About the Test
Purpose of the test
A urine culture test detects and identifies bacteria and yeasts in the urine, which may be causing a UTI.
Urine contains low levels of microbes, such as bacteria or yeasts, which move from the skin into the urinary tract and grow and multiply, causing a UTI.
Your doctor might order a urine culture if you have symptoms of a UTI, which can include a frequent urge to urinate, pain or burning during urination, cloudy or strong-smelling urine, or lower back pain.
Urine can be used to detect some sexually transmitted diseases (STDs). However, a urine culture is not the test of choice for STDs in adults. Some STDs such as chlamydia may be tested using a urine sample, but the testing method used detects chlamydia genetic material in the urine and is not a culture.
What does the test measure?
The urine culture is used, along with results from a urinalysis, to diagnose a UTI and identify the bacteria or yeasts causing the infection. If a urine culture is positive, susceptibility testing may be done to determine which antibiotics will inhibit the growth of the microbe causing the infection. The results will help your doctor determine which drugs are likely to be most effective in treating your infection.
When should I get this test?
A urine culture may be used to help diagnose infections of the kidneys or lower urinary tract. Typically, this test requires that the first urine voided in the morning be collected. The most common reason a urine culture is ordered is if you have symptoms of a UTI, including:
- A strong, frequent urge to urinate, even when you have just gone and there is little urine voided
- Pain and/or a burning sensation during urination
- Cloudy, strong-smelling urine
- Lower back pain
Additionally, a urine culture is used to screen pregnant women for asymptomatic bacteriuria, a condition in which significant amounts of bacteria are in the urine but do not cause symptoms. About 2% to 10% of pregnant women in the U.S. have this condition which can lead to a more serious kidney infection as well as an increased risk of preterm delivery and low birth weight.
Tell your doctor if you suspect an STD is causing symptoms so they can order the appropriate test. Urine cultures may be used to test for some STDs, but generally not for adults.
Finding a Urine Culture Test
How can I get a urine culture test?
Usually, your doctor orders a urine culture that is performed in the office of your health care provider or a lab. Often, a urine culture is done in conjunction with a urinalysis test. If you choose, you can order a urinalysis with reflex to culture online. The test includes a routine urinalysis and based on the presence of cells, protein, and other components, it can include a urine culture.
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 health care practitioner.
Can I take the test at home?
You can collect a sample at home for a urine culture and send it to a lab. UTI test kits are available online, or your doctor might provide a kit. Another option is to order an online urinalysis with reflex to culture that allows you to collect a urine specimen at home and send it to the participating lab.
At-home UTI tests are usually qualitative and test positive or negative. An in-lab urine culture allows laboratory professionals to study the colonies, their size, shape, and color to identify the type of bacteria.
Regardless of where or how you take the test, you should report the results to your doctor.
How much does the test cost?
The cost of a urine culture test depends on the type of test, where it is taken, and if you have insurance. Testing costs can include a doctor’s office visit, lab fee, and laboratory analysis.
Keep in mind that if you have insurance, the cost depends on your plan, and you are responsible for deductibles and copays that vary based on your plan. Refer to your doctor, lab, and health plan for cost details.
Taking a Urine Culture Test
Although there are several types of urine samples, the mid-stream clean catch is the type most commonly submitted for culture.
Before the test
Generally, no preparation is needed, but depending on the type of culture, you may be given special instructions. For example, you may be asked not to urinate for at least one hour before the test and/or to drink a glass of water 15 to 20 minutes before sample collection. This will help to ensure that you can produce enough urine for the test.
Sometimes you may be instructed to collect the first urine you void in the morning. Antibiotics taken prior to the test may affect your results. Tell your health care practitioner if you have taken antibiotics recently.
During the test
For the mid-stream clean catch, first wash your hands. Then, clean the genital area before collecting your urine. This reduces the potential to contaminate the urine with bacteria and cells from the surrounding skin during collection (particularly in women).
Start to urinate, let some urine fall into the toilet, and then collect one to two ounces of urine directly into the sterile container provided. Void the rest into the toilet. Do not allow the inside of the container to come into contact with skin and do not collect the urine from the toilet (or any other container). The provided container is sanitized and prepared especially for your specimen.
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 health care practitioner. The urine is collected in a sterile container at the other end of the tube. Rarely, a needle and syringe may be used to collect by aspirating urine directly from the bladder. For infants, a collection bag may be used to gather the specimen.
After the test
There are no restrictions after providing a sample for a urine culture. You can carry on with your everyday activities.
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 UTI. If there is suspicion of a complicated infection or symptoms do not respond to initial therapy, then a culture of the urine is recommended.
Urine Culture Test Results
Receiving test results
You can expect your urine culture results within three to four days of the specimen arriving at the laboratory if you order a kit online. But if you get the test directly through your health care provider, it can be as soon as one to two business days.
Interpreting test results
Results of a urine culture are often interpreted in conjunction with the results of a urinalysis and depend on how the sample was collected and whether symptoms are present. Some urine samples have the potential to be contaminated with bacteria normally found on the skin (normal flora). Test results generally reveal the number of colony-forming units (CFU) per milliliter.
Positive urine culture: 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)/milliliter of one type of bacteria usually indicate infection.
- In some cases, 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) indicate infection, especially if symptoms are present.
- 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 are generally considered significant.
Results from a urinalysis can be used to help interpret the results of a urine culture. For example, a positive leukocyte esterase (a marker of white blood cells) and nitrite (a marker for bacteria) can indicate a UTI.
Occasionally, a UTI may be due to yeast, such as Candida albicans. Although a variety of bacteria can cause UTIs, most are due to Escherichia coli (E. coli), bacteria that are common in the digestive tract and routinely found in stool. Other bacteria that commonly cause UTIs include:
- Proteus
- Klebsiella
- Enterobacter
- Staphylococcus
- Enterococcus
If a culture is positive, susceptibility testing may be performed to guide treatment.
Negative urine culture: A culture reported as “no growth in 24 or 48 hours” usually indicates no evidence of infection. But if symptoms persist, a urine culture may be repeated on another sample to look for the presence of bacteria at lower colony counts or other microorganisms that can cause symptoms. For example, if you are symptomatic, the presence of white blood cells and low numbers of microorganisms in your urine is known as acute urethral syndrome.
Contamination: If a culture shows several types of bacteria, the growth is likely due to contamination, especially in voided urine samples if the organisms include Lactobacillus and/or other common vaginal bacteria in women. If symptoms persist, your doctor may order a culture on a more carefully collected sample. But if one type of bacteria has significantly higher colony counts (like 100,000 versus 1,000 CFUs/mL), more testing can find the predominant bacteria.
A doctor can address detailed questions about UTIs, getting a urine culture, and your test results. Some questions that you might wish to review with your doctor include:
- If my test is positive, how quickly should I feel relief after beginning treatment?
- Are there any follow-up tests that may be beneficial given my test result?
- What puts me at risk for recurring UTIs?
