Deck 20: Antimicrobial Drugs

Question 1

In what way are semisynthetic penicillins and natural penicillins alike?

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

Answer 1

D

Question 2

Which of the following antibiotics causes misreading of mRNA?

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

Answer 2

C

Question 3

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

Answer 3

B

Question 4

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 5

In the presence of penicillin, a cell dies because

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

Question 6

Figure 20.1

The antibiotic tetracycline binds to the 30S subunit of the ribosome, as shown in Figure 20.1. The effect is to

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

Question 7

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

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

Question 8

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

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

Question 9

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

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

Question 10

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

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

Question 11

Table 20.1
The following data were obtained from a broth dilution test.

In Table 20.1, the minimal bactericidal concentration of antibiotic X is

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

Question 12

Figure 20.4

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

Question 13

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

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

Question 14

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

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

Question 15

Which of the following methods of action would be bacteriostatic?

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

Question 16

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

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

Question 17

More than half of our antibiotics are

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

Question 18

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}{c}\begin{array}{lll} \text {Antibiotic}\\ \text {B \( 7 \mathrm{~mm} \)}\\ \text {C \( 0 \mathrm{~mm} \)}\\ \text {D \( 10 \mathrm{~mm} \)}\end{array}\begin{array}{lll}\text { Zone of Inhibition A } \\\\\\\\\end{array}\begin{array}{lll}3 \mathrm{~mm} \\\\\\\\\end{array}\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 19

Which of the following antibiotics is NOT bactericidal?

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

Question 20

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 21

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

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

Question 22

Antimicrobial peptides work by

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

Question 23

Figure 20.2

The antibiotic cycloheximide binds to the 60S subunit of the ribosome, as shown in Figure 20.2. The effect is to

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

Question 24

Which of the following is mismatched?

A) Florey and Chain - identification of Penicillium as the producer of penicillin
B) Fleming - identification of penicillin
C) Ehrlich - "magic bullet" theory
D) Kirby and Bauer - disc- diffusion method
E) None of these is mismatched.

Question 25

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

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

Question 26

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

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

Question 27

Most of the available antimicrobial agents are effective against

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

Question 28

The antimicrobial drugs with the broadest spectrum of activity are

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

Question 29

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

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

Question 30

Which of the following does NOT affect eukaryotic cells?

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

Question 31

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

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

Question 32

Which of the following statements about drug resistance is FALSE?

A) It may be due to enzymes that degrade some antibiotics.
B) It may be carried on a plasmid.
C) It is found only in gram- negative bacteria.
D) It may be due to increased uptake of a drug.
E) It may be transferred from one bacterium to another during conjugation.

Question 33

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

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

Question 34

Which compound would be the most useful to treat candidiasis?

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

Question 35

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

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

Question 36

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

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

Question 37

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

Question 38

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

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

Question 39

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

Question 40

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

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

Question 41

Which of the following statements is FALSE?

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

Question 42

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

Question 43

Only microbes produce antimicrobial peptides.

Question 44

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

Question 45

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

-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 46

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

Question 47

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

Question 48

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

-The data in Table 20.3 show that these bacteria

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

Question 49

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

Question 50

Table 20.1
The following data were obtained from a broth dilution test.

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

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

Question 51

Antiviral drugs target viral processes that occur during viral infection.

Question 52

Drug resistance occurs

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

Question 53

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

Question 54

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

Question 55

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