Pharmacology Exam Pack: Antibiotic
Resistance – Verified 150-Item Solved Test
Bank . Answers And Rationale Included
(2025/2026)
1. Which of the following is a common mechanism by which bacteria
develop resistance to β-lactam antibiotics?
A. Increased ribosomal binding
B. Production of β-lactamase enzymes
C. Altered DNA gyrase
D. Efflux pump overexpression
Rationale: β-lactamases hydrolyze the β-lactam ring of penicillins and
cephalosporins, rendering these antibiotics ineffective.
2. Methicillin-resistant Staphylococcus aureus (MRSA) is resistant to
methicillin due to:
A. Increased drug efflux
B. Enzyme inactivation
C. Altered penicillin-binding proteins (PBPs)
D. Ribosomal mutation
Rationale: MRSA acquires the mecA gene, which encodes an altered
PBP (PBP2a) with low affinity for β-lactams.
3. Extended-spectrum β-lactamases (ESBLs) confer resistance to:
A. Aminoglycosides
B. Cephalosporins and penicillins
C. Macrolides
D. Tetracyclines
Rationale: ESBLs hydrolyze most β-lactams, including third-generation
cephalosporins, but are usually inhibited by clavulanic acid.
, 4. Carbapenem-resistant Enterobacteriaceae (CRE) typically resist
carbapenems via:
A. Ribosomal methylation
B. Carbapenemase production
C. DNA gyrase mutation
D. Altered folate metabolism
Rationale: Carbapenemases, such as KPC, hydrolyze carbapenems and
other β-lactams.
5. Which mechanism explains vancomycin resistance in Enterococci
(VRE)?
A. Increased drug efflux
B. Ribosomal alteration
C. Altered cell wall precursors (D-Ala-D-Lac)
D. β-lactamase production
Rationale: VRE replace D-Ala-D-Ala with D-Ala-D-Lac in the cell wall,
reducing vancomycin binding.
6. Efflux pumps contribute to antibiotic resistance by:
A. Hydrolyzing drugs
B. Expelling drugs out of the bacterial cell
C. Altering target enzymes
D. Inhibiting drug absorption
Rationale: Efflux pumps decrease intracellular drug concentration,
reducing efficacy.
7. Which of the following antibiotics is most affected by ribosomal
methylation resistance mechanisms?
A. Aminoglycosides
B. Macrolides
, C. β-lactams
D. Fluoroquinolones
Rationale: Ribosomal methylation at the 23S rRNA prevents macrolide
binding, conferring resistance.
8. Quinolone resistance often involves:
A. β-lactamase production
B. Mutations in DNA gyrase or topoisomerase IV
C. Ribosomal methylation
D. Altered cell wall synthesis
Rationale: Mutations in gyrA or parC genes reduce fluoroquinolone
binding to DNA gyrase/topoisomerase IV.
9. Plasmid-mediated resistance is significant because:
A. It reduces bacterial growth
B. It only affects gram-positive bacteria
C. It allows horizontal gene transfer between bacteria
D. It decreases antibiotic absorption
Rationale: Resistance genes on plasmids can spread between bacterial
species, increasing resistance prevalence.
10. Which of the following antibiotics is least likely to develop
resistance via enzymatic inactivation?
A. Penicillin
B. Cephalosporin
C. Aminoglycoside
D. Fluoroquinolone
Rationale: Fluoroquinolones act by inhibiting DNA
gyrase/topoisomerase; enzymatic degradation is not a common
resistance mechanism.
, 11. Inducible clindamycin resistance in Staphylococcus aureus
can be detected by:
A. Kirby-Bauer disk diffusion
B. D-test
C. MIC determination only
D. ELISA
Rationale: The D-test identifies inducible erm-mediated macrolide-
lincosamide-streptogramin B resistance.
12. The main reason for multidrug resistance (MDR) in
Pseudomonas aeruginosa is:
A. Ribosomal mutation
B. β-lactamase only
C. Efflux pumps combined with low membrane permeability
D. Altered folate synthesis
Rationale: Pseudomonas has multiple efflux pumps and a low-
permeability outer membrane, promoting MDR.
13. Which antibiotic class targets the bacterial 30S ribosomal
subunit?
A. Macrolides
B. Chloramphenicol
C. Aminoglycosides and tetracyclines
D. Glycopeptides
Rationale: Aminoglycosides and tetracyclines bind 30S, inhibiting
protein synthesis.
14. Bacteria resistant to aminoglycosides may possess:
A. Mutated PBPs
B. Aminoglycoside-modifying enzymes
Resistance – Verified 150-Item Solved Test
Bank . Answers And Rationale Included
(2025/2026)
1. Which of the following is a common mechanism by which bacteria
develop resistance to β-lactam antibiotics?
A. Increased ribosomal binding
B. Production of β-lactamase enzymes
C. Altered DNA gyrase
D. Efflux pump overexpression
Rationale: β-lactamases hydrolyze the β-lactam ring of penicillins and
cephalosporins, rendering these antibiotics ineffective.
2. Methicillin-resistant Staphylococcus aureus (MRSA) is resistant to
methicillin due to:
A. Increased drug efflux
B. Enzyme inactivation
C. Altered penicillin-binding proteins (PBPs)
D. Ribosomal mutation
Rationale: MRSA acquires the mecA gene, which encodes an altered
PBP (PBP2a) with low affinity for β-lactams.
3. Extended-spectrum β-lactamases (ESBLs) confer resistance to:
A. Aminoglycosides
B. Cephalosporins and penicillins
C. Macrolides
D. Tetracyclines
Rationale: ESBLs hydrolyze most β-lactams, including third-generation
cephalosporins, but are usually inhibited by clavulanic acid.
, 4. Carbapenem-resistant Enterobacteriaceae (CRE) typically resist
carbapenems via:
A. Ribosomal methylation
B. Carbapenemase production
C. DNA gyrase mutation
D. Altered folate metabolism
Rationale: Carbapenemases, such as KPC, hydrolyze carbapenems and
other β-lactams.
5. Which mechanism explains vancomycin resistance in Enterococci
(VRE)?
A. Increased drug efflux
B. Ribosomal alteration
C. Altered cell wall precursors (D-Ala-D-Lac)
D. β-lactamase production
Rationale: VRE replace D-Ala-D-Ala with D-Ala-D-Lac in the cell wall,
reducing vancomycin binding.
6. Efflux pumps contribute to antibiotic resistance by:
A. Hydrolyzing drugs
B. Expelling drugs out of the bacterial cell
C. Altering target enzymes
D. Inhibiting drug absorption
Rationale: Efflux pumps decrease intracellular drug concentration,
reducing efficacy.
7. Which of the following antibiotics is most affected by ribosomal
methylation resistance mechanisms?
A. Aminoglycosides
B. Macrolides
, C. β-lactams
D. Fluoroquinolones
Rationale: Ribosomal methylation at the 23S rRNA prevents macrolide
binding, conferring resistance.
8. Quinolone resistance often involves:
A. β-lactamase production
B. Mutations in DNA gyrase or topoisomerase IV
C. Ribosomal methylation
D. Altered cell wall synthesis
Rationale: Mutations in gyrA or parC genes reduce fluoroquinolone
binding to DNA gyrase/topoisomerase IV.
9. Plasmid-mediated resistance is significant because:
A. It reduces bacterial growth
B. It only affects gram-positive bacteria
C. It allows horizontal gene transfer between bacteria
D. It decreases antibiotic absorption
Rationale: Resistance genes on plasmids can spread between bacterial
species, increasing resistance prevalence.
10. Which of the following antibiotics is least likely to develop
resistance via enzymatic inactivation?
A. Penicillin
B. Cephalosporin
C. Aminoglycoside
D. Fluoroquinolone
Rationale: Fluoroquinolones act by inhibiting DNA
gyrase/topoisomerase; enzymatic degradation is not a common
resistance mechanism.
, 11. Inducible clindamycin resistance in Staphylococcus aureus
can be detected by:
A. Kirby-Bauer disk diffusion
B. D-test
C. MIC determination only
D. ELISA
Rationale: The D-test identifies inducible erm-mediated macrolide-
lincosamide-streptogramin B resistance.
12. The main reason for multidrug resistance (MDR) in
Pseudomonas aeruginosa is:
A. Ribosomal mutation
B. β-lactamase only
C. Efflux pumps combined with low membrane permeability
D. Altered folate synthesis
Rationale: Pseudomonas has multiple efflux pumps and a low-
permeability outer membrane, promoting MDR.
13. Which antibiotic class targets the bacterial 30S ribosomal
subunit?
A. Macrolides
B. Chloramphenicol
C. Aminoglycosides and tetracyclines
D. Glycopeptides
Rationale: Aminoglycosides and tetracyclines bind 30S, inhibiting
protein synthesis.
14. Bacteria resistant to aminoglycosides may possess:
A. Mutated PBPs
B. Aminoglycoside-modifying enzymes
