Enrichment and detection of Escherichia coli O157:H7 from water samples using an antibody modified microfluidic chip

Low abundant (<100 cells mL(-1)) E. coli O157:H7 cells were isolated and enriched from environmental water samples using a microfluidic chip. The poly(methylmethacrylate), PMMA, chip contained 8 devices, each equipped with 16 curvilinear high aspect ratio channels that were covalently decorated with polyclonal anti-O157 antibodies (pAb) and could search for rare cells through a pAb mediated process. The chip could process independently 8 different samples or one sample using 8 different parallel inputs to increase volume processing throughput. After cell enrichment, cells were released and enumerated using benchtop real-time quantitative polymerase chain reaction (PCR), targeting genes which effectively discriminated the O157:H7 serotype from other nonpathogenic bacteria. The recovery of target cells from water samples was determined to be approximately 72%, and the limit-of-detection was found to be 6 colony forming units (cfu) using the slt1 gene as a reporter. We subsequently performed analysis of lake and wastewater samples. The simplicity in manufacturing and ease of operation makes this device attractive for the selection of pathogenic species from a variety of water supplies suspected of containing bacterial pathogens at extremely low frequencies.