During pharmacology class, a nursing professor poses the ...

[CQXA]

During pharmacology class, a nursing professor poses the following question: We have learned that certain medications, such as fluoroquinolones, are effective because they inhibit bacterial DNA replication.
 
  Why don't these medications cause harm to the nonbacterial cells in the body? Which student nurse answered the question correctly?
  1. Student B: Medications such as fluoroquinolones do not appear to affect human DNA because human DNA is very similar to bacterial cell DNA.
  2. Student D: Human DNA is inherently healthier than bacterial DNA, so medications such as fluoroquinolones do not affect their replication.
  3. Student C: Medications such as fluoroquinolones don't appear to affect human DNA replication because of the difference between the enzymes needed for bacterial and human DNA replication.
  4. Student A: These medications protect healthy human cells while they attempt to disrupt bacterial DNA replication.

Question 2

A client has been diagnosed with a gram-negative bacterial infection and has been prescribed a fluoroquinolone for treatment of this infection.
 
  What step of the bacterial DNA replication process is most likely being affected by the use of this medication?
  1. It inhibits the enzyme DNA polymerase necessary for DNA replication.
  2. It binds to the enzyme topoisomerase IV, preventing the new DNA strands from migrating to opposite sides of the cell, thus preventing bacterial cell replication.
  3. It inhibits the relaxation of the supercoil prior to the unwinding process, which terminates replication.
  4. It inhibits the unwinding of the two strands of the supercoil, thus terminating replication.

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Answer to Question 1

Correct Answer: 3
Rationale 1: Human DNA and bacterial DNA have vastly different enzymes necessary for replication.
Rationale 2: Fluoroquinolones affect enzymes needed for bacterial DNA replication, and they do not target the enzymes present in human DNA cells. There is no indication that human DNA is healthier than bacterial DNA.
Rationale 3: It is thought that medications such as fluoroquinolones are very safe to use because they do not affect human DNA replication. This is because the enzymes that the medications affect in bacterial DNA replication are very different from the enzymes present in human DNA cells.
Rationale 4: Fluoroquinolones offer no protection to human DNA. They do not affect human DNA replication because the enzymes needed for human DNA replication are different from the enzymes needed for bacterial DNA replication.
Global Rationale: These drugs have no effect on human enzymes involved in DNA replication because of significant differences in the chemical structures of the human and bacterial enzymes. These differences account for their selective toxicity on bacteria, and their favorable safety profile. The statement regarding DNA health is inaccurate. These drugs offer no protection to human DNA.

Answer to Question 2

Correct Answer: 3
Rationale 1: Fluoroquinolones do not appear to affect the enzyme DNA polymerase.
Rationale 2: Fluoroquinolones do not prevent migration of the new DNA strands in order to prevent bacterial cell replication.
Rationale 3: It is thought that fluoroquinolones fight gram-negative organisms by binding to DNA gyrase, thereby inhibiting the ability of the supercoil to relax, resulting in termination of bacterial cell replication.
Rationale 4: Fluoroquinolones do not appear to affect the unwinding process of the supercoil.
Global Rationale: The fluoroquinolone antibiotics act on two enzymes in the DNA replication process. First, they bind to DNA gyrase, inhibiting its ability to relax the supercoiling of the bacterial DNA. When the replication enzymes reach an area still in a supercoiled state, replication terminates. A second mechanism is binding to topoisomerase IV. When this occurs, the two daughter DNA strands cannot migrate to opposite sides of the cell, and division cannot be completed. They do not appear to affect the unwinding process itself or to prevent migration, and do not affect the enzyme DNA polymerase.

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