NUR 631 Antibiotics Exam 2026/2027 – Comprehensive
Complete Questions & Verified Answers with
Rationales
Topics: Antibacterial pharmacology, mechanisms of action, resistance,
pharmacokinetics, adverse effects, drug interactions, stewardship, antimicrobial
susceptibility, major bacterial infections, and clinical decision-making.
Section I — General Antimicrobial Principles
1. What is the primary distinction between bactericidal and bacteriostatic
antibiotics?
A. Bactericidal agents inhibit bacterial growth only
B. Bactericidal agents kill bacteria directly
C. Bacteriostatic agents kill all bacteria immediately
D. Bactericidal agents work only against viruses
Answer: B
Rationale: Bactericidal antibiotics directly kill susceptible bacteria, whereas
bacteriostatic agents primarily inhibit bacterial growth and replication, allowing
host defenses to eliminate the organisms.
2. Which characteristic best describes selective toxicity?
A. The drug damages host cells more than bacterial cells
B. The drug targets microbial structures or processes with limited host-cell effects
C. The drug affects every cell equally
D. The drug only works against viruses
Answer: B
Rationale: Selective toxicity allows an antimicrobial to interfere preferentially
with microbial targets such as bacterial cell walls, ribosomes, or metabolic
pathways.
,3. Which bacterial structure is absent in human cells and therefore represents
an important antibiotic target?
A. Cell membrane
B. Peptidoglycan cell wall
C. DNA
D. Ribosomes
Answer: B
Rationale: Human cells lack peptidoglycan cell walls, allowing beta-lactam and
glycopeptide antibiotics to selectively target bacterial cell-wall synthesis.
4. Which antibiotic class inhibits bacterial cell-wall synthesis?
A. Beta-lactams
B. Macrolides
C. Fluoroquinolones
D. Tetracyclines
Answer: A
Rationale: Penicillins, cephalosporins, carbapenems, and monobactams inhibit
steps in bacterial peptidoglycan synthesis.
5. Which antibiotic class primarily inhibits bacterial protein synthesis by acting
on the 30S ribosomal subunit?
A. Aminoglycosides
B. Macrolides
C. Lincosamides
D. Glycopeptides
Answer: A
Rationale: Aminoglycosides bind the 30S subunit and cause abnormal protein
synthesis and misreading of mRNA.
6. Which antibiotic class primarily binds the 50S subunit?
A. Aminoglycosides
B. Macrolides
,C. Fluoroquinolones
D. Sulfonamides
Answer: B
Rationale: Macrolides bind the 50S ribosomal subunit and inhibit bacterial protein
synthesis.
7. Which class inhibits bacterial DNA gyrase and topoisomerase IV?
A. Fluoroquinolones
B. Tetracyclines
C. Penicillins
D. Glycopeptides
Answer: A
Rationale: Fluoroquinolones interfere with bacterial DNA replication by inhibiting
DNA gyrase and/or topoisomerase IV.
8. Which class inhibits bacterial folate synthesis?
A. Sulfonamides
B. Aminoglycosides
C. Macrolides
D. Glycopeptides
Answer: A
Rationale: Sulfonamides inhibit dihydropteroate synthase, disrupting folate
synthesis.
9. Trimethoprim primarily inhibits:
A. DNA gyrase
B. Dihydrofolate reductase
C. Cell-wall transpeptidase
D. RNA polymerase
Answer: B
Rationale: Trimethoprim inhibits bacterial dihydrofolate reductase and is often
combined with sulfamethoxazole for sequential folate-pathway blockade.
, 10. Which mechanism describes antimicrobial resistance?
A. The organism becomes more susceptible after exposure
B. The organism develops or acquires mechanisms that reduce antibiotic
effectiveness
C. The host develops immunity to every antibiotic
D. The drug becomes a vaccine
Answer: B
Rationale: Resistance can arise through mutation or acquisition of resistance
genes, reducing antimicrobial activity.
11. Which mechanism allows bacteria to destroy beta-lactam antibiotics?
A. Beta-lactamase production
B. Ribosomal methylation only
C. Reduced folate synthesis
D. Increased peptidoglycan production
Answer: A
Rationale: Beta-lactamases hydrolyze susceptible beta-lactam structures and can
confer resistance to penicillins, cephalosporins, and other beta-lactams.
12. What is the purpose of an antimicrobial susceptibility test?
A. Determine whether a microorganism is susceptible to particular antimicrobial
agents
B. Identify the patient's allergy history
C. Determine renal function
D. Measure serum drug concentration directly
Answer: A
Rationale: Susceptibility testing helps clinicians select active therapy once a
pathogen is identified.
13. Why should culture specimens ideally be obtained before antibiotics are
started when clinically feasible?
Complete Questions & Verified Answers with
Rationales
Topics: Antibacterial pharmacology, mechanisms of action, resistance,
pharmacokinetics, adverse effects, drug interactions, stewardship, antimicrobial
susceptibility, major bacterial infections, and clinical decision-making.
Section I — General Antimicrobial Principles
1. What is the primary distinction between bactericidal and bacteriostatic
antibiotics?
A. Bactericidal agents inhibit bacterial growth only
B. Bactericidal agents kill bacteria directly
C. Bacteriostatic agents kill all bacteria immediately
D. Bactericidal agents work only against viruses
Answer: B
Rationale: Bactericidal antibiotics directly kill susceptible bacteria, whereas
bacteriostatic agents primarily inhibit bacterial growth and replication, allowing
host defenses to eliminate the organisms.
2. Which characteristic best describes selective toxicity?
A. The drug damages host cells more than bacterial cells
B. The drug targets microbial structures or processes with limited host-cell effects
C. The drug affects every cell equally
D. The drug only works against viruses
Answer: B
Rationale: Selective toxicity allows an antimicrobial to interfere preferentially
with microbial targets such as bacterial cell walls, ribosomes, or metabolic
pathways.
,3. Which bacterial structure is absent in human cells and therefore represents
an important antibiotic target?
A. Cell membrane
B. Peptidoglycan cell wall
C. DNA
D. Ribosomes
Answer: B
Rationale: Human cells lack peptidoglycan cell walls, allowing beta-lactam and
glycopeptide antibiotics to selectively target bacterial cell-wall synthesis.
4. Which antibiotic class inhibits bacterial cell-wall synthesis?
A. Beta-lactams
B. Macrolides
C. Fluoroquinolones
D. Tetracyclines
Answer: A
Rationale: Penicillins, cephalosporins, carbapenems, and monobactams inhibit
steps in bacterial peptidoglycan synthesis.
5. Which antibiotic class primarily inhibits bacterial protein synthesis by acting
on the 30S ribosomal subunit?
A. Aminoglycosides
B. Macrolides
C. Lincosamides
D. Glycopeptides
Answer: A
Rationale: Aminoglycosides bind the 30S subunit and cause abnormal protein
synthesis and misreading of mRNA.
6. Which antibiotic class primarily binds the 50S subunit?
A. Aminoglycosides
B. Macrolides
,C. Fluoroquinolones
D. Sulfonamides
Answer: B
Rationale: Macrolides bind the 50S ribosomal subunit and inhibit bacterial protein
synthesis.
7. Which class inhibits bacterial DNA gyrase and topoisomerase IV?
A. Fluoroquinolones
B. Tetracyclines
C. Penicillins
D. Glycopeptides
Answer: A
Rationale: Fluoroquinolones interfere with bacterial DNA replication by inhibiting
DNA gyrase and/or topoisomerase IV.
8. Which class inhibits bacterial folate synthesis?
A. Sulfonamides
B. Aminoglycosides
C. Macrolides
D. Glycopeptides
Answer: A
Rationale: Sulfonamides inhibit dihydropteroate synthase, disrupting folate
synthesis.
9. Trimethoprim primarily inhibits:
A. DNA gyrase
B. Dihydrofolate reductase
C. Cell-wall transpeptidase
D. RNA polymerase
Answer: B
Rationale: Trimethoprim inhibits bacterial dihydrofolate reductase and is often
combined with sulfamethoxazole for sequential folate-pathway blockade.
, 10. Which mechanism describes antimicrobial resistance?
A. The organism becomes more susceptible after exposure
B. The organism develops or acquires mechanisms that reduce antibiotic
effectiveness
C. The host develops immunity to every antibiotic
D. The drug becomes a vaccine
Answer: B
Rationale: Resistance can arise through mutation or acquisition of resistance
genes, reducing antimicrobial activity.
11. Which mechanism allows bacteria to destroy beta-lactam antibiotics?
A. Beta-lactamase production
B. Ribosomal methylation only
C. Reduced folate synthesis
D. Increased peptidoglycan production
Answer: A
Rationale: Beta-lactamases hydrolyze susceptible beta-lactam structures and can
confer resistance to penicillins, cephalosporins, and other beta-lactams.
12. What is the purpose of an antimicrobial susceptibility test?
A. Determine whether a microorganism is susceptible to particular antimicrobial
agents
B. Identify the patient's allergy history
C. Determine renal function
D. Measure serum drug concentration directly
Answer: A
Rationale: Susceptibility testing helps clinicians select active therapy once a
pathogen is identified.
13. Why should culture specimens ideally be obtained before antibiotics are
started when clinically feasible?
