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A urine culture is a test to find and identify germs (usually bacteria) that may be causing a urinary tract infection (UTI). Urine in the bladder normally is sterile—it does not contain any bacteria or other organisms (such as fungi). But bacteria can enter the urethra and cause an infection.
A urine sample is kept under conditions that allow bacteria and other organisms to grow. If few or no organisms grow, the test is negative. If organisms grow in numbers large enough to indicate an infection, the culture is positive. The type of organisms causing the infection are identified with a microscope or by chemical tests.
Urinary tract infections are more common in women and girls than in men. This may be partly because the female urethra is shorter and closer to the anus, which allows bacteria from the intestines to come into contact more easily with the urethra. Men also have an antibacterial substance in their prostate gland that reduces their risk.
If the urine culture is positive, other tests may be done to help choose which antibiotic will do the best job treating the infection. This is called sensitivity testing.
A urine culture may be done to:
You do not need to do anything before you have this test. If you are taking or have recently taken antibiotics, tell your doctor.
You will need to collect a urine sample. Avoid urinating just before having this test.
Talk to your doctor about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results will mean. To help you understand the importance of this test, fill out the medical test information form(What is a PDF document?).
You will be asked to collect a clean-catch midstream urine sample for testing. The first urine of the day is preferred because bacterial levels will be higher.
This method helps protect the urine sample from germs that are normally found on the penis or vagina.
Collecting a urine sample does not cause pain.
There is no chance for problems while collecting a urine sample.
A urine culture is a test to detect and identify organisms (usually bacteria) that may be causing a urinary tract infection (UTI). Urine culture results are usually ready in 1 to 3 days. Some organisms take longer to grow in the culture; for this reason, results may not be available for several days.
No bacteria or other organisms (such as fungi) grow in the culture. The culture result is negative.
Organisms (usually bacteria) grow in the culture. The culture result is positive.
A count of 100,000 or more bacteria per milliliter (mL) of urine may be caused by an infection. A count ranging from 100 to 100,000 could be either caused by infection or by contamination of the sample (you may need a repeat urine culture). If the count is 100 or less, infection is unlikely; however, a count of 100 or less may also be seen if you are already taking antibiotics.
If test results are positive, sensitivity testing may be done to help make decisions about treatment.
Reasons you may not be able to have the test or why the results may not be helpful include:
Other Works Consulted
- Chernecky CC, Berger BJ (2008). Laboratory Tests and Diagnostic Procedures, 5th ed. St. Louis: Saunders.
- Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.
- Pagana KD, Pagana TJ (2010). Mosby’s Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby Elsevier.
|Primary Medical Reviewer||E. Gregory Thompson, MD - Internal Medicine|
|Specialist Medical Reviewer||W. David Colby IV, MSc, MD, FRCPC - Infectious Disease|
|Last Revised||May 21, 2012|
Last Revised: May 21, 2012
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