Also Known As
Urine Culture and Sensitivity
Urine C and S
Formal Name
Culture, Urine
This article was last reviewed on
This article waslast modified on
January 15, 2018.
At a Glance
Why Get Tested?
When To Get Tested?

When you experience symptoms of a UTI, such as frequent and painful urination, and/or when a urinalysis indicates you may have a UTI

Sample Required?

A mid-stream clean catch urine sample (women should spread the labia of the vagina and clean from front to back; men should wipe the tip of the penis; start to urinate, let some urine fall into the toilet, then collect one to two ounces of urine in the container provided, then void the rest into the toilet); sometimes a urine sample obtained via catheter

Test Preparation Needed?

Generally none, but you may be instructed not to urinate for at least one hour before the test and/or to drink a glass of water 15-20 minutes before sample collection.

You may be able to find your test results on your laboratory's website or patient portal. However, you are currently at Lab Tests Online. You may have been directed here by your lab's website in order to provide you with background information about the test(s) you had performed. You will need to return to your lab's website or portal, or contact your healthcare practitioner in order to obtain your test results.

Lab Tests Online is an award-winning patient education website offering information on laboratory tests. The content on the site, which has been reviewed by laboratory scientists and other medical professionals, provides general explanations of what results might mean for each test listed on the site, such as what a high or low value might suggest to your healthcare practitioner about your health or medical condition.

The reference ranges for your tests can be found on your laboratory report. They are typically found to the right of your results.

If you do not have your lab report, consult your healthcare provider or the laboratory that performed the test(s) to obtain the reference range.

Laboratory test results are not meaningful by themselves. Their meaning comes from comparison to reference ranges. Reference ranges are the values expected for a healthy person. They are sometimes called "normal" values. By comparing your test results with reference values, you and your healthcare provider can see if any of your test results fall outside the range of expected values. Values that are outside expected ranges can provide clues to help identify possible conditions or diseases.

While accuracy of laboratory testing has significantly evolved over the past few decades, some lab-to-lab variability can occur due to differences in testing equipment, chemical reagents, and techniques. This is a reason why so few reference ranges are provided on this site. It is important to know that you must use the range supplied by the laboratory that performed your test to evaluate whether your results are "within normal limits."

For more information, please read the article Reference Ranges and What They Mean.

What is being tested?

Urine is the fluid that contains water and wastes and that is produced by the kidneys. It travels from the kidneys, through tubes called ureters to the bladder, and then is eliminated from the body through the urethra. The urine culture is a test that detects and identifies bacteria and yeast in the urine, which may be causing a urinary tract infection (UTI).

For a urine culture, a small sample of urine is placed on one or more agar plates (a thin layer of a nutrient media) and incubated at body temperature. Any bacteria or yeast that are present in the urine sample grow over the next 24 to 48 hours as small circular colonies. The size, shape, and color of these colonies help to identify which bacteria are present, and the number of colonies indicates the quantity of bacteria originally present in the urine sample. A laboratorian observes the colonies on the agar plate, counting the total number and determining how many types have grown. Ideally, if a good clean catch sample was collected for the test (see below), then the only bacteria present should be due to an infection. Typically, this will be a single type of bacteria that will be present in relatively large numbers. Sometimes, more than one type of bacteria will be present. This may be due to an infection that involves more than one pathogen; however, it is more likely to be due to contamination from the skin picked up during the urine collection.

The laboratorian will take a colony from each type and perform a gram stain. The laboratorian examines the microorganisms under the microscope. Different types of bacteria will exhibit characteristic colors and shapes. For instance, the bacterium Escherichia coli, which causes the majority of urinary tract infections, will appear as pink (gram-negative) rods under the microscope. Lactobacillus, which is a common vaginal contaminant in women's urine samples, will appear as thin purple (gram-positive) rods. Some of the bacteria, such as Lactobacillus, are easy for an experienced laboratorian to identify, are nonpathogenic, and do not require any further investigation. Others, such as gram-negative rods, represent groups of similar bacteria and will require additional testing to determine exactly which type of bacteria is present.

If there is no or little growth on the agar after 24 to 48 hours of incubation, the urine culture is considered negative for pathogens and the culture is complete. If there are one or more pathogens present, further testing is performed. Testing is done to identify which bacteria are present and susceptibility testing is done to identify antibiotics that are likely to cure the infection.

How is the sample collected for testing?

Because of the potential to contaminate urine with bacteria and cells from the surrounding skin during collection (particularly in women), it is important to first clean the genital area. Women should spread the labia of the vagina and clean from front to back; men should wipe the tip of the penis. Start to urinate, let some urine fall into the toilet, then collect one to two ounces of urine in the sterile container provided, then void the rest into the toilet. This type of collection is called a mid-stream clean catch urine.

For catheterized specimens, a urine sample is taken by inserting a thin flexible tube or catheter through the urethra into the bladder. This is performed by a trained healthcare practitioner. The urine is collected in a sterile container at the other end of the tube.

Is any test preparation needed to ensure the quality of the sample?

Generally none; however, you may be instructed not to urinate for at least an hour before the test and/or to drink a glass of water 15-20 minutes before sample collection. This will help to ensure that you can produce enough urine for the sample. Follow the instructions provided for collecting a clean catch urine sample.

Accordion Title
Common Questions
  • How is it used?

    The urine culture is used to diagnose a urinary tract infection (UTI) and to identify the bacteria or yeast causing the infection. It may be done in conjunction with susceptibility testing to determine which antibiotics will inhibit the growth of the microbe causing the infection. The results will help a healthcare practitioner determine which drugs are likely to be most effective in treating a person's infection.

    Urine is produced by the kidneys, a pair of bean-shaped organs that are located at the bottom of the ribcage in the right and left sides of the back. The kidneys filter waste out of the blood and produce urine, a yellow fluid, to carry wastes out of the body. Urine travels through tubes called ureters from the kidneys to the bladder, where it is stored temporarily, and then through the urethra as it is voided. Urine is generally sterile, but sometimes bacteria or, more rarely, yeast can move from the skin outside the urethra and migrate back up the urinary tract to cause a urinary tract infection.

    Most UTIs are considered uncomplicated and are easily treated. However, if they are not addressed, the infection may spread up through the ureters and into the kidneys. A kidney infection is more dangerous and can lead to permanent kidney damage. In some cases, a urinary tract infection may lead to an infection in the bloodstream (sepsis, septicemia) that can be life-threatening.

    People with kidney disease or with other conditions that affect the kidneys, such as diabetes or kidney stones, and people with weakened immune systems may be more prone to frequent, repeated and/or complicated UTIs.

    For more on how the urine culture is performed, see the "What is being tested?" section.

  • When is it ordered?

    A urine culture may be ordered when a person has symptoms that indicate the possibility of a urinary tract infection (UTI), such as:

    • A strong, persistent desire to urinate
    • A burning sensation during urination
    • A cloudy, strong-smelling urine
    • Lower back pain

    People with UTIs may also have pressure in the lower abdomen and small amounts of blood in the urine. If the UTI is more severe and/or has spread into the kidneys, it may cause flank pain, high fever, shaking, chills, nausea or vomiting.

    Sometimes, antibiotics may be prescribed without requiring a urine culture for young women with signs and symptoms of a UTI and who have an uncomplicated lower urinary tract infection. If there is suspicion of a complicated infection or symptoms do not respond to initial therapy, then a culture of the urine is recommended.

    Pregnant women without any symptoms are recommended to be screened during the first trimester or first prenatal visit for bacteria in their urine, which could affect the health of the developing baby.

    A urine culture may be ordered with a urinalysis or as follow up to abnormal results on a urinalysis.

  • What does the test result mean?

    Results of a urine culture are often interpreted in conjunction with the results of a urinalysis and with regard to how the sample was collected and whether symptoms are present. Since some urine samples have the potential to be contaminated with bacteria normally found on the skin (normal flora), care must be taken with interpreting some culture results.

    Typically, the presence of a single type of bacteria growing at high colony counts is considered a positive urine culture. For clean catch samples that have been properly collected, cultures with greater than 100,000 colony forming units (CFU)/mL of one type of bacteria usually indicate infection. In some cases, however, there may not be a significantly high number of bacteria even though an infection is present. Sometimes lower numbers (1,000 up to 100,000 CFU/mL) may indicate infection, especially if symptoms are present. Likewise, for samples collected using a technique that minimizes contamination, such as a sample collected with a catheter, results of 1,000 to 100,000 CFU/mL may be considered significant.

    Although a variety of bacteria can cause UTIs, most are due to Escherichia coli, bacteria that are common in the digestive tract and routinely found in stool. Other bacteria that may cause UTIs include species of Proteus, Klebsiella, Enterococcus, and Staphylococcus. Occasionally, a UTI may be due to a yeast, such as Candida albicans; urethritis is often due to a sexually transmitted disease such as herpes, chlamydia, or gonorrhea.

    A culture that is reported as "no growth in 24 or 48 hours" usually indicates that there is no infection. If the symptoms persist, however, a urine culture may be repeated on another sample to look for the presence of bacteria at lower colony counts or other microorganisms that may cause these symptoms. The presence of white blood cells and low numbers of microorganisms in the urine of a symptomatic person is a condition known as acute urethral syndrome.

    If a culture shows growth of several different types of bacteria, then it is likely that the growth is due to contamination. This is especially true in voided urine samples if the organisms present include Lactobacillus and/or other common nonpathogenic vaginal bacteria in women. If the symptoms persist, the healthcare practitioner may request a repeat culture on a sample that is more carefully collected. However, if one type of bacteria is present in significantly higher colony counts than the others, for example, 100,000 CFUs/mL versus 1,000 CFUs/mL, then additional testing may be done to identify the predominant bacteria.

    If a culture is positive, susceptibility testing may be performed to guide treatment. Any bacterial infection may be serious and can spread to other areas of the body if not treated. Pain is often the first indicator of an infection. Prompt treatment, usually with antibiotics, will help to alleviate the pain.

  • Is there anything else I should know?

    Women and girls get urinary tract infections (UTIs) more often than men and boys. Even preteen girls may have frequent UTIs. For men and boys with a culture-proven UTI, further tests may be done to rule out the presence of a kidney stone or structural abnormality that could cause the infection.

    If someone has frequent and/or recurrent UTIs, culture and susceptibility testing may be performed with each infection. For those who have frequent UTIs, their bacteria may become resistant to antibiotics over time, making careful selection of antibiotic and the full course of treatment essential.

  • The doctor’s office called back to say they need a new urine sample, the first was contaminated. What happened?

    If the skin and genital area were not cleaned well prior to collecting the sample, the urine culture may grow three or more different types of bacteria and is assumed to be contaminated. The culture will be discarded because it cannot be determined if the bacteria originated inside or outside the urinary tract. A contaminated specimen can be avoided by following the directions to carefully clean yourself and by collecting a mid-stream clean catch urine sample.

  • My doctor said I had symptoms of a urinary tract infection and prescribed antibiotics without performing a urine culture. Why?

    Bacteria known as Escherichia coli (E. coli) cause the majority of lower urinary tract infections. This microorganism is usually susceptible to a variety of antibiotics, such as trimethoprim-sulfamethoxazole, ciprofloxacin, and nitrofurantoin. In most people with uncomplicated disease, the UTI will be resolved after therapy with one of these antibiotics. Based on this information, your healthcare practitioner may prescribe one of them without performing a culture.

  • What happens if my infection goes untreated?

    If your infection is not treated, it can move from the lower urinary tract to the upper urinary tract and infect the kidney itself, and possibly, enter the bloodstream, causing septicemia. Signs and symptoms of septicemia include fever, chills, elevated white blood cell count, and fatigue. If a healthcare practitioner suspects that you have septicemia, he or she will typically order a blood culture and will prescribe antibiotics accordingly.

  • What puts me at risk for recurrent urinary tract infections?

    There are a wide variety of factors that predispose a person to get a UTI. After the neonatal period, the incidence in females is higher than in males due to the anatomical differences in the female genitourinary tract. In infants and young children, congenital abnormalities are associated with UTI. In adults, sexual intercourse, diaphragm use, diabetes, pregnancy, reflux, neurologic dysfunction, kidney stones, and tumors all predispose to UTI. In a hospital, nursing home, or home care setting, indwelling catheters and instrumentation of the urinary tract are major contributing factors to acquiring a UTI.

View Sources

Sources Used in Current Review

(2012 May 24). Urinary Tract Infections in Adults. National Kidney and Urologic Diseases Information Clearinghouse, NIDDK. [On-line information]. Available online at http://kidney.niddk.nih.gov/KUDiseases/pubs/utiadult/index.aspx. Accessed December 2015.

(© 1995-2015). Bacterial Culture, Aerobic, Urine. Mayo Clinic Mayo Medical Laboratories [On-line information]. Available online at http://www.mayomedicallaboratories.com/test-catalog/Overview/8105. Accessed December 2015.

Brusch, J. (Updated Aug 19, 2015). Cystitis in Females. Medscape Reference [On-line information]. Available online at http://emedicine.medscape.com/article/233101-overview. Accessed December 2015.

(July 23, 2015) Mayo Clinic. Urinary Tract Infections, Causes. Available online at http://www.mayoclinic.org/diseases-conditions/urinary-tract-infection/basics/causes/con-20037892. Accessed January 2015.

Sources Used in Previous Reviews

Thomas, Clayton L., Editor (1997). Taber's Cyclopedic Medical Dictionary. F.A. Davis Company, Philadelphia, PA [18th Edition].

Pagana, Kathleen D. & Pagana, Timothy J. (2001). Mosby's Diagnostic and Laboratory Test Reference 5th Edition: Mosby, Inc., Saint Louis, MO.

Pagana, Kathleen D. & Pagana, Timothy J. (© 2007). Mosby's Diagnostic and Laboratory Test Reference 8th Edition: Mosby, Inc., Saint Louis, MO. Pp 981-983.

Wu, A. (2006). Tietz Clinical Guide to Laboratory Tests, Fourth Edition. Saunders Elsevier, St. Louis, Missouri. Pp 1621-1622.

Thomas, Clayton L., Editor (1997). Taber's Cyclopedic Medical Dictionary. F.A. Davis Company, Philadelphia, PA [18th Edition]. Pp 2037-2038.

Forbes, B. et. al. (© 2007). Bailey & Scott's Diagnostic Microbiology, Twelfth Edition: Mosby Elsevier Press, St. Louis, Missouri. Pp 842-855.

(2007 August). Your Urinary System and How It Works. National Kidney and Urologic Diseases Information Clearinghouse [On-line information]. Available online at http://kidney.niddk.nih.gov/kudiseases/pubs/yoururinary/. Accessed March 2009.

(2008). Existing Recommendations for Bacteriuria Screening Upheld. Medscape from Reuters Health Information [On-line information]. Available online at http://www.medscape.com/viewarticle/576888. Accessed March 2009.

Stanley Hellerstein, S. (2008 September 17). Urinary Tract Infection. EMedicine [On-line information]. Available online at http://emedicine.medscape.com/article/969643-overview. Accessed March 2009.

(2005 November, Revised). Approach to the Renal Patient. Merck Manual for Healthcare Professionals [On-line information]. Available online at http://www.merck.com/mmpe/sec17/ch226/ch226b.html#sec17-ch226-ch226b-21. Accessed March 2009.

Barclay, L. and Murata, P. (2007 May 17). Perineal/Genital Cleaning During Urine Collection May Minimize Contamination. Medscape Medical News [On-line CME]. Available online at http://www.medscape.com/viewarticle/556640. Accessed March 2009.

McCarter, Y.S., E.M. Burd, G.S. Hall, and M. Zervos. 2009. Cumitech 2C, Laboratory Diagnosis of Urinary Tract Infections. Coordinating ed. S.E. Sharp. ASM Press, Washington, DC.

Kasper DL, Braunwald E, Fauci AS, Hauser SL, Longo DL, Jameson JL eds (2005). Harrison's Principles of Internal Medicine. 16th Edition, McGraw Hill, Pp 1715 and 1718.

MedlinePlus Medical Encyclopedia. Urine culture, catheterized. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003752.htm. Accessed April 2010.

Pagana, K. D. & Pagana, T. J. (© 2011). Mosby's Diagnostic and Laboratory Test Reference 10th Edition: Mosby, Inc., Saint Louis, MO. Pp 1017-1019.

(2012 May 24). Urinary Tract Infections in Adults. National Kidney and Urologic Diseases Information Clearinghouse, NIDDK. [On-line information]. Available online at http://kidney.niddk.nih.gov/KUDiseases/pubs/utiadult/index.aspx. Accessed October 2012.

(© 1995-2012). Bacterial Culture, Aerobic, Urine. Mayo Clinic Mayo Medical Laboratories [On-line information]. Available online at http://www.mayomedicallaboratories.com/test-catalog/Overview/8105. Accessed October 2012.

Johnson, J. et. al. (2011 December 4). Do Urine Cultures for Urinary Tract Infections Decrease Follow-up Visits? Medscape Today News from J Am Board Fam Med. V 24(6):647-655. [On-line information]. Available online at http://www.medscape.com/viewarticle/753802. Accessed October 2012.

Brusch, J. (Updated 2012 February 1). Cystitis in Females. Medscape Reference [On-line information]. Available online at http://emedicine.medscape.com/article/233101-overview. Accessed October 2012.

Graneto, J. and Bechtel, K. (2011 November 8). Emergent Management of Pediatric Patients with Fever. Medscape Reference [On-line information]. Available online at http://emedicine.medscape.com/article/801598-overview#a1. Accessed October 2012.

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