Bacterial culture, middle ear fluid
What is this test?
This test detects and identifies bacteria from fluid or discharge found in the middle ear. It is used to help treat acute otitis media (inflammation of the middle ear) and chronic purulent otitis media. A sample of fluid or discharge from the middle ear may be collected by sterile swab, tympanocentesis or myringotomy.
What are related tests?
- Gram stain method
Why do I need this test?
Laboratory tests may be done for many reasons. Tests are performed for routine health screenings or if a disease or toxicity is suspected. Lab tests may be used to determine if a medical condition is improving or worsening. Lab tests may also be used to measure the success or failure of a medication or treatment plan. Lab tests may be ordered for professional or legal reasons. You may need this test if you have:
- Acute middle ear infection
- Chronic middle ear infections with pus
When and how often should I have this test?
When and how often laboratory tests are done may depend on many factors. The timing of laboratory tests may rely on the results or completion of other tests, procedures, or treatments. Lab tests may be performed immediately in an emergency, or tests may be delayed as a condition is treated or monitored. A test may be suggested or become necessary when certain signs or symptoms appear.
Due to changes in the way your body naturally functions through the course of a day, lab tests may need to be performed at a certain time of day. If you have prepared for a test by changing your food or fluid intake, lab tests may be timed in accordance with those changes. Timing of tests may be based on increased and decreased levels of medications, drugs or other substances in the body.
The age or gender of the person being tested may affect when and how often a lab test is required. Chronic or progressive conditions may need ongoing monitoring through the use of lab tests. Conditions that worsen and improve may also need frequent monitoring. Certain tests may be repeated to obtain a series of results, or tests may need to be repeated to confirm or disprove results. Timing and frequency of lab tests may vary if they are performed for professional or legal reasons.
How should I get ready for the test?
Ask the healthcare worker for information about how to prepare for this test.
If tympanocentesis or myringotomy will be done, a written consent may be required. Review the consent form with the healthcare worker and ask any questions that you have before signing the consent form. Before either of these procedures are done, healthcare workers may remove earwax and other material from your ear.
How is the test done?
Methods used to obtain a sample for culture vary and will depend on the healthcare worker. For perforated (burst) eardrums, fluid or pus may be collected from your ear canal. The sample may be obtained using a sterile cotton-tipped swab. The sample is placed in a sterile container, and sent to the laboratory for testing.
For intact eardrums, a tympanocentesis may be done. An ear speculum and a special magnifying tool called an operative otoscope are used to locate and inspect your eardrum. The healthcare worker will puncture your eardrum with a needle, and remove the fluid using a syringe. The fluid sample from the middle ear is collected using a sterile swab, and placed in a container to be tested.
If a myringotomy is done, an ear speculum and a special magnifying tool called an operative otoscope are used to locate and inspect your eardrum. The healthcare worker will make a small cut on your eardrum. The fluid sample from the middle ear is collected into a sterile suction trap or device. It is gathered using a sterile swab, and placed in a container for testing.
How will the test feel?
The amount of discomfort you feel will depend on many factors, including your sensitivity to pain. Communicate how you are feeling with the person doing the test. Inform the person doing the test if you feel that you cannot continue with the test.
There is usually no pain experienced when a sample from the middle ear is collected by a sterile swab. This method of collection is usually done for perforated eardrums when fluid or pus is already draining from the ear.
If tympanocentesis or myringotomy will be done, general or local anesthesia may be used. General anesthesia is done by an anesthesiologist. During general anesthesia, you receive medication that puts you into a deep sleep where you are unable to feel pain.
During local anesthesia, a topical anesthetic (numbing medicine) is instilled into the eardrum. You may feel some discomfort when tools are used to inspect the eardrum. There could be pain or discomfort when the eardrum is punctured or cut. Once the fluid has been drained, there will be a feeling of relief from the pain or pressure caused by the fluid that had gathered in the middle ear.
What should I do after the test?
Depending on the procedure used to obtain the sample of middle ear fluid, ask the healthcare worker for any special instructions for you to follow.
What are the risks?
Ask the healthcare worker to explain the risks of this test or procedure to you before it is performed.
What are normal results for this test?
Laboratory test results may vary depending on your age, gender, health history, the method used for the test, and many other factors. If your results are different from the results suggested below, this may not mean that you have a disease. Contact your healthcare worker if you have any questions. The following is considered to be a normal result for this test:
- No growth of pathogenic organisms
What follow up should I do after this test?
Ask your healthcare worker how you will be informed of the test results. You may be asked to call for results, schedule an appointment to discuss results, or notified of results by mail. Follow up care varies depending on many factors related to your test. Sometimes there is no follow up after you have been notified of test results. At other times follow up may be suggested or necessary. Some examples of follow up care include changes to medication or treatment plans, referral to a specialist, more or less frequent monitoring, and additional tests or procedures. Talk with your healthcare worker about any concerns or questions you have regarding follow up care or instructions.
Where can I get more information?
- American Academy of Pediatrics - http://www.aap.org
- Centers for Disease Control and Prevention (CDC) - http://www.cdc.gov/
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 Subcommittee on Management of Acute Otitis Media: Diagnosis and management of acute otitis media. Pediatrics 2004; 113:1451-1465.
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Last Updated: 11/4/2014