A 68-year-old man is evaluated in the hospital on the third day of an admission for commun… — USMLE Step 2 CK

A $68$ -year-old man is evaluated in the hospital on the third day of an admission for community-acquired pneumonia. At the time of admission, he had a fever, productive cough, and a right lower lobe infiltrate on chest radiograph. He was started on empiric therapy with intravenous ceftriaxone and azithromycin. Sputum Gram stain and culture were obtained prior to the administration of antibiotics.

Currently, the patient feels much better. His temperature is $37.1^\circ\text{C}$ ( $98.8^\circ\text{F}$ ), blood pressure is $124/78\text{ mm Hg}$ , pulse is $76/\text{min}$ , and respirations are $16/\text{min}$ . Oxygen saturation is $96\%$ on room air. He is tolerating a regular diet.

Sputum culture has grown heavy *Streptococcus pneumoniae*. Antimicrobial susceptibility testing of the isolate shows the following:

Antimicrobial	Susceptibility
Penicillin	Susceptible
Amoxicillin	Susceptible
Ceftriaxone	Susceptible
Azithromycin	Resistant
Levofloxacin	Susceptible

The patient is ready for discharge to home. Which of the following is the most appropriate antibiotic regimen to prescribe for this patient upon discharge?

Oral amoxicillinAnswer
B
Oral levofloxacin
C
Oral amoxicillin-clavulanate
D
Oral azithromycin and oral cefpodoxime
E
Intravenous ceftriaxone

Answer

Oral amoxicillin

The correct answer is oral amoxicillin. This patient was admitted with community-acquired pneumonia and initially treated appropriately with empiric intravenous ceftriaxone and azithromycin. He is now clinically stable, afebrile, and tolerating oral intake, making him an ideal candidate to transition from intravenous to oral therapy. His sputum culture definitively grew *Streptococcus pneumoniae* that is susceptible to penicillin and amoxicillin. The core principles of antibiotic stewardship dictate that once a pathogen and its susceptibilities are known, antimicrobial therapy should be narrowed to the most targeted, effective agent. For penicillin-susceptible *S. pneumoniae*, high-dose oral amoxicillin is the preferred narrow-spectrum step-down therapy.

Step-by-Step Solution

Evaluate the patient's clinical stability and readiness for hospital discharge.

The patient is afebrile, hemodynamically stable, has adequate oxygenation on room air, and is tolerating an oral diet.

Clinical stability indicates that intravenous antibiotics are no longer required and the patient can be safely transitioned to an oral regimen.

Analyze the sputum culture and susceptibility results.

The causative organism is *Streptococcus pneumoniae*. It is susceptible to penicillin and amoxicillin, but resistant to azithromycin.

To identify the precise pathogen in order to tailor the ongoing antimicrobial therapy.

Select the most appropriate step-down oral antibiotic based on stewardship guidelines.

Oral amoxicillin is chosen as the definitive therapy.

Antibiotic stewardship principles require narrowing the therapy to the most targeted, effective agent to minimize resistance, adverse effects, and healthcare costs.

Key Concept

Clinically stable hospitalized patients with community-acquired pneumonia should be transitioned from intravenous to oral antibiotics, and the empiric regimen should be narrowed to the most targeted agent based on culture and susceptibility data.

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