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A 59-year-old diabetic woman has a temporary indwelling catheter placed to receive dialysis. Five days after the placement of her catheter she develops a fever. Examination at this time reveals erythema and tenderness at the access site but is otherwise normal. The line is removed and blood cultures are drawn. An initial Gram stain reveals Gram-positive cocci in clusters, which are later confirmed to be methicillin-sensitive Staphylococcus aureus colonies. Twenty-four hours after line removal and initiation of intravenous nafcillin, the patient becomes afebrile. Which of the following is the most appropriate next step in management?
A. Intravenous nafcillin for 1 week of treatment
B. Intravenous nafcillin for 2 weeks of treatment
C. Oral dicloxacillin for 2 weeks of treatment
D. Transesophageal echocardiogram (TEE)
E. Transthoracic echocardiogram (TTE)
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D. Transesophageal echocardiogram (TEE)
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The correct answer is D. Current recommendations for Staphylococcus aureus bacteremia is that patients should receive a TEE. Given the low sensitivity of TTE (choice E), and the affinity of S. aureus for heart valves, TEE has been found to be a cost-effective strategy in determining who should receive antibiotics and for how long. If this patient has infective endocarditis (IE), she will likely need 4 to 6 weeks of treatment.
Intravenous nafcillin (or other anti-Staphylococcus antibiotic) for 1 week (choice A) is appropriate for line infections that cause simple bacteremia. Simple bacteremia is classified as bacteremia in patients with no clinical evidence of IE, a negative TEE within 7 days of starting antibiotics, and defervescence within 72 hours of starting treatment. No predisposing factors to endocarditis (prosthetic valves, damaged heart valves, etc.) should be present, and follow-up cultures need to be negative for a patient to be defined as having simple bacteremia.
Intravenous nafcillin (or other anti-Staphylococcus antibiotic) for 2 weeks (choice B) is appropriate for line infections that cause uncomplicated bacteremia. Uncomplicated Staphylococcus bacteremia is defined as bacteremia occurring when preexisting IE risk factors exist, such as valvular lesions, but a TEE is negative. These patients may have a fever lasting up to 72 hours after initiating therapy, but should have negative surveillance cultures.
In general, oral dicloxacillin (choice C) is not recommended for bacteremic patients. Given the relative virulence of the organism, the high and steady serum drug concentrations obtained with intravenous antibiotics are necessary.
