Chapter 15

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1

What do hyaluronidase and kinase have in common?

They are both enzymes involved in evading host defense.

2

According to your Concept Map, which of the following organisms exhibits antigenic variation?

N. gonorrheae

3

Which of the following virulence factors could directly prevent phagocytosis and/or phagocytic degradation?

all of the above- capsules, M proteins, waxy lipids.

4

In mice, the LD50 for staphylococcal enterotoxin is 1350 ng/kg, and the LD50 for Shiga toxin is 250 ng/kg. Which of the following statements is true?

Shiga toxin is more lethal than staphylococcal enterotoxin.

5

Which of the following would be an example of an infection initiated via the parenteral route?

An individual contracts hepatitis B from an accidental stick with a contaminated needle.

6

Which statement regarding endotoxins is true?

One consequence of endotoxins is the activation of blood-clotting proteins.

7

Which type of bacterial enzyme helps spread Streptococcus pyogenes by digesting blood clots?

fibrinolysin

8

In which of the following cases would the Limulus amebocyte lysate (LAL) assay be used?

to ensure that a sterilized medical device is free of endotoxin

9

Which of the following toxins does NOT match the description?

Vibrio enterotoxin: a superantigen that destroys epithelial cells

10

Which disease would be potentially propagated in an environment without functional plumbing and in which drinking water is contaminated with sewage?

cholera

11

The most frequently used portal of entry for pathogens is the

mucous membranes of the respiratory tract.

12

The ability of some microbes, such as Trypanosoma or Giardia to alter their surface molecules and evade destruction by the hosts antibodies is called

antigenic variation.

13

Most pathogens that gain access through the skin

enter through hair follicles and sweat ducts.

14

Which of the following statements is FALSE?

Coagulase destroys blood clots.

15

Which of the following statements about exotoxins is generally FALSE?

They are resistant to heat.

16

Endotoxins are

part of the gram-negative cell wall.

17

Cytopathic effects are changes in host cells due to

viral infections.

18

Many pathogens use the same portal for entry and exit from the body.

True

19

Most symptoms of endotoxins can be treated with administration of anti-endotoxin antibodies.

False

20

Ergot and aflatoxin are toxins sometimes found in grains contaminated with fungi.

True

21

In A-B exotoxins, the A component binds to the host cell receptor so that the B component can enter the cell.

False

22

Cytopathic effects, such as inclusion bodies and syncytium formation, are the visible signs of viral infections.

True

23

The M protein enhances the virulence of Streptococcus by preventing phagocytosis.

True

24

Nonpathogenic Vibrio cholerae can acquire the cholera toxin gene by

transduction.

25

In response to the presence of endotoxin, phagocytes secrete tumor necrosis factor. This causes

a decrease in blood pressure.

26

Bacteria such as E. coli and Salmonella produce invasins that bind host cells, thus causing the cells to

engulf the bacteria.

27

All of the following bacteria release endotoxin EXCEPT

Clostridium botulinum.

28

Polio is transmitted by ingestion of water contaminated with feces containing polio virus. What portal of entry does polio virus use?

mucous membranes only

29

Which of the following is NOT a membrane-disrupting toxin?

A-B toxin

30

All of the following are methods of avoiding host antibodies EXCEPT

membrane-disrupting toxins.

31

All of the following organisms produce exotoxins EXCEPT

Salmonella typhi.

32

Which of the following statements about staphylococcal enterotoxin is FALSE?

It is produced by Staphylococcus aureus growing in the host's intestines.