Introduction: Inhibitors of protein synthesis MCQs With Answer provide B. Pharm students a focused review of antibiotics that target bacterial ribosomes, mechanisms of action, resistance pathways, clinical uses, and adverse effects. This concise, keyword-rich introduction covers protein synthesis inhibitors such as aminoglycosides, tetracyclines, macrolides, chloramphenicol, oxazolidinones and streptogramins, emphasizing ribosomal binding sites (30S vs 50S), translation blockade, mitochondrial toxicity, and therapeutic monitoring. Understanding pharmacokinetics, drug interactions, and resistance mechanisms (methylation, efflux, enzymatic modification) is essential for rational antibiotic use. These MCQs will strengthen exam readiness and clinical pharmacology competence. Now let’s test your knowledge with 50 MCQs on this topic.
Q1. Which ribosomal subunit is the primary target of aminoglycosides?
- 50S ribosomal subunit
- 30S ribosomal subunit
- Large eukaryotic ribosomal subunit
- Peptidyl transferase center of 50S
Correct Answer: 30S ribosomal subunit
Q2. Which mechanism best describes how tetracyclines inhibit protein synthesis?
- Blocking peptidyl transferase activity
- Preventing formation of initiation complex
- Inhibiting tRNA binding to the A site
- Causing miscoding during translation
Correct Answer: Inhibiting tRNA binding to the A site
Q3. Macrolides primarily inhibit bacterial protein synthesis by:
- Binding to 16S rRNA of 30S and causing misreading
- Inhibiting peptide bond formation at the peptidyl transferase center
- Blocking translocation by binding to the 50S subunit
- Cleaving mRNA
Correct Answer: Blocking translocation by binding to the 50S subunit
Q4. Chloramphenicol’s major severe adverse effect is:
- Ototoxicity
- Gray baby syndrome
- Aplastic anemia
- Nephrotoxicity
Correct Answer: Aplastic anemia
Q5. Linezolid belongs to which antibiotic class?
- Macrolides
- Oxazolidinones
- Aminoglycosides
- Tetracyclines
Correct Answer: Oxazolidinones
Q6. Which of the following drugs causes irreversible binding to the 50S subunit and inhibits initiation complex formation?
- Gentamicin
- Clindamycin
- Linezolid
- Chloramphenicol
Correct Answer: Linezolid
Q7. Aminoglycosides exhibit which bactericidal property?
- Time-dependent killing
- Concentration-dependent killing with post-antibiotic effect
- Bacteriostatic action only
- Inhibition of cell wall synthesis
Correct Answer: Concentration-dependent killing with post-antibiotic effect
Q8. The most common mechanism of macrolide resistance in bacteria is:
- Enzymatic acetylation
- Methylation of 23S rRNA
- Efflux pump overexpression only in Gram-negatives
- Mutation in 30S subunit
Correct Answer: Methylation of 23S rRNA
Q9. Which protein synthesis inhibitor is contraindicated in pregnancy due to effects on fetal bone and teeth?
- Tetracycline
- Azithromycin
- Linezolid
- Clindamycin
Correct Answer: Tetracycline
Q10. Which antibiotic binds within the A site of the 50S subunit and is associated with severe colitis as a side effect?
- Clindamycin
- Gentamicin
- Tigecycline
- Rifampicin
Correct Answer: Clindamycin
Q11. Which drug class is known for causing ototoxicity and nephrotoxicity?
- Aminoglycosides
- Macrolides
- Tetracyclines
- Oxazolidinones
Correct Answer: Aminoglycosides
Q12. Which of the following inhibits peptidyl transferase activity on the 50S ribosome?
- Chloramphenicol
- Tetracycline
- Aminoglycoside
- Macrolide
Correct Answer: Chloramphenicol
Q13. Which agent is effective against MRSA and acts by preventing formation of the initiation complex?
- Vancomycin
- Linezolid
- Azithromycin
- Tetracycline
Correct Answer: Linezolid
Q14. Resistance due to enzymatic inactivation (acetylation, phosphorylation) commonly affects which class?
- Macrolides
- Aminoglycosides
- Oxazolidinones
- Rifamycins
Correct Answer: Aminoglycosides
Q15. Which drug is associated with the “gray baby syndrome” in neonates?
- Chloramphenicol
- Gentamicin
- Tetracycline
- Azithromycin
Correct Answer: Chloramphenicol
Q16. Tetracyclines are primarily bacteriostatic because they:
- Cause misreading of mRNA
- Inhibit 50S translocation
- Block attachment of aminoacyl-tRNA to the A site
- Inhibit DNA gyrase
Correct Answer: Block attachment of aminoacyl-tRNA to the A site
Q17. Which laboratory monitoring is most important during prolonged aminoglycoside therapy?
- Liver function tests
- Serum creatinine and audiometry
- Complete blood count only
- Coagulation profile
Correct Answer: Serum creatinine and audiometry
Q18. Macrolides inhibit CYP3A4; which consequence is clinically relevant?
- Increased metabolism of warfarin
- Decreased levels of theophylline
- Increased plasma levels of statins leading to myopathy
- Enhanced renal clearance of aminoglycosides
Correct Answer: Increased plasma levels of statins leading to myopathy
Q19. Which antibiotic class can cause mitochondrial protein synthesis inhibition leading to lactic acidosis and neuropathy?
- Oxazolidinones (linezolid)
- Tetracyclines
- Macrolides
- Aminoglycosides
Correct Answer: Oxazolidinones (linezolid)
Q20. Streptogramins (e.g., quinupristin-dalfopristin) act primarily by:
- Binding to 30S and causing misreading
- Inhibiting two distinct steps on the 50S subunit leading to synergistic action
- Inhibiting folate synthesis
- Disrupting cell membrane integrity
Correct Answer: Inhibiting two distinct steps on the 50S subunit leading to synergistic action
Q21. The post-antibiotic effect is most pronounced with which class?
- Tetracyclines
- Aminoglycosides
- Macrolides
- Chloramphenicol
Correct Answer: Aminoglycosides
Q22. Which drug is known for good intracellular penetration and activity against atypical organisms?
- Tetracycline
- Gentamicin
- Vancomycin
- Streptomycin
Correct Answer: Tetracycline
Q23. Which mechanism confers resistance to tetracyclines?
- Methylation of 23S rRNA
- Efflux pumps and ribosomal protection proteins
- Beta-lactamase production
- Altered folate pathway
Correct Answer: Efflux pumps and ribosomal protection proteins
Q24. Aminoglycosides require oxygen-dependent transport to enter bacteria; this means they are less active against:
- Anaerobic bacteria
- Gram-negative aerobes
- Mycobacteria
- Intracellular pathogens
Correct Answer: Anaerobic bacteria
Q25. Which antibiotic is commonly used topically for wounds and inhibits protein synthesis by binding the 50S subunit?
- Mupirocin
- Neomycin
- Tetracycline ointment
- Fusidic acid
Correct Answer: Mupirocin
Q26. Which protein synthesis inhibitor is associated with anemia, leukopenia, and thrombocytopenia on prolonged use?
- Chloramphenicol
- Azithromycin
- Gentamicin
- Tigecycline
Correct Answer: Chloramphenicol
Q27. Dosing of aminoglycosides is often optimized by:
- Continuous infusion to maintain troughs high
- Once-daily high-dose administration for concentration-dependent killing
- Small frequent doses due to time-dependent killing
- Co-administration with macrolides always
Correct Answer: Once-daily high-dose administration for concentration-dependent killing
Q28. Which test helps determine the susceptibility of bacteria to protein synthesis inhibitors?
- Minimum inhibitory concentration (MIC)
- Gram staining only
- Serum drug level without MIC
- Blood glucose measurement
Correct Answer: Minimum inhibitory concentration (MIC)
Q29. Which antibiotic can cause cholestatic hepatitis and prolonged QT interval?
- Clindamycin
- Macrolides (e.g., erythromycin)
- Aminoglycosides
- Linezolid
Correct Answer: Macrolides (e.g., erythromycin)
Q30. Tigecycline, a glycylcycline, differs from tetracyclines by:
- Lack of activity against MRSA
- Being unaffected by common tetracycline resistance mechanisms
- Causing nephrotoxicity commonly
- Binding to 50S subunit rather than 30S
Correct Answer: Being unaffected by common tetracycline resistance mechanisms
Q31. Which antibiotic binds to the 50S subunit and is often used for community-acquired pneumonia and atypical pathogens?
- Azithromycin
- Streptomycin
- Gentamicin
- Tetracycline
Correct Answer: Azithromycin
Q32. Which adverse effect is most associated with prolonged use of linezolid?
- Neurotoxicity and thrombocytopenia
- Severe ototoxicity
- Red man syndrome
- Hypoglycemia
Correct Answer: Neurotoxicity and thrombocytopenia
Q33. Which of the following best explains why macrolides are effective against intracellular pathogens?
- They are large polar molecules that remain extracellular
- They accumulate within phagocytes and reach intracellular concentrations
- They require active oxygen transport to enter bacteria
- They inhibit DNA synthesis
Correct Answer: They accumulate within phagocytes and reach intracellular concentrations
Q34. Which feature differentiates bacteriostatic from bactericidal protein synthesis inhibitors clinically?
- Bacteriostatic agents always cause cell lysis
- Bactericidal agents kill bacteria while bacteriostatic agents inhibit growth
- Bacteriostatic agents are never used clinically
- Bactericidal agents inhibit ribosomal 30S only
Correct Answer: Bactericidal agents kill bacteria while bacteriostatic agents inhibit growth
Q35. Which antibiotic interaction is a concern when combining aminoglycosides with loop diuretics?
- Reduced aminoglycoside efficacy due to diuretics
- Increased risk of nephrotoxicity and ototoxicity
- Enhanced hepatic clearance of aminoglycosides
- No clinically significant interaction
Correct Answer: Increased risk of nephrotoxicity and ototoxicity
Q36. Which is a common clinical use for clindamycin related to its activity against anaerobes?
- Treatment of urinary tract infections caused by E. coli
- Management of aspiration pneumonia and anaerobic soft tissue infections
- First-line therapy for viral pharyngitis
- Treatment of fungal skin infections
Correct Answer: Management of aspiration pneumonia and anaerobic soft tissue infections
Q37. Ribosomal protection proteins confer resistance to tetracyclines by:
- Degrading the antibiotic enzymatically
- Displacing tetracycline from the ribosome
- Pumping the drug out of the cell
- Methylating 23S rRNA
Correct Answer: Displacing tetracycline from the ribosome
Q38. Which macrolide is least likely to inhibit CYP3A4 and therefore has fewer drug interactions?
- Erythromycin
- Clarithromycin
- Azithromycin
- Telithromycin
Correct Answer: Azithromycin
Q39. Which antibiotic is used as second-line therapy for multi-drug resistant tuberculosis and targets the 30S subunit?
- Linezolid
- Streptomycin
- Chloramphenicol
- Rifampicin
Correct Answer: Streptomycin
Q40. Which effect explains why chloramphenicol therapy requires monitoring of complete blood counts?
- Risk of reversible neutrophilia
- Risk of idiosyncratic aplastic anemia
- Common hemolytic anemia in children
- Platelet hyperfunction
Correct Answer: Risk of idiosyncratic aplastic anemia
Q41. Which protein synthesis inhibitor is preferred for community-acquired MRSA skin infections in outpatient settings?
- Tigecycline
- Linezolid
- Streptomycin
- Chloramphenicol
Correct Answer: Linezolid
Q42. Which statement about aminoglycoside pharmacodynamics is true?
- Efficacy correlates best with time above MIC
- Efficacy correlates best with peak concentration/MIC ratio
- They are ineffective against Gram-negative bacteria
- They are primarily bacteriostatic
Correct Answer: Efficacy correlates best with peak concentration/MIC ratio
Q43. Which antibiotic may cause pseudomembranous colitis by overgrowth of Clostridioides difficile?
- Clindamycin
- Tetracycline
- Linezolid
- Aminoglycosides
Correct Answer: Clindamycin
Q44. Which of the following is a mechanism by which bacteria reduce drug binding to macrolides?
- Production of beta-lactamase
- Methylation of adenine residues in 23S rRNA
- Alteration of DNA gyrase
- Increase in outer membrane porins
Correct Answer: Methylation of adenine residues in 23S rRNA
Q45. The clinical significance of mitochondrial ribosome similarity to bacterial ribosomes explains which toxicity?
- Macrolide-induced hepatotoxicity
- Aminoglycoside nephrotoxicity due to mitochondrial damage
- Chloramphenicol-induced bone marrow suppression and lactic acidosis with oxazolidinones
- Reduced efficacy of tetracyclines
Correct Answer: Chloramphenicol-induced bone marrow suppression and lactic acidosis with oxazolidinones
Q46. Which agent inhibits isoleucyl-tRNA synthetase and is used topically for nasal carriage of Staphylococcus?
- Mupirocin
- Gentamicin
- Linezolid
- Chloramphenicol
Correct Answer: Mupirocin
Q47. Which laboratory parameter is most useful when adjusting dosing for aminoglycosides?
- Liver enzymes
- Serum creatinine and estimated glomerular filtration rate (eGFR)
- Fasting blood sugar
- Serum sodium
Correct Answer: Serum creatinine and estimated glomerular filtration rate (eGFR)
Q48. Which antibiotic is best avoided with serotonergic drugs due to risk of serotonin syndrome?
- Clindamycin
- Linezolid
- Aminoglycosides
- Tetracycline
Correct Answer: Linezolid
Q49. Which of the following is true regarding protein synthesis inhibitors and their selectivity?
- They equally affect human cytosolic ribosomes and bacterial ribosomes
- Selectivity is due to structural differences between bacterial 70S and eukaryotic 80S ribosomes
- They target human mitochondrial ribosomes exclusively
- Selectivity depends solely on drug lipophilicity
Correct Answer: Selectivity is due to structural differences between bacterial 70S and eukaryotic 80S ribosomes
Q50. Combining a bacteriostatic protein synthesis inhibitor with a bactericidal beta-lactam may be antagonistic because:
- Bacteriostatic drugs enhance cell wall synthesis
- Beta-lactams require active bacterial growth for maximal killing, which bacteriostatic agents inhibit
- Bacteriostatic agents degrade beta-lactams enzymatically
- There is no known interaction between these classes
Correct Answer: Beta-lactams require active bacterial growth for maximal killing, which bacteriostatic agents inhibit
I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.
Mail- Sachin@pharmacyfreak.com