Submitted to: Food Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/2020
Publication Date: 7/2/2020
Citation: Capobianco Jr, J.A., Armstrong, C.M., Lee, J., Gehring, A.G. 2020. Detection of pathogenic bacteria in large volume food samples using an enzyme-linked immunoelectrochemical biosensor. Food Control. https://doi.org/10.1016/j.foodcont.2020.107456.
Interpretive Summary: Food producers and regulators alike desire fast in-line or near-line tests for the detection of bad bacteria in foods. Speed of testing is needed so that product may be released as soon as possible for sale in order to increase revenue and minimizing the need to store product. As these bacteria may only be present in very small numbers, tests with extremely high sensitivity are required. Current tests use as much as 325 g of food added to approx. 1 L of growth media for culture enrichment, often at elevated temperatures for 1-2 days, to effectively increase the number of bacteria that promotes accurate testing. Researchers with ARS (Wyndmoor, Pennsylvania) have demonstrated that their provisionally patented test (an immunoelectrochemical biosensor) may be used to interrogate unusually large volumes (up to 1 L) of liquid meat samples for fast capture and detection of relatively low numbers of bad bacteria (e.g., E. coli O157:H7 and Salmonella) without the need for culture enrichment. Using this novel test, as low as 400 cells/mL of these bacteria could be detected within 3 hours of testing.
Technical Abstract: Increased speed and sensitivity of testing are always desired for the detection of pathogens in foods. Presented a test sample with low microbial analyte concentration, it is an advantage to analyze as much volume as possible of the sample in order to attain the best limit of detection (LOD). Therefore, a rapid screening method using a novel flow-through immunoelectrochemical biosensor was developed for the detection of pathogenic bacteria (E. coli O157:H7 and Salmonella) in food (ground beef). As the working electrode employed was comprised of a porous, antibody-coated graphite felt electrode that served as both biorecognition-element coated solid support for capture of targeted pathogens as well as a signal transducer, high volumes of aqueous sample could be rapidly exposed to the solid support via gravity flow. Flow rates as high as 16.7 mL/min and 12.3 mL/min could be achieved for bacterial samples in buffer and 1:4 ground meat (beef) homogenate, respectively, with no significant effect on LOD. Fastest flow rates for beef homogenate, without clogging of the porous electrode as well as reduction in apparent electrochemical interference, was realized with a tandem combination of sample pretreatment strategies that included filtration with glass wool and graphite felt as well as continuous flow centrifugation. The LOD for 10,000 E. coli O157:H7 cells in 5, 60, and 1000 mL of buffer was 2000, 170, and 10 cells/mL, respectively in a total assay time of 3 hours whereas the LOD for E. coli O157:H7 was 400 cells/mL in 1:4 beef homogenate.