Wireless sensor device detects E. coli in less than eight hours

The autonomous, wireless, in-situ (AWISS) device, which contains a prototype optical sensor, is designed to measure changes in fluorescence intensity in a water sample. In the presence of E. coli bacteria, an enzymatic reaction causes an increase in fluorescence. According to the researchers, the battery powered prototype can detect high concentrations of bacteria in less than one hour and lower concentrations in less than eight hours. This compares to current methods which typically require 24-48 hours to produce a result. The Johns Hopkins University team utilised the AWISS in a seven day demonstration to record the bacterial water quality of the St. Joseph River in Indiana. Every six hours, a new sample was drawn into a custom designed stop-flow reaction chamber and injected with a soluble reagent. A wireless transmitter then sent intensity data to a remote monitoring station. The deployment produced 19 individual sampling events, of which 13 correctly identified the presence or absence of an E. coli concentration. "This relatively simple demonstration indicates that the AWISS prototype holds promise as a tool for rapidly detecting and alerting authorities to the presence of E. coli in recreational waters," said Jeffrey Talley of Johns Hopkins University."The sensor correctly alerted in under six hours almost 90% of the time." Talley says the prototype sensor is both rugged and relatively low cost compared to systems currently available. He also claims it displays characteristic current practices cannot: reliability, accuracy and timeliness operation. The researchers are now focusing their efforts on reducing costs, lowering the limits of detection and improving sensitivity and specificity.