Mechanisms of action
Mechanisms of action ( 5 Questions)
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.)
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.
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 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 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 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.
These are examples of antibiotic combinations that have synergistic effects, meaning they enhance each other’s bacterial killing when used together.
Choice A is correct because 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 is correct because 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 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 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 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.