Understanding Your Laboratory Test: What It Is, How the Sample Is Collected, and What Happens in the Lab

This test measures specific substances in your body to help your healthcare provider evaluate your overall health, check how well certain organs are working, or look for signs of a medical condition. Your provider ordered this test because the results can guide important decisions about your diagnosis, treatment, or ongoing care.

A sputum bacterial culture is a laboratory test that detects and identifies bacteria growing in your sputum. Sputum is the thick mucus (also called phlegm) that you cough up from your lungs, not saliva from your mouth. This test uses aerobic culture methods, meaning it grows bacteria in the presence of oxygen to identify specific types of organisms causing your respiratory infection.

A trained professional will usually collect a small sample, most often by drawing blood from a vein in your arm, though some tests use a urine sample, a swab, or another method depending on what your provider ordered. The collection process is typically quick and comfortable, and most people can return to their normal activities right afterward.

You will be asked to cough deeply from your lungs to produce sputum. Rinse your mouth with water first to remove food particles and bacteria from the mouth. Do not use mouthwash. Spit the sputum into the sterile container provided. If you have difficulty producing sputum, your healthcare provider may use a procedure called bronchoscopy to collect a sample directly from your airways.

Once your sample reaches the laboratory, trained technicians carefully prepare it and analyze it using specialized instruments and testing methods to measure what your provider asked about. The results are then reviewed for accuracy, compiled into a report, and sent to your healthcare provider, who will contact you to explain the findings and discuss any next steps.

The sputum sample is placed in special culture dishes and incubated in an oxygen-rich environment. Laboratory technicians observe the sample over several days to see which bacteria grow. When bacteria are found, they are identified and may be tested for antibiotic sensitivity (susceptibility testing) to determine which antibiotics will effectively treat the infection.