ANTIBIOTICS QUICK REFERENCE CHEAT SHEET 2026/2027 |
Sarah Michelle NP Review | Complete Guide by Condition,
Drug Class & Board Highlights | Pass Guaranteed - A+
Graded
SECTION 1: PENICILLINS & CEPHALOSPORINS (20 Questions)
Q1: A 28-year-old female presents with acute bacterial sinusitis persisting for 12 days
without improvement. She has no penicillin allergy and is otherwise healthy. Which
antibiotic is the first-line treatment according to current IDSA guidelines?
A. Azithromycin
B. Levofloxacin
C. Amoxicillin-clavulanate [CORRECT]
D. Trimethoprim-sulfamethoxazole
Correct Answer: C
Rationale: Amoxicillin-clavulanate is first-line for acute bacterial sinusitis due to
coverage of Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella
catarrhalis, including beta-lactamase producers. Azithromycin is reserved for
penicillin-allergic patients due to rising resistance. Levofloxacin is not first-line due to
adverse effect profile. TMP-SMX lacks adequate sinusitis coverage.
Q2: A 45-year-old male is diagnosed with community-acquired pneumonia (CURB-65
score 0). He has no comorbidities or recent antibiotic use. Which cephalosporin
provides appropriate empiric coverage when combined with a macrolide?
A. Cefazolin
B. Ceftriaxone [CORRECT]
C. Cefuroxime axetil
D. Cephalexin
Correct Answer: B
Rationale: Ceftriaxone (3rd generation) covers typical pathogens including S.
pneumoniae and H. influenzae, making it appropriate for CAP when combined with
atypical coverage (macrolide). Cefazolin (1st gen) lacks respiratory pathogen coverage.
,Cefuroxime has inferior S. pneumoniae coverage. Cephalexin is not used for
pneumonia.
Q3: A 62-year-old patient with diabetic foot infection and no drug allergies requires
empiric coverage for Pseudomonas aeruginosa, enteric gram-negatives, and anaerobes.
Which penicillin-based regimen is most appropriate?
A. Ampicillin-sulbactam
B. Piperacillin-tazobactam [CORRECT]
C. Amoxicillin-clavulanate
D. Penicillin VK
Correct Answer: B
Rationale: Piperacillin-tazobactam (Zosyn) provides broad gram-negative,
anti-pseudomonal, and anaerobic coverage essential for diabetic foot infections.
Ampicillin-sulbactam lacks Pseudomonas coverage. Amoxicillin-clavulanate has no
anti-pseudomonal activity. Penicillin VK is narrow-spectrum and inappropriate.
Q4: A 34-year-old female with a documented severe anaphylactic reaction to penicillin
requires treatment for methicillin-sensitive Staphylococcus aureus (MSSA) cellulitis.
Which cephalosporin is SAFE to administer given the allergy history?
A. Cefazolin
B. Cephalexin
C. Ceftaroline [CORRECT]
D. Ceftriaxone
Correct Answer: C
Rationale: Ceftaroline is a 5th generation cephalosporin with unique anti-MRSA activity
and no cross-reactivity with penicillin in patients with severe anaphylaxis. 1st-4th
generation cephalosporins share a beta-lactam ring and should be avoided in severe
penicillin allergy due to potential cross-reactivity (approximately 10%).
Q5: A 5-year-old child weighs 20 kg and has acute otitis media. The mother requests the
standard high-dose amoxicillin regimen. What is the appropriate total daily dose?
A. 400 mg/day
B. 800 mg/day
C. 1,600 mg/day
D. 1,800 mg/day [CORRECT]
,Correct Answer: D
Rationale: High-dose amoxicillin for acute otitis media is 80-90 mg/kg/day divided BID.
For a 20 kg child: 20 × 90 mg = 1,800 mg/day. This dosing overcomes
intermediate-resistant S. pneumoniae. Lower doses are subtherapeutic for high-risk
populations.
Q6: A patient with community-acquired pneumonia requires hospitalization (non-ICU).
The NP selects ceftriaxone plus azithromycin. What is the primary mechanism of action
of ceftriaxone?
A. Inhibition of folic acid synthesis
B. Inhibition of bacterial protein synthesis
C. Inhibition of cell wall synthesis [CORRECT]
D. Inhibition of DNA gyrase
Correct Answer: C
Rationale: Ceftriaxone, like all beta-lactams, inhibits bacterial cell wall synthesis by
binding to penicillin-binding proteins (PBPs), preventing cross-linking of peptidoglycan.
This mechanism is bactericidal against susceptible organisms.
Q7: A 70-year-old male with healthcare-associated pneumonia is started on empiric
antibiotics. The culture returns showing ESBL-producing Klebsiella pneumoniae. Which
carbapenem is appropriate for this patient?
A. Ertapenem
B. Meropenem [CORRECT]
C. Imipenem-cilastatin
D. All of the above
Correct Answer: B
Rationale: Meropenem is preferred for ESBL-producing organisms in critically ill patients
due to superior CNS penetration and lower seizure risk compared to imipenem.
Ertapenem lacks Pseudomonas coverage but covers ESBLs; however, meropenem is the
broadest and safest choice for HA pneumonia.
Q8: A 25-year-old patient has streptococcal pharyngitis confirmed by rapid antigen
detection test. She has no drug allergies. What is the treatment of choice?
A. Azithromycin
B. Cephalexin
, C. Penicillin VK or amoxicillin [CORRECT]
D. Clindamycin
Correct Answer: C
Rationale: Penicillin VK or amoxicillin remains first-line for group A streptococcal
pharyngitis due to narrow spectrum, excellent efficacy, and low cost. Macrolides are
alternatives for penicillin-allergic patients. Cephalexin is acceptable for penicillin-allergic
patients but not first-line.
Q9: A patient with a severe penicillin allergy (anaphylaxis) requires treatment for a
complicated urinary tract infection. Which antibiotic is LEAST appropriate due to
significant cross-reactivity?
A. Aztreonam
B. Ceftriaxone [CORRECT]
C. Levofloxacin
D. Gentamicin
Correct Answer: B
Rationale: Ceftriaxone (3rd generation cephalosporin) shares the beta-lactam ring with
penicillin and has approximately 10% cross-reactivity in patients with severe
IgE-mediated penicillin allergy. Aztreonam (monobactam) has negligible
cross-reactivity. Fluoroquinolones and aminoglycosides are structurally unrelated.
Q10: A 55-year-old patient with a prosthetic joint infection requires MRSA coverage.
Which 5th generation cephalosporin provides coverage against MRSA and is approved
for acute bacterial skin and skin structure infections?
A. Ceftazidime
B. Ceftaroline [CORRECT]
C. Ceftriaxone
D. Cefepime
Correct Answer: B
Rationale: Ceftaroline is the only cephalosporin with reliable MRSA coverage due to high
affinity for PBP2a. It is FDA-approved for ABSSSI and CABP. Other cephalosporins listed
lack MRSA activity.
Q11: A 40-year-old patient with a history of recurrent UTIs is prescribed cephalexin for
uncomplicated cystitis. What generation cephalosporin is cephalexin?
Sarah Michelle NP Review | Complete Guide by Condition,
Drug Class & Board Highlights | Pass Guaranteed - A+
Graded
SECTION 1: PENICILLINS & CEPHALOSPORINS (20 Questions)
Q1: A 28-year-old female presents with acute bacterial sinusitis persisting for 12 days
without improvement. She has no penicillin allergy and is otherwise healthy. Which
antibiotic is the first-line treatment according to current IDSA guidelines?
A. Azithromycin
B. Levofloxacin
C. Amoxicillin-clavulanate [CORRECT]
D. Trimethoprim-sulfamethoxazole
Correct Answer: C
Rationale: Amoxicillin-clavulanate is first-line for acute bacterial sinusitis due to
coverage of Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella
catarrhalis, including beta-lactamase producers. Azithromycin is reserved for
penicillin-allergic patients due to rising resistance. Levofloxacin is not first-line due to
adverse effect profile. TMP-SMX lacks adequate sinusitis coverage.
Q2: A 45-year-old male is diagnosed with community-acquired pneumonia (CURB-65
score 0). He has no comorbidities or recent antibiotic use. Which cephalosporin
provides appropriate empiric coverage when combined with a macrolide?
A. Cefazolin
B. Ceftriaxone [CORRECT]
C. Cefuroxime axetil
D. Cephalexin
Correct Answer: B
Rationale: Ceftriaxone (3rd generation) covers typical pathogens including S.
pneumoniae and H. influenzae, making it appropriate for CAP when combined with
atypical coverage (macrolide). Cefazolin (1st gen) lacks respiratory pathogen coverage.
,Cefuroxime has inferior S. pneumoniae coverage. Cephalexin is not used for
pneumonia.
Q3: A 62-year-old patient with diabetic foot infection and no drug allergies requires
empiric coverage for Pseudomonas aeruginosa, enteric gram-negatives, and anaerobes.
Which penicillin-based regimen is most appropriate?
A. Ampicillin-sulbactam
B. Piperacillin-tazobactam [CORRECT]
C. Amoxicillin-clavulanate
D. Penicillin VK
Correct Answer: B
Rationale: Piperacillin-tazobactam (Zosyn) provides broad gram-negative,
anti-pseudomonal, and anaerobic coverage essential for diabetic foot infections.
Ampicillin-sulbactam lacks Pseudomonas coverage. Amoxicillin-clavulanate has no
anti-pseudomonal activity. Penicillin VK is narrow-spectrum and inappropriate.
Q4: A 34-year-old female with a documented severe anaphylactic reaction to penicillin
requires treatment for methicillin-sensitive Staphylococcus aureus (MSSA) cellulitis.
Which cephalosporin is SAFE to administer given the allergy history?
A. Cefazolin
B. Cephalexin
C. Ceftaroline [CORRECT]
D. Ceftriaxone
Correct Answer: C
Rationale: Ceftaroline is a 5th generation cephalosporin with unique anti-MRSA activity
and no cross-reactivity with penicillin in patients with severe anaphylaxis. 1st-4th
generation cephalosporins share a beta-lactam ring and should be avoided in severe
penicillin allergy due to potential cross-reactivity (approximately 10%).
Q5: A 5-year-old child weighs 20 kg and has acute otitis media. The mother requests the
standard high-dose amoxicillin regimen. What is the appropriate total daily dose?
A. 400 mg/day
B. 800 mg/day
C. 1,600 mg/day
D. 1,800 mg/day [CORRECT]
,Correct Answer: D
Rationale: High-dose amoxicillin for acute otitis media is 80-90 mg/kg/day divided BID.
For a 20 kg child: 20 × 90 mg = 1,800 mg/day. This dosing overcomes
intermediate-resistant S. pneumoniae. Lower doses are subtherapeutic for high-risk
populations.
Q6: A patient with community-acquired pneumonia requires hospitalization (non-ICU).
The NP selects ceftriaxone plus azithromycin. What is the primary mechanism of action
of ceftriaxone?
A. Inhibition of folic acid synthesis
B. Inhibition of bacterial protein synthesis
C. Inhibition of cell wall synthesis [CORRECT]
D. Inhibition of DNA gyrase
Correct Answer: C
Rationale: Ceftriaxone, like all beta-lactams, inhibits bacterial cell wall synthesis by
binding to penicillin-binding proteins (PBPs), preventing cross-linking of peptidoglycan.
This mechanism is bactericidal against susceptible organisms.
Q7: A 70-year-old male with healthcare-associated pneumonia is started on empiric
antibiotics. The culture returns showing ESBL-producing Klebsiella pneumoniae. Which
carbapenem is appropriate for this patient?
A. Ertapenem
B. Meropenem [CORRECT]
C. Imipenem-cilastatin
D. All of the above
Correct Answer: B
Rationale: Meropenem is preferred for ESBL-producing organisms in critically ill patients
due to superior CNS penetration and lower seizure risk compared to imipenem.
Ertapenem lacks Pseudomonas coverage but covers ESBLs; however, meropenem is the
broadest and safest choice for HA pneumonia.
Q8: A 25-year-old patient has streptococcal pharyngitis confirmed by rapid antigen
detection test. She has no drug allergies. What is the treatment of choice?
A. Azithromycin
B. Cephalexin
, C. Penicillin VK or amoxicillin [CORRECT]
D. Clindamycin
Correct Answer: C
Rationale: Penicillin VK or amoxicillin remains first-line for group A streptococcal
pharyngitis due to narrow spectrum, excellent efficacy, and low cost. Macrolides are
alternatives for penicillin-allergic patients. Cephalexin is acceptable for penicillin-allergic
patients but not first-line.
Q9: A patient with a severe penicillin allergy (anaphylaxis) requires treatment for a
complicated urinary tract infection. Which antibiotic is LEAST appropriate due to
significant cross-reactivity?
A. Aztreonam
B. Ceftriaxone [CORRECT]
C. Levofloxacin
D. Gentamicin
Correct Answer: B
Rationale: Ceftriaxone (3rd generation cephalosporin) shares the beta-lactam ring with
penicillin and has approximately 10% cross-reactivity in patients with severe
IgE-mediated penicillin allergy. Aztreonam (monobactam) has negligible
cross-reactivity. Fluoroquinolones and aminoglycosides are structurally unrelated.
Q10: A 55-year-old patient with a prosthetic joint infection requires MRSA coverage.
Which 5th generation cephalosporin provides coverage against MRSA and is approved
for acute bacterial skin and skin structure infections?
A. Ceftazidime
B. Ceftaroline [CORRECT]
C. Ceftriaxone
D. Cefepime
Correct Answer: B
Rationale: Ceftaroline is the only cephalosporin with reliable MRSA coverage due to high
affinity for PBP2a. It is FDA-approved for ABSSSI and CABP. Other cephalosporins listed
lack MRSA activity.
Q11: A 40-year-old patient with a history of recurrent UTIs is prescribed cephalexin for
uncomplicated cystitis. What generation cephalosporin is cephalexin?
