Blood is normally sterile. Any bacteria in the bloodstream is abnormal.
A blood culture is collected to detect the presence of bacteria in the bloodstream. Blood is collected into appropriate media to allow for growth and identification of bacteria or other organisms that may be in the patient's bloodstream.
A blood culture set usually consists of two bottles: an aerobic bottle and an anaerobic bottle. Blood cultures are usually ordered in multiple sets drawn with each set drawn from separate sites at different times.
An improperly collected blood culture can have a serious impact on the care and treatment of a patient. If bacteria enters the culture vial from sources other than the blood, as a result of improper specimen collection, a patient may needlessly be treated for an infection that is not present. On the other hand, some collection errors may cause negative culture results when the patient actually has bacteria in his/her blood. A false-negative culture result could be a life-threatening error.