BIOS 251 Exam 3 HW - What portal of entry does polio virus use? –A...

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BIOS 251 Exam 3 HW

• Polio is transmitted by ingestion of water contaminated with feces contain- ing polio virus.

What portal of entry does polio virus use?–Answer mucous membranes only

• The ID50 is

the dose that will cause an infection in 50 percent of the test population. the dose that will kill 50 percent of the test population.the dose that will kill some of the test population. a measure of pathogenicity.the dose that will cause an infection in some of the test population.–Answer the dose that will cause an infection in 50 percent of the test population.

• Bacterium Portal of Entry ID50 Staphylococcus

aureus Wound <10 Staphylococcus aureus Wound + Ampicillin 300 39) Table 15.1 shows the ID50 for Staphylococcus aureus in wounds with and without the administration of ampicillin before surgery. Based on the data, the administration of ampicillin before surgery

• decreases the risk of staphylococcal infection.
• increases the risk of staphylococcal infection.
• has no effect on risk of infection.
• replaces tetracycline.
• The answer cannot be determined based on the information provided.

–Answer A

• A pathogen that is capable of antigenic variation can

–Answer avoid host immune defenses

• Bacteria such as E. coli and Salmonella produce invasins that bind host cells, thus causing 1 / 3

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the cells to –Answer engulf the bacteria

• Exotoxins and endotoxins are two fundamentally different types of bacte- rial toxins. In

this activity, you will determine whether each of the following statements applies to exotoxins or endotoxins. Some statements may apply to both types of toxins.Drag each statement to the appropriate box, indicating whether the statement applies to exotoxins, endotoxins, or both exotoxins and endotoxins –Answer Exotoxins –Answer

• These toxins are produced and secreted by actively growing cells. 2. The host typically

responds by producing antibodies called antitoxin. 3.These toxins may be toxic in very tiny (nanogram) amounts. 4.These toxins may be produced by gram-negative or gram-positive bacteria. 5. Examples include tetanus toxin, cholera toxin, and staphylococcal enterotoxin. 6.These toxins may be found in foods but are usually inactivated by cooking.Endotoxins –Answer

• These toxins are often released upon phagocytosis of or death of bacterial cells. 2. This toxin

may survive sterilization techniques and contaminate medications and medical devices even though the medication or device is com- pletely free of bacteria. 3. These toxins are produced exclusively by gram-negative bacteria. 4. These toxins are responsible for much of the pathology caused by Salmonella typhi and Neisseria meningitidis.Both exo and endo –Answer

• These toxins may be lethal to the host 2.These toxins are produced by bacteria but not by

viruses.

• Mechanisms of Exotoxins and Endotoxins - Foundation Figure 15.4

Part B - Mechanism of Action of A-B Exotoxins The majority of exotoxins are A-B toxins, which are composed of two polypep- tide subunits referred to as A and B. 2 / 3

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The B component functions to bind or attach to the host cell, whereas the A component exerts its toxic effects on the cell. This activity asks you to place the images in the correct order as they occur when an A-B toxin interacts with the host cell.Drag the images below into boxes to indicate the correct order of events illustrating the mechanism of action of an A-B exotoxin.–Answer Correct You have correctly placed each of the steps in the mechanism of action of a typical A-B exotoxin.An understanding of this process may reveal possible strategies to block or inhibit it and potentially prevent or reduce toxin-mediated damage to the host.

• Which of the following strategies might be used to block the activity of an A-B toxin?

Select all of the strategies below that might inhibit or block the action of an A-B toxin.–Answer

• blocking host cell receptors to which A-B toxins bind
• blocking receptor-mediated endocytosis in cells targeted by the A-B toxin
• inhibiting the secretion of proteins from a bacterial cell
• blocking the binding sites on the B portion of an A-B toxin
• blocking separation of the A and B components of the toxin
• Consider the structure of a plasma membrane. Select the mechanisms through which a toxin

is likely to disrupt the plasma membrane of a host cell. Select all that apply.–Answer

• insertion of a protein channel in the host cell plasma membrane
• disruption of phospholipid bilayer

• Select the statements that correctly describe endotoxins

–Answer

• Endotoxins may cause a life-threatening drop in blood pressure known as endotoxic shock.
• Endotoxins can cause fever, chills, weakness, and fatigue.
• Symptoms caused by endotoxins may actually worsen after treatment of an infection

caused by gram-negative bacteria.

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