Solid-phase capture of proteins, spores, and bacteria

Current methods for the detection of pathogens in food and water samples generally require a preenrichment step that allows selective enrichment of the test organism. The objective of this research was to eliminate an enrichment step to allow detection of bacteria directly in food and water samples in 30 min. A high-flow-rate, fluidized bed to capture and concentrate large (bacteria and spores) and small (protein) molecules was developed. This format, ImmunoFlow, is volume independent and uses large beads (greater than 3 mm in diameter) when capturing bacteria to prevent sample clogging when testing food samples. Detection of bound targets was done using existing enzyme-linked immunosorbent assay (ELISA) protocols. Four antibodies (anti-Escherichia coli O157:H7, -Bacillus globigii, -bovine serum albumin BSA], and -ovalbumin OVA]) were covalently coupled to various glass and ceramic beads. Very small amounts of BSA (<1 ng) and OVA (0.2 to 4.0 microg) were detected. Various industrial and environmental samples were used to observe the effect of the sample composition on the capture of anti-B. globigii and anti-E. coli O157:H7 modified beads. The lower limit of detection for both E. coli O157:H7 and B. globigii was 1 spore/cell independent of the sample size. The activity of anti-B. globigii modified beads declined after 3 days. Anti-E. coli O157:H7 modified beads declined in their capture ability after 2 days in various storage buffers. Storage temperature (4 and 25 degrees C) did not influence the stability. The ImmunoFlow technology is capable of capturing bacteria and spores directly from samples, with subsequent detection in an ELISA format in 30 min.