ASAP Bloodstream Pathogen Identification and Susceptibility Testing: When Rapid Is Not Fast Enough

The identification of bacteria and yeast from blood culture is one of the most important functions of the microbiology laboratory because for every hour that appropriate antimicrobial therapy is delayed, morbidity and mortality increase (1). Blood culture is the gold standard for blood pathogen detection, and in the past few years, there has been an explosion of assays that rapid identify bloodstream pathogens from positive blood culture broth (2–6). These assays have shortened the amount of time for pathogen identification from approximately 24 h using traditional culture and biochemical testing to 0.5 to 2.5 h following a blood culture bottle signaling positive. This reduction in time does not affect the amount of time a blood culture is incubated before signaling positive, which generally ranges from 8 to 48 h depending on the bacterial burden in the blood, the pathogen doubling time, and the volume of blood submitted for culture. Nevertheless, the results of these assays allow clinicians to tailor their patients' empiric antimicrobial therapy so that they are more rapidly receiving effective treatment. Several studies have shown that rapid blood pathogen assays are associated with improved patient outcomes, such as decreased hospital length of stay, decreased intensive care unit length of stay, and reduced 30-day all-cause mortality, as well as an overall reduction in hospitalization costs (7).