Deck 20: Antimicrobial Drugs

Question 1

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

A) fungi.
B) gram-positive bacteria.
C) mycobacteria.
D) wall-less bacteria.
E) gram-negative bacteria.

Answer 1

A

Question 2

Figure 20.1 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 peptide bond formation.
B) stop the ribosome from moving along the mRNA.
C) prevent transcription.
D) interfere with the attachment of the tRNA to mRNA-ribosome complex.
E) prevent attachment of DNA.

Answer 2

D

Question 3

In what way are semisynthetic penicillins and natural penicillins alike?

A) Both are resistant to stomach acids.
B) Both are bactericidal.
C) Both are broad spectrum.
D) Both are based on β-lactam.
E) Both are resistant to penicillinase.

Answer 3

D

Question 4

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

A) prevent peptide bond formation in prokaryotes.
B) prevent transcription in prokaryotes.
C) prevent polypeptide elongation in eukaryotes.
D) prevent ribosome formation in bacteria.
E) prevent mRNA-ribosome binding in eukaryotes.

Question 5

Which compound would be the most useful to treat candidiasis?

A) thymine
B) flucytosine
C) penicillin
D) uracil
E) guanine

Question 6

Table 20.1
The following data were obtained from a broth dilution test. $\begin{array}{|l|l|l|}\hline\text { Concentration of AntibioticX } & \text { Growth } & \frac{\text { Growth in }}{\text { Subculture }} \\\hline 2 \mu \mathrm{g} / \mathrm{ml} & + & + \\\hline 10 \mu \mathrm{g} / \mathrm{ml} & - & + \\\hline 15 \mu \mathrm{g} / \mathrm{ml} & - & - \\\hline 25 \mu \mathrm{g} / \mathrm{ml} & - & - \\ \hline\end{array}$

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

A) 10 ?g/ml.
B) 2 ?g/ml.
C) 25 ?g/ml.
D) 15 ?g/ml.
E) The answer cannot be determined based on the information provided.

Question 7

More than half of our antibiotics are

A) synthesized in laboratories.
B) produced by Fleming.
C) produced by eukaryotic organisms.
D) produced by fungi.
E) produced by bacteria.

Question 8

Antimicrobial peptides (AMPs) frequently work by

A) disrupting the plasma membrane.
B) hydrolyzing peptidoglycan.
C) complementary base pairing with DNA.
D) inhibiting cell-wall synthesis.
E) inhibiting protein synthesis.

Question 9

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

A) polymyxin
B) penicillin
C) bacitracin
D) cephalosporin
E) polyenes

Question 10

Which of the following methods of action would be bacteriostatic?

A) competitive inhibition with folic acid synthesis
B) competitive inhibition with DNA gyrase
C) injury to plasma membrane
D) inhibition of protein synthesis
E) inhibition of cell wall synthesis

Question 11

Which of the following is mismatched?

A) Fleming  initial identification of penicillinʹs effect on gram-positive microbial growth
B) Florey and Chain  identification of Penicillium as the producer of penicillin
C) Kirby and Bauer  disc-diffusion method
D) Ehrlich  ʺmagic bulletʺ theory
E) None of these is mismatched.

Question 12

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

A) streptomycin
B) chloramphenicol
C) erythromycin
D) penicillin
E) tetracycline

Question 13

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

A) cephalosporin
B) monobactam
C) penicillin
D) bacitracin
E) streptomycin

Question 14

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

A) Bacillus
B) Paenibacillus
C) Streptomyces
D) Penicillium
E) Cephalosporium

Question 15

Most of the available antimicrobial agents are effective against

A) bacteria.
B) viruses.
C) protozoa.
D) fungi.
E) All of the answers are correct.

Question 16

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

A) trimethoprim
B) ethambutol
C) sulfonamide
D) streptomycin
E) isoniazid

Question 17

Penicillin was considered a ʺmiracle drugʺ for all of the following reasons EXCEPT

A) it was the first antibiotic.
B) it has selective toxicity.
C) it does not affect eukaryotic cells.
D) it kills bacteria.
E) it inhibits gram-positive cell wall synthesis.

Question 18

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

A) polymyxin
B) bacitracin
C) amphotericin B
D) cephalosporin
E) penicillin

Question 19

Which of the following antibiotics is NOT bactericidal?

A) polyenes
B) cephalosporins
C) penicillin
D) aminoglycosides
E) rifampins

Question 20

Table 20.1
The following data were obtained from a broth dilution test. $\begin{array}{|l|l|l|}\hline\text { Concentration of AntibioticX } & \text { Growth } & \frac{\text { Growth in }}{\text { Subculture }} \\\hline 2 \mu \mathrm{g} / \mathrm{ml} & + & + \\\hline 10 \mu \mathrm{g} / \mathrm{ml} & - & + \\\hline 15 \mu \mathrm{g} / \mathrm{ml} & - & - \\\hline 25 \mu \mathrm{g} / \mathrm{ml} & - & - \\ \hline\end{array}$

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

A) 25 ?g/ml.
B) 15 ?g/ml.
C) 2 ?g/ml.
D) 10 ?g/ml.
E) The answer cannot be determined based on the information provided.

Question 21

Drug resistance occurs

A) when antibiotics are taken after the symptoms disappear.
B) against antibiotics and not against synthetic chemotherapeutic agents.
C) because bacteria are normal microbiota.
D) when antibiotics are used indiscriminately.
E) All of the answers are correct.

Question 22

Which of the following statements about drug resistance is FALSE?

A) It may be transferred from one bacterium to another during conjugation.
B) It may be carried on a plasmid.
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.

Question 23

Table 20.2
The following results were obtained from a disk-diffusion test for microbial susceptibility to antibiotics. Staphylococcus aureus was the test organism. $$\begin{array} { | l | l | } \hline { \text { Antibiotic } } & \text { Zone of Inhibition } \\\hline \mathrm { A } & 3 \mathrm {~mm} \\\hline \mathrm { B } & 7 \mathrm {~mm} \\\hline \mathrm { C } & 0 \mathrm {~mm} \\\hline \mathrm { D } & 10 \mathrm {~mm} \\\hline\end{array}$$

-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.

Question 24

Lamisil is an allylamine used to treat dermatomycoses. Lamisilʹs method of action is similar to that of

A) polymyxin B.
B) echinocandins.
C) bacitracin.
D) azole antibiotics.
E) griseofulvin.

Question 25

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

A) a
B) b
C) c
D) d
E) e

Question 26

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

A) helminths.
B) gram-positive bacteria.
C) Mycobacterium tuberculosis.
D) viruses.
E) gram-negative bacteria.

Question 27

Table 20.3 The following data were obtained from a broth dilution test: $$\begin{array} { | c | c | } \hline \begin{array} { c } \text { Concentration } \\\text { of Antibiotic } \\X\end{array} & \text { Growth } \\\hline 2.0 \mu \mathrm { g } / \mathrm { ml } & - \\\hline 1.0 \mu \mathrm { ml } & - \\\hline 0.5 \mu \mathrm { ml } / \mathrm { ml } & - \\\hline 0.25 \mu \mathrm { g } / \mathrm { ml } & + \\\hline 0.125 \mu \mathrm { g } / \mathrm { ml } & + \\\hline 0 & + \\\hline\end{array}$$ Bacteria from the 0.25 ?g/ml tube were transferred to new growth media containing antibiotic X with the following results: $$\begin{array} { | c | c | } \hline \begin{array} { c } \text { Concentration } \\\text { of Antibiotic } \\X\end{array} & \text { Growth } \\\hline 2.0 \mu \mathrm { g } / \mathrm { ml } & - \\\hline 1.0 \mu \mathrm { ml } & + \\\hline 0.5 \mu \mathrm { ml } / \mathrm { ml } & + \\\hline 0.25 \mu \mathrm { g } / \mathrm { ml } & + \\\hline\end{array}$$ The data in Table 20.3 show that these bacteria

A) were resistant to 1.0 ?g/ml at the start of the experiment.
B) were killed by 0.5 ?g/ml of antibiotic X.
C) are pathogenic.
D) were killed by 0.125 ?g/ml of antibiotic X.
E) developed resistance to antibiotics.

Question 28

The antimicrobial drugs with the broadest spectrum of activity are

A) chloramphenicol.
B) tetracyclines.
C) penicillin G.
D) macrolides.
E) aminoglycosides.

Question 29

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

A) It lessens the toxicity of individual drugs.
B) It allows treatment to be provided prior to diagnosis.
C) It can prevent drug resistance.
D) Two are always twice as effective as one.
E) All of these are advantages of using two antibiotics together.

Question 30

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

A) penicillinase-producing Neisseria gonorrhoeae
B) helminths
C) Penicillium
D) Mycoplasma
E) Streptococcus pyogenes

Question 31

Table 20.2
The following results were obtained from a disk-diffusion test for microbial susceptibility to antibiotics. Staphylococcus aureus was the test organism. $$\begin{array} { | l | l | } \hline { \text { Antibiotic } } & \text { Zone of Inhibition } \\\hline \mathrm { A } & 3 \mathrm {~mm} \\\hline \mathrm { B } & 7 \mathrm {~mm} \\\hline \mathrm { C } & 0 \mathrm {~mm} \\\hline \mathrm { D } & 10 \mathrm {~mm} \\\hline\end{array}$$

-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.

Question 32

Table 20.2
The following results were obtained from a disk-diffusion test for microbial susceptibility to antibiotics. Staphylococcus aureus was the test organism. $$\begin{array} { | l | l | } \hline { \text { Antibiotic } } & \text { Zone of Inhibition } \\\hline \mathrm { A } & 3 \mathrm {~mm} \\\hline \mathrm { B } & 7 \mathrm {~mm} \\\hline \mathrm { C } & 0 \mathrm {~mm} \\\hline \mathrm { D } & 10 \mathrm {~mm} \\\hline\end{array}$$

-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.

Question 33

In the presence of penicillin, a cell dies because

A) it lacks a cell membrane.
B) it undergoes lysis.
C) its contents leak out.
D) it lacks a cell wall.
E) it plasmolyzes.

Question 34

Which of the following statements is FALSE?

A) Interferon inhibits glycolysis.
B) Acyclovir inhibits DNA synthesis.
C) Azoles inhibit plasma membrane synthesis.
D) Amantadine inhibits the release of viral nucleic acid.
E) Fluoroquinolone inhibits DNA synthesis.

Question 35

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 reproduce.
D) they have more genes than bacteria.
E) they do not have ribosomes.

Question 36

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

A) natural penicillins
B) semisynthetic penicillins
C) cephalosporins
D) vancomycin
E) macrolides

Question 37

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

A) inhibits plasma membrane synthesis
B) competitive inhibition
C) inhibits synthesis of neuramidase
D) inhibits cell wall synthesis
E) prevents synthesis of virus spikes

Question 38

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

A) They are used against viral infections.
B) They cause cellular plasmolysis.
C) They can affect host cell DNA synthesis.
D) They interfere with protein synthesis.
E) They can potentially cause mutations.

Question 39

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

A) streptogramin  inhibits protein synthesis
B) ethambutol  inhibits mycolic acid synthesis
C) vancomycin  inhibits peptidoglycan synthesis
D) bacitracin  inhibits peptidoglycan synthesis
E) streptomycin  inhibits protein synthesis

Question 40

Which of the following antibiotics are used to treat fungal infections? 1. aminoglycosides
2) cephalosporins
3) griseofulvin
4) polyenes
5) bacitracin

A) 1, 2, and 3
B) 3, 4, and 5
C) 3 and 4
D) 4 and 5
E) All of these antibiotics are used to treat fungal infections.

Question 41

Explain why penicillin was called the ʺmiracle drugʺ when it was first used in the 1940s.

Question 42

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

Question 43

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

Question 44

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

Question 45

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

A) the antibiotics kill susceptible bacteria, but the few that are naturally resistant live and reproduce, and their progeny repopulate the host animal.
B) bacteria from other animals replace those killed by the antibiotics.
C) the antibiotics persist in soil and water.
D) the antibiotics cause new mutations to occur in the surviving bacteria, which results in resistance to antibiotics.
E) the few surviving bacteria that are affected by the antibiotics develop immunity to the antibiotics, which they pass on to their progeny.

Question 46

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

A) translation.
B) peptide bond formation.
C) cellular respiration.
D) plasma membrane function.
E) transcription.

Question 47

Antiviral drugs target viral processes that occur during viral infection.

Question 48

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

Question 49

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

Question 50

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

Question 51

Explain the difficulties in developing antiviral drugs against DNA viruses, when compared to RNA viruses.

Question 52

Penicillin does not directly kill bacteria. Why, then, is it considered to be bacteriocidal?

Question 53

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

Question 54

Which of the following antibiotics causes misreading of mRNA?

A) tetracyclines  bind with 30S subunit
B) aminoglycoside  changes shape of 30S units
C) chloramphenicol  inhibits peptide bonds at 50S subunit
D) oxazolidinone  prevents formation of 70S ribosome
E) streptogamin  prevents release of peptide from 70S ribosome

Question 55

Can you determine both MIC and MBC from an E-test? Explain.

Question 56

An official from an international health agency predicts that if all countries enacted legislation to only sell antibiotics with a prescription, then the rate of antibiotic resistant would ʺgrind to a halt.ʺ Do you agree? Explain.

Question 57

Which of the following does NOT affect eukaryotic cells?

A) antifungal drugs
B) semisynthetic penicillins
C) antiprotozoan drugs
D) antihelminthic drugs
E) nucleotide analogs

Question 58

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

Question 59

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

A) protozoa.
B) helminths.
C) human cells.
D) bacteria.
E) fungi.

Question 60

Only microbes produce antimicrobial peptides.