Bailey And Scotts Diagnostic Microbiology 13th Edition By Patricia M. – Test Bank

Chapter 11: Principles of Antimicrobial Action and Resistance
Test Bank

MULTIPLE CHOICE

1. Antimicrobial agents that inhibit bacterial growth but generally do not kill the organism are known as:
a. bactericidal.
b. antibiotic.
c. bacteriostatic.
d. antagonistic.

ANS: C
Bacteriostatic means the inhibition of bacterial growth, whereas bactericidal means killing bacterial growth.

REF: 152 OBJ: Level: Knowledge

2. Antimicrobial agents that usually kill target organisms are said to be:
a. bactericidal.
b. antibiotic.
c. bacteriostatic.
d. antagonistic.

ANS: A
Bactericidal means killing bacterial growth, whereas Bacteriostatic means the inhibition of bacterial growth.

REF: 152 OBJ: Level: Knowledge

3. 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

ANS: A
Intrinsic resistance is considered to be a natural and consistently inherited characteristic that is associated with the vast majority of strains that constitute a particular bacterial group, genus, or species.

REF: 160 OBJ: Level: Knowledge

4. 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

ANS: 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.

REF: 160 OBJ: Level: Knowledge

5. Staphylococcus aureus is a gram-positive organism that produces the enzyme beta-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.

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

REF: 161 OBJ: Level: Application

6. 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.

ANS: 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.

REF: 163 OBJ: Level: Knowledge

7. 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

ANS: C
Penicillin, among others, is an antibiotic that acts by binding the enzymes that are involved in cell wall synthesis. Because mycoplasmas do not have cells walls, these types of antibiotics are not effective.

REF: 156 OBJ: Level: Application

8. 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.

ANS: D
Klebsiella spp. are normally resistant because of intrinsic resistance.

REF: 160 OBJ: Level: Problem Solving