Plate 50

Toxins

Toxins

• Toxins: poisonous substances produced by organisms (microorganisms, in our case)

Exotoxins

• Exotoxins: produced within cytoplasm of bacteria and released into the surrounding environment– Exo = “out”– Produced by Gram-positive

bacteria– Toxins are soluble in body

fluids

Exotoxins

• Released after bacteria cell is inside the body or in food (and consumed by host)

• Spread through body by blood and damage organs

• Effects of exotoxins:– Damage cell membranes of tissue– Interrupt metabolic function– Interfere with cellular functions

Exotoxins – Enterotoxin

• Staphylococcus aureus produce enterotoxins that are absorbed by the cells that line the intestines

• Entero = “intestine”• Symptoms:– Nausea– Vomiting– Abdominal cramps– Diarrhea

• Ex: S. aureus can result in Toxic Shock Syndrome, commonly found in menstruating women who use tampons

Staphylococcus aureus – “golden cluster seed”

Staph Infection

• Skin infections:– Pimples– Folliculitis– Impetigo

Exotoxins – Neurotoxin

• Clostridium botulinum produce neurotoxins that affect the nervous system

• Neuro = “nerve”• Prevents the release of acetylcholine (a

neurotransmitter) at neuromuscular junctions• Results in paralysis, since nerve impulses

cannot pass to muscles

Botulism

Exotoxins – Neurotoxin

• Clostridium tetani produce a neurotoxin that affects nerve cells responsible for skeletal muscle contractions

• Muscles remain constantly contracted and rigid

Tetanus

• “Lock-jaw” – muscle contraction in the face and neck

Tetanus

Exotoxins – Cytotoxin

• Corynebacterium diphtheriae kill respiratory cells by interfering with protein synthesis

• Dead respiratory cells and debris collect in mucus, block small air passageways, and make breathing difficult

• Cyto = “cell”

Diptheria

• Note the large whitish swelling in the throat

Endotoxins

• Endotoxins: made of components of bacterial cell wall– Endo = “in”– Produced by Gram-negative

bacteria–Made of lipopolysaccharides

(LPS)– Released when the bacteria

cell wall is broken down (through phagocytosis or antibiotics)

Endotoxins

• Unlike some exotoxins, endotoxins are not tissue specific – they affect a wide range of tissues (systemic)

• Symptoms:– Dilate blood vessels (lower blood pressure)– Tissue failure due to lack of nutrition and oxygen– Fever– Muscular weakness– Low levels of white blood cells– Hemorrhaging of blood vessels