How to Optimize the Use of Blood Cultures for the Diagnosis of Bloodstream Infections? A State-of-the Art

Abstract

Bloodstream infection (BSI) is a major cause of death in developed countries and the detection of microorganisms is essential in managing patients. Despite major progress has been made to improve identification of microorganisms, blood culture (BC) remains the gold standard and the first line tool for detecting BSIs. Consensus guidelines are available to ensure optimal BSI procedures, but BC practices often deviate from the recommendations. This review provides an update on clinical and technical issues related to blood collection and to BC performance, with a special focus on the blood sample strategy to optimize the sensitivity and specificity of BCs.

Keywords: blood culture; bloodstream infection; contamination; multi-sampling strategy; sensitivity; single sampling strategy; specificity.

Figure 1

Blood culture result (negative or positive) according to the amount of blood cultured at each sampling and to the microbial burden in blood. The curve represents the bacterial concentration (β) in blood that varies with time and may be very low, but never null. The limit of bacteremia detection (BC sensitivity) is indicated with dotted line. Each sample is represented by a box. (A) Culturing low volumes of blood does not ensure sensitive testing and low detection threshold, and thus leads to uncertain bacteremia detection according to time of collection. The overall results suggest an intermittent bacteremia. (B) Culturing large volumes of blood ensures low detection threshold, thus allowing detecting bacteremia whenever the sample is obtained. One sample is enough for confidently detecting bacteremia; the overall results would suggest a continuous bacteremia.