Simple, Inexpensive Pathogen Detector Developed

Candida albicans fungus cells (CDC.gov)

29 June 2017. A simple and inexpensive detection device is being created to find disease-causing microbes in samples of food, water, and human specimens. A team from Columbia University in New York describes the device and shares findings from tests of a prototype in yesterday’s issue of the journal Science Advances.

A team from the lab of Columbia chemistry professor Virginia Cornish is seeking a device that can be deployed throughout low-resource regions in the world to detect disease-causing pathogens, particularly those caused by fungi. The authors say some 2 million deaths a year worldwide result from fungal pathogens, yet today’s systems for detecting these and other disease-causing microbes are specialized, sophisticated, and expensive, and usually found in larger institutions, not in the field.

For a solution, the researchers focused their design on a biosensor that could be deployed in a wide range of locations where detection of pathogens is needed, including farms and municipal water works, as well as health care facilities. They started with baker’s yeast, a common household product with live Saccharomyces cerevisiae fungus cells that provide the platform for the biosensor. The team discovered they could genetically engineer the cells to replace natural G protein–coupled receptors, proteins on the surface of the cells, with mating peptides characteristic of other disease-causing fungi.

To be practical, however, the device also needs to indicate when a pathogen is found. For this task, the team also engineered in lycopene to the baker’s yeast genome, a natural red pigment found in tomatoes and other produce. Thus when exposed to target pathogen molecules, the altered baker’s yeast reacts and turns red, making it visible to the naked eye.

To prove the concept, Cornish and colleagues engineered baker’s yeast to express characteristic peptides of Candida albicans, a fungus living harmlessly in the human gut and skin, but when it overgrows can cause infections in the mouth and throat, known as thrush or yeast infections in the vagina. Results from lab tests show the altered baker’s yeast platform could detect Candida albicans fungi as readily and accurately as more sophisticated diagnostics using antibodies or nucleic acids.

The researchers then designed a form of dipstick, similar to home pregnancy tests, for detecting other types of fungal pathogens, to demonstrate the flexibility of the detection technology. The tests covered 10 fungi associated with diseases in humans, found in soil and plants, and responsible for food spoilage. The results show the biosensor detects all of these individual pathogens, but the technology is also easy to change from one target to another. In addition, the authors say the technology can be adapted to detect other types of pathogens, including bacteria and viruses, as well as toxins.

Cornish says in a university statement, “Our assay can be cheaply made, economically produced at large-scale, widely distributed as a stable dried product for household use, robustly applied to complex samples, is not reliant on cold-chain storage, and can be readily detected by the eye without additional equipment, making it a compelling and completely feasible tool for surveillance of pathogens around the globe.”

The university filed for a patent on the technology, but the researchers are in discussions with health, development, and citizen’s groups to determine uses for the biosensor in various countries. One immediate application is the detection of cholera, caused by ingestion of contaminated food and water in a number of developing countries.

Cornish and her team tell more about the device in the following video.

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