New light sensor can detect E.coli in minutes

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Researchers have developed a sensor capable of detecting E.coli bacteria in 15-20 minutes, much faster than traditional lab tests. The sensor, which uses a beam of light in combination with a virus that latches onto target bacteria, has been described in journal Optics Letters.

E.coli can be transmitted in contaminated food and water, posing particular risks to children and the elderly. In the late spring of 2011, a serious outbreak of E.coli bacteria killed 50 people in Germany and sickened thousands of others. 

The new sensor developed by researchers from the Photonics Research Center at the University of Quebec in Outaouais, Canada and collaborators from the Indian Institute of Technology Kanpur, Uttar Pradesh, India can quickly and cost-effectively detect E.coli over a wide temperature range.

‘Using currently available technologies, which are mostly based on amplification of the sample, it takes several hours to days to detect the presence of bacteria,’ said Saurabh Mani Tripathi, a physicist and collaborator from the Indian institute. ‘A fast and accurate detection alternative is, therefore, preferable over the existing technology.’

According to Tripathi, faster tests for the bacteria could lead to faster treatment of patients, as well as to cheaper and easier environmental monitoring.

The new sensor uses bacteriophages – viruses that can naturally latch onto and kill bacteria – to detect the presence of E.coli. The viruses are bonded to the surface of an optical fibre and will grab E.coli bacteria from a sample and keep them attached. When a beam of light strikes the surface of the fibre, the presence of E.coli shifts the wavelength of the light, which acts as a sign of bacterial contamination.

The optical properties of the fibres used in bacteria detection can be altered by changes in temperature. Therefore, sensors can give inaccurate readings even if a studied sample gets too hot or too cold.

Tripathi and his colleagues overcame this challenge through the use of an additional optical component and in effect cancelling out temperature-induced shifts. Their new device is temperature insensitive over an approximately 20°C range, starting at room temperature and going up to 40°C.

The temperature insensitivity makes the sensor more practical for outdoor applications, such as monitoring water reservoirs on-site, Tripathi said. He also noted that the food industry and pathology labs are other possible users of the new sensor. The sensor can be modified to detect other strains of bacteria by changing the bacteriophage.

‘Pathogenic bacterial infection is one of the biggest causes of death, and a fast response time is much needed for timely detection and subsequent cure of bacterial infection,’ Tripathi said. ‘I'm excited by the very low time [our sensor needs] to accurately detect the presence of E. coli bacteria in water collected from environments at different temperatures.’

The research group is currently collaborating with Security and Protection International, a Canadian company, to explore commercialising their device. Professor Wojtek J Bock, director of the research group, said that costs are hard to estimate at this stage of the research, but that the team hopes to deliver portable units for a few thousand dollars.

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Further Information:

University of Quebec 

Kanpur Institute Of Technology

Research Paper in Optics Letters