Nasopharyngeal Culture

Overview :

The patient should cough before collection of the specimen. Then, as the patient tilts his or her head backwards, the caregiver will inspect the back of the throat using a penlight and tongue depressor. A swab on a flexible wire is inserted into the nostril, back to the nasal cavity and upper part of the throat. The swab is rotated quickly and then removed. Next, the swab is placed into a sterile tube with culture fluid in it for transport to the microbiology laboratory. To prevent contamination, the swab should not touch the patient's tongue or side of the nostrils.

When the sample reaches the laboratory, the swab will be spread onto an agar plate and the agar plate incubated for 24-48 hours, to allow organisms present to grow. These organisms will be identified and any pathogenic organisms may also be tested for susceptibility to specific antibiotics. This allows the treating physician to determine which antibiotics will be effective.

Alternative procedures

In most cases of upper respiratory tract infections, a throat culture is more appropriate than a nasopharyngeal culture. However, the nasopharyngeal culture should be used in cases where throat cultures are difficult to obtain or to detect the carrier states of Harmophilus influenzae and meningococcal disease.

Some researchers regard the immunoblot method as preferable to a standard culture to detect certain species of pneumococci and other organisms that cause pneumonia. The immunoblot method uses a membrane that changes color in response to a specific antigen-antibody reaction.

As of the early 2000s, polymerase chain reaction (PCR) analysis is considered more sensitive than standard culture in detecting Bordetella pertussis, the bacterium that causes whooping cough. PCR has the additional advantage of providing test results more rapidly than culture.