Throat Culture

Test Overview

A throat culture is a test to find germs (such as bacteria or a fungus) that can cause an infection. A sample of cells from the back of your throat is added to a substance that promotes the growth of germs. If no germs grow, the culture is negative. If germs that can cause infection grow, the culture is positive. The type of germ may be identified using a microscope or chemical tests. Sometimes other tests are done to find the right medicine for treating the infection. This is called sensitivity testing.

Examples of infections that may be found during a throat culture include:

• Candida albicans. This fungus causes thrush, an infection of the mouth and tongue and sometimes of the throat.
• Group A streptococcus. This bacteria can cause strep throat, scarlet fever, and rheumatic fever. If strep throat is likely, a test called a rapid strep test (or quick strep) may be done before a throat culture. With a rapid strep test, results are ready in 10 minutes instead of 1 to 2 days with a throat culture. If the rapid strep test results are positive, antibiotics can be started immediately. A throat culture is more accurate than the rapid strep test. The rapid strep test can give false-negative results even when strep bacteria are present. When the results of a rapid strep test are negative, many doctors recommend doing a throat culture to make sure that strep throat is not present.
• Neisseria meningitidis. This bacteria can cause meningitis.

If bacteria grows in the culture, other tests may be done to check which antibiotic will treat the infection best. This is called susceptibility or sensitivity testing.

Most sore throats are caused by an infection with a virus, such as a cold or flu. Throat cultures are not done for viral infections because it is very hard to grow viruses and it is expensive.