Bioluminescent-reporter phagosensor for quantitative detection of viable Escherichia coli in water.

The detection of Escherichia coli (E. coli) is a fundamental aspect of water safety assessments, serving as an indicator of fecal contamination. However, current methods often fail to distinguish viable E. coli cells, resulting in false-positive outcomes. We have developed a facile and sensitive method combining one-step phagomagnetic separation with reporter phage amplification to address this challenge. This method employs magnetically functionalized T4 phages to selectively bind and concentrate E. coli from liquid samples. A genetically engineered phage carrying the NanoLuc luciferase gene generates a bioluminescent signal exclusively upon infecting viable E. coli cells. With a calculated detection limit of 5 CFU/mL and a linear detection range spanning 10² to 10⁵ CFU/mL, the sensor delivers accurate and rapid results. Tests with spiked liquid samples demonstrated high consistency with standard detection methods (R2 = 0.98) while significantly reducing detection time. This innovative system offers a powerful tool for on-site monitoring of viable E. coli within its host range in drinking water, enhancing the efficiency and reliability of drinking water safety protocols.