Self Quiz for "Bacterial Pathogenesis: Factors that Damage the Host"
2. Producing Harmful Exotoxins
c. Type III Toxins that Interfere with Host Cell Function

Study the material in this section and then write out the answers to these questions.
Do not just click on the answers and write them out. This will not test your understanding of this tutorial.

1. State the functions of the A component and the B component in A-B toxins. (ans).

2. Match the following descriptions with the exotoxin:

_____ Produced by certain strains of Escherichia coli such as E. coli O157:H7. These toxins kill intestinal epithelial cells of the colon and cause bloody diarrhea. Less commonly, the toxins enter the blood and are carried to the kidneys where they damage endothelial cells of the blood vessels and cause hemolytic uremic syndrome (HUS). (ans)

_____ Produced by a species of Clostridium. This is a neurotoxin that acts peripherally on the autonomic nervous system. This toxin binds to and enters the presynaptic neuron and blocks its release of acetylcholine. This causes a flaccid paralysis, a weakening of the involved muscles. (ans)

_____ Produced by a species of Bordetella. Catalyzes the ADP-ribosylation of a host cell protein called Gi leading to high intracellular levels of cAMP. In the respiratory epithelium, the high levels of cAMP results in increased respiratory secretions and mucous production and contributes to coughing. In the case of phagocytes, to decrease their phagocytic activities such as chemotaxis, engulfment, killing. It may also act on neurons resulting in encephalopathy. In the blood, the toxin results in increased sensitivity to histamine. This can result in increased capillary permeability, hypotension and shock. (ans)

_____ Produced by a species of Clostridium. This is a neurotoxin that binds to inhibitory interneurons of the spinal cord and blocks their release of inhibitor molecules.The toxin, by blocking the release of inhibitors, keeps the involved muscles in a state of contraction and leads to spastic paralysis, a condition where opposing flexor and extensor muscles simultaneously contract. (ans)

_____ These toxins interact with the epithelial cells of the stomach causing them to produce chemokines that attract neutrophils and macrophages. This inflammatory response and the resulting extracellular killing by the phagocytes can lead to tissue damage and ulcers. (ans)

3. Escherichia coli is normal flora of our intestinal tract and usually causes no harm in that location. Why then is there such a controversy about testing meat for E. coli to avoid the potential for bloody diarrhea and possibly hemolytic uremic syndrome? (ans)

4. Multiple Choice (ans)

• RETURN TO "BACTERIAL PATHOGENESIS: FACTORS THAT DAMAGE THE HOST - PRODUCING HARMFUL EXOTOXINS: TYPE III TOXINS THAT INTERFERE WITH HOST CELL FUNCTIONS"

• RETURN TO UNIT 2 TABLE OF CONTENTS

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