Aptamer-based surface plasmon resonance detection of legionella pneumophila in water systems ****************

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Legionnaires' disease is caused by the bacterium Legionella pneumophila (Lp). Many water systems, such as cooling towers and hot water distribution systems, are potentially contaminated by Lp. Production of aerosols by such systems enables the transmission of Lp to humans. Many outbreaks of this disease are reported each year. For example, Quebec City suffered from a major outbreak in 2012. Surveillance of water systems is crucial for limiting infection risks and outbreaks. Detection of Lp in water systems is currently performed by culturing or qPCR. These methods are expensive and tedious, and in the case of culturing, take up to two weeks to perform. In collaboration with Magnus Chemical Ltd, we propose to develop a novel detection method based on the recognition of Lp by aptamers, short DNA sequences that folds into structures binding specifically to a target. The aptamers will be developed using the "Systemic Evolution of Ligands through EXponential enrichment" (SELEX) technique. Specificity and versatility of the aptamers will be tested against a diversity of Lp isolates and other bacterial species frequently isolated form water systems. The best aptamers will be immobilized on the surface of a Surface Plasmon Resonance biosensor (SPR) prism and their ability to detect Lp in man-made water samples will be evaluated. The system will then be optimized by modifying the surface chemistry and by using a second aptamer coupled to gold nanoparticle in a "sandwich assay" to amplify the signal and improve the limit of detection (LOD). To further lower the LOD, a Lab-on-a-Chip strategy will be developed for the Lp enrichment in water samples. The aim is to reach a LOC of 10-100 CFU Lp /ml (maintenance levels). Next, the novel detection method will be tested with real water samples and compared to the current detection methods. This project should allow the development of a novel detection strategy that could be miniaturized and used to monitor the presence of Lp in water systems in a continuous manner. At term, this project will improve timely response to initiate treatment of water systems to minimize risk of Legionnaires' disease.**************************