Lifespan's A - Z Health Information Library

Ear drainage culture is a laboratory test to identify organisms that cause ear infections.

A sample of ear drainage either from the outer ear or middle ear is placed on culture media for the purpose of growing microorganisms (bacteria, fungus, or viruses) in the laboratory, which will later be identified.

The microbiologist inspects the cultures daily for growth. If microorganisms are detected, other tests may be initiated to determine the sensitivity of the organism to medications (sensitivity analysis). Antibiotic therapy can then be determined based on these results.

There is no preparation.

The specimen will be collected using a cotton swab placed gently inside the outer ear canal. No pain is associated with the test. However, ear pain may be present already if infection is suspected.

If a myringotomy (surgical opening of the eardrum) is performed for relief of a painful, bulging tympanic membrane in otitis media, fluid will be collected at this time. Rarely, a needle may be inserted through the tympanic membrane (eardrum) to obtain a sample of the fluid from the middle ear.

The test may be performed for an infection of the outer ear (see otitis externa; acute), as a routine part of myringotomy, otitis media with ruptured eardrum and draining fluid, or otitis media not responding to treatment. Most ear infections are diagnosed based on symptoms rather than by obtaining a culture.

No organisms seen on the culture is normal.

Abnormal results indicate infection. The infection may be bacterial, viral, or fungal. The test may show which specific organism is causing the effective, and guide the doctor in deciding on appropriate treatment.

No risks are involved with swabbing the ear canal. Risks of myringotomy and needle aspiration include bleeding, infection, and hearing loss.

Sometimes special stains of the fluid, such as a gram stain or KOH stain, are done to help with the initial diagnosis.