Abstract
Rapid bacterial detection using biosensors is a novel approach for microbiological testing applications. Validation of such methods is an obstacle in the adoption of new bio-sensing technologies for water testing. Therefore, establishing a quality assurance and quality control (QA/QC) plan is essential to demonstrate accuracy and reliability of the biosensor method for the detection of E. coli in drinking water samples. In this study, different reagents and assay conditions including temperatures, holding time, E. coli strains and concentrations, dissolving agents, salinity and pH effects, quality of substrates of various suppliers of 4-methylumbelliferyl glucuronide (MUG), and environmental water samples were included in the QA/QC plan and used in the assay optimization and documentation. Furthermore, the procedural QA/QC for the monitoring of drinking water samples was established to validate the performance of the biosensor platform for the detection of E. coli using a culture-based standard technique. Implementing the developed QA/QC plan, the same level of precision and accuracy was achieved using both the standard and the biosensor methods. The established procedural QA/QC for the biosensor will provide a reliable tool for a near real-time monitoring of E. coli in drinking water samples to both industry and regulatory authorities.
Highlights
Microbiological testing can provide valuable information only if sampling plans and methodology are properly designed and performed
We identified specific bacterial enzymatic-biochemical signatures that can be used in a custom designed opto-electronic biosensor platform for the detection of E. coli and other bacterial cells in water samples [5,6]
Three E. coli strains were evaluated for GUD activities, and the strain (ATCC 25922) with the highest GUD activity was selected for further studies (Figure 1)
Summary
Microbiological testing can provide valuable information only if sampling plans and methodology are properly designed and performed. Our innovative method requires minimum processing and only detects viable bacterial cells It relies on a unique reaction chemistry that enhances the quality and the intensity of measureable signals providing a near real-time assay. Some significant factors such as the sensitivity (detection limit) and specificity of the assays were tested for both tap and environmental waters and have shown a sensitivity threshold of seven E. coli cells per reaction vial. This demonstrated the highest sensitivity of the BDS1000 biosensor that was better or comparable to the sensitivity of other hand-held fluorescence detector [11]. The result showed that no significant interference from non-GUD sources in the water samples existed
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