A 67-year-old man is evaluated on hospital day 3. He was initially admitted for fever, chi… — USMLE Step 2 CK

A 67-year-old man is evaluated on hospital day 3. He was initially admitted for fever, chills, and left flank pain. His past medical history is significant for a T10 spinal cord injury resulting in neurogenic bladder, managed with intermittent clean catheterization. On presentation to the emergency department, his temperature was $39.1^\circ\text{C}$ ( $102.4^\circ\text{F}$ ), blood pressure was $92/58\text{ mmHg}$ , and heart rate was $114/\text{min}$ . Laboratory testing demonstrated a leukocyte count of $16,500/\text{mm}^3$ . He was aggressively resuscitated with intravenous fluids and empirically started on intravenous piperacillin-tazobactam and vancomycin for presumed urosepsis.

Today, the patient's temperature is $37.2^\circ\text{C}$ ( $99.0^\circ\text{F}$ ), blood pressure is $122/78\text{ mmHg}$ , and heart rate is $82/\text{min}$ . He has been afebrile for the last 36 hours and is tolerating a normal oral diet. His flank pain has resolved. The urine culture collected on admission has finalized, growing $>10^5\text{ CFU/mL}$ of *Enterococcus faecalis*. Susceptibility testing results are as follows:

Antimicrobial	Interpretation
Ampicillin	Susceptible
Vancomycin	Susceptible
Linezolid	Susceptible
Levofloxacin	Resistant

Blood cultures drawn on admission show no growth after 48 hours. Which of the following is the most appropriate next step in the patient's antimicrobial management?

Discontinue current antibiotics and start oral amoxicillinAnswer
B
Continue intravenous piperacillin-tazobactam and vancomycin
C
Discontinue piperacillin-tazobactam and continue intravenous vancomycin
D
Discontinue current antibiotics and start oral linezolid
E
Discontinue current antibiotics and start intravenous ampicillin

Answer

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

The correct action is to transition the patient to oral amoxicillin. This scenario tests the core principles of antimicrobial stewardship: de-escalation of therapy and the transition from intravenous to oral medications. The patient originally presented with urosepsis and was appropriately started on broad-spectrum empiric therapy. However, he is now hemodynamically stable, afebrile, and tolerating oral intake, making him an ideal candidate for oral step-down therapy. The culture confirms *Enterococcus faecalis* that is susceptible to ampicillin. Amoxicillin (the oral equivalent of ampicillin) is the drug of choice for ampicillin-susceptible enterococcal urinary tract infections due to its targeted narrow spectrum, high oral bioavailability, and excellent concentration in the urine.

Step-by-Step Solution

Assess the patient's current clinical status and need for intravenous therapy.

The patient is hemodynamically stable, afebrile for 36 hours, and tolerating an oral diet.

Clinical stability and intact gastrointestinal absorption indicate that the patient is eligible for transition from intravenous to oral antimicrobial therapy.

Analyze the culture and susceptibility data.

The causative pathogen is Enterococcus faecalis, which is susceptible to ampicillin, vancomycin, and linezolid.

Empiric broad-spectrum therapy must be de-escalated to the narrowest effective agent once the pathogen is identified to prevent antimicrobial resistance.

Select the optimal targeted, narrow-spectrum agent.

Oral amoxicillin is selected.

Amoxicillin provides targeted coverage for ampicillin-susceptible E. faecalis, has excellent oral bioavailability, and reaches high concentrations in the urinary tract.

Key Concept

In patients with clinical improvement and culture data, empiric broad-spectrum antibiotics should be de-escalated to targeted, narrow-spectrum oral agents to optimize therapy and adhere to antimicrobial stewardship principles.

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