A 51-year-old man is currently hospitalized for the management of acute complicated divert… — USMLE Step 2 CK

A 51-year-old man is currently hospitalized for the management of acute complicated diverticulitis. Four days ago, he presented with severe left lower quadrant abdominal pain, and a computed tomography scan revealed a $4.2\text{-cm}$ pericolic abscess. The abscess was successfully managed with computed tomography-guided percutaneous drainage. Due to a documented history of extended-spectrum beta-lactamase (ESBL) urinary tract infections, he was empirically started on intravenous meropenem upon admission.

Today, the patient reports feeling well and his abdominal pain has completely resolved. He is tolerating a regular diet without nausea. His temperature is $37.1^\circ\text{C}$ ( $98.8^\circ\text{F}$ ), blood pressure is $122/78\text{ mmHg}$ , and pulse is $76/\text{min}$ . His leukocyte count has decreased from $17,500/\text{mm}^3$ at admission to $7,200/\text{mm}^3$ . The percutaneous drain output has been negligible for the past 24 hours, and the catheter was removed this morning.

The finalized abscess fluid culture demonstrates heavy growth of *Escherichia coli* and *Bacteroides fragilis*. Susceptibility testing of the *E. coli* isolate reveals sensitivity to amoxicillin-clavulanate, ceftriaxone, and ciprofloxacin, with no evidence of ESBL production.

Which of the following is the most appropriate next step in the pharmacological management of this patient?

A
Maintain inpatient admission to complete a 14-day course of intravenous meropenem
B
Switch the antimicrobial regimen to intravenous cefepime and intravenous metronidazole
Discharge the patient with a prescription for oral amoxicillin-clavulanateAnswer
D
Discharge the patient with prescriptions for oral ciprofloxacin and oral linezolid
E
Discharge the patient with prescriptions for oral amoxicillin-clavulanate and oral vancomycin

Answer

Discharge the patient with a prescription for oral amoxicillin-clavulanate.

This patient presented with complicated diverticulitis (pericolic abscess), which was appropriately managed with percutaneous drainage and empiric broad-spectrum antibiotics (meropenem) due to his ESBL history. Now, the patient has achieved clinical stability (afebrile, normal hemodynamics), adequate source control (drain removed after minimal output), and is tolerating an oral diet. These factors make him an ideal candidate for transition from intravenous to oral antibiotic therapy. The culture results demonstrate an absence of ESBL-producing organisms, allowing for the de-escalation of the carbapenem. Amoxicillin-clavulanate provides comprehensive and targeted coverage for both the isolated enteric gram-negative rod (E. coli) and the anaerobe (B. fragilis), perfectly aligning with antibiotic stewardship guidelines.

Step-by-Step Solution

Evaluate the patient's clinical trajectory and source control status.

The patient is afebrile, tolerating oral intake, has a normalized white blood cell count, and the abscess was successfully drained and removed.

Determines if the patient is eligible for transition from intravenous to oral antibiotic therapy.

Analyze the abscess culture and susceptibility results.

Cultures grew non-ESBL E. coli and B. fragilis, both of which are fully covered by narrower-spectrum agents.

Guides antibiotic de-escalation from empiric broad-spectrum therapy to targeted therapy.

Select the most appropriate oral step-down regimen.

Oral amoxicillin-clavulanate provides excellent coverage for both enteric gram-negative rods and anaerobes without providing unnecessary coverage.

Adheres to antibiotic stewardship principles by using the narrowest effective spectrum.

Key Concept

De-escalation of empiric broad-spectrum antibiotics to targeted, narrow-spectrum oral agents in patients with complicated diverticulitis once source control is achieved and culture data are available.

Estimated Time:1m 30s

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