Chapter 20

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1

1) Penicillin was considered a "miracle drug" for all of the following reasons EXCEPT

A) it was the first antibiotic.

B) it does not affect eukaryotic cells.

C) it inhibits gram-positive cell wall synthesis.

D) it has selective toxicity.

E) it kills bacteria.

Answer: A

2

2) A drug that inhibits mitosis, such as griseofulvin, would be more effective against

A) gram-positive bacteria.

B) gram-negative bacteria.

C) fungi.

D) wall-less bacteria.

E) mycobacteria.

Answer: C

3

3) Most of the available antimicrobial agents are effective against

A) viruses.

B) bacteria.

C) fungi.

D) protozoa.

E) All of the answers are correct.

Answer: B

4

4) Antimicrobial peptides (AMPs) frequently work by

A) inhibiting protein synthesis.

B) disrupting the plasma membrane.

C) complementary base pairing with DNA.

D) inhibiting cell-wall synthesis.

E) hydrolyzing peptidoglycan.

Answer: B

5

5) In what way are semisynthetic penicillins and natural penicillins alike?

A) Both are broad spectrum.

B) Both are resistant to penicillinase.

C) Both are resistant to stomach acids.

D) Both are bactericidal.

E) Both are based on β-lactam.

Answer: E

6

6) Which of the following antibiotics is NOT bactericidal?

A) aminoglycosides

B) cephalosporins

C) polyenes

D) rifampins

E) penicillin

Answer: C

7

7) Which one of the following does NOT belong with the others?

A) bacitracin

B) cephalosporin

C) monobactam

D) penicillin

E) streptomycin

Answer: E

8
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The antibiotic tetracycline binds to the 30S subunit of the ribosome, as shown by the dark black bar on the right portion of the diagram in Figure 20.1. The effect is to

A) prevent attachment of DNA.

B) prevent peptide bond formation.

C) prevent transcription.

D) stop the ribosome from moving along the mRNA.

E) interfere with the attachment of the tRNA to mRNA-ribosome complex.

Answer: E

9
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The antibiotic chloramphenicol binds to the 50S subunit of the ribosome, as shown in Figure 20.2. The effect is to

A) prevent mRNA-ribosome binding in eukaryotes.

B) prevent peptide bond formation in prokaryotes.

C) prevent polypeptide elongation in eukaryotes.

D) prevent transcription in prokaryotes.

E) prevent ribosome formation in bacteria.

Answer: B

10

10) Which of the following antimicrobial agents has the fewest side effects?

A) streptomycin

B) tetracycline

C) penicillin

D) erythromycin

E) chloramphenicol

Answer: C

11

11) Which of the following drugs does NOT act by competitive inhibition?

A) ethambutol

B) isoniazid

C) streptomycin

D) sulfonamide

E) trimethoprim

Answer: C

12

12) Which of the following methods of action would be bacteriostatic?

A) competitive inhibition with folic acid synthesis

B) inhibition of protein synthesis

C) injury to plasma membrane

D) inhibition of cell wall synthesis

E) competitive inhibition with DNA gyrase

Anwer: B

13

13) Which of the following antibiotics is recommended for use against gram-negative bacteria?

A) polyenes

B) bacitracin

C) cephalosporin

D) penicillin

E) polymyxin

Answer: E

14

14) Which of the following antimicrobial agents is recommended for use against fungal infections?

A) amphotericin B

B) bacitracin

C) cephalosporin

D) penicillin

E) polymyxin

Answer: A

15
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15) 5) In Table 20.1, as illustrated by the data shown, the minimal bactericidal concentration of antibiotic X is

A) 2 μg/ml.

B) 10 μg/ml.

C) 15 μg/ml.

D) 25 μg/ml.

E) The answer cannot be determined based on the information provided.

Answer: C

16
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16) In Table 20.1, the minimal inhibitory concentration of antibiotic X is

A) 2 μg/ml.

B) 10 μg/ml.

C) 15 μg/ml.

D) 25 μg/ml.

E) The answer cannot be determined based on the information provided.

Answer: B

17

17) More than half of our antibiotics are

A) produced by fungi.

B) produced by bacteria.

C) synthesized in laboratories.

D) produced by Fleming.

E) produced by eukaryotic organisms.

Answer: B

18

18) To date, most of our natural antibiotics have been found to be produced by members of what genus?

A) Streptomyces

B) Bacillus

C) Penicillium

D) Paenibacillus

E) Cephalosporium

Answer: A

19

19) Which of the following is mismatched?

A) Ehrlich — "magic bullet" theory

B) Fleming — initial identification of penicillin's effect on gram-positive microbial growth

C) Florey and Chain — identification of Penicillium as the producer of penicillin

D) Kirby and Bauer — disc-diffusion method

E) None of these is mismatched.

Answer: C

20

20) Which compound would be the most useful to treat candidiasis?

A) uracil

B) thymine

C) flucytosine

D) guanine

E) penicillin

Answer: C

21

21) Which of the following antibiotics are used to treat fungal infections?

aminoglycosides

cephalosporins

griseofulvin

polyenes

bacitracin

A) 1, 2, and 3

B) 3 and 4

C) 3, 4, and 5

D) 4 and 5

E) All of these antibiotics are used to treat fungal infections.

Answer: B

22

22) Which of the following antibiotics does NOT interfere with cell wall synthesis?

A) cephalosporins

B) macrolides

C) natural penicillins

D) semisynthetic penicillins

E) vancomycin

Answer: B

23

23) The antimicrobial drugs with the broadest spectrum of activity are

A) aminoglycosides.

B) chloramphenicol.

C) penicillin G.

D) macrolides.

E) tetracyclines.

Answer: E

24

24) Which of the following statements is FALSE?

A) Fluoroquinolone inhibits DNA synthesis.

B) Acyclovir inhibits DNA synthesis.

C) Amantadine inhibits the release of viral nucleic acid.

D) Interferon inhibits glycolysis.

E) Azoles inhibit plasma membrane synthesis.

Answer: D

25

25) Protozoan and helminthic diseases are difficult to treat because

A) their cells are structurally and functionally similar to human cells.

B) they replicate inside human cells.

C) they do not have ribosomes.

D) they do not reproduce.

E) they have more genes than bacteria.

Answer: A

26

26) Which of the following organisms would MOST likely be sensitive to natural penicillin?

A) helminths

B) Streptococcus pyogenes

C) penicillinase-producing Neisseria gonorrhoeae

D) Penicillium

E) Mycoplasma

Answer: B

27

27) Which of the following statements about drug resistance is FALSE?

A) It may be carried on a plasmid.

B) It may be transferred from one bacterium to another during conjugation.

C) It may be due to enzymes that degrade some antibiotics.

D) It is found only in gram-negative bacteria.

E) It may be due to increased uptake of a drug.

Answer: D

28

28) Which of the following does NOT constitute an advantage of using two antibiotics together?

A) It can prevent drug resistance.

B) It lessens the toxicity of individual drugs.

C) Two are always twice as effective as one.

D) It allows treatment to be provided prior to diagnosis.

E) All of these are advantages of using two antibiotics together.

Answer: C

29

29) Drug resistance occurs

A) because bacteria are normal microbiota.

B) when antibiotics are used indiscriminately.

C) against antibiotics and not against synthetic chemotherapeutic agents.

D) when antibiotics are taken after the symptoms disappear.

E) All of the answers are correct.

Answer: B

30
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30) In Table 20.2, the most effective antibiotic tested was

A) A.

B) B.

C) C.

D) D.

E) The answer cannot be determined based on the information provided.

Answer: D

31
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31) In Table 20.2, the antibiotic that exhibited bactericidal action was

A) A.

B) B.

C) C.

D) D.

E) The answer cannot be determined based on the information provided.

Answer: E

32
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32) In Table 20.2, which antibiotic would be most useful for treating a Salmonella infection?

A) A

B) B

C) C

D) D

E) The answer cannot be determined based on the information provided.

Answer: E

33

33) Which of the following would be selective against the tubercle bacillus?

A) bacitracin — inhibits peptidoglycan synthesis

B) ethambutol — inhibits mycolic acid synthesis

C) streptogramin — inhibits protein synthesis

D) streptomycin — inhibits protein synthesis

E) vancomycin — inhibits peptidoglycan synthesis

Answer: B

34

34) In the presence of penicillin, a cell dies because

A) it lacks a cell wall.

B) it plasmolyzes.

C) it undergoes lysis.

D) it lacks a cell membrane.

E) its contents leak out.

Answer: C

35

35) Lamisil is an allylamine used to treat dermatomycoses. Lamisil's method of action is similar to that of

A) polymyxin B.

B) azole antibiotics.

C) echinocandins.

D) griseofulvin.

E) bacitracin.

Answer: B

36

36) Niclosamide prevents ATP generation in mitochondria. You would expect this drug to be effective against

A) gram-negative bacteria.

B) gram-positive bacteria.

C) helminths.

D) Mycobacterium tuberculosis.

E) viruses.

Answer: C

37
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The data in Table 20.3 show that these bacteria

A) are pathogenic.

B) developed resistance to antibiotics.

C) were killed by 0.125 μg/ml of antibiotic X.

D) were killed by 0.5 μg/ml of antibiotic X.

E) were resistant to 1.0 μg/ml at the start of the experiment.

Answer: B

38

38) Which of the following statements about drugs that competitively inhibit DNA polymerase or RNA polymerase is FALSE?

A) They can potentially cause mutations.

B) They are used against viral infections.

C) They can affect host cell DNA synthesis.

D) They cause cellular plasmolysis.

E) They interfere with protein synthesis.

Answer: D

39
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The substrate for transpeptidase used to synthesize peptidoglycan is shown in Figure 20.3. Which of the drugs shown would inhibit peptidoglycan synthesis?

  1. A) a
  2. B) b
  3. C) c
  4. D) d
  5. E) e

Answer: D

40
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The structures of the influenza drug Tamiflu and sialic acid, the substrate for influenza virus's neuramidase, are shown in Figure 20.4. What is the method of action of Tamiflu?

A) inhibits cell wall synthesis

B) inhibits plasma membrane synthesis

C) inhibits synthesis of neuramidase

D) competitive inhibition

E) prevents synthesis of virus spikes

Answer: D

41

41) Which of the following does NOT affect eukaryotic cells?

A) antiprotozoan drugs

B) antihelminthic drugs

C) antifungal drugs

D) nucleotide analogs

E) semisynthetic penicillins

Answer: E

42

42) Mebendazole is used to treat cestode infections. It interferes with microtubule formation; therefore, it would NOT affect

A) bacteria.

B) fungi.

C) helminths.

D) human cells.

E) protozoa.

Answer: A

43

43) Which of the following antibiotics causes misreading of mRNA?

A) aminoglycoside — changes shape of 30S units

B) chloramphenicol — inhibits peptide bonds at 50S subunit

C) oxazolidinone — prevents formation of 70S ribosome

D) streptogamin — prevents release of peptide from 70S ribosome

E) tetracyclines — bind with 30S subunit

Answer: A

44

44) The antibiotic actinomycin D binds between adjacent G-C pairs, thus interfering with

A) transcription.

B) translation.

C) cellular respiration.

D) plasma membrane function.

E) peptide bond formation.

Answer: A

45

45) Use of antibiotics in animal feed leads to antibiotic-resistant bacteria because

A) bacteria from other animals replace those killed by the antibiotics.

B) the few surviving bacteria that are affected by the antibiotics develop immunity to the antibiotics, which they pass on to their progeny.

C) the antibiotics cause new mutations to occur in the surviving bacteria, which results in resistance to antibiotics.

D) the antibiotics kill susceptible bacteria, but the few that are naturally resistant live and reproduce, and their progeny repopulate the host animal.

E) the antibiotics persist in soil and water.

Answer: D

46

1) An antibiotic that attacks the LPS layer would be expected to have a narrow spectrum of activity.

Answer: TRUE

47

2) PABA serves as the competitive inhibitor in the action of sulfanilamides.

Answer: FALSE

48

3) Undergrowth of fungi after antibiotic use is commonly referred to as a superinfection.

Answer: FALSE

49

4) Due to its target, rifamycins can be effective over a broad spectrum.

Answer: TRUE

50

5) Both trimethoprim and sulfamethoxazole inhibit reactions along the same metabolic pathway.

Answer: TRUE

51

6) Penicillin and streptomycin are commonly used in synergism because they display the same mode of action.

Answer: FALSE

52

7) Only microbes produce antimicrobial peptides.

Answer: FALSE

53

8) Community-acquired MRSA is typically more virulent than health care-associated MRSA.

Answer: TRUE

54

9) Antiviral drugs target viral processes that occur during viral infection.

Answer: TRUE

55

10) Phage therapy has been used in the past as an antiviral treatment.

Answer: FALSE