Laboratory diagnosis of bacteremia and fungemia

This article focuses on the key principles for obtaining blood cultures, including the site from which blood is obtained, antiseptic technique, volume of blood cultured, and number sets needed. Several major technical variables that form the scientific basis for current blood culture methods are addressed, including culture medium, blood-to-broth ratio, additives that bind or inactivate antimicrobials, and length of incubation. Currently available manual and instrumented blood culture systems are described and discussed, with emphasis on the benefits and limitations of each. The underlying logic for interpreting the clinical significance of positive blood cultures is addressed.