Pleural fluid culture is a test that looks at a sample of fluid from the space around the lungs to find and identify disease-causing microorganisms.

The test is performed when the health care provider suspects an infection of the pleural space, or when a chest x-ray reveals an abnormal collection of pleural fluid.

A procedure called thoracentesis is done to obtain a sample of pleural fluid. The health care provider cleans a small area on your chest with germ-killing (antibacterial) soap and numbs the area with local pain-killing medicine (anesthetic). A needle is placed between the ribs, and a sample of fluid is taken from the chest.

The sample is placed on special plates that contain a substance to help the microorganisms in the fluid grow. When colonies of microorganisms are big enough, the health care provider does a series of tests to identify the infection-causing microorganisms.

It is important not to cough, breathe deeply, or move when the fluid sample is being taken. There is no other special preparation for the test.

You may feel a stinging sensation when the anesthetic is injected. You may feel some pressure and slight pain in the area when the thoracentesis needle enters the pleural space. You may have a chest x-ray after the test to make sure the test did not affect the lung tissue or function.