Blood Culture

What To Think About

• Some types of bacteria infect the blood when another infection of the kidneys, throat, lungs, or another part of the body is present. This may not mean a serious infection of the blood.
• About 5% of blood cultures are contaminated with normal skin bacteria (a type of staph bacteria). Therefore, it is sometimes hard to see whether the bacteria that grow in the culture are the cause of the blood infection or not. This is why more than one blood sample is taken. When the same bacteria grow in several blood cultures, it is likely that those bacteria are in the blood and are causing the infection. When staph bacteria grow in the culture in less than 48 hours, it is likely that the staph bacteria are in the blood and are causing the infection.
• A culture that does not grow any bacteria does not always mean a blood infection is not present. The amount of blood taken, the timing of the blood sample, the type of culture done, and recent use of antibiotics can affect the growth of bacteria in the culture.

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Author:	Jan Nissl, RN, BS	Last Updated: February 4, 2007
Medical Review:	Patrice Burgess, MD - Family Medicine Andrew Swan, MD, CCFP, FCFP - Family Medicine Joseph O'Donnell, MD - Hematology/Oncology
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