Review Mechanisms of action

Antibiotics and Antimicrobial Agents > Pharmacology

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Mechanisms of action

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Total Questions : 5

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Question 1:

A nurse is reviewing the mechanisms of action of different antimicrobial agents. The nurse understands that antibiotics that inhibit cell wall synthesis are most effective against which type of bacteria?

A. Gram-positive bacteria B. Gram-negative bacteria C. Anaerobic bacteria D. Atypical bacteria.

Answer and Explanation

Choice A:

This is because antibiotics that inhibit cell wall synthesis are most effective against bacteria that have a thick peptidoglycan layer in their cell wall, which is characteristic of gram-positive bacteria. Peptidoglycan is a polymer of glycan and peptides that gives the cell wall its strength and rigidity. Antibiotics that inhibit cell wall synthesis, such as β-lactams and glycopeptides, prevent the formation or cross-linking of the peptidoglycan layer, resulting in cell wall defects and bacterial lysis.

Choice B:

Choice B is wrong because Gram-negative bacteria is wrong because gram-negative bacteria have a thin peptidoglycan layer and an outer membrane that protects them from antibiotics that target cell wall synthesis. Some gram-negative bacteria also have efflux pumps or β-lactamases that can expel or degrade these antibiotics.

Choice C:

Choice C is wrong because Anaerobic bacteria is wrong because anaerobic bacteria can be either gram-positive or gram-negative, and their susceptibility to antibiotics that inhibit cell wall synthesis depends on their cell wall structure and resistance mechanisms.

Choice D:

Choice D is wrong because Atypical bacteria is wrong because atypical bacteria are bacteria that lack a cell wall, such as Mycoplasma and Chlamydia. These bacteria are naturally resistant to antibiotics that inhibit cell wall synthesis, as they do not have a peptidoglycan layer to target.

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Question 2:

A nurse is caring for a client who has a severe infection and is receiving a combination of antibiotics. The nurse knows that some antibiotics have synergistic effects when used together. Which of the following are examples of antibiotic combinations that have synergistic effects? (Select all that apply.)

A. Ampicillin and gentamicin B. Trimethoprim and sulfamethoxazole C. Clindamycin and erythromycin D. Metronidazole and ciprofloxacin E. Vancomycin and rifampin.

Answer and Explanation

Choice A:

Ampicillin and gentamicin are synergistic against enterococcal infections.

Ampicillin inhibits the cell wall synthesis of enterococci, while gentamicin damages their ribosomes and interferes with protein synthesis.

Choice B:

Trimethoprim and sulfamethoxazole are synergistic against many gram-negative and gram-positive bacteria.

Trimethoprim inhibits the enzyme dihydrofolate reductase, while sulfamethoxazole inhibits the enzyme dihydropteroate synthase.

Both enzymes are involved in the synthesis of folic acid, which is essential for bacterial DNA replication.

Choice C:

Choice C is wrong because clindamycin and erythromycin are antagonistic, meaning they interfere with each other’s activity when used together.Both antibiotics bind to the same site on the bacterial ribosome and block protein synthesis, but clindamycin has a higher affinity and displaces erythromycin.

Choice D:

Choice D is wrong because metronidazole and ciprofloxacin are not synergistic, but additive, meaning they have independent effects when used together.Metronidazole damages the bacterial DNA by generating reactive oxygen species, while ciprofloxacin inhibits the enzyme DNA gyrase that unwinds the DNA for replication.

Choice E:

Choice E is wrong because vancomycin and rifampin are not synergistic, but indifferent, meaning they have no effect on each other’s activity when used together.Vancomycin inhibits the cell wall synthesis of gram-positive bacteria by binding to the peptidoglycan precursors, while rifampin inhibits the bacterial RNA polymerase that transcribes DNA into RNA.

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Question 3:

A nurse is teaching a client who has a urinary tract infection about the prescribed antibiotic, ciprofloxacin. The nurse instructs the client to avoid taking the medication with dairy products.
The client asks, “Why do I have to avoid dairy products?” What is the best response by the nurse?

A. “Dairy products can increase the risk of kidney stones with this medication.” B. “Dairy products can reduce the absorption of this medication in your stomach.” C. “Dairy products can cause allergic reactions with this medication.” D. “Dairy products can interfere with the metabolism of this medication in your liver."

Answer and Explanation

Choice A:

Choice A is wrong because dairy products do not increase the risk of kidney stones with this medication. There is no evidence to support this claim.

Choice B:

This means that less of the drug will get into your bloodstream and it may not work as well to treat your infection. According to one source, dairy products can reduce the bioavailability of ciprofloxacin by 30 to 36 percent and the peak concentration by 36 percent.

Choice C:

Choice C is wrong because dairy products do not cause allergic reactions with this medication. Allergic reactions are possible with any medication, but they are not related to dairy products.

Choice D:

Choice D is wrong because dairy products do not interfere with the metabolism of this medication in your liver. Ciprofloxacin is mainly eliminated by the kidneys, not the liver. To avoid this interaction, you should take ciprofloxacin at least 2 hours before or 6 hours after dairy products.

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Question 4:

A nurse is monitoring a client who is receiving antiviral therapy for influenza.
The nurse expects that the antiviral drug will have which of the following effects?

A. “It will kill the influenza virus in your body.” B. “It will reduce the duration and severity of your symptoms.” C. “It will prevent the transmission of the virus to others.” D. “It will stimulate your immune system to fight off the virus."

Answer and Explanation

Choice A:

Choice A is wrong because antiviral drugs do not kill the influenza virus, but only prevent it from multiplying.

Choice B:

Antiviral drugs for influenza can reduce the duration and severity of symptoms by inhibiting the replication of the virus in the body. They are most effective when started within 48 hours of illness onset.

Choice C:

Choice C is wrong because antiviral drugs do not prevent the transmission of the virus to others, but only reduce the amount of virus shed by infected persons. People who take antiviral drugs should still practice good hygiene and avoid close contact with others.

Choice D:

Choice D is wrong because antiviral drugs do not stimulate the immune system to fight off the virus, but only interfere with the viral enzymes that are essential for viral replication. Antiviral drugs are not a substitute for vaccination, which can induce protective immunity against influenza.

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Question 5:

A nurse is administering an antifungal medication to a client who has a systemic fungal infection.
The nurse understands that antifungal drugs have a higher risk of toxicity than antibacterial drugs because:

A. fungi have cell walls that are difficult to penetrate. B. fungi are more resistant to drug therapy than bacteria. C. fungi and human cells have similar structures and functions. D. fungi can mutate rapidly and develop drug resistance.

Answer and Explanation

Choice A:

Choice A is wrong because fungi do not have cell walls that are difficult to penetrate. Fungi have cell walls that are composed of chitin, glucan, and mannoproteins, which are different from the peptidoglycan cell walls of bacteria. Antifungal drugs can target these components and disrupt the integrity of the fungal cell wall.

Choice B:

Choice B is wrong because fungi are not more resistant to drug therapy than bacteria. Fungi can develop resistance to antifungal drugs, but this is not a common mechanism of antifungal drug failure. Bacteria can also develop resistance to antibacterial drugs through various mechanisms, such as producing enzymes that degrade or modify the drugs, altering the target sites of the drugs, or pumping out the drugs from the cell.

Choice C:

This means that antifungal drugs have to target specific components of the fungal cell that are different from the human cell, such as the cell membrane or the cell wall. However, this also increases the risk of toxicity to human cells, especially those that have high turnover rates, such as liver and kidney cells.

Choice D:

Choice D is wrong because fungi do not mutate rapidly and develop drug resistance. Fungi have a slower rate of mutation than bacteria because they have a more complex genome and a more efficient DNA repair system

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Mechanisms of action

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