Wireless device rapidly detects E. coli in potentially contaminated water
MedWire News: Researchers have developed an accurate and economic sensor-based device for detecting Escherichia coli in water samples within 8 hours.
Current methods to detect E. coli, a bacterium highly indicative of the presence of fecal matter in water, typically require 24-48 hours to yield results. In addition, these methods are unable to rapidly react to changing conditions, do not perform well in complex water matrices, and often require a trained specialist to analyze the sample.
To overcome these barriers, Jeffrey Talley (Johns Hopkins University, Baltimore, Maryland, USA) and colleagues developed an autonomous, wireless, in situ (AWISS) battery-powered device containing a prototype optical sensor that is capable of measuring changes in fluoresce intensity in potentially contaminated water samples.
Changes in fluorescence intensity occur when the E. coli-synthesized beta-glucuronidase enzyme hydrolyzes the reagent's glycosidic bond, releasing fluorophores into the solution.
When the team tested the unit in the laboratory, they found that the AWISS device was capable of detecting low concentrations of E. coli (less than 100 colony-forming units [CFU]/100 mL) in less than 8 hours. Higher concentrations (more than 5000 CFU/100 mL) indicative of possible sewage overflow were detected in under 1 hour.
Testing of bacterial water quality of the St Joseph River in South Bend, Indiana, USA was then performed using the AWISS device for a 7-day period. The team collected a water sample every 6 hours into a custom-designed stop-flow reaction chamber, which was then injected with a soluble reagent.
Data about the sample was then transmitted wirelessly to a remote monitoring station. Of the obtained 19 samples, 15 were compared with culture methods approved by the US Environmental Protection Agency (USEPA).
Of these verified samples, 13 were found to correctly identify the presence or absence of an E. coli concentration defined as significant by the USEPA and Indiana Department of Environmental Management thresholds of 125 CFU/100 mL.
"Even at lower concentrations, the results obtained from the AWISS are more timely and relevant that the current USEPA-approved culture methods," write the authors in the journal Environmental Engineering Science.
Talley and team says that the findings "indicate that the AWISS prototype holds promise as a tool for rapidly detecting and alerting authorities to the presence of E. coli in recreational waters."
By Ingrid Grasmo