Electrochemical sensing of bacteria via secreted redox active compounds using conducting polymers

•Extracellular electron transfer used for electrochemical detection of bacteria.•Rapid potentiometric detection using an all organic, screen printed two electrode sensor.•Detection and quantification of Salmonella in less than 15 min.•Diagnostic application shown by detection of all major uropathogenic bacterial species. Bacterial infections and antibiotic resistance represent major global threats to public health. Current diagnostics use culture based assays that are reliable but slow, hence appealing for new rapid methods. Here we describe redox sensing as a novel concept for rapid, label-free detection of bacteria. We utilize a two-electrode poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) based sensor for detection of bacterially secreted redox-active compounds. Using purified redox-active compounds, we show the ability of the sensor to detect and quantify compounds in micromolar concentrations within minutes. When applied for detection and quantification of Salmonella, we show that secreted, low molecular weight redox compounds cause reduction of the PEDOT:PSS electrode. A potential role of redox sensing in infection diagnostics was demonstrated as uropathogenic strains of E. coli, Staphylococcus, Enterococcus, Pseudomonas, Proteus, and Klebsiella spp., major causes of complicated urinary tract infections, were successfully detected in complex media or processed urine. Since numerous bacterial species are capable of extracellular electron transfer, redox sensing may find use as a generic method for bacterial detection with applications in research laboatories, the clinic and industry alike.