Sputum or Phlegm Bacteria Culture Lab Test

What is a sputum culture?

The material which is coughed up from the lungs and then spat out or expectorated is called sputum or sometimes referred to as phlegm. A sputum culture is done to identify the microorganism causing lower respiratory tract infections such as pneumonia and tuberculosis. A fever with a chronic cough , along with blood or pus-like material in the sputum, is usually an indication for undertaking a sputum culture.

Collection of Sputum Specimen

The sputum should be collected in a sterile container, preferably early in the morning before eating or drinking anything. The mouth should be rinsed with water to rinse out bacteria from the mouth and dilute the saliva which may contaminate the specimen. With a forceful cough, the sputum should be spat out into the sterile container immediately, avoiding prolonged collection in the mouth cavity. Three consecutive samples may have to be collected if testing for tuberculosis.

A special stain called the acid-fast stain may be done in the laboratory to identify the tuberculous bacilli. Different types of microorganisms may be identified using gram stain. A fungal culture may be done if a fungal infection is suspected and a viral culture is done to detect viral infection such as pneumonia. Due to the prevalence of bacterial respiratory tract infections, most sputum samples are first tested for bacteria.

Sputum Culture Report

Bacterial Culture

The initial report indicating the presence of any bacteria may be available on the same day. The final report will take one to three days and this will include identification of the specific type and quantity of bacteria as well as the antibiotics most effective against it. Culture for tuberculosis may take two to four weeks.

Fungal Culture

Reports may take several weeks.

Viral Culture

It may take several days to several weeks to get the report depending on the type of virus present.