NURS 5334 Antimicrobials:
Questions With Solutions (Correct
& Verified)
Question 1: Cell Wall Synthesis Inhibitors
A 45-year-old patient with a history of anaphylaxis to penicillin is admitted with methicillin-
sensitive Staphylococcus aureus (MSSA) bacteremia. Which of the following is the most
appropriate alternative agent?
A) Cephalexin
B) Aztreonam
C) Vancomycin
D) Ampicillin/sulbactam
Correct Answer: C) Vancomycin
Solution:
Patients with a history of anaphylaxis to penicillin should not receive cephalosporins (A) due to
cross-reactivity risk (though low with later generations, it is contraindicated in severe reactions).
Aztreonam (B) is a monobactam that is safe in penicillin allergy but only covers aerobic gram-
negative rods, not MSSA. Ampicillin/sulbactam (D) is a penicillin derivative and contraindicated.
Vancomycin (C) is the drug of choice for serious MSSA infections in penicillin-allergic patients.
Question 2: Macrolide Mechanism
A patient is prescribed azithromycin for community-acquired pneumonia. The nurse practitioner
understands that the primary mechanism of action for macrolides is:
A) Inhibition of cell wall synthesis
B) Inhibition of protein synthesis via 50S ribosomal subunit binding
,C) Inhibition of DNA gyrase
D) Disruption of the bacterial cell membrane
Correct Answer: B) Inhibition of protein synthesis via 50S ribosomal subunit binding
Solution:
Macrolides (azithromycin, clarithromycin, erythromycin) bind reversibly to the 50S ribosomal
subunit, blocking translocation steps in protein synthesis. This is bacteriostatic but can be
bactericidal at high concentrations against certain organisms.
Question 3: Fluoroquinolone Adverse Effect
A 72-year-old patient is prescribed levofloxacin for acute exacerbation of chronic bronchitis.
Which of the following adverse effects is most critical to counsel the patient about due to this
patient’s age?
A) Photosensitivity
B) Tendon rupture
C) QT prolongation
D) Clostridioides difficile infection
Correct Answer: B) Tendon rupture
Solution:
Fluoroquinolones carry a black box warning for tendinitis and tendon rupture, with risk
significantly increased in patients over 60 years old, those on corticosteroids, and organ
transplant recipients. While QT prolongation (C) and C. diff (D) are also risks, tendon rupture is
particularly relevant in older adults and requires immediate discontinuation if pain or swelling
occurs.
Question 4: Tetracycline Contraindication
A 23-year-old female is prescribed doxycycline for acne vulgaris. What critical counseling point
must be included?
A) Take with dairy products to reduce GI upset
B) Avoid pregnancy due to risk of permanent tooth discoloration in the fetus
C) Monitor for hearing loss
D) Take on an empty stomach with a full glass of water
,Correct Answer: B) Avoid pregnancy due to risk of permanent tooth discoloration in the fetus
Solution:
Tetracyclines are contraindicated in pregnancy (category D) and in children under 8 years due to
permanent tooth discoloration and inhibition of bone growth. Doxycycline should not be taken
with dairy products (A) due to chelation and reduced absorption. Hearing loss (C) is associated
with aminoglycosides.
Question 5: Aminoglycoside Monitoring
A patient receiving gentamicin for a gram-negative infection has a trough level of 2.5 mcg/mL. The
next dose is due in 2 hours. What is the appropriate action?
A) Administer the dose as scheduled
B) Hold the dose and notify the provider
C) Increase the dose to achieve higher peak levels
D) Administer the dose and increase the dosing interval
Correct Answer: B) Hold the dose and notify the provider
Solution:
Aminoglycoside trough levels should be <1–2 mcg/mL to prevent nephrotoxicity and ototoxicity.
A trough of 2.5 mcg/mL indicates drug accumulation, likely due to impaired renal function. The
dose should be held, renal function assessed, and the dosing interval extended or dose adjusted.
Question 6: Beta-Lactam Allergy Cross-Reactivity
Which of the following antimicrobials is safest to administer to a patient with a severe, immediate
hypersensitivity (anaphylaxis) to penicillin?
A) Cefazolin
B) Imipenem-cilastatin
C) Aztreonam
D) Amoxicillin
Correct Answer: C) Aztreonam
Solution:
Aztreonam is a monobactam with a unique beta-lactam ring structure that does not show cross-
reactivity with penicillins. Carbapenems (B) have significant cross-reactivity (about 1–10%).
, Cephalosporins (A) have lower cross-reactivity but are generally avoided in severe penicillin
anaphylaxis. Amoxicillin (D) is directly contraindicated.
Question 7: MRSA Treatment
A patient with a history of IV drug use presents with fever, chills, and a painful, erythematous area
on the arm. Blood cultures grow MRSA. Which of the following is first-line therapy?
A) Cephalexin
B) Vancomycin
C) Clindamycin
D) Linezolid
Correct Answer: B) Vancomycin
Solution:
Vancomycin remains the first-line agent for invasive MRSA infections (bacteremia, endocarditis,
osteomyelitis). Clindamycin (C) and linezolid (D) are alternatives but not first-line for bacteremia
due to concerns with bacteriostatic activity and resistance. Cephalexin (A) has no MRSA
coverage.
Question 8: Drug-Drug Interaction
A patient on warfarin is prescribed trimethoprim-sulfamethoxazole (TMP-SMX) for a urinary tract
infection. The NP should be concerned about:
A) Increased risk of QT prolongation
B) Enhanced anticoagulant effect leading to elevated INR
C) Decreased renal excretion of warfarin
D) Increased risk of hepatotoxicity
Correct Answer: B) Enhanced anticoagulant effect leading to elevated INR
Solution:
TMP-SMX potentiates the anticoagulant effect of warfarin by inhibiting CYP2C9 (metabolism of
the more potent S-warfarin isomer) and possibly displacing warfarin from protein binding. This
can lead to significantly elevated INR and bleeding risk. Close monitoring is essential.
Questions With Solutions (Correct
& Verified)
Question 1: Cell Wall Synthesis Inhibitors
A 45-year-old patient with a history of anaphylaxis to penicillin is admitted with methicillin-
sensitive Staphylococcus aureus (MSSA) bacteremia. Which of the following is the most
appropriate alternative agent?
A) Cephalexin
B) Aztreonam
C) Vancomycin
D) Ampicillin/sulbactam
Correct Answer: C) Vancomycin
Solution:
Patients with a history of anaphylaxis to penicillin should not receive cephalosporins (A) due to
cross-reactivity risk (though low with later generations, it is contraindicated in severe reactions).
Aztreonam (B) is a monobactam that is safe in penicillin allergy but only covers aerobic gram-
negative rods, not MSSA. Ampicillin/sulbactam (D) is a penicillin derivative and contraindicated.
Vancomycin (C) is the drug of choice for serious MSSA infections in penicillin-allergic patients.
Question 2: Macrolide Mechanism
A patient is prescribed azithromycin for community-acquired pneumonia. The nurse practitioner
understands that the primary mechanism of action for macrolides is:
A) Inhibition of cell wall synthesis
B) Inhibition of protein synthesis via 50S ribosomal subunit binding
,C) Inhibition of DNA gyrase
D) Disruption of the bacterial cell membrane
Correct Answer: B) Inhibition of protein synthesis via 50S ribosomal subunit binding
Solution:
Macrolides (azithromycin, clarithromycin, erythromycin) bind reversibly to the 50S ribosomal
subunit, blocking translocation steps in protein synthesis. This is bacteriostatic but can be
bactericidal at high concentrations against certain organisms.
Question 3: Fluoroquinolone Adverse Effect
A 72-year-old patient is prescribed levofloxacin for acute exacerbation of chronic bronchitis.
Which of the following adverse effects is most critical to counsel the patient about due to this
patient’s age?
A) Photosensitivity
B) Tendon rupture
C) QT prolongation
D) Clostridioides difficile infection
Correct Answer: B) Tendon rupture
Solution:
Fluoroquinolones carry a black box warning for tendinitis and tendon rupture, with risk
significantly increased in patients over 60 years old, those on corticosteroids, and organ
transplant recipients. While QT prolongation (C) and C. diff (D) are also risks, tendon rupture is
particularly relevant in older adults and requires immediate discontinuation if pain or swelling
occurs.
Question 4: Tetracycline Contraindication
A 23-year-old female is prescribed doxycycline for acne vulgaris. What critical counseling point
must be included?
A) Take with dairy products to reduce GI upset
B) Avoid pregnancy due to risk of permanent tooth discoloration in the fetus
C) Monitor for hearing loss
D) Take on an empty stomach with a full glass of water
,Correct Answer: B) Avoid pregnancy due to risk of permanent tooth discoloration in the fetus
Solution:
Tetracyclines are contraindicated in pregnancy (category D) and in children under 8 years due to
permanent tooth discoloration and inhibition of bone growth. Doxycycline should not be taken
with dairy products (A) due to chelation and reduced absorption. Hearing loss (C) is associated
with aminoglycosides.
Question 5: Aminoglycoside Monitoring
A patient receiving gentamicin for a gram-negative infection has a trough level of 2.5 mcg/mL. The
next dose is due in 2 hours. What is the appropriate action?
A) Administer the dose as scheduled
B) Hold the dose and notify the provider
C) Increase the dose to achieve higher peak levels
D) Administer the dose and increase the dosing interval
Correct Answer: B) Hold the dose and notify the provider
Solution:
Aminoglycoside trough levels should be <1–2 mcg/mL to prevent nephrotoxicity and ototoxicity.
A trough of 2.5 mcg/mL indicates drug accumulation, likely due to impaired renal function. The
dose should be held, renal function assessed, and the dosing interval extended or dose adjusted.
Question 6: Beta-Lactam Allergy Cross-Reactivity
Which of the following antimicrobials is safest to administer to a patient with a severe, immediate
hypersensitivity (anaphylaxis) to penicillin?
A) Cefazolin
B) Imipenem-cilastatin
C) Aztreonam
D) Amoxicillin
Correct Answer: C) Aztreonam
Solution:
Aztreonam is a monobactam with a unique beta-lactam ring structure that does not show cross-
reactivity with penicillins. Carbapenems (B) have significant cross-reactivity (about 1–10%).
, Cephalosporins (A) have lower cross-reactivity but are generally avoided in severe penicillin
anaphylaxis. Amoxicillin (D) is directly contraindicated.
Question 7: MRSA Treatment
A patient with a history of IV drug use presents with fever, chills, and a painful, erythematous area
on the arm. Blood cultures grow MRSA. Which of the following is first-line therapy?
A) Cephalexin
B) Vancomycin
C) Clindamycin
D) Linezolid
Correct Answer: B) Vancomycin
Solution:
Vancomycin remains the first-line agent for invasive MRSA infections (bacteremia, endocarditis,
osteomyelitis). Clindamycin (C) and linezolid (D) are alternatives but not first-line for bacteremia
due to concerns with bacteriostatic activity and resistance. Cephalexin (A) has no MRSA
coverage.
Question 8: Drug-Drug Interaction
A patient on warfarin is prescribed trimethoprim-sulfamethoxazole (TMP-SMX) for a urinary tract
infection. The NP should be concerned about:
A) Increased risk of QT prolongation
B) Enhanced anticoagulant effect leading to elevated INR
C) Decreased renal excretion of warfarin
D) Increased risk of hepatotoxicity
Correct Answer: B) Enhanced anticoagulant effect leading to elevated INR
Solution:
TMP-SMX potentiates the anticoagulant effect of warfarin by inhibiting CYP2C9 (metabolism of
the more potent S-warfarin isomer) and possibly displacing warfarin from protein binding. This
can lead to significantly elevated INR and bleeding risk. Close monitoring is essential.
