Pharm.D. Doctor of Pharmacy Microbiology and Infectious Diseases 1 — Questions and Answers
Question 1: Which antibiotic class inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs)?
- Fluoroquinolones
- Beta-lactams (Correct answer)
- Aminoglycosides
- Macrolides
Correct answer: Beta-lactams
Beta-lactams (penicillins, cephalosporins, carbapenems) inhibit bacterial cell wall synthesis by covalently binding to penicillin-binding proteins, preventing peptidoglycan cross-linking.
Question 2: What is the primary mechanism of action of fluoroquinolone antibiotics?
- Inhibit bacterial cell wall synthesis
- Inhibit DNA gyrase and topoisomerase IV (Correct answer)
- Inhibit protein synthesis at the 30S ribosomal subunit
- Inhibit RNA polymerase
Correct answer: Inhibit DNA gyrase and topoisomerase IV
Fluoroquinolones inhibit DNA gyrase and topoisomerase IV, enzymes essential for bacterial DNA replication and transcription, leading to double-strand DNA breaks and cell death.
Question 3: Which organism is the most common bacterial cause of community-acquired pneumonia (CAP) in otherwise healthy adults?
- Staphylococcus aureus
- Klebsiella pneumoniae
- Streptococcus pneumoniae (Correct answer)
- Haemophilus influenzae
Correct answer: Streptococcus pneumoniae
Streptococcus pneumoniae (pneumococcus) is the most frequently identified bacterial pathogen in community-acquired pneumonia across all age groups.
Question 4: What is the drug of choice for confirmed methicillin-resistant Staphylococcus aureus (MRSA) bacteremia?
- Oxacillin
- Vancomycin (Correct answer)
- Azithromycin
- Clindamycin
Correct answer: Vancomycin
Vancomycin is first-line for MRSA bacteremia because MRSA is resistant to beta-lactams, and vancomycin inhibits cell wall synthesis via a different mechanism (binding D-Ala-D-Ala termini).
Question 5: Which antifungal class inhibits the enzyme lanosterol 14-alpha-demethylase (CYP51), thereby reducing ergosterol synthesis in fungal cells?
- Polyenes (e.g., amphotericin B)
- Echinocandins (e.g., micafungin)
- Azoles (e.g., fluconazole) (Correct answer)
- Allylamines (e.g., terbinafine)
Correct answer: Azoles (e.g., fluconazole)
Azoles inhibit lanosterol 14-alpha-demethylase (CYP51), reducing ergosterol synthesis and disrupting fungal cell membrane integrity, resulting in fungistatic activity.
Question 6: According to current IDSA/SHEA guidelines, which antibiotic is preferred over oral vancomycin for initial non-severe Clostridioides difficile infection due to lower recurrence rates?
- Metronidazole
- Fidaxomicin (Correct answer)
- Rifaximin
- Linezolid
Correct answer: Fidaxomicin
Fidaxomicin is preferred over oral vancomycin for non-severe CDI due to its narrow spectrum against C. difficile and superior rates of sustained clinical cure with lower recurrence.
Question 7: Which antibiotic is contraindicated near term in pregnancy due to the risk of 'gray baby syndrome' in neonates?
- Tetracyclines
- Penicillins
- Chloramphenicol (Correct answer)
- Cephalosporins
Correct answer: Chloramphenicol
Chloramphenicol is contraindicated near term because neonates have immature hepatic glucuronosyltransferase, leading to drug accumulation and gray baby syndrome (cardiovascular collapse).
