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Zorluk: OrtaInfectious Diseases

A 6868-year-old man is evaluated in the hospital on the 33 rd day of admission for sepsis secondary to a complicated urinary tract infection. He initially presented to the emergency department with fever, severe chills, and left-sided flank pain. His medical history includes benign prostatic hyperplasia and type 2 diabetes mellitus. On admission, his blood pressure was 88/5688/56 mm Hg and his heart rate was 112112/min. He received aggressive intravenous fluid resuscitation and was started on empiric intravenous vancomycin and cefepime.

Currently, the patient is clinically stable. His temperature is 37.1∘C37.1^\circ\text{C} (98.8∘F98.8^\circ\text{F}), blood pressure is 126/82126/82 mm Hg, and pulse is 7878/min. He reports that his flank pain has significantly improved.

Blood and urine cultures obtained on admission both grow >100,000>100,000 CFU/mL of *Enterococcus faecalis*. Antimicrobial susceptibility testing results are as follows:

Ampicillin: Susceptible
Vancomycin: Susceptible
Linezolid: Susceptible
Daptomycin: Susceptible
Ciprofloxacin: Resistant

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

  1. A
    Maintain the patient on intravenous vancomycin alone
  2. Transition therapy to intravenous ampicillin aloneCevap
  3. C
    Maintain the current empiric regimen without changes
  4. D
    Transition therapy to intravenous linezolid alone
  5. E
    Maintain the patient on intravenous cefepime alone

Cevap

Transition therapy to intravenous ampicillin alone
The correct answer is to transition therapy to intravenous ampicillin alone. The patient has *Enterococcus faecalis* bacteremia secondary to a urinary source. The fundamental principle of antimicrobial stewardship is to de-escalate broad-spectrum empiric therapy to the narrowest, most effective, and safest targeted agent once culture and susceptibility data are available. *Enterococcus faecalis* is uniquely susceptible to ampicillin, which is the drug of choice for susceptible isolates. Cefepime, a fourth-generation cephalosporin, has no in vitro or clinical activity against enterococci and must be discontinued. While the organism is susceptible to vancomycin, ampicillin is preferred because it is narrower in spectrum, highly effective, and avoids the unnecessary evolutionary pressure that leads to vancomycin-resistant enterococci (VRE).

Adım Adım Çözüm

1
Analyze the patient's clinical trajectory and microbiological data.
The patient has clinically improved from sepsis. Cultures confirm a definitive pathogen (*Enterococcus faecalis*) with available susceptibility data.
Establishing stability and reviewing culture results are prerequisites for safely narrowing antibiotic therapy.
2
Evaluate the efficacy and spectrum of the current empiric regimen against the isolated pathogen.
Cefepime lacks activity against enterococci. Vancomycin is active but overly broad given the isolate's susceptibility profile.
Empiric regimens are designed for broad coverage; once a pathogen is identified, the regimen must be reassessed for appropriateness.
3
Apply antimicrobial stewardship principles to select the optimal definitive therapy.
Ampicillin is selected because it is the drug of choice for susceptible enterococci, offering narrow-spectrum, bactericidal activity.
De-escalating to the narrowest effective agent minimizes toxicity and prevents the emergence of multi-drug resistant organisms like VRE.

Anahtar Kavram

Antimicrobial stewardship dictates de-escalating empiric broad-spectrum antibiotics to the narrowest effective targeted therapy, utilizing ampicillin as the first-line agent for susceptible Enterococcus faecalis infections while recognizing that cephalosporins have no intrinsic anti-enterococcal activity.
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Infectious Diseases

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