Revolutionary Approach for Early Detection of Foodborne Bacteria

To protect consumers from potential illness, common produce items such as lettuce and spinach undergo regular testing for foodborne pathogens like salmonella, listeria monocytogenes, and certain types of E. coli. Although rapid testing methods exist, it still takes time to identify affected individuals and determine the source of contamination. Unfortunately, by the time this information becomes available, many Americans may have already consumed the contaminated produce. Consequently, the typical response is a multi-state recall aimed at mitigating the damage.

Researchers from the University of Delaware, in collaboration with Biospection, a Delaware-based startup, aim to detect these harmful bacteria even before anyone falls ill. Their efforts, described in an article published in the Journal of Food Safety, focus on accelerating testing processes. Harsh Bais, Kali Kniel, and Nick Johnson from the university, along with Biospection's Andy Ragone, have devised a method to identify foodborne pathogens within three to six hours.

Kniel, an expert in microbiology and crossover pathogens like salmonella, highlights the potential of such tools to enhance risk reduction strategies employed by the produce industry. As a professor of microbial food safety, she actively collaborates with industry and government agencies to minimize the risk of foodborne illnesses. Kniel emphasizes the significance of collaborations between academic institutions and biotechnology companies in improving technology and its impact on food safety and public health.

These pathogens easily infiltrate plants, which serve as unwitting hosts without the ability to pinpoint the presence of unwelcome guests. Similar to humans, plants employ defense mechanisms to combat diseases. However, certain human-borne pathogens have learned to exploit stomates, which are openings found in leaves or stems, gaining access to the plant and establishing themselves within its tissues.

''Because these bacteria are not true pathogens for plants, you cannot physically see early signs that the plant is under stress. Biospection's technology allows us to say, very quickly, if the opportunistic human pathogen is present in the plant." Harsh Bais, UD professor of plant biology

Ragone, a chemical physicist based in Wilmington, established a connection with Kniel and Bais through Delaware's scientific community and their shared use of laboratory equipment. Over time, their relationship grew stronger, leading to a joint effort in applying for and receiving research funding from a Delaware Biotechnology Institute Center for Advanced Technology (CAT) grant, focused on scientific technology and intellectual property. The researchers combined their interdisciplinary expertise to address the longstanding challenge of reducing the risk of foodborne illnesses. The outcome of their collaboration was the development of a multi-spectral imaging platform designed to examine the response of plants, acting as sentinels, to potential pathogens. The ultimate aim was to employ this technique directly on a conveyor system, allowing for the scanning of lettuce before it reaches grocery stores.

But how can you detect symptoms that are not visible to the naked eye? The researchers utilized multispectral imaging and deep UV sensing to scan the leaves when the plants were being targeted by these pathogens. When harmless bacteria were examined, minimal changes were observed. However, when harmful pathogens originating from humans were present, the test could detect discernible differences in the plant's response.

Bais explained, using listeria as an example, that within three to six hours, a significant decrease in chlorophyll pigments was observed—a strong indicator of the plant's physiological response and an indication of unusual bacterial presence.

This novel multi-spectral imaging technique is non-invasive and remarkably faster compared to current methods, which involve laboratory scientists extracting a leaf, grinding it up, plating the bacteria, and searching for signs of disease. While the current method is not commercially available, Biospection secured a National Science Foundation Small Business Innovation Research grant in 2022 to develop and commercialize it into a real-time imaging sensor for inspecting plants and identifying diseases and other stress factors.

Vertical farming, a sector of agriculture that emphasizes sustainability by utilizing less water and space, stands to benefit significantly from this new technology. Despite its advantages, vertical farms are just as susceptible to disease outbreaks as traditional outdoor agriculture. An incident involving E. coli, for instance, can result in an entire harvest being discarded.

Biospection is already collaborating with agricultural companies to integrate the imaging sensor into the shelves of vertical farms and crop drones for outdoor farms.

Ragone, the founder and chief technology officer of Biospection, acknowledged the instrumental role played by Bais and Kniel in developing the multi-spectral imaging techniques and the use of deep ultraviolet fluorescence. They successfully built a portable instrument with potential for commercialization.

Looking ahead, Bais is interested in exploring whether this technology can differentiate between various microbes.

"If the sentinel response differs among different microbes, it would allow us to identify the specific microbe based on the plant sentinel response. Although we haven't reached that stage yet, it would be the ultimate achievement," Bais stated. "With just one sentinel, we could differentiate between the impacts of benign and harmful microbes."

Source : University of Delaware