Microbiology: chapter 15 quiz Flashcards


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1

The most frequently used portal of entry for pathogens is the

mucous membranes of the respiratory tract.

2

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

antigenic variation.

3

Most pathogens that gain access through the skin

enter through hair follicles and sweat ducts.

4

The ID50 is

the dose that will cause an infection in 50 percent of the test population.

5

All of the following contribute to a pathogen's invasiveness EXCEPT

toxins

6

Which of the following statements is FALSE?

Coagulase destroys blood clots.

7

Which of the following statements about exotoxins is generally FALSE?

They are resistant to heat.

8

Endotoxins are

part of the gram-negative cell wall.

9

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

A-B toxin

10

Cytopathic effects are changes in host cells due to

viral infections

11

Which disease-associated fungi or fungal characteristics are mismatched?

Claviceps purpura - aflatoxin

12

All of the following are methods of avoiding host antibodies EXCEPT

membrane-disrupting toxins.

13

Siderophores are bacterial proteins that compete with the host's

iron-transport proteins.

14

The fimbriae of Neisseria gonorrhea and enteropathogenic E. coli are examples of

adhesins and ligands.

15

All of the following are examples of entry via the parenteral route EXCEPT

hair follicle

16

Superantigens produce intense immune responses by stimulating lymphocytes to produce

cytokines

17

Botulism is caused by ingestion of a proteinaceous exotoxin; therefore, it can easily be prevented by

boiling food prior to consumption

18

All of the following organisms produce exotoxins EXCEPT

Salmonella typhi.

19

Which of the following cytopathic effects is cytocidal?

release of enzymes from lysosomes

20

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

A-B TOXINS

21

Symptoms of protozoan and helminthic diseases are due to

tissue damage due to growth of the parasite on the tissues, waste products excreted by the parasite, and products released from damaged tissues.

22

Which of the following statements about staphylococcal enterotoxin is FALSE?

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

23

Which of the following contributes to the virulence of a pathogen?

numbers of microorganisms that gain access to a host, evasion of host defenses, and toxin production

24

Lysogenic bacteriophages contribute to bacterial virulence because bacteriophages
Correct!

give new gene sequences to the host bacteria.

25

Twenty-five people developed symptoms of nausea, vomiting, and diarrhea three to six hours after attending a church picnic where they ate a ham and green bean casserole with cream sauce. The most likely cause of this case of food intoxication is

staphylococcal enterotoxin.

26

Which of the following statements about M protein is FALSE?

It is readily digested by phagocytes.

27

Symptoms of intense inflammation and shock occur in some gram-positive bacterial infections due to

superantigens.

28

Which of the following is an example of direct damage due to bacterial infection?

the invasion and lysis of intestinal cells by E. coli

29

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

mucous membranes only

30

All of the following bacteria release endotoxin EXCEPT

Clostridium botulinum

31

Cholera toxin polypeptide A binds to surface gangliosides on target cells. If the gangliosides were removed,

polypeptide B would not be able to enter the cells.

32

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

engulf the bacteria.

33

Which of the following mechanisms is used by gram-negative bacteria to cross the blood-brain barrier?
Correct!

inducing TNF

34

Injectable drugs are tested for endotoxins by

the Limulus amoebocyte lysate test.

35

Endotoxins in sterile injectable drugs could cause

septic shock symptoms.

36

Gram-negative septic shock results from the following events. What is the second step?

LPS is released from gram-negative bacteria.

37

Antibiotics can lead to septic shock if used to treat

gram-negative bacterial infections

38

Which of the following is NOT a cytopathic effect of viruses?

toxin production

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.

40

Which organism in Table 15.2 most easily causes an infection?

Legionella pneumophila

41

Which organism in Table 15.2 causes the most severe disease?

It cannot be determined from the information provided.

42

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

streptococcal colonization is necessary for periodontal disease.

43

Nonpathogenic Vibrio cholerae can acquire the cholera toxin gene by

lysogenic conversion.

44

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

a decrease in blood pressure.

45

Patients developed inflammation a few hours following eye surgery. Instruments and solutions were sterile, and the Limulus assay was positive. The patients' inflammation was due to

endotoxin

46

The best description of direct damage by a pathogen is

host cells destroyed when pathogens metabolize and multiply.

47

Which is NOT specifically employed by pathogens to avoid destruction by phagocytosis?

producing superantigens

48

A retired contract administrator who enjoyed gardening sought medical attention for what appeared to be a sinus infection. He received antimicrobials but the conditioned worsened and he was experiencing severe painful spasms in his jaw. He admitted to injuring himself with a gardening tool while wearing sandals in the yard but did not seek medical attention for the wound. The man is likely experiencing

intoxication caused by a focal C. tetani infection.

49

For what reason might the ID50 for Salmonella Typhi decrease when a rat simultaneously ingests sulfa drugs with the pathogen?

The antimicrobial interferes with the microbiome enabling the pathogen to more easily establish infection.

50

Which pathogen and virulence factor are mismatched?

Shigella sonnei - coagulase