The process can identify the presence of E. coli bacteria in a urine sample in 25 minutes and could make UTI testing more widely available in developing nations and remote regions thanks to its potential to be made portable, and more cheaply than lab-based tests.
As well as a smartphone camera, the test, which could be adapted to detect a variety of bacterial infections, is said to take advantage of widely available reagents and new micro-engineered materials.
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Described in Biosensors and Bioelectronics, the test uses antibodies to capture bacterial cells in capillaries within a plastic strip, detecting and identifying the cells optically rather than through microbiological methods.
"Currently, bacterial infections in UTIs are confirmed via microbiological testing of a urine sample,” said Dr Nuno Reis, from Bath's Department of Chemical Engineering who led the development of the test. “That is accurate, but time-consuming, taking several days. We hope that giving medical professionals the ability to quickly rule in or rule out certain conditions will allow them to treat patients more quickly and help them make better decisions about the prescription of antibiotics."
According to Bath University, the lack of rapid diagnostics for UTIs has often led to a catch-all prescription of potentially unnecessary antibiotics, which increases the risk of bacteria becoming resistant to treatment, a phenomenon accepted as one of the biggest threats to global health.
The test is carried out by passing a urine sample over a ridged plastic micro-capillary strip, containing an immobilising antibody that recognises E. coli bacterial cells. If E. coli is present in the sample, antibodies in the reagents will bind with it, stopping it from passing through the section of plastic strip. Finally, an enzyme is added that causes a change in colour that can be picked up by a smartphone camera.
The system, which has passed the proof-of-concept stage, also measures the concentration of E. coli in the sample by analysing an image taken by the camera. The procedure is simple and could be manually operated or fully automated without any need for a mains power supply.
To date, bodies such as the US Food & Drug Administration have not granted approval to techniques that use smartphones - citing the potential for non-lab conditions and software updates to the phone to make tests unscientific. Dr Reis hopes that the way the test uses a variable scale to digitally compare the pixels within an image will convince regulators to allow the treatment to move toward eventual production.
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