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Zorluk: OrtaInfectious Diseases

An infectious diseases consultation is requested for a 48-year-old female who was admitted to the hospital three days ago with subacute onset of fever, fatigue, and dyspnea. Initial evaluation revealed a new holosystolic murmur radiating to the axilla. A transesophageal echocardiogram confirmed a 1.4 cm1.4\text{ cm} oscillating vegetation on the posterior mitral leaflet. Upon admission, three sets of blood cultures were drawn, and she was started on empiric intravenous vancomycin and ceftriaxone. Today, the patient is clinically stable, and her temperature is 37.0∘C37.0^\circ\text{C} (98.6∘F98.6^\circ\text{F}). The microbiology laboratory reports that all three blood culture sets are growing *Streptococcus mutans*. The isolate has a penicillin minimum inhibitory concentration (MIC) of 0.06 mcg/mL0.06 \text{ mcg/mL} (highly susceptible) and is also susceptible to ceftriaxone. Based on the culture and susceptibility data, which of the following is the most appropriate modification to her pharmacotherapy?

  1. Discontinue vancomycin and continue intravenous ceftriaxoneCevap
  2. B
    Continue the current regimen of intravenous vancomycin and ceftriaxone
  3. C
    Discontinue ceftriaxone and continue intravenous vancomycin
  4. D
    Switch the regimen to intravenous piperacillin-tazobactam
  5. E
    Switch the regimen to intravenous daptomycin

Cevap

Discontinue vancomycin and continue intravenous ceftriaxone
The correct response reflects fundamental antimicrobial stewardship principles. The patient has native valve infective endocarditis (IE) caused by *Streptococcus mutans*, a species of viridans group streptococci (VGS). The isolate is highly susceptible to penicillin. According to current guidelines, empiric broad-spectrum therapy must be narrowed to targeted therapy once susceptibility data are available. For highly penicillin-susceptible VGS native valve IE, standard therapy involves a 4-week course of intravenous ceftriaxone or intravenous aqueous crystalline penicillin G. Ceftriaxone is an excellent choice due to its efficacy and convenient once-daily dosing. Vancomycin provides unnecessary MRSA coverage and must be discontinued to minimize toxicity.

Adım Adım Çözüm

1
Identify the patient's diagnosis and current clinical status.
The patient has native valve infective endocarditis caused by Streptococcus mutans and is currently receiving empiric intravenous vancomycin and ceftriaxone.
Establishing the baseline clinical scenario and active treatments is necessary to guide management.
2
Interpret the microbiological data.
The isolate is a viridans group streptococcus that is highly susceptible to penicillin (MIC 0.06 mcg/mL) and ceftriaxone.
Definitive therapy for endocarditis relies heavily on specific minimum inhibitory concentration (MIC) data.
3
Apply antimicrobial stewardship principles to optimize the regimen.
The broad-spectrum empiric agent (vancomycin) is discontinued, and the targeted, highly effective beta-lactam (ceftriaxone) is continued.
Narrowing the antibiotic spectrum reduces toxicity, prevents the emergence of resistance, and utilizes the most bactericidal agent for the specific isolate.

Anahtar Kavram

Antimicrobial stewardship in infective endocarditis requires narrowing empiric broad-spectrum therapy to a targeted regimen (e.g., ceftriaxone monotherapy) once susceptibility data indicate a highly susceptible organism.
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Infectious Diseases

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