A urine culture is a test to find and identify germs (usually bacteria) that may be causing a urinary tract infection (UTI). Urine in the bladder normally is sterile-it does not contain any bacteria or other organisms (such as fungi). But bacteria can enter the urethra and cause an infection.
A urine sample is kept under conditions that allow bacteria and other organisms to grow. If few or no organisms grow, the test is negative. If organisms grow in numbers large enough to indicate an infection, the culture is positive. The type of organisms causing the infection are identified with a microscope or by chemical tests.
Urinary tract infections are more common in women and girls than in men. This may be partly because the female urethra is shorter and closer to the anus, which allows bacteria from the intestines to come into contact more easily with the urethra. Men also have an antibacterial substance in their prostate gland that reduces their risk.
If the urine culture is positive, other tests may be done to help choose which antibiotic will do the best job treating the infection. This is called sensitivity testing.
Why It Is Done
A urine culture may be done to:
- Find the cause of a urinary tract infection (UTI).
- Make decisions about the best treatment for a UTI. This is called sensitivity testing.
- Find out whether treatment for a UTI worked.
How To Prepare
You do not need to do anything before you have this test. If you are taking or have recently taken antibiotics, tell your doctor.
You will need to collect a urine sample. Avoid urinating just before having this test.
Talk to your doctor about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results will mean. To help you understand the importance of this test, fill out the medical test information form(What is a PDF document?).
How It Is Done
You will be asked to collect a clean-catch midstream urine sample for testing. The first urine of the day is preferred because bacterial levels will be higher.
Clean-catch midstream urine collection
This method helps protect the urine sample from germs that are normally found on the penis or vagina.
Wash your hands before collecting the urine.
- If the collection container has a lid, remove it carefully and set it down with the inner surface up.
- Clean the area around your penis or vagina.
- A man should retract the foreskin, if present, and clean the head of his penis thoroughly with medicated towelettes or swabs.
- A woman should spread open the folds of skin around her vagina with one hand, then use her other hand to clean the area around her vagina and urethra thoroughly with medicated towelettes or swabs. She should wipe the area from front to back to avoid spreading bacteria to the vagina that is normally found around the anus.
- Begin urinating into the toilet or urinal. A woman should continue holding apart the folds of skin around the vagina while she is urinating.
- After the urine has flowed for several seconds, place the collection container in the stream and collect about 60 mL (2 fl oz) of this "midstream" urine without stopping the flow.
- Do not touch the rim of the container to your genital area.
- Do not get toilet paper, hair, feces, or menstrual blood in the urine sample.
- Finish urinating into the toilet or urinal.
- Carefully replace the lid on the container. Wash your hands. Return the urine sample to the lab. If you are collecting the urine at home and cannot get it to the lab within an hour, refrigerate the sample. It can be refrigerated for up to 24 hours. Follow the instructions from your lab.