What is urine culture test?

Urine culture test is a laboratory test that checks for microorganisms like bacteria and yeast in urine, the fluid produced by kidneys, which carries waste material and excess water out of the body. The test can detect the presence of a urinary tract infection (UTI) in both children and adults.

In people who have frequent UTIs, other tests like a susceptibility test might be performed with each infection.

  1. Why is urine culture test performed?
  2. How do you prepare for urine culture test?
  3. How is urine culture test performed?
  4. Urine culture test results and normal range

Doctors recommend a urine culture test for the following reasons:

  • To identify the cause of a UTI
  • Sensitivity testing or to determine the best medicine for the treatment of UTI
  • To check if the treatment provided for the UTI worked

This test is also recommended when an individual has symptoms of bladder infection or UTI such as burning or painful sensation while urinating. (Read more: Painful urination causes)

No special preparations are required for this test. Individuals should inform the healthcare provider about any antibiotics taken recently. The individual is advised not to urinate for at least 1 hour before giving the urine sample. Individuals will be asked to have a glass of water about 20 minutes before collecting the urine sample for the test to get the right amount of urine volume.

Individuals will be asked to collect a midstream urine sample. Typically, the first urine of the day should be collected as it has the best amount of bacterial levels. The following steps should be taken while collecting the urine sample:

  • Women should clean their genital area and men should wipe the tip of their penis before collecting the urine sample to avoid contaminating the sample with bacteria from the surrounding skin
  • The genitals should be cleaned from front to back in women
  • The first few drops of urine should not be taken
  • About 60 ml of urine should be collected in the given sterile container
  • The container should be sealed with a cap and sent to the laboratory

For people with urine catheters, a trained healthcare professional collects the urine sample by inserting a thin, flexible catheter or tube in the urethra. If the urine sample cannot be sent to the laboratory within an hour, the sample should be placed in a refrigerator.

There is a small risk of perforation of the bladder or urethra if a catheter is used to collect the urine sample.

It takes 1 to 3 days for the results of the urine culture test to arrive. However, it may take longer as certain microorganisms take longer to grow.

Normal results:

A normal urine culture test indicates that the person has no infection. The normal values of the test vary among different laboratories.

Abnormal results:

Abnormal urine culture or a positive urine culture denotes the presence of yeast or bacteria in the culture, which might indicate the possibility of a bladder infection or urinary tract infection. The following results are obtained in a positive urine culture test:

  • Less than 100 bacteria/mL: Indicates the absence of infection or the individual may be taking an antibiotic
  • 100 to 100,000 bacteria/mL: This indicates contamination of the urine sample or infection (the urine culture may need to be repeated)
  • 100,000 bacteria/mL: Indicates an infection

A sensitivity test may be ordered if a positive result is obtained on the urine culture test.

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. This is information purely from the educational point of view and is in no way a substitute for medical advice by a qualified doctor.

References

  1. Dean AJ, Lee DC. Bedside laboratory and microbiologic procedures. In: Roberts JR, Custalow CB, Thomsen TW, eds. Roberts and Hedges' Clinical Procedures in Emergency Medicine and Acute Care. 7th ed. Philadelphia, PA: Elsevier; 2019:chap 67.
  2. Germann CA, Holmes JA. Selected urologic disorders. In: Walls RM, Hockberger RS, Gausche-Hill M, eds. Rosen's Emergency Medicine: Concepts and Clinical Practice. 9th ed. Philadelphia, PA: Elsevier; 2018:chap 89.
  3. Schaeffer AJ, Matulewicz RS, Klumpp DJ. Infections of the urinary tract. In: Wein AJ, Kavoussi LR, Partin AW, Peters CA, eds. Campbell-Walsh Urology. 11th ed. Philadelphia, PA: Elsevier; 2016:chap 12.
  4. National Institute of Diabetes and Digestive and Kidney Diseases [internet]: US Department of Health and Human Services; Bladder Infection (Urinary Tract Infection—UTI) in Adults
  5. Michigan Medicine: University of Michigan [internet]; Urine Culture
  6. MedlinePlus Medical Encyclopedia: US National Library of Medicine; Urine culture

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