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 Endospores carry the genomic information of the vegetative cell

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? 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 Can survive the following conditions drying high heat UV irradiation low pH high osmolarity low temperature Conditions that most vegetative cells cannot survive

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 Causes botulism (food posioning) Causes infant botulism from honey Abundant in soil throughout the world Type A C. botulinum—found in neutral/alkaline soil west of the Mississippi River Type B C. botulinum—found in eastern part of the country Type C C. botulinum—found in wet soils (can effect fish)

Botulism cases are rare Foodborn botulism—50 cases per annum usually due to home canning of food (Type A and Type B) or preserved fish (Type E) Infant botulism—100 cases per annum usually due to spores present in honey that is introduced to formula

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 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) 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) 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) 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

Treatment 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 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 B. cereus is facultatively anaerobic and found in every environment. Causes abdominal pain and diarrhea AND/OR Nausea/vomiting

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