A 29-year-old woman is evaluated on the medical ward on hospital day 3 for acute pyeloneph… — USMLE Step 2 CK

A $29$ -year-old woman is evaluated on the medical ward on hospital day $3$ for acute pyelonephritis. On admission, she reported a $2$ -day history of high fever, dysuria, and severe right-sided back pain. She works as a nurse and has a history of recurrent urinary tract infections. Due to local antibiogram data showing high rates of fluoroquinolone resistance and her recent healthcare exposure, she was started empirically on intravenous piperacillin-tazobactam. The patient has improved significantly; she has been afebrile for $24$ hours, her flank pain is minimal, and she is tolerating oral intake perfectly. Her temperature is $37.1^\circ\text{C}$ ( $98.8^\circ\text{F}$ ), blood pressure is $112/70\text{ mm Hg}$ , and pulse is $76/\text{min}$ . Final urine culture results from admission demonstrate $>100,000$ colony-forming units/mL of *Klebsiella pneumoniae*. Susceptibility testing shows the isolate is resistant to ampicillin, but sensitive to ceftriaxone, cefazolin, ciprofloxacin, and piperacillin-tazobactam. Which of the following is the most appropriate next step in management?

Transition to oral ciprofloxacinAnswer
B
Continue intravenous piperacillin-tazobactam
C
Switch to intravenous ceftriaxone
D
Transition to oral nitrofurantoin
E
Transition to oral amoxicillin

Answer

Transition to oral ciprofloxacin is the correct next step because it provides targeted, highly bioavailable therapy for a susceptible isolate in a clinically stable patient.

Transitioning to oral ciprofloxacin is the standard of care for a patient with acute pyelonephritis who has stabilized on empiric intravenous therapy (afebrile for

24

hours, improving symptoms, tolerating oral intake) and whose urine culture isolate is susceptible to fluoroquinolones. Ciprofloxacin provides excellent bioavailability and renal tissue penetration, allowing for a safe hospital discharge and completion of the treatment course at home.

Step-by-Step Solution

Evaluate the patient's clinical stability for oral transition.

The patient is afebrile, hemodynamically stable, has improving symptoms, and tolerates oral intake.

These are the standard criteria for stepping down from intravenous to oral antimicrobial therapy, which reduces hospital stay and catheter-associated risks.

Analyze the culture and susceptibility data.

The causative organism is Klebsiella pneumoniae, which is susceptible to ciprofloxacin.

Targeted therapy should be guided by finalized in vitro susceptibility results to ensure efficacy and narrow the spectrum of coverage.

Select the optimal oral agent for pyelonephritis.

Oral ciprofloxacin is selected.

Fluoroquinolones have excellent oral bioavailability and achieve high tissue concentrations in the renal parenchyma, making them ideal for the definitive treatment of pyelonephritis when the organism is susceptible.

Key Concept

Antimicrobial stewardship and criteria for intravenous-to-oral transition in acute pyelonephritis.

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