Examkin

Soru

Zorluk: KolayGeneral Internal Medicine

A 54-year-old man is hospitalized for fever, chills, and a rapidly expanding area of erythema on his right lower leg. He has a medical history of type 2 diabetes mellitus. On admission, his temperature is 38.8∘C38.8^\circ\text{C} (101.8∘F101.8^\circ\text{F}), blood pressure is 118/76118/76 mm Hg, pulse is 102102/min, and respirations are 1818/min. Physical examination reveals a warm, tender, sharply demarcated erythematous plaque on the right calf. Blood cultures are drawn, and the patient is empirically started on intravenous vancomycin and piperacillin-tazobactam.

By hospital day 3, the patient's temperature has normalized, and the leg erythema has significantly receded. The blood cultures drawn on admission return positive for *Staphylococcus aureus* in two out of two bottles. Antimicrobial susceptibility testing demonstrates that the isolate is susceptible to oxacillin, cefazolin, and trimethoprim-sulfamethoxazole, but resistant to penicillin G.

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

  1. Discontinue both current antibiotics and initiate intravenous cefazolinCevap
  2. B
    Discontinue piperacillin-tazobactam and continue intravenous vancomycin
  3. C
    Discontinue vancomycin and continue intravenous piperacillin-tazobactam
  4. D
    Continue both intravenous vancomycin and piperacillin-tazobactam
  5. E
    Discontinue both current antibiotics and initiate intravenous linezolid

Cevap

Discontinue both current antibiotics and initiate intravenous cefazolin
The correct course of action is to discontinue the broad-spectrum empiric regimen and start a targeted, narrow-spectrum beta-lactam. The patient's blood cultures grew Staphylococcus aureus that is susceptible to oxacillin, which definitively identifies it as methicillin-susceptible S. aureus (MSSA). For systemic MSSA infections, first-generation cephalosporins (such as intravenous cefazolin) or antistaphylococcal penicillins (such as nafcillin or oxacillin) are the drugs of choice. They provide superior bactericidal activity compared to vancomycin and properly narrow the antimicrobial spectrum, adhering to the core principles of antimicrobial stewardship.

Adım Adım Çözüm

1
Interpret the blood culture susceptibility report.
The organism is Staphylococcus aureus susceptible to oxacillin.
Oxacillin susceptibility defines the isolate as methicillin-susceptible Staphylococcus aureus (MSSA).
2
Determine the optimal treatment for MSSA bacteremia.
Targeted therapy with an antistaphylococcal penicillin (e.g., nafcillin, oxacillin) or a first-generation cephalosporin (e.g., cefazolin) is indicated.
These agents have superior bactericidal activity against MSSA compared to alternative antibiotics.
3
Apply antimicrobial stewardship principles to the current empiric regimen.
Discontinue the broad-spectrum vancomycin and piperacillin-tazobactam, and start targeted intravenous cefazolin.
De-escalating therapy minimizes collateral damage to the patient's microbiome, limits the development of resistance, and avoids the inferior outcomes associated with treating MSSA with vancomycin.

Anahtar Kavram

Targeted antibiotic de-escalation for methicillin-susceptible Staphylococcus aureus (MSSA)
Tahmini Süre:1m 0s
Bu soruyu puanla

Konular

General Internal Medicine

Bu konudan daha fazla soru