Plant compounds enhance the assay sensitivity for detection of active Bacillus cereus toxin.

Reuven Rasooly,Xiaohua He,Mendel Friedman,Bradley Hernlem

doi:10.3390/toxins7030835

Reuven Rasooly, Xiaohua He + Show 2 more

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https://doi.org/10.3390/toxins7030835

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Abstract

Bacillus cereus is an important food pathogen, producing emetic and diarrheal syndromes, the latter mediated by enterotoxins. The ability to sensitively trace and identify this active toxin is important for food safety. This study evaluated a nonradioactive, sensitive, in vitro cell-based assay, based on B. cereus toxin inhibition of green fluorescent protein (GFP) synthesis in transduced monkey kidney Vero cells, combined with plant extracts or plant compounds that reduce viable count of B. cereus in food. The assay exhibited a dose dependent GFP inhibition response with ~25% inhibition at 50 ng/mL toxin evaluated in culture media or soy milk, rice milk or infant formula, products associated with food poisonings outbreak. The plant extracts of green tea or bitter almond and the plant compounds epicatechin or carvacrol were found to amplify the assay response to ~90% inhibition at the 50 ng/mL toxin concentration greatly increasing the sensitivity of this assay. Additional studies showed that the test formulations also inhibited the growth of the B. cereus bacteria, likely through cell membrane disruption. The results suggest that the improved highly sensitive assay for the toxin and the rapid inactivation of the pathogen producing the toxin have the potential to enhance food safety.

Highlights

Bacillus cereus a Gram-positive, rod-shaped, beta hemolytic bacterium with an infective dose as low as 103 bacteria per gram of food, is an important cause of foodborne pathogenesis
To monitor the effectiveness of plant compounds on B. cereus viability in food items that have been involved in B. cereus outbreaks, soy milk, infant formula Similac® and control Luria Broth (LB) media were spiked with B. cereus and treated with the plant formulation of interest and cultured on LB plates
We first determined the levels of the Bacillus cereus toxin in commercial soy milk, rice milk, and baby formula using a nonradioactive in vitro cell assay based on toxin inhibition of a green fluorescent protein (GFP) synthesis in transduced monkey kidney Vero cells

Summary

Introduction

Bacillus cereus a Gram-positive, rod-shaped, beta hemolytic bacterium with an infective dose as low as 103 bacteria per gram of food, is an important cause of foodborne pathogenesis. In the United States up to 84,000 cases of food poisoning occur each year, resulting in major product recalls and substantial economic loss. This bacterium contaminates numerous foods including infant formula [1], infant rice cereal [2], cooked rice [3], dried milk products [4], dehydrated potato products [5], eggs, meat, and spices [6], causing illness worldwide. B. cereus produces toxins causing two different types of food poisoning: emetic and diarrheal syndromes [8]. The diarrheal type of food poisoning is caused by enterotoxins produced during vegetative growth of bacteria in the small intestine [9], which act on the epithelial cells, causing massive secretion of fluid into the intestinal lumen, leading to diarrhea [10]

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