A 59-year-old male with a history of alcohol-associated cirrhosis is evaluated in the hosp… — USMLE Step 2 CK

A $59$ -year-old male with a history of alcohol-associated cirrhosis is evaluated in the hospital. Three days ago, he was admitted with a temperature of $38.3^\circ\text{C}$ ( $100.9^\circ\text{F}$ ), diffuse abdominal tenderness, and lethargy. Diagnostic paracentesis on admission yielded ascitic fluid with a neutrophil count of $550/\mu\text{L}$ . Given his recent hospitalization for pneumonia one month ago, he was empirically started on intravenous meropenem along with intravenous albumin.

Today, the patient is alert and fully oriented. His temperature is $37.1^\circ\text{C}$ ( $98.8^\circ\text{F}$ ), blood pressure is $112/70\text{ mmHg}$ , and pulse is $82/\text{min}$ . The abdomen is distended with shifting dullness but is no longer tender to palpation.

Laboratory studies today show:

Laboratory Test	Result
Serum sodium	$136\text{ mEq/L}$
Serum potassium	$4.1\text{ mEq/L}$
Serum chloride	$109\text{ mEq/L}$
Serum bicarbonate	$18\text{ mEq/L}$

The ascitic fluid culture from admission now grows *Escherichia coli*. Susceptibility testing demonstrates that the organism is resistant to ampicillin, but susceptible to ceftriaxone, cefotaxime, piperacillin-tazobactam, and meropenem.

Based on the patient's clinical improvement and laboratory data, which of the following is the most appropriate next step in management?

Transition to intravenous ceftriaxoneCevap
B
Proceed with the ongoing meropenem regimen
C
Change the antibiotic to intravenous piperacillin-tazobactam
D
Administer an infusion of sodium bicarbonate
E
Obtain a general surgery evaluation for exploratory laparotomy

Cevap

Transition to intravenous ceftriaxone

The correct course of action is to narrow the antibiotic coverage. The patient was appropriately started on empiric meropenem due to his healthcare exposure risk. However, with the patient clinically improving and cultures confirming an *Escherichia coli* strain susceptible to third-generation cephalosporins, the regimen should be de-escalated. Intravenous ceftriaxone or cefotaxime is the standard targeted therapy for SBP caused by susceptible Enterobacteriaceae. De-escalation limits the development of carbapenem-resistant organisms.

Adım Adım Çözüm

Diagnose the primary condition and evaluate clinical trajectory.

The patient has spontaneous bacterial peritonitis (SBP) which is clinically improving on empiric broad-spectrum therapy.

Establishing the clinical trajectory ensures the patient is stable enough for antibiotic modification rather than requiring escalation of care.

Analyze the culture and susceptibility results.

Ascitic fluid grew E. coli that is susceptible to ceftriaxone, a third-generation cephalosporin.

Culture data dictates the definitive, targeted antimicrobial therapy, overriding the need for broad empiric coverage.

Apply principles of antimicrobial stewardship.

The current regimen (meropenem) is de-escalated to ceftriaxone.

Narrowing the antibiotic spectrum reduces the risk of selecting for multidrug-resistant organisms and minimizes collateral damage to the microbiome.

Anahtar Kavram

Antimicrobial stewardship in Spontaneous Bacterial Peritonitis (SBP) requires de-escalation from broad-spectrum empiric therapy (e.g., carbapenems) to targeted, narrower-spectrum agents (e.g., third-generation cephalosporins) once culture and susceptibility results are available.

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