American Board of Internal Medicine (ABIM) Certification Practice Exam

For patients with Staphylococcus aureus Bacteremia, how often should blood cultures be repeated until they return negative?

1. Every day

2. Every 1-2 days

3. Every 2-4 days

4. Every week

The correct answer is: Every 2-4 days

In the management of Staphylococcus aureus bacteremia, it is critical to monitor the effectiveness of treatment and the resolution of bacteremia. Repeating blood cultures until they return negative is an essential practice because the presence of Staphylococcus aureus in the bloodstream can indicate a serious infection that requires prompt and effective intervention. The appropriate interval for repeating blood cultures is every 2-4 days. This frequency strikes a balance between ensuring timely detection of resolution of the bacteremia and avoiding unnecessary repetition that may not provide additional clinical benefit. Blood cultures taken too frequently may lead to an overwhelming patient burden and increase the risk of false positives due to contamination, while cultures taken too infrequently may delay treatment modifications if the infection persists. Specifically, in the case of Staphylococcus aureus bacteremia, the 48 to 96 hours interval allows adequate time for the antimicrobial therapy to take effect, enabling a reliable assessment of whether the organism has been cleared from the bloodstream. Monitoring blood cultures in this manner is crucial for decision-making regarding the continuation of treatment and management strategies going forward.