Low cost bioluminescence imaging as an alternative to in vivo bioassays for quantifying biologically active staphylococcal enterotoxin type E

Authors: Rasooly, Reuven; Do, Paula; Hernlem, Bradley - Brad

Submitted to: Sensors and Actuators B: Chemical
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/13/2017
Publication Date: 12/15/2017
Citation: Rasooly, R., Do, P.M., Hernlem, B.J. 2017. Low cost bioluminescence imaging as an alternative to in vivo bioassays for quantifying biologically active staphylococcal enterotoxin type E. Sensors and Actuators B: Chemical. 259:357-393. https://doi.org/10.1016/j.snb.2017.12.079.
DOI: https://doi.org/10.1016/j.snb.2017.12.079

Interpretive Summary: Staphylococcal food poisoning is a stomach and intestinal illness caused by eating foods contaminated with toxins produced by the bacterium Staphylococcus aureus. The current method for detecting the effects of these active toxins uses live animals. In this study we evaluated a low cost camera in combination with a cell based assay for detecting and measuring levels of active staphylococcal enterotoxin type E, the causative agent in outbreaks in USA, France and UK. The assay we developed is a billion times more sensitive than live animal testing and can tell the difference between the active form of toxin that sickens consumers from toxin inactivated by heat treatment. The low cost camera device compared favorably against a much more costly commercial plate reader. This inexpensive device should make toxin testing more available, especially in resource poor regions.

Technical Abstract: Staphylococcus aureus is a major causative agent implicated in outbreaks of food poisoning, acting through the production of a range of toxins including staphylococcal enterotoxin type E (SEE). While tests such as enzyme-linked immunosorbent (ELISA) exist to detect the toxin molecules, existing methods to distinguish active toxin from inactivated are costly and require the use of live animal testing. In this study we constructed and evaluated a low cost charge-coupled device (CCD) camera device in conjunction with a cell based assay for active SEE employing a genetically engineered T-cell line with a luciferase reporter regulated by nuclear factor of activated T-cells combined with a B-cell line for toxin presentation. The emitted light intensity from the T-cells is proportional to SEE concentration over an 8-log range with sensitivity as low as 100 fg/mL which is a billion times more sensitive than the methods using live animal testing and can discern active toxin from toxin inactivated by heat treatment. The assay was verified in sample food matrices by spiking white grape and peach mango juices as well as apple cider. The low cost imaging device compared favorably against the expensive commercial plate reader using the same cell based assay. The low cost camera device should improve the availability of active toxin testing, especially in resource poor regions.