Demonstration of an optical biosensor for the detection of faecal indicator bacteria in freshwater and coastal bathing areas
ColiSense, an early warning system developed for Escherichia coli detection, is assessed using environmental samples. The system relies on the detection of β-glucuronidase (GUS), a biomarker enzyme for E. coli. In contrast with other rapid GUS-based methods, ColiSense is the only method that uses 6-chloro-4-methyl-umbelliferyl-β-d-glucuronide (6-CMUG) as a fluorogenic substrate. The system measures a direct kinetic response of extracted GUS, and the detection was carried out in the absence of particles or bacteria. It is necessary to evaluate the system with environmental samples to establish the relationship between faecal indicator bacteria E. coli and the response measured by the ColiSense. This paper presents the results of tests carried out with the ColiSense system for 2 trials, one conducted with freshwater samples collected from rivers in the Dublin area and a second conducted with seawater samples from coastal areas collected over the bathing season. A positive linear correlation was found between E. coli (MPN 100 mL−1) and ColiSense response (R2 = 0.85, N = 125, p < 0.01) for the seawater sample. A ColiSense response threshold was identified as 0–1.8 pmol min−1 100 mL−1, equivalent to 0–500 E. coli 100 mL−1. Using this threshold, 96.8% of the samples were correctly classified as being above or below 500 E. coli 100 mL−1 by the ColiSense system. Results presented demonstrate that the ColiSense system can be used as an early warning tool with potential for active management of bathing areas by providing results in 75 min from sample collection.
KeywordsFaecal pollution E. coli β-Glucuronidase Water Optical sensor
The authors wish to thank Fingal City Council team (George Sharpson, Martin A. Daly, Orla P. Haldon, Louise McIntyre, and Sinead Clarke) for facilitating the testing during a busy bathing season, for providing the bathing water samples, and for sharing the microbiological laboratory results.
This work was performed as part of a Feasibility Study for an Innovation Partnership Programme IP/2016/0437/Y and was funded by Enterprise Ireland and Fingal City Council.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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