Question 1

Relatively nontoxic antimicrobial therapeutic agents include all of the following except:
A)heavy metals.
B)antibiotics.
C)preservatives.
D)antiseptics.

Accepted Answer

Heavy metals, although they have antimicrobial properties, are highly toxic to patients.Antimicrobial agents include antiseptics, antibiotics, preservatives, sterilants, and disinfectants; all have the capacity to kill or suppress the growth of microorganisms.

Question 2

The outer membrane of gram-negative bacteria is composed of:
A)lipopolysaccharides, phospholipids, and porin proteins.
B)peptidoglycan, phospholipids, and proteins.
C)enzymes, cholesterol, and carbohydrates.
D)carbohydrates, peptidoglycan, and proteins.

Accepted Answer

The outer membrane of gram-negative bacteria is composed of lipopolysaccharides, phospholipids, and porin proteins, and it is separated from the cytoplasmic membrane by a periplasmic space.

Question 3

Antibiotics work by targeting all of the following except:
A)DNA replication.
B)bacterial plasmid DNA.
C)bacterial cell wall.
D)RNA transcription.

Accepted Answer

Antibiotics target the bacterial cell wall and the cellular machinery responsible for the synthesis of precursor molecules; cellular targets include DNA replication, RNA transcription, and mRNA translation.Although numerous antibiotic classes exist with different modes of action, bacteria evolved and adopted numerous strategies to counteract the action of antibiotics.

Question 4

These antibiotics are cationic carbohydrate-containing molecules, and their positive charge provides the basis for their interaction with the 30S ribosomal subunit.What class of antibiotic are these?
A)Sulfamethoxazole
B)Trimethoprim
C)Aminoglycosides
D)Peptidoglycans

Accepted Answer

Aminoglycosides are cationic carbohydrate-containing molecules, and their positive charge provides the basis for their interaction with a specific region in the 30S ribosomal subunit.Binding of the aminoglycosides to the 30S subunit prevents the docking of aminoacyl-tRNA, resulting in mistranslation and subsequent production of aberrant proteins.The incorporation of aberrant proteins into the cell wall also results in cell leakage and enhanced cellular penetration of additional antibiotic.

Question 5

All of the following are b-lactam antibiotics except:
A)penems.
B)monobactams.
C)carbapenems.
D)monoterpenes.

Accepted Answer

b-Lactam antibiotics, such as penems, cephems, carbapenems, and monobactams, act by binding to penicillin-binding proteins, which are bifunctional transpeptidases/transglycosylases that cross-link peptidoglycan.Without this cross-linking of the peptidoglycan, the cell walls break down.

Question 6

Which antibiotic inhibits folate synthesis, which provides the essential precursor molecule, pyridine thymidylate, needed in DNA synthesis?
A)Vancomycin
B)Quinolones
C)Aminoglycosides
D)Sulfamethoxazole

Accepted Answer

Sulfamethoxazole blocks the step leading to the formation of one of the enzymes needed for folate synthesis.Because folate synthesis forms the essential precursor molecule-pyridine thymidylate, needed in DNA biosynthesis-the bacteria cannot replicate its DNA and dies.

Question 7

All of the following antibiotics target the 50S ribosomal subunit to prevent mRNA translation in the bacteria except:
A)macrolides.
B)quinolones.
C)oxazolidinones.
D)streptogramins.

Accepted Answer

The bacterial ribosome is a primary target of numerous antibiotics with some targeting the 30S ribosomal subunit (i.e., aminoglycosides, tetracyclines, glycylcycline) and others the 50S ribosomal subunit (i.e., macrolides, oxazolidinones, streptogramins).

Question 8

Mechanisms that mediate intrinsic antibiotic resistance include all the following except:
A)cell wall impermeability.
B)biofilm formation.
C)expression of genes mediating inactivating enzymes.
D)alternate biosynthetic pathways.

Accepted Answer

Antibiotic resistance may be characterized as intrinsic and is an inherent genotypic characteristic of the microorganism disseminated vertically to progeny.Mechanisms that mediate intrinsic resistance to antibiotics include cell wall impermeability, efflux, biofilm formation, and the expression of genes producing inactivating enzymes.

Question 9

Which two classes of antibiotics allow initiation and mRNA translation to begin, but they act by inhibiting peptide elongation?
A)Aminoglycosides and glycopeptidians
B)Aminoglycosides and quinolones
C)Macrolides and tetracyclines
D)Macrolides and quinolones

Accepted Answer

The macrolides and tetracyclines allow initiation and mRNA translation to begin, but they act by inhibiting peptide elongation.

Question 10

The members of the macrolide class of antibiotics include all the following except:
A)rifamycin.
B)erythromycin.
C)clarithromycin.
D)azithromycin.

Accepted Answer

Macrolides such as erythromycin, clarithromycin, and azithromycin target the 50S subunit specifically by binding to the peptidyltransferase cavity on the rRNA.

Question 11

In gram-positive bacteria, what is substantially thicker and more multilayered than in gram-negative bacteria?
A)Lipopolysaccharide
B)Phospholipid
C)Peptidoglycan
D)Cholesterol

Accepted Answer

In gram-positive bacteria, the peptidoglycan is substantially thicker and more multilayered than in gram-negative bacteria.

Question 12

Both gram-positive and gram-negative bacteria have an inner cytoplasmic membrane that is composed of:
A)nucleotides.
B)phospholipids and proteins.
C)cholesterol and carbohydrates.
D)lipopolysaccharides.

Accepted Answer

The cytoplasmic membrane, composed of phospholipids and proteins, surrounds the cytoplasm, acts as an osmotic barrier, and is the location of the electron transport chain responsible for energy production.

Question 13

Antibiotic mechanisms of action target all the following except:
A)blocking the Embden-Meyerhof pathway.
B)bacterial cell wall synthesis.
C)DNA replication.
D)RNA transcription.

Accepted Answer

Although the classification scheme and number of antibiotics is complex and continues to expand as new classes emerge or existing classes are modified, their mechanisms of action target bacterial cell wall biosynthesis, folate synthesis, DNA replication, RNA transcription, and mRNA translation.These are logical targets critical to the survival of the microorganism.

Question 14

All of the following are recently approved classes of antibiotics that target protein synthesis except:
A)sixth generation cephalosporins.
B)oxazolidinones.
C)streptogramin.
D)glycylcycline.

Accepted Answer

The most recently approved classes of antibiotics targeting protein synthesis are oxazolidinones (linezolid), streptogramin (dalfopristin-quinupristin), and glycylcycline (tigecycline).

Question 15

Which antibiotic interferes with DNA transcription by blocking of RNA chain elongation?
A)Rifampin
B)Quinolone
C)Trimethoprim
D)Glycopeptide

Accepted Answer

Rifampin, a synthetic derivative of rifamycin B, is used in combination with other antibiotic classes to treat Mycobacterium tuberculosis by targeting transcription of DNA.The target of rifampin in M.tuberculosis is the RNA polymerase b subunit at an allosteric site, with the subsequent blocking of RNA chain elongation.As a result, RNA transcription is aborted at the initiation step.

Question 16

Which antibiotic affects the DNA replication by targeting topoisomerases II and IV, enzymes considered important in controlling DNA replication?
A)Glycopeptide
B)Sulfamethoxazole
C)Trimethoprim
D)Quinolone

Accepted Answer

Quinolones disrupt the DNA replication cycle of bacteria by targeting topoisomerases II and IV.Interestingly, the targets of quinolones appear to be selective, targeting DNA gyrase in gram-negative bacteria and topoisomerase IV in gram-positive bacteria.However, newer quinolones appear to have high affinity for both targets.

Question 17

The members of the polyketide class of antibiotics include all the following except:
A)tetracycline.
B)doxycycline.
C)minocycline.
D)oxycycline.

Accepted Answer

The clinically useful tetracyclines are members of the polyketide class of antibiotics and are represented by tetracycline, doxycycline, and minocycline.

Question 18

Which of the following public health issues is uniting scientists from across the world to develop strategies to address it?
A)Reclassifying bacteria according to their genomes
B)The shortage of low toxicity antifungal drugs
C)Antibiotic resistance
D)Emerging pathogens

Accepted Answer

Antibiotic resistance emerged soon after the discovery of antibiotics and is associated with the overuse of antimicrobial agents.Although antibiotics allow the medical community to make great strides in human health and welfare, their use also causes selective pressure, allowing only the fittest and less susceptible bacterial populations to thrive.Antibiotic resistance and its associated clinical failure is an issue of public health concern that is uniting scientists from across the world to develop strategies to address it.

Question 19

Penicillins, cephalosporins, monobactams, and carbapenems all have what ring in their structure that is responsible for inhibiting the transpeptidation reaction, resulting in bacterial lysis and cell death?
A)Benzene
B)b-Lactam
C)a-Lactam
D)D-Cephems

Accepted Answer

The active moiety of b-lactam antibiotics is the four-membered b-lactam ring-a ring structure found in penicillins, cephalosporins, monobactams, and carbapenems.The four-membered ring represented by the structure labeled b-lactam functions as a structural analogue of the normal substrate, and inhibits the transpeptidation reaction, resulting in bacterial lysis and cell death.

Question 20

What is the mechanism of action of the glycopeptides (vancomycin and teicoplanin)?
A)The glycopeptides inhibit folate synthesis and prevent the bacteria from using this as an energy source.
B)The glycopeptides interfere with DNA replication and disrupt the protein synthesis operation.
C)The glycopeptides bind to the substrate of the transpeptidation enzyme and disrupt the cell membrane construction.
D)The glycopeptides interfere with transfer RNA production and disrupt the protein synthesis operation.

Accepted Answer

Glycopeptides, such as vancomycin and the investigational drug teicoplanin, act by complexing the non-cross-linked peptide strands of peptidoglycan units having the pentapeptidyl tails ending in D-ala-D-ala.This prevents their incorporation into the peptidoglycan chain by blocking the transpeptidation step.Glycopeptides bind to the substrate of the transpeptidation enzyme, and penicillins bind to the enzyme mediating the transpeptidation reaction.

Quiz 12: Antimicrobial Agent Mechanisms of Action and Resistance

Relatively nontoxic antimicrobial therapeutic agents include all of the following except:

The outer membrane of gram-negative bacteria is composed of:

Antibiotics work by targeting all of the following except:

These antibiotics are cationic carbohydrate-containing molecules, and their positive charge provides the basis for their interaction with the 30S ribosomal subunit.What class of antibiotic are these?

All of the following are b-lactam antibiotics except:

Which antibiotic inhibits folate synthesis, which provides the essential precursor molecule, pyridine thymidylate, needed in DNA synthesis?

All of the following antibiotics target the 50S ribosomal subunit to prevent mRNA translation in the bacteria except:

Mechanisms that mediate intrinsic antibiotic resistance include all the following except:

Which two classes of antibiotics allow initiation and mRNA translation to begin, but they act by inhibiting peptide elongation?

The members of the macrolide class of antibiotics include all the following except:

In gram-positive bacteria, what is substantially thicker and more multilayered than in gram-negative bacteria?

Both gram-positive and gram-negative bacteria have an inner cytoplasmic membrane that is composed of:

Antibiotic mechanisms of action target all the following except:

All of the following are recently approved classes of antibiotics that target protein synthesis except:

Which antibiotic interferes with DNA transcription by blocking of RNA chain elongation?

Which antibiotic affects the DNA replication by targeting topoisomerases II and IV, enzymes considered important in controlling DNA replication?

The members of the polyketide class of antibiotics include all the following except:

Which of the following public health issues is uniting scientists from across the world to develop strategies to address it?

Penicillins, cephalosporins, monobactams, and carbapenems all have what ring in their structure that is responsible for inhibiting the transpeptidation reaction, resulting in bacterial lysis and cell death?

What is the mechanism of action of the glycopeptides (vancomycin and teicoplanin) ?