True Bacteremia: at least one positive blood culture, not otherwise considered a contaminant. Contaminant: a positive blood culture in which the isolate was a common skin organism (such as diphtheroids, micrococcus, or coagulase negative Staphylococcus) isolated in one bottle, or when the medical records reported the positive cultures as contaminants.
Persistent Bacteremia: positive blood cultures for the same original organism in a sample drawn at least 24 hours after the initial culture. We considered any positive blood culture within 24 hours of the first positive as being part of the same episode.
Medical disease (vs. Surgical Disease): disease in which the source of bacteremia does not require surgical resolution. Of note, in our series, intravenous-catheter-related infections were categorized as medical diseases, even when the resolution required the surgical removal of the source.
Serious Skin Infections: severe cellulitis, necrotizing fasciitis, and skin abscesses.
Febrile: Patients were considered febrile if their recorded temperature was >100.4oF when at least one of the follow up blood cultures was drawn.
In our cohort, approximately 5 FUBC were needed in order to yield one positive result; however, when considering only GNB bacteremia, it took 17 FUBC to yield a one positive result.
First, we eliminated contaminants upfront, likely skewing the distribution of the true positive cultures.
Second, the medical records examined did not offer an explanation of why the FUBC were ordered. That kind of explanation might open opportunities to educate physicians on the actual indication for blood cultures.
Third, and related to the previous one, there is no explanation on whether a perception of disease severity played a role in the decision to obtain FUBC only in 77% of our cohort, and not in all of it.
Finally, the analysis of risk factors for positive GNB FUBC is limited by the low incidence of such event.