MD INDE 247B Foundations of Medicine V B –
Microbiology Capstone, Pharmacology Capstone,
MIC/CMS Study Guide, Original Practice Questions
& Answers, Stanford Medical School Exam
Preparation, Comprehensive Medical Science
Review, Clinical Microbiology, Infectious Diseases,
Antimicrobial Therapy, Pharmacology, Drug
Mechanisms, Adverse Effects, Drug Interactions,
Diagnostic Testing, Pathophysiology & Clinical
Decision-Making
Question 1: A 68-year-old male with a history of type 2 diabetes and
peripheral vascular disease presents with a 3-day history of a painful, swollen,
erythematous left foot. He reports stepping on a nail a week ago. Vital signs
are T 38.5°C, HR 110 bpm, BP 145/90 mmHg. Examination reveals a 2 cm
ulcer on the plantar surface with purulent discharge and surrounding cellulitis
extending to the mid-foot. Gram stain of the wound shows gram-positive cocci
in clusters. Which of the following is the most appropriate empiric antibiotic
regimen for this patient?
A. Ampicillin-sulbactam
B. Vancomycin and piperacillin-tazobactam
C. Cefazolin
D. Clindamycin
CORRECT ANSWER: B. Vancomycin and piperacillin-tazobactam
Rationale: This patient presents with a severe diabetic foot infection complicated by
systemic signs of infection (fever, tachycardia) and deep tissue involvement (cellulitis
extending to the mid-foot). The gram stain showing gram-positive cocci in clusters is
concerning for methicillin-resistant Staphylococcus aureus (MRSA), for which vancomycin
is the drug of choice. Piperacillin-tazobactam provides broad-spectrum coverage
including Pseudomonas aeruginosa and anaerobes, which are common in these deep,
purulent infections. Ampicillin-sulbactam lacks reliable anti-pseudomonal coverage,
cefazolin is not effective against MRSA, and clindamycin is not ideal for empiric severe
polymicrobial infections.
Question 2: A 32-year-old female with a history of recurrent urinary tract
infections is started on trimethoprim-sulfamethoxazole for a suspected acute
pyelonephritis. She has a known allergy to sulfa drugs. Which of the following
mechanisms is responsible for the most common type of hypersensitivity
reaction to sulfonamides?
A. Type I IgE-mediated reaction
B. Type II antibody-dependent cellular cytotoxicity
,C. Type III immune-complex deposition
D. Type IV T-cell mediated delayed hypersensitivity
CORRECT ANSWER: D. Type IV T-cell mediated delayed hypersensitivity
Rationale: The most common hypersensitivity reaction to sulfonamides is a delayed, T-
cell mediated (Type IV) reaction, which presents as a maculopapular rash. While Type I
reactions (anaphylaxis) can occur, they are less common. Type II (cytotoxic) and Type
III (immune-complex) reactions are not typical for sulfonamides.
Question 3: A 45-year-old male is being treated for community-acquired
pneumonia with levofloxacin. He calls the clinic complaining of sudden onset
of pain and swelling in his right ankle. Which of the following is the most
significant adverse effect associated with fluoroquinolones that this patient is
likely experiencing?
A. Achilles tendon rupture
B. Prolonged QT interval
C. Peripheral neuropathy
D. Hepatotoxicity
CORRECT ANSWER: A. Achilles tendon rupture
Rationale: Fluoroquinolones, including levofloxacin, are associated with an increased
risk of tendinopathy and tendon rupture, particularly of the Achilles tendon. This risk is
increased in patients over 60, those with renal impairment, and those on concomitant
corticosteroids. While QT prolongation, peripheral neuropathy, and hepatotoxicity are
also adverse effects, tendonitis and rupture are the most characteristic of this class.
Question 4: A 22-year-old female presents with a fever, severe sore throat, and
tender anterior cervical lymphadenopathy. A rapid strep test is positive for
Group A Streptococcus. She is prescribed amoxicillin. What is the primary
mechanism of action of amoxicillin against this organism?
A. Inhibition of DNA gyrase
B. Binding to the 50S ribosomal subunit to inhibit protein synthesis
C. Inhibition of cell wall synthesis by binding to penicillin-binding proteins
D. Disruption of the bacterial cell membrane
CORRECT ANSWER: C. Inhibition of cell wall synthesis by binding to
penicillin-binding proteins
Rationale: Amoxicillin is a beta-lactam antibiotic. Its mechanism of action involves
binding to penicillin-binding proteins (PBPs) located on the bacterial cell wall. This
inhibits transpeptidase activity, preventing the cross-linking of peptidoglycan strands,
,which leads to cell wall weakening and bacterial lysis. Option A is the mechanism for
fluoroquinolones, Option B for macrolides, and Option D for polymyxins.
Question 5: A 65-year-old male with heart failure is started on spironolactone.
The physician reminds him to avoid potassium supplements. What is the
primary mechanism by which spironolactone can cause hyperkalemia?
A. Blockade of aldosterone receptors in the collecting duct
B. Inhibition of the Na-K-2Cl cotransporter in the thick ascending limb
C. Activation of the epithelial sodium channel (ENaC)
D. Inhibition of carbonic anhydrase in the proximal tubule
CORRECT ANSWER: A. Blockade of aldosterone receptors in the collecting
duct
Rationale: Spironolactone is a potassium-sparing diuretic that acts as a competitive
antagonist of aldosterone receptors in the principal cells of the collecting duct. By
blocking aldosterone, it inhibits the expression of ENaC and the Na/K-ATPase pump,
reducing sodium reabsorption and, consequently, potassium secretion into the urine.
This can lead to hyperkalemia. Option B describes loop diuretics, Option C is incorrect
as spironolactone inhibits ENaC activation, and Option D describes carbonic anhydrase
inhibitors.
Question 6: A 72-year-old man with a history of atrial fibrillation is on
warfarin for stroke prevention. His INR is checked regularly. Which vitamin is
essential for the synthesis of the clotting factors that warfarin inhibits?
A. Vitamin A
B. Vitamin D
C. Vitamin E
D. Vitamin K
CORRECT ANSWER: D. Vitamin K
Rationale: Warfarin exerts its anticoagulant effect by inhibiting vitamin K epoxide
reductase. This enzyme is responsible for the regeneration of reduced vitamin K, which
is a required cofactor for the gamma-carboxylation of glutamic acid residues on clotting
factors II, VII, IX, and X, as well as proteins C and S. Deficiency of reduced vitamin K
leads to the production of functionally inactive clotting factors. Vitamins A, D, and E are
not involved in this process.
Question 7: A 28-year-old woman is 32 weeks pregnant and is diagnosed with
a urinary tract infection. Which of the following antibiotics would be
considered the safest and most appropriate first-line option in pregnancy?
, A. Ciprofloxacin
B. Doxycycline
C. Amoxicillin
D. Nitrofurantoin
CORRECT ANSWER: C. Amoxicillin
Rationale: Amoxicillin is generally considered safe during pregnancy (Category B) and
is a common first-line treatment for asymptomatic bacteriuria and UTIs in pregnant
women, though local resistance patterns must be considered. Nitrofurantoin is also
Category B but is typically avoided near term (38+ weeks) due to the risk of neonatal
hemolytic anemia in G6PD-deficient infants. Ciprofloxacin (Category C) is generally
avoided due to concerns about fetal cartilage and joint toxicity. Doxycycline (Category
D) is contraindicated due to risks of fetal tooth discoloration and skeletal growth
inhibition.
Question 8: A 55-year-old female is diagnosed with a severe infection caused
by methicillin-resistant Staphylococcus aureus (MRSA). The isolate is
confirmed to be vancomycin-resistant. Which of the following agents is most
appropriate for treating this infection?
A. Linezolid
B. Gentamicin
C. Clindamycin
D. Cefazolin
CORRECT ANSWER: A. Linezolid
Rationale: Linezolid is an oxazolidinone antibiotic that is effective against MRSA and
vancomycin-resistant S. aureus (VRSA) and vancomycin-resistant enterococci (VRE). It
has excellent tissue penetration and acts by inhibiting protein synthesis at the 50S
ribosomal subunit. Gentamicin is not used as monotherapy for serious MRSA infections.
Clindamycin is an option for susceptible strains but does not cover VRSA. Cefazolin is a
cephalosporin that is not effective against MRSA.
Question 9: A 60-year-old male with chronic obstructive pulmonary disease
(COPD) is prescribed a long-acting beta-agonist (LABA) and an inhaled
corticosteroid (ICS) for maintenance therapy. Which of the following is the
primary mechanism of action for the LABA component in this regimen?
A. Antagonism of muscarinic receptors leading to bronchodilation
B. Stimulation of beta-2 adrenergic receptors leading to smooth muscle relaxation
C. Inhibition of phosphodiesterase-4 leading to reduced inflammation
D. Stabilization of mast cells to prevent degranulation
Microbiology Capstone, Pharmacology Capstone,
MIC/CMS Study Guide, Original Practice Questions
& Answers, Stanford Medical School Exam
Preparation, Comprehensive Medical Science
Review, Clinical Microbiology, Infectious Diseases,
Antimicrobial Therapy, Pharmacology, Drug
Mechanisms, Adverse Effects, Drug Interactions,
Diagnostic Testing, Pathophysiology & Clinical
Decision-Making
Question 1: A 68-year-old male with a history of type 2 diabetes and
peripheral vascular disease presents with a 3-day history of a painful, swollen,
erythematous left foot. He reports stepping on a nail a week ago. Vital signs
are T 38.5°C, HR 110 bpm, BP 145/90 mmHg. Examination reveals a 2 cm
ulcer on the plantar surface with purulent discharge and surrounding cellulitis
extending to the mid-foot. Gram stain of the wound shows gram-positive cocci
in clusters. Which of the following is the most appropriate empiric antibiotic
regimen for this patient?
A. Ampicillin-sulbactam
B. Vancomycin and piperacillin-tazobactam
C. Cefazolin
D. Clindamycin
CORRECT ANSWER: B. Vancomycin and piperacillin-tazobactam
Rationale: This patient presents with a severe diabetic foot infection complicated by
systemic signs of infection (fever, tachycardia) and deep tissue involvement (cellulitis
extending to the mid-foot). The gram stain showing gram-positive cocci in clusters is
concerning for methicillin-resistant Staphylococcus aureus (MRSA), for which vancomycin
is the drug of choice. Piperacillin-tazobactam provides broad-spectrum coverage
including Pseudomonas aeruginosa and anaerobes, which are common in these deep,
purulent infections. Ampicillin-sulbactam lacks reliable anti-pseudomonal coverage,
cefazolin is not effective against MRSA, and clindamycin is not ideal for empiric severe
polymicrobial infections.
Question 2: A 32-year-old female with a history of recurrent urinary tract
infections is started on trimethoprim-sulfamethoxazole for a suspected acute
pyelonephritis. She has a known allergy to sulfa drugs. Which of the following
mechanisms is responsible for the most common type of hypersensitivity
reaction to sulfonamides?
A. Type I IgE-mediated reaction
B. Type II antibody-dependent cellular cytotoxicity
,C. Type III immune-complex deposition
D. Type IV T-cell mediated delayed hypersensitivity
CORRECT ANSWER: D. Type IV T-cell mediated delayed hypersensitivity
Rationale: The most common hypersensitivity reaction to sulfonamides is a delayed, T-
cell mediated (Type IV) reaction, which presents as a maculopapular rash. While Type I
reactions (anaphylaxis) can occur, they are less common. Type II (cytotoxic) and Type
III (immune-complex) reactions are not typical for sulfonamides.
Question 3: A 45-year-old male is being treated for community-acquired
pneumonia with levofloxacin. He calls the clinic complaining of sudden onset
of pain and swelling in his right ankle. Which of the following is the most
significant adverse effect associated with fluoroquinolones that this patient is
likely experiencing?
A. Achilles tendon rupture
B. Prolonged QT interval
C. Peripheral neuropathy
D. Hepatotoxicity
CORRECT ANSWER: A. Achilles tendon rupture
Rationale: Fluoroquinolones, including levofloxacin, are associated with an increased
risk of tendinopathy and tendon rupture, particularly of the Achilles tendon. This risk is
increased in patients over 60, those with renal impairment, and those on concomitant
corticosteroids. While QT prolongation, peripheral neuropathy, and hepatotoxicity are
also adverse effects, tendonitis and rupture are the most characteristic of this class.
Question 4: A 22-year-old female presents with a fever, severe sore throat, and
tender anterior cervical lymphadenopathy. A rapid strep test is positive for
Group A Streptococcus. She is prescribed amoxicillin. What is the primary
mechanism of action of amoxicillin against this organism?
A. Inhibition of DNA gyrase
B. Binding to the 50S ribosomal subunit to inhibit protein synthesis
C. Inhibition of cell wall synthesis by binding to penicillin-binding proteins
D. Disruption of the bacterial cell membrane
CORRECT ANSWER: C. Inhibition of cell wall synthesis by binding to
penicillin-binding proteins
Rationale: Amoxicillin is a beta-lactam antibiotic. Its mechanism of action involves
binding to penicillin-binding proteins (PBPs) located on the bacterial cell wall. This
inhibits transpeptidase activity, preventing the cross-linking of peptidoglycan strands,
,which leads to cell wall weakening and bacterial lysis. Option A is the mechanism for
fluoroquinolones, Option B for macrolides, and Option D for polymyxins.
Question 5: A 65-year-old male with heart failure is started on spironolactone.
The physician reminds him to avoid potassium supplements. What is the
primary mechanism by which spironolactone can cause hyperkalemia?
A. Blockade of aldosterone receptors in the collecting duct
B. Inhibition of the Na-K-2Cl cotransporter in the thick ascending limb
C. Activation of the epithelial sodium channel (ENaC)
D. Inhibition of carbonic anhydrase in the proximal tubule
CORRECT ANSWER: A. Blockade of aldosterone receptors in the collecting
duct
Rationale: Spironolactone is a potassium-sparing diuretic that acts as a competitive
antagonist of aldosterone receptors in the principal cells of the collecting duct. By
blocking aldosterone, it inhibits the expression of ENaC and the Na/K-ATPase pump,
reducing sodium reabsorption and, consequently, potassium secretion into the urine.
This can lead to hyperkalemia. Option B describes loop diuretics, Option C is incorrect
as spironolactone inhibits ENaC activation, and Option D describes carbonic anhydrase
inhibitors.
Question 6: A 72-year-old man with a history of atrial fibrillation is on
warfarin for stroke prevention. His INR is checked regularly. Which vitamin is
essential for the synthesis of the clotting factors that warfarin inhibits?
A. Vitamin A
B. Vitamin D
C. Vitamin E
D. Vitamin K
CORRECT ANSWER: D. Vitamin K
Rationale: Warfarin exerts its anticoagulant effect by inhibiting vitamin K epoxide
reductase. This enzyme is responsible for the regeneration of reduced vitamin K, which
is a required cofactor for the gamma-carboxylation of glutamic acid residues on clotting
factors II, VII, IX, and X, as well as proteins C and S. Deficiency of reduced vitamin K
leads to the production of functionally inactive clotting factors. Vitamins A, D, and E are
not involved in this process.
Question 7: A 28-year-old woman is 32 weeks pregnant and is diagnosed with
a urinary tract infection. Which of the following antibiotics would be
considered the safest and most appropriate first-line option in pregnancy?
, A. Ciprofloxacin
B. Doxycycline
C. Amoxicillin
D. Nitrofurantoin
CORRECT ANSWER: C. Amoxicillin
Rationale: Amoxicillin is generally considered safe during pregnancy (Category B) and
is a common first-line treatment for asymptomatic bacteriuria and UTIs in pregnant
women, though local resistance patterns must be considered. Nitrofurantoin is also
Category B but is typically avoided near term (38+ weeks) due to the risk of neonatal
hemolytic anemia in G6PD-deficient infants. Ciprofloxacin (Category C) is generally
avoided due to concerns about fetal cartilage and joint toxicity. Doxycycline (Category
D) is contraindicated due to risks of fetal tooth discoloration and skeletal growth
inhibition.
Question 8: A 55-year-old female is diagnosed with a severe infection caused
by methicillin-resistant Staphylococcus aureus (MRSA). The isolate is
confirmed to be vancomycin-resistant. Which of the following agents is most
appropriate for treating this infection?
A. Linezolid
B. Gentamicin
C. Clindamycin
D. Cefazolin
CORRECT ANSWER: A. Linezolid
Rationale: Linezolid is an oxazolidinone antibiotic that is effective against MRSA and
vancomycin-resistant S. aureus (VRSA) and vancomycin-resistant enterococci (VRE). It
has excellent tissue penetration and acts by inhibiting protein synthesis at the 50S
ribosomal subunit. Gentamicin is not used as monotherapy for serious MRSA infections.
Clindamycin is an option for susceptible strains but does not cover VRSA. Cefazolin is a
cephalosporin that is not effective against MRSA.
Question 9: A 60-year-old male with chronic obstructive pulmonary disease
(COPD) is prescribed a long-acting beta-agonist (LABA) and an inhaled
corticosteroid (ICS) for maintenance therapy. Which of the following is the
primary mechanism of action for the LABA component in this regimen?
A. Antagonism of muscarinic receptors leading to bronchodilation
B. Stimulation of beta-2 adrenergic receptors leading to smooth muscle relaxation
C. Inhibition of phosphodiesterase-4 leading to reduced inflammation
D. Stabilization of mast cells to prevent degranulation
