A 72-year-old man is evaluated in the hospital on day 3 of admission for community-acquire… — USMLE Step 2 CK

A 72-year-old man is evaluated in the hospital on day 3 of admission for community-acquired pneumonia. He initially presented to the emergency department with a 2-day history of fever, productive cough, and shortness of breath. His medical history is significant for hypertension and mild chronic obstructive pulmonary disease. On admission, his temperature was $38.9^\circ\text{C}$ ( $102^\circ\text{F}$ ), blood pressure was $118/76\text{ mmHg}$ , pulse was $102/\text{min}$ , and respiratory rate was $22/\text{min}$ . Oxygen saturation was $92\%$ on room air. Chest radiography revealed a right lower lobe consolidation. He was empirically started on intravenous ceftriaxone and intravenous azithromycin. Today, the patient is afebrile, his pulse is $82/\text{min}$ , and his respiratory rate is $16/\text{min}$ . He is resting comfortably and eating a regular diet. Blood cultures drawn on admission are now growing *Streptococcus pneumoniae*. Susceptibility testing shows the organism is highly susceptible to penicillin, amoxicillin, ceftriaxone, and levofloxacin, but resistant to azithromycin. Which of the following is the most appropriate next step in antibiotic management?

Discontinue current antibiotics and begin oral amoxicillinCevap
B
Discontinue current antibiotics and begin oral levofloxacin
C
Discontinue current antibiotics and begin oral amoxicillin-clavulanate
D
Continue intravenous ceftriaxone and discontinue intravenous azithromycin
E
Continue intravenous ceftriaxone and intravenous azithromycin

Cevap

The most appropriate step is to discontinue current antibiotics and begin oral amoxicillin.

The correct approach is to transition the patient to oral amoxicillin. This decision is based on two core principles of antimicrobial stewardship: IV-to-PO conversion and de-escalation (spectrum narrowing). The patient has demonstrated clinical stability (afebrile, normalizing vital signs) and is tolerating an oral diet, satisfying the criteria for transition to oral therapy. Furthermore, the blood cultures have identified Streptococcus pneumoniae that is highly susceptible to penicillin. Therefore, empiric therapy (ceftriaxone and azithromycin) should be discontinued in favor of amoxicillin, which is the most appropriate, narrow-spectrum oral agent to complete the treatment course.

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Assess the patient's clinical stability and ability to take oral medications.

The patient is afebrile, hemodynamically stable, has a normal respiratory rate, and is eating a regular diet.

Patients hospitalized with pneumonia who demonstrate clinical improvement and can tolerate oral intake should be transitioned from intravenous to oral antibiotics.

Review culture and susceptibility data to direct targeted therapy.

Blood cultures isolate S. pneumoniae that is highly susceptible to penicillin and amoxicillin.

Empiric broad-spectrum therapy should be de-escalated to the narrowest effective agent once an organism is identified to prevent collateral damage (e.g., C. difficile infection) and antimicrobial resistance.

Select the optimal oral agent based on the susceptibility profile.

Oral amoxicillin is selected.

Amoxicillin is a narrow-spectrum beta-lactam highly effective against penicillin-susceptible S. pneumoniae, making it superior to broader agents like fluoroquinolones or beta-lactamase inhibitor combinations.

Anahtar Kavram

In patients treated for community-acquired pneumonia, therapy should be transitioned from intravenous to targeted, narrow-spectrum oral antibiotics once clinical stability is achieved and culture susceptibilities are known.

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