Culture, Sputum

The culture, sputum test is advised to detect and identify the cause of bacterial pneumonia or some other lower respiratory tract infections. It also helps to monitor the efficacy of the suggested treatment. 

The culture, sputum test detects the presence of disease-causing pathogens in those patients who are under suspicion of having bacterial pneumonia or other lower respiratory tract infections. Sputum is thick mucus or phlegm which is expelled from the lower respiratory tract through coughing. Sputum is not saliva or spit. During the sample collection process, it is to be ensured that the sample is collected from the lower respiratory tract and not from the upper respiratory tract.  

The pathogen is identified by the culture, sputum test and accordingly, after susceptibility testing, the treatment is initiated. At times, a respiratory infection can be caused by a pathogen that cannot be grown and identified with culture, sputum test. In such a case, other tests such as culture and stain AFB or culture fungus or culture viral can be advised. 

In case of a bacterial pathogen, the first step in the routine analysis of a sputum sample is a Gram stain which helps to identify the presence of a general type of bacteria. Further, the sample is placed on the appropriate nutrient media and is then incubated. The media encourages the bacteria growth which is present in the sputum sample.

Normally, the sputum is not sterile (free from bacteria), as harmless bacteria are usually present in the mouth or throat as a part of normal flora. In case of respiratory infections, disease-causing pathogens are also present which are detected by the culture, sputum test.