Chapter.20 Antimicrobial Medications Exam Questions nan

Nester’s Microbiology, 9e (Anderson)

Chapter 20 Antimicrobial Medications

1) One of the earliest researchers to explore the use of chemicals to kill microbial pathogens was

A) Koch.

B) Ehrlich.

C) Hooke.

D) Fleming.

E) Salvarsan.

2) The arsenic compound that proved highly effective in treating syphilis was called

A) penicillin.

B) sulfa.

C) erythromycin.

D) Salvarsan.

E) erlichsan.

3) The first example of an antimicrobial drug synthesized in the laboratory was

A) penicillin.

B) sulfa.

C) erythromycin.

D) Salvarsan.

E) Erlichsan.

4) Prontosil effectively acted on streptococci when the drug was split by enzymes to produce

A) penicillin.

B) sulfanilamide.

C) erythromycin.

D) Salvarsan.

E) Salvarsan AND penicillin.

5) The use of Salvarsan and Prontosil to treat microbial infections were early examples of

A) antibiotics.

B) toxins.

C) chemotherapy.

D) inhibitors.

E) vaccination.

6) Penicillin was discovered by

A) Fleming.

B) Koch.

C) Hooke.

D) Ehrlich.

E) Pasteur.

7) The most effective form of penicillin is

A) penicillin A.

B) penicillin B.

C) penicillin E.

D) penicillin G.

E) penicillium.

8) One of the earliest antimicrobials isolated from a bacterium was

A) penicillin.

B) ampicillin.

C) streptomycin.

D) Salvarsan.

E) tetracycline.

9) Which of the following groups of microorganisms produces antibiotics?

A) Penicillium AND Bacillus

B) Streptomyces AND Bacillus

C) Bacillus, Penicillium, AND Streptomyces

D) Penicillium AND Streptomyces

E) Clostridium AND Streptomyces

10) An antibiotic made by microorganisms and modified by chemists is called

A) anti-metabolic.

B) catabolic.

C) semi-synthetic.

D) synthetic.

E) semi-catabolic.

11) The antimicrobials produced by some molds and bacteria are generally called

A) insecticides.

B) biocides.

C) antiseptics.

D) antibiotics.

E) pesticides.

12) The toxicity of a given drug is expressed as the

A) selective toxicity.

B) therapeutic index.

C) biocide index.

D) biostatic index.

E) bacteriostatic window.

13) A high therapeutic index is

A) more toxic to the patient.

B) less toxic to the patient.

C) has no effect on the patient.

D) has no effect on the pathogen.

E) more toxic to the patient AND has little effect on the pathogen.

14) Drugs that are bacteriostatic

A) kill all bacteria.

B) promote bacterial growth.

C) inactivate bacterial spores.

D) inhibit the growth of bacteria.

E) kill infected host cells.

15) Antimicrobials that kill microorganisms have the suffix

A) -cidal.

B) -static.

C) -anti.

D) -genic.

E) -acto.

16) Antimicrobials that inhibit the growth of microorganisms have the suffix

A) -cidal.

B) -static.

C) -anti.

D) -genic.

E) -acto.

17) Antibiotics that affect various strains of Gram-positive bacteria and various strains of Gram-negative bacteria are called

A) isolate usable.

B) stress-induced.

C) broad-spectrum.

D) narrow-spectrum.

E) intermediate.

18) The rate of elimination of an antimicrobial is expressed as its

A) metabolic destructive rate.

B) half-life.

C) effective time.

D) dosage rate.

E) therapeutic index.

19) Antibiotics that are most likely to disrupt the normal microbiota are termed

A) broad-spectrum.

B) narrow-spectrum.

C) targeted spectrum.

D) semi-synthetic.

E) therapeutic.

20) Drugs that are more effective when taken together are 

A) energetic.

B) antagonistic.

C) synergistic.

D) subtractive.

E) symbiotic.

21) If drugs are less effective when taken together than when each is taken separately, they are 

A) energetic.

B) antagonistic.

C) additive.

D) synergistic.

E) commensal.

22) Antimicrobials may cause all of the following EXCEPT

A) allergic reactions.

B) toxic effects.

C) suppression of normal microbiota.

D) dysbiosis.

E) resistance in people.

23) Which of the following bacteria have an innate resistance to penicillin?

A) S. aureus

B) Mycoplasma

C) S. epidermidis

D) M. luteus

E) All of the answer choices are correct.

24) Which of the following drugs does NOT target peptidoglycan?

A) Penicillin

B) Cephalosporin

C) Vancomycin

D) Bacitracin

E) Doxycycline

25) All members of the penicillin family have

A) beta-lactam rings.

B) alpha-lactam rings.

C) phenolic rings.

D) sulfanilic rings.

E) sulfanilic hexons.

26) Penicillin-binding proteins

A) primarily function in the cell to bind to beta-lactam drugs.

B) are enzymes.

C) are involved in cell wall synthesis.

D) inhibit non-growing bacteria.

E) are enzymes AND are involved in cell wall synthesis.

27) Beta-lactamases

A) bind to penicillin-binding proteins.

B) break the beta-lactam ring.

C) bind to peptides.

D) prevent the linking of glycan chains in peptidoglycan.

E) bind to carbohydrates.

28) The major class(es) of antibiotics that inhibit protein synthesis include all of the following EXCEPT

A) bacitracins.

B) aminoglycosides.

C) tetracyclines.

D) macrolides.

E) streptogramins.

29) Inhibitors of protein synthesis typically act on

A) peptidoglycan precursors.

B) penicillin-binding proteins.

C) ribosomes.

D) porin proteins.

E) transfer RNA.

30) Which is true of aminoglycosides?

A) They are bacteriostatic AND they reversibly bind to the 30S ribosomal subunit.

B) They irreversibly bind to the 30S ribosomal subunit AND they block DNA replication.

C) They block peptidoglycan synthesis AND they  bind to the 80S ribosomal subunit.

D) They are bactericidal AND they block DNA replication.

E) They irreversibly bind to the 30S ribosomal subunit AND they are bactericidal.

31) Fluoroquinolones typically target

A) ribosomes.

B) DNA gyrase.

C) penicillin-binding proteins.

D) peptidoglycan.

E) cytoplasmic membranes.

32) Sulfonamide and trimethoprim are both

A) examples of metabolic inhibitors.

B) folate inhibitors.

C) protein synthesis inhibitors.

D) inhibitors of cell wall synthesis.

E) examples of metabolic inhibitors AND folate inhibitors.

33) Folic acid is ultimately used in the synthesis of

A) topoisomerases.

B) proteins.

C) DNA gyrases.

D) sulfonamides.

E) coenzymes.

34) Sulfonamides are similar in structure to

A) DNA gyrases.

B) PABA.

C) LPS.

D) ribosomes.

E) peptidoglycan.

35) Sulfonamides work as

A) competitive inhibitors.

B) noncompetitive inhibitors.

C) ribosome-binding molecules.

D) feedback inhibitors.

E) coenzymes.

36) Trimethoprim and sulfonamides have a(n)

A) antagonistic effect.

B) synergistic effect.

C) energetic effect.

D) subtractive effect.

E) counteractive effect.

37) Mycolic acids are targeted by isoniazid in the treatment of

A) S. aureus.

B) S. epidermidis.

C) M. luteus.

D) M. tuberculosis.

E) E. coli.

38) The lowest concentration of a drug that prevents growth of a microorganism is the

A) infectious effective dose.

B) minimum inhibitory concentration.

C) lethal dose.

D) most effective concentration.

E) minimal death dose.

39) The minimum bactericidal concentration is the lowest concentration of a specific antimicrobial drug that kills ________ of a specific type of bacteria.

A) 10%

B) 50%

C) 99.9%

D) 100%

E) 25%

40) The diffusion bioassay

A) determines the concentration of antimicrobial necessary to kill a bacteria.

B) determines the concentration of antimicrobial necessary to inhibit growth of a bacteria.

C) is similar in principle to the Kirby-Bauer test.

D) determines the concentration of antimicrobial in a fluid.

E) is similar in principle to the Kirby-Bauer AND determines the concentration of antimicrobial in a fluid.

41) Which test is used to determine the susceptibility of a microorganism to an antimicrobial?

A) Minimum inhibitory concentration

B) Minimum bactericidal concentration

C) Minimally-lethal dose

D) Antibiotic stimulating zone test

E) Kirby-Bauer test

42) The zone size obtained in the Kirby-Bauer test is influenced by the drug's

A) molecular weight AND concentration.

B) stability.

C) concentration AND stability.

D) molecular weight AND stability.

E) molecular weight, stability, AND concentration.

43) A commercial modification of the disk diffusion test is called the

A) E test.

B) D test.

C) C test.

D) B test.

E) A test.

44) Bacteria may become antibiotic resistant due to

A) drug-inactivating enzymes.

B) alteration in the target molecule.

C) decreased uptake of the drug.

D) increased elimination of the drug.

E) All of the choices are correct.

45) Spontaneous development of resistance to a particular antimicrobial is difficult if the drug

A) targets a single type of molecule AND binds to a single site on that target molecule.

B) targets several different molecules AND affects the cytoplasmic membrane.

C) affects only one molecule.

D) affects the cytoplasmic membrane.

E) binds to several sites on the target molecule AND targets several different molecules.

46) The most common method of transfer of antimicrobial resistance is through the use of

A) viruses.

B) R plasmids.

C) introns.

D) exons.

E) F plasmids.

47) Compliance problems are leading to a large increase in antibiotic resistant strains of

A) Mycobacterium.

B) Streptococcus.

C) Staphylococcus.

D) Pseudomonas.

E) Mycoplasma.

48) Antiviral drugs may target all of the following EXCEPT

A) viral uncoating.

B) viral ribosomes.

C) nucleic acid synthesis.

D) viral assembly.

E) viral entry.

49) The target of most antifungal drugs is

A) the ribosome AND the cytoplasmic membrane.

B) the nucleus AND mitochondria.

C) cholesterol.

D) ergosterol.

E) cholesterol AND ergosterol.

50) The key characteristic of a useful antimicrobial is selective toxicity.

51) Antimicrobials that have a high therapeutic index are less toxic to the patient.

52) Broad-spectrum antibiotics have minimal effect on the normal microbiota.

53) Certain antimicrobials may be life-threatening.

54) Drugs that target peptidoglycan do not affect eukaryotes.

55) Beta-lactam drugs are only effective against growing bacteria.

56) The MBC may be determined by an extension of the MIC.

57) Antimicrobial resistance can be due to spontaneous mutation or gene acquisition.

58) Viruses are very effectively treated with antibiotics.

59) Antifungal drugs usually target the cell membrane.

60) In what clinical situation is it most appropriate to use a broad-spectrum antimicrobial?

A) In an example of a viral pediatric otitis media (middle ear) infection. We can't properly test for the specific drug that would best eliminate the infection due to its location, so we use a broad-spectrum drug instead.

B) In a case of viral meningitis. The infection spreads so quickly that we must treat it with an antibacterial drug as quickly as possible. We don't have time to determine which drug will work best, because the patient will die in the meantime.

C) In a case of bacterial meningitis. The infection spreads so quickly that we must treat it with an antibacterial drug as quickly as possible. We don't have time to determine which drug will work best, because the patient will die in the meantime.

D) In a case of Staphylococcus aureus skin infection. Since this microbe can be resistant to several types of drugs, we want to use one that has the broadest spectrum possible to treat this microbe-specific infection.

E) There are no appropriate situations for using broad-spectrum antibiotics, because they almost always lead to resistance. It is much better to use a narrow-spectrum medication.

61) Why would antimicrobials that have toxic side effects be used at all? (select the BEST reason)

A) We want the largest possible number of choices of drugs in case a microbe shows resistance. With more possible weapons (even toxic ones), we have greater ability to eliminate infections.

B) Every person is different.  What is toxic to one person may not be toxic to another person. To eliminate a useful drug because it's toxic to 1% of people treated is a waste.

C) Depending on the location of the infection, we may have no choice but to utilize a drug that has some toxic side effects to the patient.

D) They shouldn't be used. We have enough of a selection of drugs that we can always select a drug with no toxicity. Drugs with toxicity are simply leftovers from a time when we didn't have as many drug options.

E) These are all reasons to use antimicrobials that have a low therapeutic index.

62) Why would co-administration of a bacteriostatic drug interfere with the effects of penicillin?

A) Since most bacteriostatic drugs are produced from bacteria but penicillin is produced from mold, the two drugs are incompatible with each other.

B) A bacteriostatic drug interferes with the ability of a bacterial cell to take in compounds from the outside environment. Penicillin must be taken in by the cell in order to have its effect, so this would directly inhibit it.

C) The bacteriostatic drugs would bind directly to the penicillin, preventing both its uptake by the cell and its ability to perform its duty within the bacterial cell.

D) Penicillin interferes with cell wall production so it only works when the cells are actively replicating and MAKING new peptidoglycan. A bacteriostatic drug works by shutting down replication, holding the cells "static." This would interfere with the mode of action required by the penicillin.

E) Nothing interferes with the effects of penicillin. It is the most effective medication that we have, so is never used with the addition of a second drug when treating a person.

63) Why would it be important for the Kirby-Bauer disc diffusion test to use a standard concentration (number of cells in the sample) of each of the bacterial strains being tested?

A) If you were to use one strain that was stationary phase (high concentration, replicating very slowly or not at all), and another strain that was just beginning log phase (low concentration but replicating quickly), you could see different results in the test, affecting your interpretation. 

B) Growth on the Mueller-Hinton agar plates utilized is very sensitive to the phase of the growth curve the bacteria are in when they are placed on the plate.  If they are not in the log phase when they are placed on the plate, they will not grow and the test will be worthless.

C) Antibiotic resistance is usually only manifested by bacteria that have achieved a very high concentration. It's important to use bacteria specifically at this particular point for disc diffusion testing.

D) Antibiotics only work within a narrow range of cell concentrations. If you use a concentration that is too low or too high, you will get inaccurate measurements of the zone of inhibition.

E) Bacteria only develop resistance when there are more than 1012 cells/ mL. If resistance is to be detected, the test must use at least this concentration of cells. If fewer cells are used, no zone of inhibition will develop.

64) Explain how using a combination of two antimicrobial drugs helps prevent the development of spontaneously resistant mutants.

A) All drugs work synergistically with each other. Their combined effects are far greater than either could achieve individually. Two drugs together helps to eliminate microbes, even if they have developed spontaneous mutations that would make them resistant to the drugs.

B) It is highly unlikely that the microbe might spontaneously develop two specific mutations to resist the effects of a pair of drugs. As such, even if one drug is resisted by the microbe, the second drug will eliminate the mutated microbe, thus preventing the development of spontaneously resistant mutants overall.

C) All drugs work antagonistically with each other. Their combined effects are far greater than either could achieve individually. Two drugs together helps to eliminate microbes, even if they have developed spontaneous mutations that would make them resistant to the drugs.

D) Drugs can also select for mutations that will enhance the activity of another drug. Therefore, each of the paired drugs will help to select for spontaneous mutations that enhance the activity of the other drug in the pair.

E) Bacteria can only ever develop resistance to a single antibiotic. If more than one drug is used, the organisms will definitely become resistant to one of them but it will not become resistant to both of them. The second antibiotic will kill the organism.

65) Why are nucleoside analogs active only against replicating viruses?

A) These drugs can only be taken up by cells that are infected by viruses. They are shut out from non-infected cells. This makes them effective only against cells where viruses are replicating.

B) Each of these drugs is specifically activated by enzymes produced by the viruses. The viruses will only produce these enzymes when they are replicating, so the drugs can only become activated when these processes are occurring.

C) Nucleoside analogs work by directly inhibiting the activity of nucleic acid polymerases. If the virus isn't actively replicating, there's no DNA/RNA polymerase active for the drug to inhibit, so the drug cannot work.

D) Nucleoside analogs work by being incorporated into growing strands of DNA/RNA. This indirectly shuts down further extension of these chains. However, new strands of viral DNA/RNA are only being created when the virus is replicating. Thus, these drugs can only work when the virus is actively replicating as well.

E) Nucleoside analogs work by being incorporated into growing strands of amino acids during enzyme synthesis. This indirectly shuts down further extension of these chains. However, new viral proteins are only being created when the virus is replicating, so these medications only work if that is the case.

66) Which is the correct definition of selective toxicity?

A) A medication causing greater harm to a pathogen than to the host.

B) A medication causing greater harm to a host than to a pathogen.

C) The lowest dose of a medication toxic to the pathogen.

D) The range between the therapeutic dose and the toxic dose of a medication.

E) A medication that only targets Gram-negative bacteria.

67) What allows for selective toxicity in a medication?

A) The medication acts against an essential component or biochemical process of microorganisms that does not exist in human cells.

B) The medication is converted into a non-toxic form by the liver in people, but remains highly toxic in bacteria which cannot process the drug.

C) The medication acts against an essential component or biochemical process of human cells that does not exist in microorganisms.

D) Only some medications cross from the blood into the cerebrospinal fluid of humans.

E) Some medications have a very extended half-life AND only some medications cross from the blood into the cerebrospinal fluid of humans.

68) Please select the FALSE statement regarding tissue distribution, metabolism, and excretion of medications.

A) Patients who have liver dysfunction often metabolize medications more slowly, so their doses must be adjusted to avoid toxic levels.

B) The half-life of a medication is the time it takes for the serum concentration of that chemical to decrease by 100%.

C) Medications that are unstable at low pH are typically given by intravenous or intramuscular injection.

D) A medication with a half-life of over 24 hours is taken only once a day or less.

E) A medication that has a very short half-life usually needs to be taken several times a day.

69) Please select the TRUE statement regarding bacterial resistance to antimicrobials.

A) Gram-positive bacteria are intrinsically resistant to certain medications because the lipid bilayer of their outer membrane prevents the molecules from entering.

B) Intrinsic resistance  generally occurs through spontaneous mutation or horizontal gene transfer.

C) The genes for antimicrobial resistance are often carried on fertility plasmids (F plasmids).

D) Mycoplasma species lack a cell wall, so they are resistant to penicillin that interferes with peptidoglycan synthesis. This is an example of intrinsic resistance.

E) Acquired resistance is very limited because microorganisms cannot evolve, so are incapable of developing mechanisms to avoid the effects of medications. 

70) Which of the following would you prescribe to treat a person with M. pneumoniae?

A) A β-lactam antibiotic such as penicillin

B) A glycopeptide antibiotic such as vancomycin

C) Bacitracin

D) A macrolide such as erythromycin

E) Bacitracin OR penicillin

71) Which statement about penicillins is INCORRECT?

A) Penicillins + β-lactamase inhibitor is a combination of agents that protects the penicillin against enzymatic digestion.

B) Broad-spectrum penicillins are active against penicillin-sensitive Gram-positive bacteria and also many Gram-negative bacteria.

C) Some S. aureus strains have the ability to make altered penicillin binding proteins to which most β-lactam antibiotics do not bind as well.

D) The penicillins produced naturally by the mold P. chrysogenum are broad-spectrum, effective against all Gram-positive and many Gram-negative bacteria.

E) Bacteria that produce penicillinase are resistant to the natural penicillins.

72) Carbapenems are easily inactivated by the extended-spectrum β-lactamases (ESBLs) produced by certain Gram-negative bacteria so cannot be used to treat these infections.

73) Why must vancomycin be administered intravenously except when used to treat intestinal infections?

A) Vancomycin is poorly absorbed from the intestinal tract.

B) Vancomycin is toxic but less so if injected intravenously.

C) Injected vancomycin is easier to target to the site of infection.

D) Vancomycin is effective against only Gram-positive bacteria.

E) Vancomycin has a high therapeutic index.

74) What is the minimum inhibitory concentration (MIC)?

A) It is the lowest concentration of a specific antimicrobial medication needed to prevent the visible growth of a given bacterial strain in vitro.

B) It is the highest concentration of a specific antimicrobial medication needed to prevent the visible growth of a given bacterial strain in vitro.

C) It is the lowest concentration of a specific antimicrobial medication needed to prevent the visible growth of a given bacterial strain in vivo.

D) It is the highest concentration of a specific antimicrobial medication needed to prevent the visible growth of a given bacterial strain in vivo.

E) It is the lowest concentration of a specific antimicrobial medication that kills 99.9% of cells of a given bacterial strain in vitro.

75) What are two advantages of automated tests used to determine antimicrobial susceptibility?

A) They are easier to perform.

B) They produce results more quickly than conventional tests.

C) They produce results more quickly than conventional tests AND they are easier to perform.

D) They take longer to perform BUT they give fewer false results.

E) They are cheaper than conventional tests AND they give more accurate results.

76) Please select the statement regarding antimicrobial testing that is FALSE.

A) Commercial tests for determining antimicrobial sensitivity are less labor-intensive and often more rapid than conventional tests.

B) Disc diffusion tests can determine whether an organism is susceptible, intermediate, or resistant to a variety of different antimicrobials.

C) The MIC and the MBC are quantitative measures of a bacterial strain's susceptibility to an antimicrobial medication.

D) In the Kirby-Bauer test, the clear area in which there is no visible growth of bacteria is called a zone of inhibition.

E) In the Kirby-Bauer disc diffusion test, a clear zone around the antibiotic disc following incubation indicates that the antibiotic is bactericidal.

77) Please select the FALSE statement regarding antibiotic resistance.

A) Modifications in the penicillin-binding proteins (PBPs) prevent β-lactam antibiotics from binding to them.

B) Some antibiotic-inactivating enzymes have an extended spectrum and confer resistance to a wide variety of antibiotics.

C) Changes in the porin proteins can prevent certain antimicrobials from entering a cell's periplasm or cytoplasm.

D) The bacterial enzyme chloramphenicol acetyltransferase confers resistance to the penicillins.

E) Bacteria that produce efflux pumps sometimes become resistant to several different antimicrobials simultaneously.

78) Which statement about antiviral medications is INCORRECT?

A) Viral replication generally uses host cell machinery; because of this, there are many targets for selectively toxic antiviral medications.

B) Sofosbuvir is a nucleotide analog that interferes with HCV's replicase and is extremely effective when used in combination with at least one other anti-HCV medication.

C) Nucleoside analogs and nucleotide analogs that interfere with the activity of reverse transcriptase are used in HIV treatment, along with at least one antiviral other medication.

D) Neuraminidase inhibitors inhibit neuraminidase, an enzyme encoded by influenza viruses that is important for the release of viral particles from infected host respiratory epithelial cells.

E) Available antivirals are virus-specific and target viral entry, viral uncoating, nucleic acid synthesis, integrase, and the assembly and release of viral particles.

Gonorrhea is a sexually transmitted infection (STI) caused by the diplococcus Neisseria gonorrhoeae, commonly called gonococcus (GC). This organism developed resistance to penicillin and tetracycline in the 1980s, after which fluoroquinolones were the recommended drugs for treating GC. Subsequent resistance to the fluoroquinolones has led to the current recommended treatment of injected ceftriaxone in combination with oral azithromycin. Although this approach continues to be effective, recent data from the CDC indicates that resistance to azithromycin is emerging.

79) Initially, GC was treated with penicillin, which targets ________, and tetracycline which targets ________.

A) protein synthesis; peptidoglycan synthesis

B) peptidoglycan synthesis; protein synthesis

C) protein synthesis; capsule formation

D) capsule formation; ergesterol formation

E) cell membrane integrity; folic acid synthesis

80) Penicillin is a(n)

A) β-lactam antibiotic and has a low therapeutic index, meaning that it is of high toxicity to the host.

B) carbapenam and is thus resistant to extended spectrum β-lactamases.

C) glycopeptide antibiotic and is thus used as an antibiotic of last resort.

D) β-lactam antibiotic and has a high therapeutic index, meaning that it is of low toxicity to the host.

E) aminoglycoside and may sometimes cause kidney damage.

81) Fluoroquinolones act by inhibiting DNA gyrase, an enzyme involved in DNA replication. Resistance to this antibiotic is most commonly by

A) a change in the DNA gyrase target, an example of acquired resistance.

B) enzymatic modification of the ribosomal target, an example of innate resistance.

C) a change in the DNA gyrase target, an example of innate resistance.

D) due to a mutation in the gene that encodes RNA polymerase, an example of adaptive resistance.

E) increased efflux of the drug from the target cell, an example of innate resistance.

82) Azithromycin is a bacteriostatic antibiotic that interferes with protein synthesis. Ceftriaxone is a β-lactam antibiotic and is primarily bactericidal. This means that

A) azithromycin kills bacterial cells while ceftriaxone inhibits the growth of bacterial cells.

B) bacteria are sensitive to azithromycin but are resistant to ceftriaxone.

C) azithromycin inhibits the growth of bacterial cells while ceftriaxone kills bacterial cells.

D) bacteria are resistant to azithromycin but are susceptible to ceftriaxone.

E) azithromycin can only be used against Gram-positive bacteria.

83) The situation in which the effect of two antimcrobials given together is more effective than the effect of either medication given individually is referred to as 

A) synergism.

B) antagonism.

C) nihilism.

D) symbiosis.

E) dysbiosis.

84) Which of the following targets would you expect to be the most selective with respect to toxicity?

A) Peptidoglycan synthesis

B) 70S ribosome

C) DNA synthesis

D) Glycolysis

E) Cytoplasmic membrane function

An elderly patient comes to see you complaining of a very painful rash. When he lifts his shirt, you see that he has a rash of small blisters (vesicles) on one side of his back. You think he likely has shingles, caused by varicella-zoster virus (VZV), a double-stranded DNA virus that belongs to the Herpesviridae family. You explain this to your patient, who asks you to please give him an antibiotic for his infection. You tell him an antibiotic will not help him, and give him information on virus infections and their treatment.

85) Antibiotics are effective in treating viral infections provided that they are given early in the course of illness.

86) Viruses are completely unaffected by antibiotics because

A) they rely almost completely on the host cell's metabolic machinery for their replication, making it difficult to find a target for selective toxicity.

B) they have no cell wall, ribosomes, or any other structure targeted by antibiotics.

C) they rely almost completely on the host cell's metabolic machinery for their replication, making it difficult to find a target for selective toxicity AND most viruses are innately resistant to broad- and narrow-spectrum antibiotics.

D) They have no cell wall, ribosomes, or any other structure targeted by antibiotics AND they rely almost completely on the host cell's metabolic machinery for their replication, making it difficult to find a target for selective toxicity.

E) most viruses are innately resistant to broad- and narrow-spectrum antibiotics.

87) Several diseases caused by herpesviruses are treated with a medication called acyclovir. This medication is a nucleoside analog, meaning

A) it contains a nucleotide analog and a phosphate.

B) it contains a nucleotide analog, a phosphate, and a sugar.

C) it contains a nucleotide analog and a sugar.

D) it is composed of NAG, NAM, and tetrapeptides.

E) it is composed of NAG, NAM, and a sugar.

88) A nucleoside analog can be phosphorylated in vivo by a virally encoded or normal cellular enzyme to form a nucleotide analog—a chemical structurally similar to the building blocks of DNA and RNA. Nucleotide analogs interfere with

A) viral protein synthesis.

B) viral nucleic acid synthesis.

C) viral peptidoglycan synthesis.

D) viral replicases.

E) All of these choices are correct

89) Acyclovir is selective and low in toxicity, causing little harm to uninfected cells, because

A) only a virally encoded enzyme can convert the medication into its active form (from nucleoside analog to nucleotide analog). 

B) only a virally encoded enzyme can convert the medication into its active form (from nucleotide analog to nucleoside analog). 

C) viral DNA is structurally very different from cellular DNA.

D) host cells have the ability to repair the damage caused by nucleotide analogs.

E) host cells have an enzyme that prevents the conversion of the medication into its active form.

90) Acyclovir interferes with viral DNA replication. Other mechanisms of antiviral medications include all of the following EXCEPT

A) preventing fusion and inhibiting viral entry into a host cell.

B) interfering with viral uncoating and release of viral nucleic acid in a host cell.

C) preventing the assembly viral proteins to form capsids.

D) inhibition of viral particle release from host cells.

E) destroying viral ribosomes and preventing protein synthesis.