A net fishing enrichment strategy for colorimetric detection of E. coli O157:H7

Authors: REN, WEN - Purdue University; LIU, WENJIE - Purdue University; IRUDAYARAJ, JOSEPH - Purdue University

Submitted to: Sensors and Actuators B: Chemical
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/17/2017
Publication Date: 3/19/2017
Citation: Ren, W., Liu, W., Irudayaraj, J. 2017. A net fishing enrichment strategy for colorimetric detection of E. coli O157:H7. Sensors and Actuators B: Chemical. 247:923-929.

Interpretive Summary: It is challenging to detect harmful bacteria from complex food systems. A unique strategy for the enrichment of pathogens, based on a concept termed as net fishing was developed. In net fishing, we use antibodies bound to a membrane substrates to fish and specifically capture the harmful bacteria from liquid samples. The large surface area of the membranes proved to be very useful for the net fishing approach. The net fishing enrichment requires 2 hours to capture the harmful bacteria and 30 minutes for detection. Using the important foodborne pathogen E. coli O157:H7, the net fishing method was very sensitive, detecting a few as 100 cells in a one milliliter sample. This approach can be very useful for detecting harmful bacteria in liquid food samples.

Technical Abstract: The strict regulatory requirements for pathogen monitoring in food systems to ensure safety demands that the detection method can recognize small numbers of pathogens. Although significant efforts on the development of biosensors have been reported with marked improvement in sensitivity, appropriate enrichment strategies are still needed in a detection scheme. Herein we proposed a unique strategy for the enrichment of pathogens, based on a concept termed as net fishing, to capture target bacteria with antibodies functionalized on porous substrates to fish the target from samples. Because of their large surface area porous nitrocellulose membranes (NC membranes) were used as substrates for target capture. By immersing the antibody modified NC membrane into liquid samples and upon mixing, we expect to anchor target pathogens on the membrane due to the specific interaction between antibody and target, where the nonspecific enrichment could be reduced compared to methods such as filtration. Meanwhile the net fishing enrichment requires 2 h, less than common culture methods. An enzyme enhanced procedure was performed with the NC membrane after the capture to obtain colorimetric signal. Gold nanoparticle (GNP) probes conjugated with horseradish peroxidase (HRP) and antibody were used to label capture target bacteria, and the presence of pathogens was determined by the colorimetric signal generated from HRP catalyzed TMB reaction. With E. coli 0157:H7 as target, we investigated the detection performance of the proposed net fishing strategy with an enzyme amplification step for colorimetric reporting. After optimization of detection conditions, we show that as low as 100 CFU/mlE. coli O157:H7 could be detected. The feasibility was then demonstrated using pineapple juice as a food model.