MCB 15 Flashcards


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1

How are immune cells able to detect foreign pathogens?

A. They can compare the DNA sequences from the foreign cells to host DNA.

B. They detect foreign, unfamiliar chemical substances released by the invading cells.

C. They are able to detect structures on the surfaces of foreign cells that are not found in the host.

C

2

How does a capsule help certain bacteria evade detection by the immune system?

A. Capsules allow the bacteria to stick together, creating a larger mass that is too big for immune cells to engulf.

B. The capsule is composed of polysaccharides that are similar to those found in the host; thus, the immune system does not recognize it as foreign.

C. Capsules have the ability to destroy antibodies secreted by the immune system.

D. The capsule makes the bacterium too sticky to be phagocytosed by the immune cells.

B

3

Which of the following microorganisms actually grows inside the macrophage?

A. Tuberculosis bacterium

B. Leishmania

C. Shigella

D. Legionella

E. Streptococcus pneumoniae

A

4

How does the protozoan Trypanosoma evade detection by the immune system?

A. It can change the surface antigens frequently, preventing the immune system from tracking it.

B. It prevents phagosome-lysosome fusion.

C. It produces a capsule which is composed of polysaccharides similar to those found in the host.

D. It can resist oxidation inside macrophages.

A

5

What are leukocidins?

A. Molecules that are capable of destroying phagocytes

B. Molecules that destroy the complement proteins

C. Molecules that can degrade IgA

A

6

Measles viruses are capable of inactivating host defenses by

A. destroying complement proteins.

B. suppressing the immune system.

C. producing leukocidins.

D. producing superantigens.

B

7

Meningitis and gonorrhea are caused by

A.Pseudomonas species.

B. Neisseria species.

C. measles virus.

B

8

How do superantigens enable pathogens to hide from the immune system if they actually stimulatethe immune system?

A. They cause fever, which destroys the complement proteins.

B. They cause the immune system to turn on itself.

C. They cause the immune system to produce an exaggerated response, distracting it from the actual pathogen.

D. They cause the immune system to destroy IgA antibodies.

C

9

How can capsules enable bacteria to evade the immune system?

A. A capsule is a superantigen that distracts the immune system.

B. Capsules block the complement biding sites on the surface of the pathogen.

C. Capsules can bind up IgA, rendering it inactive.

B

10

Endotoxins are also known as

A. prostaglandins.

B. Lipid A.

C. interleukin-1.

D. cytokines.

B

11

When would endotoxins be released from a bacterial cell?

A. When the cell attaches to a host cell in the human body

B. During bacterial conjugation

C. When the cell moves toward a energy source

D. When the cell dies

D

12

Which of the following would be the first sign of an infection that resulted in the release of endotoxin?

A. Nausea

B. Fever

C. Weakness

D. Pain

B

13

Why is a release of endotoxin into the bloodstream potentially deadly?

A. It causes necrosis of the liver.

B. Endotoxin can quickly enter the brain from the bloodstream, causing brain damage.

C. It can lower blood pressure and cause the patient to go into shock.

D. It results in dehydration of the patient.

C

14

An exotoxin that has the ability to kill or damage host cells is referred to as a(n)

A. cytotoxin.

B. A-B toxin.

C. enterotoxin.

D. neurotoxin.

E. superantigen.

A

15

Which domain of the A-B toxin binds to cell surface receptors on the host cell?

A. A domain

B. Both the A and B domains have the ability to bind to cell surface receptors.

C. A-B toxins do not bind to cell surfaces.

D. B domain

D

16

How are superantigens different from other types of exotoxins?

A. Superantigens must be endocytosed into a target cell before becoming active.

B. Superantigens only act against host neurons.

C. Superantigens cause an overstimulation of the host immune system.

D. Superantigens comprise two functional domains.

C

17

A person who attended a picnic early in the day develops a very high fever and is unresponsive by the evening. This person most likely has been exposed to a(n)

A. cytotoxin.

B. superantigen.

C. membrane disrupting toxin.

D. enterotoxin.

B

18

A patient who has been hospitalized with uncontrolled muscle spasms has probably been infected with bacteria that secrete a(n)

A. superantigen.

B. enterotoxin.

C. neurotoxin.

D. membrane disrupting toxin.

C

19

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?

A. Shiga toxin is more lethal than staphylococcal enterotoxin.

B. Staphylococcal enterotoxin is the more lethal of the two toxins.

C. The parenteral route is the preferred portal entry for Shigella bacteria.

D. More organisms of Staphylococcal bacteria must be ingested to cause infection, as compared Shigellabacteria.

A

20

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

A. An individual contracts a hookworm infection as a result of walking around outside barefoot.

B. An individual contracts a gastrointestinal infection by consuming contaminated water.

C. An individual contracts gonorrhea as a result of unprotected sex.

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

D

21

Which statement regarding endotoxins is true?

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

B. Endotoxins are part of the outer portion of the cell wall of gram-positive bacteria.

C. Endotoxins induce host cells to produce effective antitoxins that help to protect them against the toxin's effects.

D. The effects of endotoxins vary greatly, depending on the specific bacterium the produces them.

A

22

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

A. fibrinolysin

B. hyaluronidase

C. collagenase

D. coagulase

A

23

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

A. to detect the presence of the botulinum toxin

B. to confirm the diagnosis of gas gangrene

C. to check for enterotoxins

D. to ensure that a sterilized medical device is free of endotoxin

D

24

Which of the following statements about adherence is true?

A. Most bacterial adhesins are glycoproteins or lipoproteins.

B. Most bacteria can adhere to any cell in the host.

C. Adhesins are always located on the bacterium's cell membrane.

D. The host cell receptors for bacterial adhesins are usually proteins.

A

25

Which of the following toxins does NOT match the description?

A. hemolysins: membrane-disrupting toxins that destroy erythrocytes

B. tetanus toxin: an A-B neurotoxin that causes uncontrollable muscle contractions

C. streptococcal erythrogenic toxin: a superantigen that damages capillaries and results in a characteristic rash

D. Vibrio enterotoxin: a superantigen that destroys epithelial cells

D

26

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

A. yellow fever

B. influenza

C. cholera

D. ringworm

C

27

Which of the following statements about lysogenic conversion is true?

A. Endotoxin production by bacteria is frequently the result of a lysogenic infection.

B. Lysogenic bacteria are always less virulent than nonlysogenic bacteria because the viral infection weakens them.

C. Lysogenic conversion is a result of the transfer of plasmids from one bacterium to another.

D. Exotoxin production by bacteria is frequently the result of a lysogenic infection.

D

28

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

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

B. An individual contracts gonorrhea as a result of unprotected sex.

C. An individual contracts a hookworm infection as a result of walking around outside barefoot.

D. An individual contracts a gastrointestinal infection by consuming contaminated water.

A

29

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

True or False

True

30

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

A. antigenic variation.

B. cytopathic effect.

C. virulence.

D. lysogenic conversion.

E. cytocidal effect.

A

31

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

A. skin only

B. parenteral only

C. mucous membranes only

D. skin and parenteral

E. skin, parenteral, and mucous membranes

C

32

Nonpathogenic Vibrio cholerae can acquire the cholera toxin gene by

A. infecting a pathogenic Vibrio cholerae.

B. transduction.

C. transformation.

D. phagocytosis.

E. conjugation.

B

33

Endotoxins are

.A molecules that bind nerve cells.

B. part of the gram-negative cell wall.

C. excreted from the cell.

D. associated with gram-positive bacteria

E. .A-B toxins.

B

34

Antibiotics can lead to septic shock if used to treat

.A gram-positive bacterial infections.

B. gram-negative bacterial infections.

C. protozoan infections.

D. viral infections.

E. helminth infestations.

B

35

Endotoxins in sterile injectable drugs could cause

.A infection.
B. no damage, because they are sterile.
C. giant cell formation.
D. septic shock symptoms.
E. nerve damage.

D

36

Bacteria that cause periodontal disease have adhesins for receptors on streptococci that colonize on teeth. This indicates that

A. streptococci get bacterial infections.

B. bacteria that cause periodontal disease adhere to gums and teeth.

C. streptococcal colonization is necessary for periodontal disease.

D. bacteria that cause periodontal disease adhere to teeth.

E. streptococci cause periodontal disease.

C

37

The most frequently used portal of entry for pathogens is the

A. parenteral route.

B. mucous membranes of the respiratory tract.

C. skin.

D. mucous membranes of the gastrointestinal tract.

E. All of these portals are used equally.

B

38

All of the following are used by bacteria to attach to host cells EXCEPT

A. fimbriae.

B. capsules.

C. A-B toxins.

D. ligands.

E. M protein

C