Urinary tract infections (UTI) affect the bladder and/or the kidneys. Urine is made by your kidneys and collects in your bladder until you urinate. Normally, urine in the bladder contains no bacteria - it is sterile – but if bacteria or yeast get into the urinary tract, they can cause an infection.
Bladder infections are common, and they mostly happen to women. They are due to bacteria getting into the urethra – the tube that runs from the bladder to the vagina or penis – and travelling up into the bladder. Bladder infections are known as uncomplicated UTIs or cystitis. A complicated UTI is when the infection travels beyond the bladder up to the kidneys. This is a more serious condition.
In many situations, a urine culture is not needed before you start treatment. If you are a woman and have symptoms that are typical of bladder infection, you can seek help from your GP or pharmacist who may prescribe antibiotics without ordering tests. Antibiotic treatment can usually be started based on your symptoms alone or on the results of a dipstick urinalysis test. This will usually be an antibiotic that is known to work in most cases of UTI. By far the most common type of bacteria found in a UTI is E. coli and it can be treated successfully with several different antibiotics.
Who is more likely to need a urine culture?
Yeast infections
Yeast infections as the cause of UTIs are rare, and generally only occur when someone has a urinary catheter or other urinary instrumentation in place – usually in hospital. When yeast is found in a urine sample, it may be because the sample has been contaminated by yeast infection (thrush) of the vaginal area.
How is the sample tested?
When the sample arrives in the lab it is investigated under a microscope or placed in a cell counting instrument where the cells are counted. If there are large numbers of white blood cells – called ‘pus cells’ – it is very likely you have a UTI.
A small amount of urine is then cultured. To do a urine culture, a sample of your urine will be put into a special substance called a culture medium that helps the bacteria or yeasts to grow. Plates of culture medium are placed in an incubator for 24 hours. The culture is usually termed ‘negative’ if no growth is found on the plates after 24 hours. If there are bacteria or yeasts growing, they are counted.
Next, susceptibility tests are carried out to decide which antimicrobials are likely to be effective in treating the infection.
Sample
You need to collect a mid-stream urine sample. This means you don’t collect the first or last part of the urine that comes out. This is important because it is very easy for your urine sample to be contaminated if it touches the skin around your urethra. By only collecting the mid-stream of urin, bacteria on your skin can be washed away in the first part of your urine stream. Everyone has bacteria on their skin including around the opening of the urethra that opens into the vagina or penis.
Your doctor, collection centre or pharmacist will give you a sterile pot with a lid and a bag in which to put it. Here are a few steps:
If you can’t hand your sample in within an hour you need to put it in the fridge. Make sure you don’t freeze it.
Any preparation?
None.
Reading your test report
Your results will generally be presented along with those of your other tests on the same form. You will see separate columns or lines for each of these tests.
The number of organisms in a urine sample is given as colony forming units per litre (CFU/L). Your result will be negative or positive.
A negative culture – no pus cells or bacteria found in your urine culture. | This means that there is no laboratory evidence of infection. UTI is unlikely and antibiotic treatment is usually not indicated. However, if your symptoms continue you may be asked to give another urine sample so that another culture can be done. |
A positive culture - pus cells and bacteria have been found in your urine culture. You have symptoms of UTI. | If you have symptoms of a UTI, and your result shows you have pus cells and bacteria, it is likely you will have an infection and you need prompt antibiotic treatment to prevent any possible complications. |
Bacteria in your urine culture. You have no symptoms of UTI. | If you have no symptoms of a UTI but there are bacteria in the urine sample, this is termed ‘asymptomatic bacteriuria’ and antibiotic treatment should be avoided. Treating with antibiotics where there are no symptoms does not give any benefit and may cause side-effects. It can also lead to antibiotic-resistant bacteria. Treatment of asymptomatic bacteriuria is only needed in pregnant women. |
A mix of bacterial types or a large number of skin cells. | If mixed bacterial types are found on urine culture or there are a large number of skin cells, this usually points to the sample having been contaminated when it was collected. Another sample needs to be collected. |
The choice of tests your doctor makes will be based on your medical history and symptoms. It is important that you tell them everything you think might help.
You play a central role in making sure your test results are accurate. Do everything you can to make sure the information you provide is correct and follow instructions closely.
Talk to your doctor about any medications you are taking. Find out if you need to fast or stop any particular foods, medications or supplements. These may affect your results. Ask:
Pathology and diagnostic imaging reports can be added to your My Health Record.
You and your healthcare provider can now access your results whenever and wherever needed. Get further trustworthy health information and advice from healthdirect.