Microbiology: An Introduction, 13e (Tortora et al.)
Chapter 20 Antimicrobial Drugs
20.1 Multiple-Choice Questions
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.
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.
3) Most of the available antimicrobial agents are effective against
A) viruses.
B) bacteria.
C) fungi.
D) protozoa.
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.
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.
6) Which one of the following antibiotics is NOT bactericidal?
A) aminoglycosides
B) cephalosporins
C) polyenes
D) rifampins
E) penicillin
7) Which one of the following does NOT belong with the others?
A) bacitracin
B) cephalosporin
C) monobactam
D) penicillin
E) streptomycin
Figure 20.1
8) 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.
9) 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.
Figure 20.2
10) 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.
11) 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.
12) Which of the following antimicrobial agents has the fewest side effects?
A) streptomycin
B) tetracycline
C) penicillin
D) erythromycin
E) chloramphenicol
13) Which of the following drugs does NOT act by competitive inhibition?
A) ethambutol
B) isoniazid
C) streptomycin
D) sulfonamide
E) trimethoprim
14) 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
15) Which of the following antibiotics is recommended for use against gram-negative bacteria?
A) polyenes
B) bacitracin
C) cephalosporin
D) penicillin
E) polymyxin
16) Which of the following antimicrobial agents is recommended for use against fungal
infections?
A) amphotericin B
B) bacitracin
C) cephalosporin
D) penicillin
E) polymyxin
Table 20.1
The following data were obtained from a broth dilution test.
Concentration of Antibiotic X Growth Growth in Subculture
2 μg/ml + +
10 μg/ml – +
15 μg/ml – –
25 μg/ml – –
17) 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.
18) 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.
19) 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.
20) 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.
21) 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
22) 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.
23) Which compound would be the most useful to treat candidiasis?
A) uracil
B) thymine
C) flucytosine
D) guanine
E) penicillin
24) 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.
25) Which of the following antibiotics does NOT interfere with cell wall synthesis?
A) cephalosporins
B) macrolides
C) natural penicillins
D) semisynthetic penicillins
E) vancomycin
26) The antimicrobial drugs with the broadest spectrum of activity are
A) aminoglycosides.
B) chloramphenicol.
C) penicillin G.
D) macrolides.
E) tetracyclines.
27) 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.
28) 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.
29) 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
30) 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.
31) 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.
32) 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.