Why always an old diagnosis for urinary tract infections?

If you’ve had a urinary tract infection (UTI) before, you know how painful it can be. Not only because of the physical pain it causes, but because it can also be very painful to go to the doctor, provide a urine sample and wait for your results.

UTIs are extremely common, with almost half of women having one at some point in their lives. In order to test for a UTI, a urine sample must be sent to a hospital microbiology laboratory. There they will look for bacteria that cause infections and check if these bacteria are resistant to antibiotics. This is usually done using a technique called agar.

A small amount of urine is placed in a small round dish filled with a nutrient jelly called agar, which is kept warm overnight to allow any bacteria to grow. This common technique has been around for nearly 140 years and remains the clinical standard in many hospitals. But in a time when we can instantly test for a Covid-19 infection, measure blood sugar with an electronic meter, and wear wristwatches that track our heart rate, why do we still use that old method that takes days to accurately diagnose? a urinary tract infection?

It’s actually quite smart. If an infection is suspected, it is important to know what type of bacteria (if any) are present, how many are present in your urine, and which antibiotic these bacteria can be treated with. But urine samples can also contain many other substances, such as urea and salts, as well as different levels of acidity, which can affect the detection of bacteria. Smearing the urine on agar removes anything that might interfere with bacterial growth. This technique also allows individual cells in the sample to form drops (called colonies) that are easy to count. The shape, color, size, and even the smell of colonies can be used to indicate what types of bacteria are present.

The current agar plating method takes several days to identify which antibiotics would best treat the infection – too long for a patient to wait. This means we need to start treating patients before test results are known. Sometimes this means that patients have to switch medications after a few days, which is inconvenient and expensive. Using more antibiotics fuels antibiotic resistance, which makes the problem worse in the future. These issues are helping to drive innovation in microbiology testing.

Although current tests can measure bacterial and antibiotic resistance in urine, we need tests that can do this faster to allow testing to take place before treatment. Ideally, these methods should be portable and inexpensive so that we can use them in the community, without sending samples to labs. Recent advances suggest this might be possible. For example, digital cameras can detect whether bacterial cells are growing at the microscopic scale or in dilute urine.

Although these methods take a few hours to check if an antibiotic will work, it’s still much faster than agar. Some hospital labs 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 at the research stage. Many of these technologies are also too large and expensive for a GP or pharmacy. We’ve already discovered that we can make smaller, more portable tests that are just as accurate as agar – and the results can be recorded with an inexpensive digital camera such as a smartphone. Our next research step is to verify that these “small tests” work with real patient samples.

It will take some time before these and other new technologies are routinely used for diagnosis. For now, people who suspect they have a UTI should always see their GP in order to be diagnosed and given the appropriate medication.

((Edwards is Associate Professor of Biomedical Technology and Needs, Postdoctoral Research Associate, University of Reading; The Conversation)