If an infection is suspected, it is important to know what type of bacteria (if any) is present, how much is in the urine, and what antibiotic can be used to treat the bacteria.
But urine samples also contain many other things – such as urea and salts, and varying levels of acidity – that can affect the detection of bacteria. Cultivating the urine sample on nutrient agar media (a polysaccharide composed of a large number of galactose molecules) removes anything that could interfere with bacterial growth.
This technique also allows individual cells in the sample to form spots (called colonies) that are easy to count. The shape, color, size, and even smell of the colonies can be used to indicate what types of bacteria are present. Some samples contain several different types of bacteria, which must be isolated and tested separately.
It is surprisingly difficult to find alternative methods that can do all these essential things without being affected by other components of urine.
The results have to wait a few days
The current method of culturing the sample with agar takes several days to determine which antibiotics would best treat the infection – which is too long for the patient to wait. This means that doctors have to start therapy even before they get the test results.
Sometimes this means that patients have to change medications after a few days, which is not at all advisable since the use of more antibiotics encourages resistance, which worsens the problem in the future. That is why there are numerous attempts to improve these forms of microbiological testing.
New technologies have yet to be improved
Existing tests can detect bacterial and antibiotic resistance in urine, but doctors need tests that can detect this more quickly to speed up the treatment process. These methods ideally need to be portable and inexpensive so that they can be used without sending samples to a laboratory.
Certain inventions hint that such a thing would soon be possible. For example, digital cameras can detect whether bacterial cells are growing on a microscopic scale or in diluted urine. Although these methods take a few hours to see if the antibiotic will work, it is still much faster than agar assays.
Some hospital laboratories also now routinely use a technique called mass spectrometry, which measures fragments of a bacterial sample and compares them to a database to identify the bacteria. This speeds up the testing of colonies found on agar plates, replacing the days of work previously required to accurately identify bacterial species.
But while these new methods show promise, many are still in the research phase. And in the case of mass spectrometry, antibiotic susceptibility testing still requires agar plating. Many of these technologies are also complicated and expensive, so urine samples still have to be transported to hospital laboratories for analysis.
Fast, reliable and affordable tests needed
In the future, such technologies should reduce the time it takes for a patient to receive a diagnosis, while being as reliable and affordable as agar. This is something that many researchers are working on.
It is vital that some of the new, rapid tests for urinary infections enter routine practice, to ensure that each case is treated quickly and effectively with the appropriate antibiotic.
However, experts still think it will be some time before these and other new technologies are routinely used for diagnosis.
For now, people who suspect they have a urinary tract infection still need to see their GP who will refer them for a urine culture test to make a diagnosis and give the appropriate medication.
Comments are closed.