Follow-up blood cultures in Staphylococcus aureus bacteremia: a probability-based optimization

Area of Science:

• Infectious Diseases
• Clinical Microbiology
• Medical Diagnostics

Background:

• Staphylococcus aureus bacteremia (SAB) requires diligent follow-up to ensure effective treatment.
• Follow-up blood cultures (BC) are critical for monitoring treatment response in SAB patients.

Purpose of the Study:

• To determine the optimal number and timing of follow-up blood cultures (BC) for detecting persistent Staphylococcus aureus bacteremia (SAB).
• To evaluate the impact of BC volume on the detection of ongoing bacteremia and associated phenomena like skip infections.

Main Methods:

• Retrospective analysis of 317 patients with SAB over a 6-year period.
• Logistic mixed-effects modeling to correct BC positivity rates.
• Binomial distributions used to calculate detection probabilities based on observed frequencies.

Main Results:

• BC positivity decreased from 66.7% on day 1 to 48.5% on day 4 post-therapy.
• One set of follow-up BC detected 73.4% of persistent SABs.
• Two BC sets on days 2 and 4 achieved ≥90% detection probability, with fewer skip phenomena compared to single sets.

Conclusions:

• Recommends two BC sets on days 2 and 4 post-therapy for ≥90% detection of persistent SAB.
• Advocates against single BC sets for SAB follow-up due to lower detection rates and increased skip phenomena.
• Optimizing BC strategy balances detection efficacy with reduced blood volume and potential complications.