Team:NYU-AD/Description
Issue
In many developing countries, rapid urbanization leaves people with limited access to cooking facilities, resulting in a large dependence on reasonably priced and conveniently available street foods. These foods, however, pose a high risk of food poisoning due to microbial contamination. According to WHO statistics, food poisoning kills 420,000 people a year worldwide[1]. One of the primary microbial contaminants is the Shiga toxin-producing Escherichia coli (or E. coli) O157:H7 (STEC). These particular pathogenic bacteria cause severe diseases in humans worldwide by secreting a toxin called Shiga-like toxin (SLT). Research shows that E. coli causes 73,000 illnesses in the United States every year. It is even estimated that STEC causes 2,801,000 acute illnesses worldwide annually, leading to 3890 cases of Hemolytic Uremic Syndrome, 270 cases of End-stage renal disease, and 230 deaths[2]. Currently, Shiga toxin detection must be conducted in a laboratory environment utilizing time-consuming PCR and assay techniques, so consumers have no way of protecting themselves without strong legislation.
Project
Lack of action taken by governments and street food vendors in developing countries lead to the prevalence of street food-related illnesses, and call for the necessity of consumer awareness. Ultimately, our project is to create a device that would detect the Shiga-like toxin in foods more conveniently and more quickly than current available methods.
Shiga-like toxins are exotoxins, which consist of a toxic enzymatic A subunit and a cell-binding B subunit. The latter binds to a globotriaosylceramide (Gb3) receptor, expressed on the surface of the target cells[3]. This interaction is responsible for the toxin's entry into the host cell. Through our device, we exploit the binding of Gb3 to subunit B and compare the migration pattern of the bound Gb3-subunit B complex to a non bound subunit B. A shift in migration pattern on a PAGE gel will occur when Gb3 is bound indicating the presence of the toxin in the food sample. If no shift occurs in the SLT migration pattern, this implies the absence of the toxin within the sample, and reflects the safety of the food.
In summary, we will be creating a portable device that would evaluate the safety of food by detecting a specific contaminant, Shiga-like toxin, for street vendors and restaurant owners and even government agencies to use and reassure consumers who rely heavily on their foods. Our device is designed to detect for the Shiga toxin in at most 45 minutes. This is quicker than the fastest laboratory detection method[4].
Initially, our target audience was the consumer, but as we developed our project, there were several factors such as affordability and accessibility that made it difficult for consumers to use the device. We hope that by providing a device that is more convenient and produces results faster than current detection methods, entities responsible for food safety regulation such as governmental agencies and even food vendors themselves will be motivated to take stronger action towards maintaining food safety.
Ideation Process
Before making our final decision, we explored an extremely diverse range of project topics such as blockage of oil pipes, controlling fruit ripening, detecting milk adulteration, biodegradable plastics, bioelectronics, preventing the coral reefs bleaching, bio-art, smoking, monitoring air quality, and more. After extensive research and intense discussion, we decided to move forward with the idea of detecting pathogenic SLT-producing E. coli in street foods. SLT is highly toxic due to its low LD50 and the A subunit’s protein synthesis inhibitory action, so it would have been too dangerous to work with given our lab environments. Keeping the validation process in mind, we decided to use only the SLT B subunit as our method of verification[5].
In addition to our main project, we have improved the characterization and validated the functionality of a previously submitted part by NYUAD iGEM team 2015. We have performed an Indole detection test to validate proper expression of indole of e.coli cells. Non-transformed cells were used as negative controls and pure indole solution served as positive control. Our experiment showed a highly significant colorimetric change corresponding to a high level synthesis of indole in transformed cells. Figures displaying this outcome and relevant protocols are shown both in our experiments and results pages.
Improvement to IIT Madras 2013 Project
Improving on the IIT Madras project on spreading awareness related to the toxic effects of Shiga Toxin in developing countries, the NYU-AD iGEM team decided to build a portable device that would detect the presence of Shiga Toxin in street food, especially in meat products. Furthermore, we also made a brochure outlining information related to the potency of the Shiga Toxin. Whereas the IIT Madras team focused on expressing an anti-toxin against the deadly Shiga Toxin and tried to target the mechanism by which the Shiga Toxin is formed in E.coli, the NYU-AD iGEM team took a giant leap ahead by incorporating the practices of synthetic biology into the real world. We designed the various aspects of our project so that the prototype could be as user-friendly as possible. Furthermore, we also reduced the time for each individual step in the process to ensure that the detection could take place as quickly as possible. For instance, we used the zinc-stain, which takes 15 minutes compared to other staining techniques which usually take around an hour.
References
- "WHO's First Ever Global Estimates of Foodborne Diseases Find Children under 5 Account for Almost One Third of Deaths." World Health Organization. World Health Organization, 3 Dec. 2015. Web.
- Frenzen, Paul D., et al. "Economic cost of illness due to Escherichia coli O157 infections in the United States." Journal of Food Protection® 68.12 (2005): 2623-2630.
- Melton-Celsa, Angela R. "Shiga toxin (Stx) classification, structure, and function." Microbiology spectrum 2.2 (2014).
- Bélanger, Simon D., et al. "Rapid detection of Shiga toxin-producing bacteria in feces by multiplex PCR with molecular beacons on the smart cycler." Journal of clinical microbiology 40.4 (2002): 1436-1440.
- US Department of Health and Human Services, Centers for Disease Control and Prevention, and National Institutes of Health. "Biosafety in microbiological and biomedical laboratories . LC Chosewood & DE Wilson." (2009).
