Laboratory technicians conduct a blood culture test to see if there is some sort of infection in the blood system. Because healthy blood does not normally have bacteria in it, so when bacteria find their way into the blood, serious illness can follow. This is when a blood culture test can show that there is a threatening bacteria present. In addition, the test might be able to identify the bacteria, which could lead to remedies.

The simple test involves gathering a small amount of blood from the individual. This sample is placed in a container with other ingredients/substances that encourage bacteria or even unusual fungus to grow. Additional testing using specific chemicals can show what type of bacteria or fungus is in the blood. Much of the identification process takes place when a laboratory staff member examines the sample under a microscope. Sometimes there are two or more samples taken, often from different parts of the body, to determine location in the blood system as well.

The results of a blood culture test is usually expressed as positive, meaning that bacteria or fungus is present, or negative, meaning that these aren’t in the blood. The simplest explanation for a blood culture test is this: It is a test used to find a bacterial infection in the blood. Some of the common, well-known infections that might be found with such a test are meningitis and pneumonia. A blood culture test can also find a fungus infection (yeast is one example).

Following the original blood culture test to determine if bacteria or fungus are present, a laboratory might test the sample to see which antibiotics are called for to eliminate the invading item. Medical personnel often use the blood culture test when a person is suffering from elevated body temperature (fever).
According to most medical guidelines, the nurse or laboratory technician takes 10 ml of blood from the patient (as a minimum). This is accomplished by puncturing the vein with a sterile, hollow needle that allows blood to be taken into a vial or other receptacle. All of the items used to collect the blood culture sample must be perfectly sterile so that the test shows only bacteria or other items in the blood.

In recent years, laboratories used electro-mechanical equipment that keeps the sample at body temperature. This equipment “reads” the sample and determines if bacteria are in the blood, for instance. The basic method for doing this measures carbon dioxide that is put out by bacteria. For many years, physicians, nurses and laboratory staff identified bacterial and fungal infections in the blood by sight, using a limited number of ingredients (agents) to cause certain changes that could be seen.

The positive blood culture test is often followed by a quick “stain” test to help identify the bacteria. The sample is further tested so that specific types of bacterial infection can be identified. The entire process, from taking a sample to reporting final results, may take several days.

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Lucas Beaumont
Generalist. Wikipedia contributor. Elementary school teacher from Saskatchewan, Canada.