A blood culture is a test that checks for foreign invaders like bacteria, yeast, and other

microorganisms in your blood. Having these pathogens in your bloodstream can be a sign of

a blood infection, a condition known as bacteremia. A positive blood culture means that you

have bacteria in your blood.This type of infection involves the blood that circulates within

your entire body. Bacteria that start on your skin or in your lungs, urine, or gastrointestinal

tract are common sources of blood infections.