Question 1

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?

Accepted Answer

A)  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.
B)  Antibiotic resistance is usually only manifested by bacteria that have achieved a very high concentration (i.e.they are in the very end of the stationary phase of the growth curve) .It's important to use bacteria specifically at this particular point for disc diffusion testing.
C)  If you were to use 1 strain that was in 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 dramatically different results in the disc diffusion test.This could skew your interpretations of resistance/susceptibility.
D)  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.E) B) and D)
F) All of the above

Question 2

Why are nucleoside analogs active only against replicating viruses?

Accepted Answer

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.As such, these drugs can only work when the virus is actively replicating as well.E) A) and B)
F) A) and C)

Question 3

The antimicrobials produced by some molds and bacteria are generally called

Accepted Answer

A)  insecticides.
B)  biocides.
C)  antiseptics.
D)  antibiotics.E) B) and D)
F) A) and B)

Question 4

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

Accepted Answer

A)  penicillin.
B)  sulfa.
C)  erythromycin.
D)  Salvarsan.E) B) and C)
F) B) and D)

Question 5

Antimicrobials that inhibit the growth of microorganisms have the suffix

Accepted Answer

A)  -cidal.
B)  -static.
C)  -anti.
D)  -genic.E) A) and B)
F) All of the above

Question 6

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

Accepted Answer

A)  antibiotics.
B)  toxins.
C)  inhibitors.
D)  chemotherapy.E) B) and C)
F) A) and B)

Question 7

Broad-spectrum antibiotics have minimal effect on the normal flora.

Accepted Answer

A) True 
 B)False

Question 8

Sulfonamides are similar in structure to

Accepted Answer

A)  DNA gyrases.
B)  LPS.
C)  ribosomes.
D)  PABA.E) C) and D)
F) A) and B)

Question 9

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

Accepted Answer

A)  energetic.
B)  antagonistic.
C)  additive.
D)  synergistic.E) All of the above
F) B) and C)

Question 10

Bacteria may become antibiotic resistant due to

Accepted Answer

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.F) A) and B)
G) A) and C)

Question 11

Penicillin was discovered by

Accepted Answer

A)  Koch.
B)  Hooke.
C)  Fleming.
D)  Ehrlich.E) A) and C)
F) A) and B)

Question 12

The target of most antifungal drugs is

Accepted Answer

A)  the ribosome.
B)  nucleus.
C)  cholesterol.
D)  ergosterol.
E)  cholesterol AND ergosterol.F) A) and D)
G) A) and C)

Question 13

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

Accepted Answer

A) True 
 B)False

Question 14

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

Accepted Answer

A)  penicillin.
B)  sulfanilamide.
C)  erythromycin.
D)  Salvarsan.E) B) and C)
F) All of the above

Question 15

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

Accepted Answer

A)  binds to several sites on the target molecule.
B)  targets several different molecules.
C)  affects only one molecule.
D)  affects the plasma membrane.
E)  binds to several sites on the target molecule AND targets several different molecules.F) None of the above
G) All of the above

Question 16

A commercial modification of the disk diffusion test is called the

Accepted Answer

A)  A test.
B)  B test.
C)  C test.
D)  D test.
E)  E test.F) All of the above
G) C) and D)

Question 17

A high therapeutic index is

Accepted Answer

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) A) and B)
F) A) and C)

Question 18

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

Accepted Answer

A)  infectious dose.
B)  lethal dose.
C)  effective dose.
D)  minimum inhibitory concentration.E) A) and D)
F) None of the above

Question 19

Which is true of aminoglycosides?

Accepted Answer

A)  They are bacteriostatic.
B)  They irreversibly bind to the 30S ribosomal subunit.
C)  They block peptidoglycan synthesis.
D)  They are bactericidal.
E)  They irreversibly bind to the 30S ribosomal subunit AND they are bactericidal.F) C) and E)
G) A) and B)

Question 20

Fluoroquinolones typically target

Accepted Answer

A)  ribosomes.
B)  penicillin-binding proteins.
C)  peptidoglycan.
D)  DNA gyrase.E) All of the above
F) B) and C)

Exam 20: Antimicrobial Medications

The antimicrobials produced by some molds and bacteria are generally called

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

Why are nucleoside analogs active only against replicating viruses?

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

Which is true of aminoglycosides?

Correct AnswerverifiedShow Answer

A high therapeutic index is

Correct AnswerverifiedShow Answer

A commercial modification of the disk diffusion test is called the

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

Penicillin was discovered by

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

Fluoroquinolones typically target

Correct AnswerverifiedShow Answer

Bacteria may become antibiotic resistant due to

Correct AnswerverifiedShow Answer

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?

Correct AnswerverifiedShow Answer

Antimicrobials that inhibit the growth of microorganisms have the suffix

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

Sulfonamides are similar in structure to

Correct AnswerverifiedShow Answer

The target of most antifungal drugs is

Correct AnswerverifiedShow Answer

Broad-spectrum antibiotics have minimal effect on the normal flora.

Correct AnswerverifiedShow Answer

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