What It Is
A blood culture is a laboratory test used to detect the presence of bacteria or fungi in the bloodstream, a condition that doesn't normally contain these organisms in a healthy person.
What It Checks
A blood culture identifies whether microorganisms are present in the blood, and if so, helps identify the specific type. Further testing on a positive sample can also determine which antimicrobial medications are likely to be effective against the specific organism identified.
Why It's Used
Blood cultures are commonly used when a bloodstream infection is suspected, particularly in the context of symptoms like high fever with chills, or in situations where an infection elsewhere in the body may have spread into the bloodstream.
How It's Done
A blood culture requires a blood sample, drawn using careful sterile technique from a vein, which is then placed into special culture bottles containing a nutrient-rich medium designed to support the growth of any microorganisms present. The sample is incubated in a laboratory, and technicians monitor for any growth over a period typically ranging from a day to several days, depending on the specific organisms being looked for.
Background
Blood culture techniques developed alongside the broader growth of microbiology in the late 19th and early 20th centuries, as researchers developed reliable methods for growing and identifying bacteria outside the body. Laboratory techniques and equipment for blood culture testing have advanced considerably since then, including the development of automated systems that can detect microbial growth more quickly than earlier manual methods, and blood cultures remain a cornerstone test for diagnosing bloodstream infections today.