Deck 20: Antimicrobial Drugs

Question 1

Which of the following is not bactericidal?

A) Natural penicillin
B) Streptomycin
C) Bacitracin
D) Tetracycline
E) Semisynthetic penicillin

Answer 1

D

Question 2

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

A) Bacitracin
B) Cephalosporin
C) Monobactam
D) Streptomycin
E) Penicillin

Answer 2

D

Question 3

Figure 20.3

The antibiotic erythromycin binds to the 50S subunit of the ribosome as shown in Figure 20.3. The effect is to

A) Prevent transcription.
B) Prevent peptide bond formation.
C) Stop the ribosome from moving along the mRNA.
D) Prevent attachment of tRNA.
E) None of the above.

Answer 3

C

Question 4

Which compound would be the most useful to treat candidiasis?

A) Thymine
B) Uracil
C) Flucytosine
D) Guanine
E) None of the above

Question 5

Table 20.3
The following data were obtained from a broth dilution test:

$\begin{array}{ll}\text { Concentration of Antibiotic } X&\text { Growth }\\\hline2.0 \mu \mathrm{g} / \mathrm{ml} & - \\1.0 \mu \mathrm{g} / \mathrm{ml} & - \\0.5 \mu \mathrm{g} / \mathrm{ml} & - \\0.25 \mu \mathrm{g} / \mathrm{ml} & + \\0.125 \mu \mathrm{g} / \mathrm{ml} & + \\0 & +\end{array}$
Bacteria from the 0.25 µg/ml tube were transferred to new growth media containing antibiotic X with the following results:

$\begin{array}{ll} \underline{\text { Concentration of Antibiotic }} X& \underline{\text { Growth} }\\2.0 \mu \mathrm{g} / \mathrm{ml} \\1.0 \mu \mathrm{g} / \mathrm{ml} & - \\0.5 \mu \mathrm{g} / \mathrm{ml} & + \\0.25 \mu \mathrm{g} / \mathrm{ml} & + \\\end{array}$

-The data in Table 20.3 show that these bacteria

A) Developed resistance to antibiotics.
B) Can be subcultured.
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 6

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

A) Gram- positive bacteria.
B) Helminths.
C) Mycobacterium tuberculosis.
D) Gram- negative bacteria.
E) Viruses.

Question 7

All of the following are advantages of using two antibiotics together except

A) Prevention of drug resistance.
B) Two are always twice as effective as one.
C) Lessening the toxicity of individual drugs.
D) Providing treatment prior to diagnosis.
E) None of the above.

Question 8

The antimicrobial drugs with the broadest spectrum of activity are

A) Chloramphenicol.
B) Tetracyclines.
C) Lincomycin.
D) Macrolides.
E) Aminoglycosides.

Question 9

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 polypeptide elongation in eukaryotes.
C) Prevent transcription in prokaryotes.
D) Prevent mRNA- ribosome binding in eukaryotes.
E) None of the above.

Question 10

All of the following antibiotics interfere with cell wall synthesis except

A) Vancomycin.
B) Macrolides.
C) Semisynthetic penicillins.
D) Natural penicillins.
E) Cephalosporins.

Question 11

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

A) Polymyxin B.
B) Echinocandins.
C) Azole antibiotics.
D) Bacitracin.
E) Griseofulvin.

Question 12

The first antibiotic discovered was

A) Penicillin.
B) Sulfa drugs.
C) Quinine.
D) Salvarsan.
E) Streptomycin.

Question 13

All of the following statements about drug resistance are true except

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

Question 14

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

-In Table 20.2, the antibiotic that exhibited bactericidal action was

A) A.
B) B.
C) C.
D) D.
E) Can't tell.

Question 15

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

A) Polyenes
B) Bacitracin
C) Polymyxin
D) Penicillin
E) Cephalosporin

Question 16

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

A) Peptide bond formation.
B) Cellular respiration.
C) Transcription.
D) Translation.
E) Plasma membrane function.

Question 17

Table 20.1
The following data were obtained from a broth dilution test. $\begin{array}{c}&&\text { Growth in }\\\text { Concentration of Antibiotic } X&\text { Growth }&\text { Subculture }\\\hline2 \mu \mathrm{g} / \mathrm{ml} &+&+\\10 \mu \mathrm{g} / \mathrm{ml}&-&+ \\15 \mu \mathrm{g} / \mathrm{ml} &-&-\\25 \mu \mathrm{g} / \mathrm{ml}&-&-\end{array}$

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

A) 15 µg/ml.
B) 2 µg/ml.
C) 25 µg/ml.
D) 10 µg/ml.
E) Can't tell.

Question 18

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

A) Human cells.
B) Bacteria.
C) Helminths.
D) Fungi.
E) Protozoa.

Question 19

Which of the following antibiotics is not bactericidal?

A) Cephalosporins
B) Aminoglycosides
C) Penicillin
D) Polyenes
E) Rifampins

Question 20

Semisynthetic penicillins differ from natural penicillins in all of the following respects except that both are

A) Resistant to stomach acids.
B) Resistant to penicillinase.
C) Broad spectrum.
D) Bactericidal.
E) None of the above.

Question 21

Which of these antimicrobial agents has the fewest side effects?

A) Streptomycin
B) Penicillin
C) Erythromycin
D) Tetracycline
E) Chloramphenicol

Question 22

Which of the following does not affect eukaryotic cells?

A) Antifungal drugs
B) Antihelminthic drugs
C) Antiprotozoan drugs
D) Nucleotide analogs
E) None of the above

Question 23

Most of the available antimicrobial agents are effective against

A) Viruses.
B) Bacteria.
C) Protozoa.
D) Fungi.
E) All of the above.

Question 24

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

A) Bacitracin
B) Polymyxin
C) Cephalosporin
D) Amphotericin B
E) Penicillin

Question 25

Figure 20.4

The antibiotic streptomycin binds to the 30S subunit of the ribosome as shown in Figure 20.4. The effect is to

A) Prevent binding of tRNA in eukaryotes.
B) Cause misreading of mRNA in 70S ribosomes.
C) Prevent peptide bond formation in prokaryotes.
D) Prevent polypeptide elongation in eukaryotes.
E) None of the above.

Question 26

Which of the following methods of action would be bacteriostatic?

A) Injury to plasma membrane
B) Competitive inhibition with folic acid synthesis
C) Inhibition of RNA synthesis
D) Inhibition of cell wall synthesis
E) None of the above

Question 27

Which of the following statements is false?

A) Fluoroquinolone inhibits DNA synthesis.
B) Acyclovir inhibits DNA synthesis.
C) Interferon inhibits glycolysis.
D) Amantadine inhibits release of viral nucleic acid.
E) None of the above.

Question 28

Which of the following antibiotics causes misreading of mRNA?

A) Chloramphenicol - inhibits peptide bonds at 50S subunit
B) Streptogamin - prevents release of peptide from 70S ribosome
C) Tetracyclines - bind with 30S subunit
D) Aminoglycoside - changes shape of 30S units
E) Oxazolidinone - prevents formation of 70S ribosome

Question 29

Drug resistance occurs

A) When antibiotics are taken after the symptoms disappear.
B) Because bacteria are normal microbiota.
C) Against antibiotics and not against synthetic chemotherapeutic agents.
D) When antibiotics are used indiscriminately.
E) All of the above.

Question 30

In the presence of penicillin a cell dies because

A) It undergoes osmotic lysis.
B) It plasmolyzes.
C) It lacks a cell membrane.
D) It lacks a cell wall.
E) None of the above.

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. $\begin{array}{lc} \underline{\text { Antibiotic} }& \underline{\text { Zone of Inhibition }}\\A&3mm\\\text { B } & 7 \mathrm{~mm} \\\text { C } & 0 \mathrm{~mm} \\\text { D } & 10 \mathrm{~mm}\end{array}$

-In Table 20.2, the most effective antibiotic tested was

A) A.
B) B.
C) C.
D) D.
E) Can't tell.

Question 32

Antimicrobial peptides work by

A) Complementary base- pairing with DNA.
B) Inhibiting protein synthesis.
C) Disrupting the plasma membrane.
D) Hydrolyzing peptidoglycan.
E) Inhibiting cell- wall synthesis.

Question 33

More than half of our antibiotics are

A) Produced by Fleming.
B) Produced by fungi.
C) Produced by bacteria.
D) Synthesized in laboratories.
E) None of the above.

Question 34

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

A) Streptomycin - inhibits protein synthesis
B) Vancomycin - inhibits peptidoglycan synthesis
C) Streptogramin - inhibits protein synthesis
D) Ethambutol - inhibits mycolic acid synthesis
E) Bacitracin - inhibits peptidoglycan synthesis

Question 35

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) 4 and 5
C) 3, 4, and 5
D) 3 and 4
E) All of the antibiotics

Question 36

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

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

Question 37

Table 20.1
The following data were obtained from a broth dilution test. $\begin{array}{c}&&\text { Growth in }\\\text { Concentration of Antibiotic } X&\text { Growth }&\text { Subculture }\\\hline2 \mu \mathrm{g} / \mathrm{ml}&+&+ \\10 \mu \mathrm{g} / \mathrm{ml}&-&+ \\15 \mu \mathrm{g} / \mathrm{ml} &-&-\\25 \mu \mathrm{g} / \mathrm{ml}&-&-\end{array}$

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

A) 15 µg/ml.
B) 25 µg/ml.
C) 2 µg/ml.
D) 10 µg/ml.
E) Can't tell.

Question 38

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

A) It doesn't affect eukaryotic cells.
B) It inhibits gram- positive cell wall synthesis.
C) It was the first antibiotic.
D) It has selective toxicity.
E) None of the above.

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 don't reproduce.
D) They don't have ribosomes.
E) None of the above.

Question 40

Which of the following statements about drugs that competitively inhibit DNA polymerase or RNA polymerase is not true?

A) They cause mutations.
B) They are too dangerous to be used.
C) They affect host cell DNA.
D) They are used against viral infections.
E) None of the above.

Question 41

Figure 20.5

If the compound shown in Figure 20.5 is the substrate for a particular enzyme, which of the drugs would be the most effective competitive inhibitor?

A) a
B) b
C) c
D) d
E) None of the above.

Question 42

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

A) Penicillinase- producing Neisseria gonorrhoeae
B) Streptococcus pyogenes
C) Mycoplasma
D) L forms
E) Penicillium

Question 43

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) Stop the ribosome from moving along the mRNA.
B) Prevent attachment of tRNA and mRNA.
C) Prevent peptide bond formation.
D) Prevent attachment of tRNA.
E) Prevent transcription.

Question 44

All of the following act by competitive inhibition except

A) Sulfonamide.
B) Ethambutol.
C) Streptomycin.
D) Isoniazid.
E) None of the above.