Camera-based method may provide cheaper toxin detection

Published on August 31, 2016
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An off-the-shelf camera, a lamp, and light filters may provide a low-cost method of detecting active toxins produced by bacteria and fungi.

The authors of two scientific articles published in Biosensors and Bioelectronics measured the effects of active and inactive forms of shiga toxin and aflatoxin on monkey kidney cells that were modified to express a green fluorescent protein gene. When the toxins were active, they prevented synthesis of that protein and the fluorescence.

As a result, a stronger glow indicated lower toxin activity. 

The authors of the shiga toxin article indicate the $300 camera used in their study can detect shiga toxin activity at a level comparable with a $30,000 fluorometer. Reuven Rasooly, PhD, a chemist for the Department of Agriculture’s Agricultural Research Service and an author of both studies, said the methods and materials—which include analysis software provided free from the National Institutes of Health—could reduce the cost of diagnostic equipment in impoverished countries.

The article on aflatoxin B1 was published this year (Biosens Bioelectron 2016;80:405-410), and the article on shiga toxin was published in 2015 (Biosens Bioelectron 2015;68:705-711). 

The shiga toxin article indicates PCR assays do not detect toxin gene expression or distinguish between live and dead organisms, and immunoassays detect only toxins and not toxin activity. Microplate readers and spectrophotometers are expensive and beyond the means of developing countries, where the risks are greatest, it states. 

Shiga toxin–producing Escherichia coli is responsible for an estimated 265,000 infections each year in the United States, with STEC O157 responsible for about one-third of this total, according to information from the Centers for Disease Control and Prevention. Aflatoxin B1, which is produced by the fungal contaminants Aspergillus flavus and A parasiticus, is a concern mostly in developing countries, where about 4.5 billion people may have chronic exposure to the toxin through their diet, according to the CDC.