A Strategy to Establish a Quality Assurance/Quality Control Plan for the Application of Biosensors for the Detection of E. coli in Water

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.

Keywords: ">d-glucuronides’; E. coli; MUG substrate; drinking water; quality assurance/quality control; rapid bacterial detection; β-.

Figure 1

Time series of hydrolysis of MUG by different strains of E. coli (100 CFU/mL).

Figure 2

Effect of temperature of incubation on GUD activities in E. coli (100 CFU/mL) as measured by fluorescence intensity.

Figure 3

Comparison of GUD response to MUG obtained from different suppliers. Note: no increasing trend in the relative fluorescence units (RFU) was noted in the control samples. The data points are the average of three replicates.

Figure 4

Impact of different solvents for dissolving MUG on assay sensitivity (fluorescence intensity).

Figure 5

Impact of buffer strength on fluorescence intensity.

Figure 6

Effect of storage condition of E. coli on GUD activities.

Figure 7

Effect of pH and salinity on the fluorescence signal in the biosensor assay. Note: Spiked water samples contained 1000 CFU/mL E. coli.

Figure 8

Effect of different assay conditions on fluorescence intensity. Note: The results have been obtained based on three replicates of each sample from three independent experiments; the units are RFU (arbitrary units) samples contained 100 CFU/mL E. coli.