Sputum culture

A sputum culture is a test to detect and identify bacteria or fungi that infect the lungs or breathing passages. Sputum is a thick fluid produced in the lungs and in the adjacent airways. A sample of sputum is placed in a sterile container and sent to the laboratory for testing. Sampling may be performed by sputum being expectorated (produced by coughing), induced (saline is sprayed in the lungs to induce sputum production), or taken via an endotracheal tube with a protected specimen brush (commonly used on patients on respirators) in an intensive care setting. For selected organisms such as Cytomegalovirus or "Pneumocystis jiroveci" in specific clinical settings (immunocompromised patients) a bronchoalveolar lavage might be taken by an experienced pneumologist. If no bacteria or fungi grow, the culture is negative. If organisms that can cause the infection (Pathogenicity organisms) grow, the culture is positive. The type of bacterium or fungus is identified by microscopy, colony morphology and biochemical tests of bacterial growth.