A 68-year-old man is evaluated in the hospital for new-onset diarrhea. He was admitted 8 d… — USMLE Step 2 CK

A $68$ -year-old man is evaluated in the hospital for new-onset diarrhea. He was admitted $8$ days ago for a chronic obstructive pulmonary disease (COPD) exacerbation and was treated with a $5$ -day course of systemic glucocorticoids and levofloxacin. Over the last $48$ hours, he has had $6$ to $8$ watery bowel movements daily, accompanied by lower abdominal cramping and low-grade fever. Vitals: T $37.9^\circ\text{C}$ ( $100.2^\circ\text{F}$ ), HR $92/\text{min}$ , BP $118/76 \text{ mmHg}$ . Physical examination reveals mild, diffuse abdominal tenderness with normal bowel sounds; there is no rebound tenderness or guarding. Laboratory studies show a leukocyte count of $16,500/\text{mm}^3$ and serum creatinine of $1.1 \text{ mg/dL}$ (baseline $0.9 \text{ mg/dL}$ ). Stool enzyme immunoassay is positive for *Clostridioides difficile* glutamate dehydrogenase antigen and toxins A and B. Which of the following is the most appropriate next step in management?

A
Intravenous vancomycin
B
Oral metronidazole
Oral fidaxomicinCevap
D
Intravenous piperacillin-tazobactam
E
Oral loperamide

Cevap

Oral fidaxomicin

This patient has an initial episode of non-fulminant *Clostridioides difficile* infection (CDI). According to updated clinical guidelines, the preferred first-line treatment for both non-severe and severe initial episodes of CDI is oral fidaxomicin. Oral vancomycin is an acceptable alternative. Fidaxomicin is a narrow-spectrum macrocyclic antibiotic that is minimally absorbed, resulting in high fecal concentrations. It targets *C. difficile* with minimal disruption to the protective normal colonic microbiome, which leads to lower rates of disease recurrence compared to older therapies.

Adım Adım Çözüm

Diagnose the patient's acute condition based on clinical presentation and laboratory findings.

The patient has an initial episode of non-fulminant Clostridioides difficile infection (CDI), evidenced by characteristic symptoms, recent antibiotic exposure, and a positive stool immunoassay.

Establishing the severity and distinguishing between an initial episode versus recurrence is necessary to select the correct guideline-directed pharmacotherapy.

Determine the most appropriate first-line pharmacotherapy for this specific diagnosis.

Oral fidaxomicin (or oral vancomycin) is selected to target the intraluminal infection.

Current guidelines recommend oral fidaxomicin as a preferred first-line agent because it is a narrow-spectrum macrocyclic antibiotic that effectively eradicates C. difficile while preserving the normal colonic flora, thereby reducing recurrence rates.

Anahtar Kavram

The first-line management for an initial episode of non-fulminant Clostridioides difficile infection is oral fidaxomicin or oral vancomycin. Systemic (intravenous) vancomycin does not reach therapeutic concentrations in the colon and is ineffective for this condition.

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Cevap

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