Fibre optic sensor offers rapid detection of E.coli bacteria

The team from the Photonics Research Center at the University of Quebec, under direction of Prof Wojtek J. Bock and collaborators from the Indian Institute of Technology Kanpur, built the new sensor that can detect E.coli over a wide range of temperatures. The researchers describe the sensor in a paper in Optics Letters.

"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. A fast and accurate detection alternative is, therefore, preferable over the existing technology," said Saurabh Mani Tripathi, a physicist at the Indian Institute of Technology Kanpur.

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

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

One of the challenges of using optical fibres for bacteria detection is that temperature changes can alter the optical properties of the materials.

Tripathi and his colleagues overcame this by adding an additional optical component, effectively negating temperature-induced shifts. Their device is said to be temperature insensitive over an approximately 20-degree Celsius range, starting at room temperature and going up to 40-degrees Celsius.

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

The research group is currently collaborating with Security and Protection International, Inc, a Canadian company, to explore commercialisation of their device. Bock 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.

"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 in a statement. "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."