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Question 1. Which of the following best defines a bactericidal agent? A) Inhibits bacterial protein synthesis B) Prevents bacterial DNA replication C) Kills bacteria directly D) Reduces bacterial adhesion to tissues Answer: C Explanation: Bactericidal drugs achieve a ≥99.9% reduction in viable organisms, whereas bacteriostatic agents only inhibit growth. Question 2. The post-antibiotic effect (PAE) is most pronounced with which class? A) β-lactams B) Aminoglycosides C) Tetracyclines D) Sulfonamides Answer: B Explanation: Aminoglycosides continue to suppress bacterial regrowth after drug concentrations fall below the MIC, resulting in a marked PAE. Question 3. For a time-dependent β-lactam, which pharmacodynamic index correlates best with efficacy? A) Cmax/MIC B) AUC/MIC C) %T>MIC D) Peak-to-trough ratio Answer: C
Explanation: Time-dependent killers require the drug concentration to remain above the MIC for a certain percentage of the dosing interval. Question 4. Which oral β-lactam has the highest bioavailability? A) Amoxicillin B) Penicillin G C) Cefuroxime axetil D) Piperacillin Answer: A Explanation: Amoxicillin’s oral bioavailability is ≈90%, far exceeding most other oral β-lactams. Question 5. A patient with meningitis is started on ceftriaxone. What pharmacokinetic property makes ceftriaxone suitable for CNS infections? A) Low protein binding B) High volume of distribution C) Good CSF penetration when meninges are inflamed D) Rapid renal clearance Answer: C Explanation: Inflamed meninges allow ceftriaxone to achieve therapeutic concentrations in cerebrospinal fluid. Question 6. Which β-lactamase inhibitor is combined with piperacillin? A) Clavulanic acid B) Tazobactam C) Sulbactam D) Avibactam Answer: B
Answer: B Explanation: Vancomycin prevents cross-linking of peptidoglycan by binding the D-ala-D-ala dipeptide. Question 10. The adverse effect “Red Man Syndrome” is associated with: A) Rapid infusion of vancomycin B) High-dose aminoglycosides C) Long-term fluoroquinolone therapy D) Oral azithromycin use Answer: A Explanation: Histamine release from rapid vancomycin infusion causes flushing and erythema. Question 11. Daptomycin is inactivated by: A) β-lactamase enzymes B) Pulmonary surfactant C) Gastric acid D) CYP3A4 metabolism Answer: B Explanation: Pulmonary surfactant binds daptomycin, preventing its activity in the lungs; thus it is not used for pneumonia. Question 12. Which of the following agents is a 30S ribosomal subunit inhibitor that requires oxygen for uptake? A) Tetracycline B) Chloramphenicol C) Aminoglycoside D) Macrolide
Answer: C Explanation: Aminoglycosides enter bacterial cells via an oxygen-dependent active transport system. Question 13. Synergy between an aminoglycoside and a β-lactam is due to: A) β-lactam-induced cell-wall damage facilitating aminoglycoside entry B) Shared metabolic pathways C) Mutual inhibition of efflux pumps D) Both drugs binding the same ribosomal site Answer: A Explanation: β-lactams disrupt the cell wall, allowing greater aminoglycoside penetration. Question 14. Which aminoglycoside is most nephrotoxic? A) Gentamicin B) Amikacin C) Tobramycin D) Streptomycin Answer: A Explanation: Gentamicin has a higher propensity for causing acute tubular necrosis compared with other aminoglycosides. Question 15. Tigecycline is classified as a: A) Glycylcycline B) Lincosamide C) Oxazolidinone D) Fluoroquinolone
D) Loop diuretics Answer: B Explanation: Linezolid is a reversible MAO-A inhibitor; co-administration with serotonergic agents can cause excess serotonin. **Question 19. Which fluoroquinolone has the highest risk of tendon rupture? ** A) Ciprofloxacin B) Levofloxacin C) Moxifloxacin D) Norfloxacin Answer: B Explanation: Levofloxacin carries a boxed warning for tendonitis and tendon rupture, especially in older adults. Question 20. The synergistic effect of TMP-SMX results from inhibition of: A) Sequential steps in folic acid synthesis B) DNA gyrase and topoisomerase IV C) Cell-wall cross-linking D) Protein elongation Answer: A Explanation: Trimethoprim blocks dihydrofolate reductase, while sulfamethoxazole inhibits dihydropteroate synthase; together they block successive steps in folate synthesis. Question 21. Metronidazole’s antimicrobial activity requires: A) Oxidation to a nitroso intermediate in anaerobic organisms B) Phosphorylation by bacterial kinases
C) Inhibition of ribosomal subunit 50S D) Binding to bacterial DNA polymerase Answer: A Explanation: In anaerobes, metronidazole is reduced to a toxic nitroso radical that damages DNA. Question 22. Amphotericin B’s major toxicity is: A) Hepatotoxicity B) Nephrotoxicity C) Ototoxicity D) Myelosuppression Answer: B Explanation: Amphotericin B binds cholesterol in renal tubular cells, causing dose-dependent nephrotoxicity. Question 23. The azole class of antifungals primarily inhibits: A) β-glucan synthesis B) Ergosterol synthesis via lanosterol 14α-demethylase inhibition C) Cell-wall chitin formation D. DNA synthesis Answer: B Explanation: Azoles block the cytochrome P-450 enzyme lanosterol 14 α-demethylase, preventing ergosterol production. Question 24. Echinocandins target which fungal structure? A) Cell membrane ergosterol B) β-1,3-D-glucan in the cell wall C) Mitochondrial DNA
C) Protease inhibitors D) Integrase strand transfer inhibitors Answer: D Explanation: Integrase inhibitors (e.g., raltegravir) prevent the insertion of HIV cDNA into host chromosomal DNA. Question 28. The direct-acting antivirals (DAAs) for hepatitis C target all EXCEPT: A) NS5A replication complex B) NS5B RNA-dependent RNA polymerase C) NS3/4A protease D) Reverse transcriptase Answer: D Explanation: HCV is an RNA virus; its lifecycle does not involve reverse transcriptase, which is a target of HIV drugs. Question 29. Which antimalarial drug is contraindicated in pregnancy due to neuro-developmental toxicity? A) Chloroquine B) Artemisinin derivatives C) Mefloquine D) Primaquine Answer: D Explanation: Primaquine can cause hemolysis in G6PD-deficient fetuses and is teratogenic; it is avoided in pregnancy. Question 30. Albendazole’s primary mechanism is inhibition of: A) Folate synthesis
B) Microtubule polymerization in helminths C) DNA gyrase D) Protein synthesis at the 30S ribosomal subunit Answer: B Explanation: Albendazole binds β-tubulin, preventing microtubule formation essential for helminth glucose uptake. Question 31. Which β-lactamase is classified as a carbapenemase (KPC)? A) TEM- 1 B) SHV- 2 C) OXA- 48 D) KPC- 2 Answer: D Explanation: KPC enzymes hydrolyze carbapenems and many other β-lactams, conferring broad resistance. Question 32. Efflux-pump mediated resistance is most commonly seen with which antibiotic class? A) Glycopeptides B) Fluoroquinolones C) Polymyxins D) Lipopeptides Answer: B Explanation: Overexpression of AcrAB-TolC and other pumps expel fluoroquinolones from Gram-negative bacteria. Question 33. The VanA phenotype of VRE is characterized by: A) Substitution of D-ala-D-ala with D-ala-D-lactate in cell-wall precursors
A) Development of new antibiotics only in human medicine B) Coordinated actions across human, animal, and environmental sectors C) Exclusive focus on hospital infection control D) Restricting all antibiotic use in agriculture immediately Answer: B Explanation: One Health integrates human health, veterinary medicine, and environmental stewardship to curb resistance. Question 37. Empiric therapy for uncomplicated cystitis in women typically includes which agent? A) Vancomycin B) Nitrofurantoin C) Cefepime D) Meropenem Answer: B Explanation: Nitrofurantoin is effective against most uropathogens causing uncomplicated cystitis and has low systemic toxicity. Question 38. For community-acquired pneumonia (CAP) in a previously healthy adult, the recommended empiric regimen is: A) Vancomycin plus cefepime B) Azithromycin monotherapy C) Amoxicillin-clavulanate plus a macrolide or doxycycline D) Levofloxacin alone Answer: C Explanation: A β-lactam plus a macrolide (or doxycycline) covers typical and atypical CAP pathogens.
Question 39. In sepsis caused by ESBL-producing E. coli, the preferred initial antimicrobial is: A) Piperacillin/tazobactam B) Ceftriaxone C) Meropenem D. Cefazolin Answer: C Explanation: Carbapenems retain activity against ESBL producers, whereas third-generation cephalosporins are hydrolyzed. Question 40. The drug of choice for bacterial meningitis caused by Neisseria meningitidis is: A) Vancomycin + cefotaxime B) Ceftriaxone alone C) Meropenem + ampicillin D) Azithromycin + rifampin Answer: B Explanation: Ceftriaxone penetrates the CSF well and has excellent activity against N. meningitidis. Question 41. Which antimicrobial is most associated with ototoxicity? A) Ciprofloxacin B) Gentamicin C) Doxycycline D) Linezolid Answer: B Explanation: Aminoglycosides, especially gentamicin, can damage the hair cells of the inner ear leading to irreversible hearing loss.
Explanation: Ribavirin interferes with aldehyde dehydrogenase, leading to accumulation of acetaldehyde and unpleasant symptoms after alcohol intake. Question 45. The primary route of elimination for most fluoroquinolones is: A) Hepatic metabolism B) Renal excretion of unchanged drug C) Biliary excretion D) Pulmonary exhalation Answer: B Explanation: Fluoroquinolones are largely excreted unchanged in the urine; dose adjustment is required in renal impairment. Question 46. Which of the following antibiotics is a known inducer of CYP3A4, potentially lowering concentrations of many drugs? A) Clarithromycin B) Rifampin C) Erythromycin D) Azithromycin Answer: B Explanation: Rifampin strongly induces CYP3A4, decreasing plasma levels of drugs metabolized by this enzyme. Question 47. The MIC (minimum inhibitory concentration) is defined as: A) The lowest drug concentration that kills 99.9% of organisms B) The lowest drug concentration that prevents visible growth after 24 h C) The highest concentration achievable in serum D) The average concentration needed for bacteriostatic effect
Answer: B Explanation: MIC is the minimal concentration that inhibits visible bacterial growth under standardized conditions. Question 48. In broth macrodilution testing, the MBC (minimum bactericidal concentration) is determined by: A) Observing turbidity after 48 h B) Sub-culturing from wells with no growth onto drug-free agar and assessing colony formation C) Measuring optical density at 600 nm D. Estimating from disc diffusion zone sizes Answer: B Explanation: MBC is the lowest concentration that reduces the original inoculum by ≥99.9% after sub-culture onto drug-free media. Question 49. Which of the following best describes the “post-antibiotic effect” (PAE) for a time-dependent agent? A) It is prominent and clinically important B) It is minimal or absent C. It increases with higher Cmax/MIC ratios D. It is independent of bacterial species Answer: B Explanation: Time-dependent agents (β-lactams) exhibit little PAE; their efficacy depends on sustained concentrations above MIC. Question 50. The volume of distribution (Vd) for a drug that is largely confined to the extracellular fluid is approximately: A) 0.1 L/kg B) 0.3 L/kg
A) Production of β-lactamase B) Methylation of the 23S rRNA target (erm genes) C. Efflux pump overexpression D. Altered PBPs Answer: B Explanation: erm-mediated methylation reduces macrolide binding to the ribosomal target, leading to resistance. Question 54. Which antibiotic class is most associated with photosensitivity reactions? A) Fluoroquinolones B. Tetracyclines C) Aminoglycosides D) Carbapenems Answer: B Explanation: Tetracyclines, especially doxycycline, can cause phototoxic skin reactions upon UV exposure. Question 55. In patients with severe hepatic impairment, which antimicrobial generally requires dose reduction? A) Levofloxacin B. Cefepime C. Azithromycin D. Gentamicin Answer: C Explanation: Azithromycin undergoes extensive hepatic metabolism and biliary excretion; dose adjustment is needed in liver disease.
Question 56. Which of the following is a contraindication for the use of fluoroquinolones in pregnancy? A) All fluoroquinolones are contraindicated due to potential cartilage damage in the fetus B) Only ciprofloxacin is contraindicated C) Only levofloxacin is contraindicated D) Fluoroquinolones are safe in pregnancy Answer: A Explanation: Fluoroquinolones have been associated with arthropathy in animal studies; they are avoided in pregnancy unless no alternatives exist. Question 57. Which of the following β-lactams has the longest half-life, allowing once-daily dosing? A) Cefazolin B) Ceftriaxone C. Cefuroxime D. Piperacillin Answer: B Explanation: Ceftriaxone’s half-life (~8 h) permits once-daily administration. Question 58. The “double-disk synergy test” is used to detect: A) ESBL production B) Carbapenemase activity C) Inducible clindamycin resistance (iMLSB) D) Vancomycin-resistant enterococci Answer: C Explanation: Placing a clindamycin disk adjacent to a erythromycin disk reveals a flattening of the inhibition zone (D-test) indicating iMLSB.
