Deck 20: Antimicrobial Drugs

Question 1

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

Answer 1

B

Question 2

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

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 2

C

Question 3

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 3

B

Question 4

Figure 20.2

In Figure 20.2,chloramphenicol binds to the 50S ribosome subunit.What effect would occur if this drug is administered to a eukaryote?

A)Nothing - eukaryotes have a 60S large ribosomal subunit,not a 50S.
B)The drug would effectively shut down protein synthesis in the eukaryote.
C)The drug would bind instead to the 30S ribosome subunit,but still shut down protein synthesis.
D)The drug would bind to the 50S ribosome subunit,but at a different location,and protein synthesis would continue.

Question 5

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

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

Question 6

From the data in Table 20.1,you can predict that the effect of the drug on a different microbe

A)will be the same.
B)will be weaker.
C)will be stronger.
D)can't be predicted from the information provided.

Question 7

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

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

Question 8

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.

Question 9

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

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

Question 10

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

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

Question 11

Figure 20.1

In Figure 20.1,why is tetracycline selectively toxic against bacteria?

A)Eukaryotic cells will enzymatically destroy the drug.
B)Eukaryotic cells will actively pump the drug out of their interiors.
C)The drug affects peptidoglycan synthesis,and eukaryotic cells have no peptidoglycan.
D)The drug binds to the 30S small ribosomal subunit - eukaryotes have a 40S small subunit.
E)Eukaryotes lack a small ribosomal subunit,so the drug cannot negatively affect them.

Question 12

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)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.

Question 13

Which one of the following antibiotics is NOT bactericidal?

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

Question 14

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.

Question 15

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.

Question 16

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 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.

Question 17

Most of the available antimicrobial agents are effective against

A)viruses.
B)bacteria.
C)fungi.
D)protozoa.

Question 18

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

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

Question 19

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.

Question 20

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 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.

Question 21

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

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

Question 22

Table 20.2
The following results were obtained from a disk-diffusion test for microbial susceptibility to antibiotics.Staphylococcus aureus was the test organism.

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 23

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.

Question 24

Which compound would be the most useful to treat candidiasis?

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

Question 25

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.

Question 26

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.

Question 27

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

Question 28

Table 20.2
The following results were obtained from a disk-diffusion test for microbial susceptibility to antibiotics.Staphylococcus aureus was the test organism.

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 29

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.

Question 30

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.

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.

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 32

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.

Question 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

Question 34

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.

Question 35

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

Question 36

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.

Question 37

If you tested a 2nd strain of S.aureus with the same method and concentrations of drugs as indicated in Table 20.2,but you found that the zone of inhibition caused by drug D had dropped to 2 mm,what does this indicate?

A)The 2nd strain of bacteria is likely resistant to drug D.
B)The 2nd strain of bacteria is much more sensitive to drug D.
C)The experiment wasn't conducted properly,and is giving inaccurate results.
D)There is no functional difference between how the 2 strains react to the drug.

Question 38

The antimicrobial drugs with the broadest spectrum of activity are

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

Question 39

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.

Question 40

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 decreased uptake of a drug.

Question 41

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

Question 42

An antibiotic that attacks the LPS layer would be expected to have a broad spectrum of activity,effective against Gram negative and Gram positive cells.

Question 43

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 44

Which of the following does NOT affect eukaryotic cells?

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

Question 45

Which one of the following anti-protozoan drugs was a traditional Chinese medicine for controlling fevers,but which has also exhibited useful anti-malarial properties?

A)Quinacrine
B)Metronidazole
C)Miltefosine
D)Mebendazole
E)Artemisinin

Question 46

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.

Question 47

Only microbes produce antimicrobial peptides.

Question 48

Community-acquired MRSA is typically less virulent than healthcare-associated MRSA.

Question 49

Antiviral drugs target viral processes that occur during viral infection.

Question 50

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

Question 51

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

Question 52

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.

Question 53

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

Question 54

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

Question 55

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.

Question 56

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

Question 57

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

Question 58

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

Question 59

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

Bacteria from the 0.25 μg/ml tube were transferred to new growth media
Containing antibiotic X with the following results:

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.

Question 60

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.

Question 61

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

Question 62

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

Question 63

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

Question 64

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 "grind to a halt." Do you agree? Explain.

Question 65

Explain why penicillin was called the "miracle drug" when it was first used in the 1940s.