A blood culture is a laboratory test to check for bacteria or other germs in a blood sample.
How the Test is Performed
A blood sample is needed.
The site where blood will be drawn is first cleaned with an antiseptic such as chlorhexidine. This reduces the chance of an organism from the skin getting into (contaminating) the blood sample and causing a false-positive result (see below).
The sample is sent to a laboratory. There, it is placed in a special dish (culture). It is then watched to see if bacteria or other disease-causing germs grow. A gram stain may also be done. A gram stain is a method of identifying bacteria using a special series of stains (colors). With some infections, bacteria can be found in the blood only intermittently. So, a series of three or more blood cultures may be done to increase the chance of finding the infection.