Examkin

Question

Difficulty: MediumInfectious Diseases

A 58-year-old woman is hospitalized for the treatment of infective endocarditis. She initially presented with a 3-week history of low-grade fever, fatigue, and a new heart murmur. Her history is notable for a dental extraction one month prior. Transesophageal echocardiography on admission revealed a 7-mm vegetation on the mitral valve leaflet. Three sets of blood cultures grew *Streptococcus sanguinis* with a penicillin minimum inhibitory concentration (MIC) of 0.05 mcg/mL. She was started on a planned 2-week synergistic regimen of intravenous aqueous penicillin G and intravenous gentamicin. On day 5 of hospitalization, the patient reports feeling clinically improved and has been afebrile for 48 hours. However, laboratory studies show her serum creatinine has increased from a baseline of 0.8 mg/dL to 2.1 mg/dL. Her urine output has mildly decreased over the past 24 hours. Which of the following is the most appropriate modification to her antimicrobial regimen?

  1. Discontinue gentamicin and continue intravenous penicillin G for a total 4-week courseAnswer
  2. B
    Discontinue both antibiotics and initiate intravenous vancomycin for a total 4-week course
  3. C
    Decrease the dose of gentamicin and continue both antibiotics for a total 2-week course
  4. D
    Discontinue penicillin G and continue intravenous gentamicin for a total 2-week course
  5. E
    Discontinue both antibiotics and initiate oral amoxicillin for a total 4-week course

Answer

Discontinue gentamicin and continue intravenous penicillin G for a total 4-week course
The correct answer identifies that the patient has developed aminoglycoside-induced acute kidney injury. Standard treatment guidelines for native valve endocarditis caused by highly penicillin-susceptible viridans group streptococci (MIC ≤ 0.12 mcg/mL) offer two primary first-line regimens: 4 weeks of IV penicillin (or ceftriaxone) monotherapy, OR a 2-week synergistic course of IV penicillin (or ceftriaxone) combined with gentamicin. If a patient experiences significant nephrotoxicity or ototoxicity while on the 2-week synergistic regimen, the aminoglycoside must be discontinued immediately. To ensure complete eradication of the infection, the patient is then transitioned to the 4-week monotherapy protocol, counting the days already completed.

Step-by-Step Solution

1
Identify the primary complication occurring in the patient.
The patient has developed acute kidney injury (AKI), evidenced by a rise in serum creatinine from 0.8 mg/dL to 2.1 mg/dL and decreased urine output.
Recognizing the complication is essential to determining which medication is causing harm.
2
Determine the likely cause of the complication.
Gentamicin is a well-known nephrotoxic aminoglycoside and is the most likely culprit for the patient's intrinsic acute tubular necrosis.
Identifying the offending agent dictates the required therapeutic modification.
3
Select the appropriate alternative evidence-based regimen for the infection.
For native valve endocarditis caused by highly penicillin-susceptible viridans group streptococci (MIC ≤ 0.12 mcg/mL), a 4-week course of intravenous penicillin G monotherapy is equivalent in efficacy to the 2-week synergistic regimen.
Stopping the toxic agent and relying on the safe, targeted monotherapy protocol prevents further renal damage while ensuring the endocarditis is fully treated.

Key Concept

In patients receiving a 2-week synergistic course of penicillin and gentamicin for highly penicillin-susceptible viridans group streptococcal endocarditis who develop acute kidney injury, the aminoglycoside should be discontinued, and penicillin monotherapy should be extended to a full 4-week course.
Rate this question

Topics

Infectious Diseases

More questions from this topic