Rapid screening of pathogenic bacteria using solid phase concentration and diffuse reflectance spectroscopy

A new methodology to rapidly screen for pathogenic bacteria in various liquids (e.g., potable water and juice) is described. It combines the selectivity of dye-labeled antibodies, the sample concentration capability of solid phase membrane filtration, and the facile readout of the concentrated, dye-labeled microorganisms by diffuse reflectance spectroscopy (DRS). Details about the selection of the most effective membrane filter, detection of target bacteria in different types of liquids, and evaluation of assay specificity in screening for E. coli O157:H7 are discussed. For this pathogen, the technique has a working range of 5 × 105 to 5 × 108 cells/mL and an overall work up time of ∼45 min. The amount of captured bacteria is directly determined in only 2 s by using a hand-held DRS instrument via comparisons to a calibration curve based on the Kubelka-Munk function. Overall, this assay system offers high speed, simplicity, and low cost, making it a potential alternative for screening of several types of bacterial contaminated samples in almost any location.