Plant Compounds Enhance the Assay Sensitivity for Detection of Active Bacillus cereus Toxin

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.

Bacillus cereus food intoxication and toxicoinfection

“…(2015) reported on the use of Vero cells transduced with the gene encoding for the green fluorescent protein. As the enterotoxins produced by B. cereus inhibit protein synthesis, a reduction in fluorescence intensity is observed when the Vero cells are exposed to B. cereus supernatant (Rasooly et al., 2015). A comparably straightforward read‐out was developed by Banerjee et al.…”

“…Although in the former a distinction was made by the authors between enterotoxins and cereulide, this was not the case for the WST-1 assay (Ngamwongsatit et al, 2008). Next to these conventional methods, Rasooly et al (2015) reported on the use of Vero cells transduced with the gene encoding for the green fluorescent protein. As the enterotoxins produced by B. cereus inhibit protein synthesis, a reduction in fluorescence intensity is observed when the Vero cells are exposed to B. cereus supernatant (Rasooly et al, 2015).…”

“…Next to these conventional methods, Rasooly et al (2015) reported on the use of Vero cells transduced with the gene encoding for the green fluorescent protein. As the enterotoxins produced by B. cereus inhibit protein synthesis, a reduction in fluorescence intensity is observed when the Vero cells are exposed to B. cereus supernatant (Rasooly et al, 2015). A comparably straightforward read-out was developed by Banerjee et al (2008) who used Ped-2E9 cells (B-lymphocytes) incapsulated in a type I collagen matrix for the detection of enterotoxins based on the release of intracellular alkaline phosphatase.…”

Butterflies Extracts Show Antibacterial Activity

“…In our previous work, we showed that green tea extract and phytochemicals like epigallocatechin gallate (EGCG) that are found in green tea, have high bactericidal activity against Gram-positive bacteria [6]. In Gram-negative bacteria such as Escherichia coli, EGCG also was shown to damage bacterial membranes and degrade exopolysaccharides, resulting in the destruction of biofilms [7].…”