Deck 10: Principles of Antimicrobial Action Resistance

Question 1

Staphylococcus aureus is a gram-positive organism that produces the enzyme b-lactamase,which renders certain types of antibiotics inactive.The mode of action that is prevented in certain antibiotics sensitive to this enzyme is:

A)cell wall synthesis.
B)protein synthesis to the 30S ribosomal subunit.
C)protein synthesis to the 50S ribosomal subunit.
D)deoxyribonucleic acid (DNA)synthesis.

Answer 1

A
b-Lactamases open the b-lactam ring of the drug,and the altered structure prohibits subsequent effective binding to penicillin-binding proteins (PBPs),enabling cell wall synthesis to continue.

Question 2

Antibiotic resistance resulting from altered cellular physiologic structure caused by changes in a microorganism's usual genetic makeup is known as __________ resistance.

A)intrinsic
B)inherent
C)acquired
D)environmentally mediated

Answer 2

C
Acquired-resistance mechanisms are all genetically encoded;therefore,the methods for acquisition are those that allow for gene change or exchange.Resistance may be acquired by genetic mutation,gene-transfer mechanisms,or a combination of mutational and gene-transfer events.

Question 3

The mechanism of acquired,high-level resistance to vancomycin involves:

A)enzymatic destruction of the antibiotic.
B)altered antibiotic targets.
C)decreased intracellular uptake of the drug.
D)production of altered cell wall precursors that do not bind the antibiotic with sufficient avidity.

Answer 3

D
The mechanism involves altered cell wall precursors that do not bind vancomycin with sufficient avidity to allow the inhibition of peptidoglycan-synthesizing enzymes.The altered targets are readily incorporated into the cell wall,enabling synthesis to progress as usual.

Question 4

MATCHING
Match the antimicrobial agent with its mode of action.
a.Cell wall synthesis inhibition
b.Cell membrane function inhibition
c.Protein synthesis inhibition
d.DNA and ribonucleic acid (RNA)synthesis inhibition
Gentamicin

Question 5

Antimicrobial agents that usually kill target organisms are said to be:

A)bactericidal.
B)antibiotic.
C)bacteriostatic.
D)antagonistic.

Question 6

Antimicrobial resistance resulting from the normal genetic,structural,or physiologic state of a microorganism is referred to as ________ resistance.

A)intrinsic
B)inherent
C)microorganism-mediated
D)clinical

Question 7

Klebsiella spp.were isolated from a sputum sample,and susceptibility testing was performed.The isolates were sensitive to several antibiotics;however,they were resistant to ampicillin.Which one of the following statements explains this discrepancy?

A)The ampicillin disk is most likely expired.
B)Because Klebsiella spp.should be sensitive to ampicillin,a technical error is to blame.
C)Ampicillin inhibits cell wall synthesis.In addition,because Klebsiella spp.do not have a cell wall,they should not have been tested for ampicillin.
D)No discrepancy is present;Klebsiella spp.are normally resistant to ampicillin.

Question 8

MATCHING
Match the antimicrobial agent with its mode of action.
a.Cell wall synthesis inhibition
b.Cell membrane function inhibition
c.Protein synthesis inhibition
d.DNA and ribonucleic acid (RNA)synthesis inhibition
Tetracycline

Question 9

Mycoplasmas are organisms without cell walls.Which antimicrobial agents would be ineffective in treating infections involving this bacterium?

A)Tetracycline
B)Aminoglycosides
C)Penicillin
D)Rifampin

Question 10

MATCHING
Match the antimicrobial agent with its mode of action.
a.Cell wall synthesis inhibition
b.Cell membrane function inhibition
c.Protein synthesis inhibition
d.DNA and ribonucleic acid (RNA)synthesis inhibition
Polymyxin B

Question 11

Antimicrobial agents that inhibit bacterial growth but generally do not kill the organism are known as:

A)bactericidal.
B)antibiotic.
C)bacteriostatic.
D)antagonistic.

Question 12

MATCHING
Match the antimicrobial agent with its mode of action.
a.Cell wall synthesis inhibition
b.Cell membrane function inhibition
c.Protein synthesis inhibition
d.DNA and ribonucleic acid (RNA)synthesis inhibition
Penicillin

Question 13

MATCHING
Match the antimicrobial agent with its mode of action.
a.Cell wall synthesis inhibition
b.Cell membrane function inhibition
c.Protein synthesis inhibition
d.DNA and ribonucleic acid (RNA)synthesis inhibition
Rifampin

Question 14

MATCHING
Match the antimicrobial agent with its mode of action.
a.Cell wall synthesis inhibition
b.Cell membrane function inhibition
c.Protein synthesis inhibition
d.DNA and ribonucleic acid (RNA)synthesis inhibition
Ciprofloxacin

Question 15

MATCHING
Match the antimicrobial agent with its mode of action.
a.Cell wall synthesis inhibition
b.Cell membrane function inhibition
c.Protein synthesis inhibition
d.DNA and ribonucleic acid (RNA)synthesis inhibition
Vancomycin