toxin
Botulism toxin
  • Toxin has no taste
  • Food is often not spoiled by the bacteria
  • A small amount of food with the toxin can be lethal
  • Botulism toxin is heat labile
infant botulism 3 20 weeks old
Infant botulism—(3-20 weeks old)
  • Toxin is formed in the infant’s colon
  • Honey has a high osmolarity; therefore, the endospores cannot germinate
  • Honey is mixed with infant formula that dilutes the honey—the infant drinks the solution
  • The spores are introduced into the stomach and move to the colon
  • The spores germinate in the colon
  • The vegetative cells produce botulism neurotoxin in the colon
clinical diseases caused by botulism neurotoxin cause
Clinical diseases caused by botulism neurotoxin (cause)
  • Foodborn botulism--12-36 hours after ingestion toxin travels to different parts of the body
  • Botulism toxin binds to acetocholine receptors on neural cells
  • Impulses are not sent from one neural cell to another
  • Muscles (smooth, involutary, motor) are not stimulated by the neurons and cannot move
  • This causes flaccid paralysis of the muscles
clinical diseases caused by botulism neurotoxin effect
Clinical diseases caused by botulism neurotoxin (effect)
  • Flaccid paralysis of muscles
  • Cranial nerves are the first affected

double vision/blurred vision

difficulty swallowing

  • Muscles in the arms and legs are next to be affected
  • Diaphragm muscles are affected causing difficulty in breathing
  • There is no fever or cell death
  • END RESULT:: paralysis and respiratory failure
  • Deliver antitoxin to the three known botulism neurotoxin
  • The antitoxin binds to the free circulating neurotoxin and prevents it from binding to acetocholine receptors
  • N.B. Bound neurotoxin cannot be inactivated as it is already bound to acetocholine receptors
  • Supportive therapy—intubation until neurons regenerate
infant botulism diseases and treatment
Infant botulism-diseases and treatment
  • Disease is slow in occurring because toxin cannot be readily absorbed from the colon
  • 2-3 days constipation
  • Difficulty swallowing—poor suckling response
  • Flaccid baby
  • Hospitalization and intubation may be required
  • Prognosis is usually good so no antitoxin is required
  • N.B. SIDS has been attributed in part to infant botulism
bacillus cereus
Bacillus cereus
  • B. cereus is facultatively anaerobic and found in every environment.
  • Causes abdominal pain and diarrhea


  • Nausea/vomiting
disease caused by b cereus
Disease caused by B. cereus
  • Disease is caused by two toxins
  • Enterotoxin—heat stable/proteolysis resistant

--Causes nausea and vomiting

--Found commonly in improperly stored rice

  • Heat labile form

--Causes watery diarrhea as water is not absorbed in the intestines

--Found commonly in contaminated meats vegetables and sauces

--Takes longer to get sick as disease is caused as B. cereus divides in the patients G-I tract