Why we still use a 140-year-old method to diagnose urinary tract infections: ScienceAlert

If you’ve ever 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 going to the doctor, providing a urine sample, and waiting for results can also be a pain.

Urinary tract infections are extremely common, and nearly half of all women will develop a UTI at some point in their lives. To test for a UTI, a urine sample needs to be sent to a hospital microbiology laboratory.

There, they’ll look for the bacteria that cause the infection and check if those bacteria are resistant to antibiotics.

This is usually done by using a technique called agar plating. A small amount of urine is placed in a small disc filled with a nutrient jelly called agar, which is incubated 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 an age where we can instantly detect a COVID-19 infection, measure blood sugar with an e-reader, and wear a watch that tracks heart rate, why do we still use this old method that takes days to accurately diagnose a UTI?

it’s actually pretty smart

If an infection is suspected, it’s important to know what types of bacteria are present (if any), how many bacteria are in the urine, and which antibiotics can treat these bacteria.

But urine samples can also contain many other substances—such as urea and salts, as well as varying degrees of acidity—that could interfere with bacterial detection. Applying urine to the agar removes anything that might interfere with bacterial growth.

This technique also allows individual cells in a sample to form spots (called colonies) that are easy to count. The shape, color, size, and even smell of the colony can be used to indicate what types of bacteria are present.

Some samples contained several different types of bacteria, and these had to be isolated and tested individually.

It’s hard to find alternatives that can do all these important things without being affected by other urine components.

most famous method

We have extensive experience using the agar plate technique as we have been using it for many years. This means that we know very well how to use these results – not only in diagnosing a person’s infection, but (if necessary) in adjusting the treatment they are given.

But that doesn’t mean the system is perfect.

The current agar plate method takes days to determine which antibiotic will work best for the infection — which is too long for patients to wait. That means we have to start treating patients before we know the test results.

Sometimes this means patients have to switch medications after a few days, which is inconvenient and expensive. Using more antibiotics can exacerbate antibiotic resistance, making the problem worse in the future.

These questions help drive innovation in microbial testing.

New technology still needs improvement

While current tests can measure bacteria and antibiotic resistance in urine, we need tests that can be tested faster so that they can be tested before treatment.

Ideally, these methods need to be portable and inexpensive so that we can use them in the community without sending samples to the lab.

Recent developments suggest this is possible.

For example, digital cameras can detect whether bacterial cells are growing on a microscopic scale or in diluted urine. While these methods take hours to check if the antibiotic is working, it is still much faster than agar plates.

Some hospital labs also now routinely use a technique called mass spectrometry, which measures fragments of bacterial samples and compares them to databases to identify bacteria.

This speeds up testing of colonies found on agar plates, replacing days of work previously required to accurately identify bacterial species.

But while these new approaches show promise, many are still in the research phase. In the case of mass spectrometry, agar plates are still required for antibiotic susceptibility testing.

Many of these techniques are also too large and expensive for a GP or pharmacy—so urine samples still need to be transported to a hospital lab for analysis.

In the future, such technologies will need to reduce the time it takes for a person to receive a diagnosis, while maintaining the same price and accessibility as agar plates. This is what our lab is working towards.

We’ve found that we can make smaller, more portable tests that are as accurate as agar plating — and the results can be recorded with inexpensive digital cameras like smartphones.

Our next phase of research is to examine these “tiny tests” with real patient samples.

Crucially, some new, rapid UTI tests enter routine practice to ensure that each case is treated quickly and effectively with the right antibiotic.

However, it will be some time before these and other new technologies are routinely used for diagnosis. Currently, people who suspect they have a UTI still need to see their GP in order to be diagnosed and given appropriate medication.

Alexander Edwards, Associate Professor of Biomedical Technology, University of Reading and Sarah Needs, Postdoctoral Research Assistant, University of Reading

This article is republished from The Conversation under a Creative Commons license. Read the original text.

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