Culture tests check for abnormal cells indicating the presence of viruses, bacteria, or fungi in body fluids or tissues. Samples are placed in culture dishes and examined regularly. Collection areas vary, and results take time. Contamination can affect accuracy. Treatment may require more refined tests.
A culture test is the evaluation of body fluids, tissues, or other products to look for the presence of abnormal cells that indicate the presence of viruses, bacteria, or fungi. Such testing usually relies on small samples collected from the body by the individual or by a doctor. These samples are placed in safe dishes called culture dishes, which contain nutrients that encourage the growth of abnormal substances, and these are then examined regularly to determine if irregular cell growth is occurring, indicating an infection. Absence of growth indicates no infectious agents are present, although cultures are not 100% accurate. Abnormal tissue growth means starting treatment or initiating further testing to find the specific infectious agent creating the disease.
Doctors or others may collect culture samples from a variety of areas on the body. Skin, blood, or urine can be cultured. Stools or mucous membranes can be tested. Fluid may be collected from the joints or around the heart, or alternatively bone marrow may be collected for a culture test.
The collection area really depends on what doctors think might be wrong, and the degree of complexity of collecting a sample depends on the targeted area. Very often the samples taken are very small. However, collecting bone marrow or pericardial fluid will require more demanding collection procedures than, for example, swabbing the throat to check for diseases such as strep throat or asking patients to provide a urine sample by urinating into a cup.
It’s also important to recognize that a culture test takes time, and how long it takes can depend on what doctors are looking for. Some cultures for diseases such as strep take a couple of days at most to get an accurate diagnosis. Other tests may take several days or weeks longer to ascertain the presence or absence of an infectious agent, or lack of presence.
An abnormal culture test result does not always mean that treatment can begin. On the other hand, if doctors suspect an antibacterial infection, they can treat with antibiotics designed to be effective against a broad spectrum of bacterial types. More refined tests may still be needed to determine specific agents causing infection so that more specific treatment can replace the initial treatments.
A culture can also be contaminated by the presence of infectious agents in the environment in which the test is performed. Failure to cleanse the skin with alcohol before piercing the skin with a needle to draw blood can introduce normal bacteria into the blood sample. Individuals who provide a urine sample are instructed to clean the genital area thoroughly to avoid providing contaminated samples. If the protocol is strictly followed, the samples are likely to be representative, but it is quite easy to contaminate them, especially if lay doctors are performing the tests. This means that not all tests will be completely accurate.
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