On October 19, 2020, a piece of devastating news caught our attention. Nine family members died after eating the bacteria-contaminated food. This incident aroused a wilder public concern, 810 million views, and 97 thousand discussions on Weibo, a leading blog platform in China. The curiosity and responsibility lead us into the field of food safety.
Food safety is a leading public health concern related to people's health and quality of life—diseases caused by ingesting contaminated and toxic food or water, known as foodborne illness(World Health, 2015). An evaluated 600 million – nearly 1 in 10 individuals within the world – fall ill after having unsafe food. In developing countries, 110 billion dollars were lost in the prevention and treatment of foodborne diseases(World Health, 2015). In China, foodborne disease is a growing public health problem. From 2003 to 2017, the recorded information showed 107,000 hospitalizations and 1,457 deaths because of unsafe food(Li et al., 2020).
Rate: number of foodborne disease outbreaks per 1 million population
Fig. 1. Number and rate of reported foodborne disease outbreaks by year in China, 2003–2017.
Integration of the literature reviews and field research on Suzhou, we conclude that the bacteria pathogen is one of the most significant causes of foodborne disease. (Li et al., 2020, Wu et al., 2018).
Chengang Teng (chief of the Department of Food Hygiene in Suzhou Centers for Disease Control and Prevention.): Bacteria is the dominant pathogenic factors causing the foodborne disease in Suzhou.
To prevent and treat the bacteria foodborne disease, a fast detection kit is demanded in food inspection and patient diagnosis. Based on literature and engagement with relaters, we found that Culturing is the most commonly used method in bacteria detection that takes about 5-7 days to grow a bacteria entity in an artificial medium(Kim and Kim, 2021). However, with the short shelf life and fast circulation of food, as well as the urgency of diagnosing patients, a fast detection kit is highly demanded. Considering the needs of our end-users and national standards, various potential bacteria pathogens need to be quantitatively tested within one sample. Overall, we integrated all the information and established our goal: Fast, Multiply bacteria detection, Quantitative, and Visible.
In our project, we used phage as the specific probe responsible for bacteria detection and conversion of the signal into the expression of foreign protein. The whole progress from the infection to release only cost no more than 3 hours. For the downstream, the in vitro transcription and translation, the reaction will take 1-2 hours. Therefore, the whole detection could be finished in 4 hours, which is absolutely shorter than the current method.
Multiply bacteria detection
A bacteriophage is a virus that infects a bacterium. The diversity of bacteriophages makes multiply bacteria detection possible. Due to the time limit, this year, we performed the T4 bacteriophage infecting Escherichia coli to test the feasibility of our design.
In order to process a quantitative detection, we use the downstream cell-free system to convert the value of the amount of foreign protein released from the upstream into a reported signal. Meanwhile, we used a bistable system to perform the easy-to-read result.
We used eGFP (enhanced GFP) as a reporter gene, which could output visible results. Depending on the high efficiency of the in vitro expression system, the fluorescent signal could be observed under natural light.