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Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
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A 29-year-old woman presents to the emergency department with a history of a fever that "won't break." She has taken acetaminophen without relief. Upon obtaining a past medical history you learn that the patient is a prostitute who is homeless with a significant history of intravenous drug use and alcohol abuse. The patient uses barrier protection occasionally when engaging in intercourse. On physical exam you note a murmur heard along the left mid-sternal border. The pulmonary exam reveals minor bibasilar crackles. Examination of the digits is notable for linea melanonychia. The patient's upper limbs demonstrate many bruises and scars in the antecubital fossa. Her temperature is 103.5°F (39.5°C), blood pressure is 100/70 mmHg, pulse is 112/min, respirations are 18/min, and oxygen saturation is 93% on room air.

The patient's BMI is 16 kg/m^2. The patient is started on vancomycin and gentamicin and sent for echocardiography. Based on the results of echocardiography the patient is scheduled for surgery the next day.

Vegetations are removed from the tricuspid valve during the surgical procedure and vancomycin and gentamicin are continued over the next 5 days. On post-operative day five, the patient presents with bleeding from her gums, oozing from her surgical sites, and recurrent epitaxis. Lab value are obtained as seen below:

Serum:
Na+: 135 mEq/L
Cl-: 90 mEq/L
K+: 4.4 mEq/L
HCO3-: 23 mEq/L
BUN: 20 mg/dL
Glucose: 110 mg/dL
Creatinine: 1.0 mg/dL
Ca2+: 10.1 mg/dL
AST: 9 U/L
ALT: 9 U/L

Leukocyte count and differential:
Leukocyte count: 6,000 cells/mm^3
Lymphocytes: 20%
Monocytes: 1%
Neutrophils: 78%
Eosinophils: 1%
Basophils: 0%
PT: 27 seconds
aPTT: 84 seconds
D-dimer: < 50 µg/L

Hemoglobin: 14 g/dL
Hematocrit: 40%
Platelet count: 150,000/mm^3
Mean corpuscular volume: 110 fL
Mean corpuscular hemoglobin concentration: 34 g/dL
RDW: 14%

Which of the following is the most likely cause of this patient's current symptoms?
assistant
Antibiotic therapy