Urine Culture

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Related tests: Urinalysis

At a Glance

Why Get Tested?

To diagnose a urinary tract infection (UTI)

When to Get Tested?

If you experience symptoms of a UTI, such as pain during urination

Sample Required?

A mid-stream "clean" urine sample

The Test Sample

What is being tested?

Urine is one of the body’s waste products. It is produced in the kidneys and collected in the bladder until a person urinates. Normally, the urine does not contain significant numbers of any microorganism. However, if bacteria or yeast are introduced into the urinary tract, they can multiply and cause a urinary tract infection, called a UTI.

Most UTIs are caused by Escherichia coli (E. coli), one of the most common human bacteria. Other frequently identified bacteria are Proteus, Klebsiella, and Staphylococcus saprophyticus.

How is the sample collected for testing?

A “mid-stream” urine sample is necessary for a culture so bacteria present around the urethra and on the hands are not introduced. The procedure for collecting a clean “mid-stream” includes the following steps:  

  • Hands should be washed just before beginning the collection.
  • A soap should be used to clean the penis in males, and females should wash the external genitalia, holding the labia apart.
  • Repeat this procedure three times.
  • Do not collect the initial stream of urine since it may be contaminated with skin and urethral bacteria.
  • Midway through the urination process, collect a sample of urine in a sterile screw-top container (hence the name “mid-stream” urine).
  • Tightly cap the container and wash your hands thoroughly.
  • The sample should be taken taken to the laboratory as quickly as possible to prevent the further growth of organisms.

Uncontaminated specimens can also be obtained from catheterised patients following the same hygienic procedures for the end of the catheter.

A sample of the urine is then streaked across the surface of one or more agar plates and placed in an incubator at body temperature for 24 hours. If there is no growth on the agar plates at the end of that time, the culture is considered negative for significant number of microorganisms that could cause an infection. If bacteria or yeast are present, the total number of organisms is counted (colony count), and the organisms are identified by additional biochemical testing. Further tests determine which antibiotics are likely to be effective in treating the infection.

NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.

Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

The Test

Common Questions

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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.