Urine Culture

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Urine Culture

Definition
Purpose
Precautions
Description
Preparation
Aftercare
Risks
Normal results
Abnormal results
Alternatives
Precautions
Side effects

Definition

A urine culture is a diagnostic laboratory test performed to detect the presence of bacteria in the urine (bacteriuria).

Purpose

Culture of the urine is a method of diagnosis for urinary tract infection that determines the number of microorganisms present in a given quantity of urine.

Precautions

If delivery of the urine specimen to the laboratory within one hour of collection is not possible, it should be refrigerated. The healthcare provider should be informed of any antibiotics currently or recently taken.

Description

There are several different methods for collection of a urine sample. The most common is the midstream clean-catch technique. Hands should be washed before beginning. For females, the external genitalia (sex organs) are washed two or three times with a cleansing agent and rinsed with water. In males, the external head of the penis is similarly cleansed and rinsed. The patient is then instructed to begin to urinate, and the urine is collected midstream into a sterile container. In infants, a urinary collection bag (plastic bag with an adhesive sealon one end) is attached over the labia in girls or a boy’s penis to collect the specimen.

Another method is the catheterized urine specimen in which a lubricated catheter (thin rubber tube) is inserted through the urethra (tube-like structure in which urine is expelled from the bladder) into the bladder. This avoids contamination from the urethra or external genitalia. If the patient already has a urinary catheter in place, a urine specimen may be collected by clamping the tubing below the collection port and using a sterile needle and syringe to obtain the urine sample; urine cannot be taken from the drainage bag, as it is not fresh and has had an opportunity to grow bacteria at room temperature. On rare occasions, the healthcare provider may collect a urine sample by inserting a needle directly into the bladder (suprapubic tap) and draining the urine; this method is used only when a sample is needed quickly.

Negative culture results showing no bacterial growth are available after 24 hours. Positive results

KEY TERMS

Bacteriuria— The presence of bacteria in the urine.

require 24-72 hours to complete identification of the number and type of bacteria found.

Preparation

Drinking a glass of water 15-20 minutes before the test is helpful if there is no urge to urinate. There are no other special preparations or aftercare required for the test.

Aftercare

No aftercare is required for a urine culture.

Risks

There are no risks associated with the culture test itself. If insertion of a urinary catheter (thin rubber tube) is required to obtain the urine, there is a slight risk of introducing infection from the catheter.

Normal results

No growth of bacteria is considered the normal result, and this indicates absence of infection.

Abnormal results

Abnormal results, or a positive test, where bacteria are found in the specimen, may indicate a urinary tract infection. Contamination of the specimen from hair, external genitalia, or the rectum may cause a false-positive result. Identification of the number and type of bacteria, with consideration of the method used in obtaining the specimen, is significant in diagnosis.

Escherichia coli causes approximately 80% of infections in patients without catheters, abnormalities of the urinary tract, or calculi (stones). Other bacteria that account for a smaller portion of uncomplicated infections include Proteus klebsiella and Enterobacter.

Alternatives

There are no alternatives to a urine culture.

Precautions

Two precautions are needed. The first is to clean the urethral meatus by urinating and then stopping the stream before collecting a specimen. The second is to use a sterile container to collect the urine specimen.

Side effects

There are no known side effects associated with a urine culture.

Resources

BOOKS

Fischbach, F. T. and M. B. Dunning. A Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams & Wilkins, 2008.

McGhee, M. A Guide to Laboratory Investigations, 5th ed. Oxford, England: Radcliffe Publishing Ltd, 2008.

Price, C. P. Evidence-Based Laboratory Medicine: Principles, Practice, and Outcomes, 2nd ed. Washington, DC: AACC Press, 2007.

Scott, M.G., A. M. Gronowski, and C. S. Eby. Tietz’s Applied Laboratory Medicine, 2nd ed. New York: Wiley-Liss, 2007.

Springhouse, A. M.. Diagnostic Tests Made Incredibly Easy!, 2nd ed. Philadelphia: Lippincott Williams & Wilkins, 2008.

PERIODICALS

Barrett, M., and V. L. Campbell. “Aerobic bacterial culture of used intravenous fluid bags intended for use as urine collection reservoirs.” Journal of the American Animal Hospital Association 44, no. 1 (2008): 2–4.

Dalen, D.M., R. K. Zvonar, and P. G. Jessamine. “An evaluation of the management of asymptomatic catheter-associated bacteriuria and candiduria at The Ottawa Hospital.” Canadian Journal of Infectious Disease and Medical Microbiology 16, no. 3 (2005): 166–170.

Mishriki, S. F., G. Nabi, and N. P. Cohen. “Diagnosis of urologic malignancies in patients with asymptomatic dipstick hematuria: prospective study with 13 years’ follow-up.” Urology 71, no. 1(2008): 13–16.

Nicolle, L. “Complicated urinary tract infection in adults.Canadian Journal of Infectious Disease and Medical Microbiology 16, no. 6 (2005): 349–360.

ORGANIZATIONS

American Foundation for Urologic Disease. 300 West Pratt St., Suite 401, Baltimore, MD 21201.

American Society for Clinical Laboratory Science. http://www.ascls.org/ (accessed April 15, 2008).

American Society of Clinical Pathologists. http://www.ascp.org/ (accessed April 15, 2008).

College of American Pathologists. http://www.cap.org/apps/cap.portal (accessed April 15, 2008).

OTHER

American Clinical Laboratory Association. Information about clinical chemistry. 2008 [cited February 24, 2008]. http://www.clinical-labs.org/ (accessed April 15, 2008).

Clinical Laboratory Management Association. Information about clinical chemistry. 2008 [cited February 22, 2008]. http://www.clma.org/ (accessed April 15, 2008).

Lab Tests On Line, 2008. http://www.labtestsonline.org/ (accessed April 15,2008).

National Accreditation Agency for Clinical Laboratory Sciences, 2008. http://www.naacls.org/ (accessed April 15, 2008).

L. Fleming Fallon, Jr, MD, DrPH

Urobilinogen test seeUrinalysis