The finding of bacteria or yeast in culture of blood is always noteworthy and requires immediate and thorough evaluation.
A truly positive blood culture is either a manifestation of uncontrolled infection at a specific body site (e.g. pyelonephritis, pneumonia) or infection of endo-vascular tissue itself (e.g. endocarditis) or, increasingly, medical devices placed within the vascular space therapeutically (e.g. central intravenous catheters).