Highly Portable and Sensitive Filter-Based Antibody-or DNA Aptamer-Enzyme-Linked Fluorescence Detection of Potential Bacterial Pathogens Proximal to Agricultural Fields

A novel, sensitive, rapid and highly portable system consisting of a membrane filtration unit connected to a large syringe with tubing was used to detect Escherchia coli and Salmonella enterica bacteria in a mobile laboratory setting. These simple fluorescent enzyme-linked molecular assays consisted of biotinylated DNA aptamers or antibodies which were allowed to bind the target bacteria and be deposited on 0.45 μm pore size membrane filters by suction, followed by binding of streptavidin-peroxidase conjugate, wash steps and development in Amplex® UltraRed (AUR; resazurin derivative) with hydrogen peroxide activation. Fluorescence values of developed AUR from the filter surface were assessed with a commercially-available handheld fluorometer. Preliminary data indicate detection limits in the range of 50–110 E. coli and Salmonella bacterial cells per sample with good specificity and total processing times under one hour.