Detecting Legionella pneumophila in Cooling Tower Water Samples with a DNAzyme/Bead-Based Fluorescence Assay

Legionella pneumophila is the causative agent behind the deadly waterborne disease Legionnaires’, which is commonly transmitted by the spread of contaminated droplets from cooling tower water samples. The lack of effective detection methods presents a challenge for L. pneumophila outbreak control. Previously, an RNA-cleaving DNAzyme called LP1 was reported to specifically target L. pneumophila. In this study, LP1 was immobilized onto agarose beads via streptavidin-biotin interaction to develop a bead-based fluorescence assay for L. pneumophila detection. This bead-based assay demonstrated excellent stability and functionality in various cooling tower water samples. To improve L. pneumophila monitoring in real-world samples, a lysozyme treatment was used to enhance L. pneumophila recognition. The limit of detection of this DNAzyme-based bead assay can reach 10³ CFUs in cell-spiked cooling tower water samples without cell culturing or signal amplification steps.