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Quantitative bioluminescence assay for measuring Bacillus cereus nonhemolytic enterotoxin complex
Reuven Rasooly1, Paula Do1, Bradley Hernlem1
1Western Regional Research Center, Foodborne Toxin Detection & Prevention Research Unit, Agricultural Research Service, United States Department of Agriculture, Albany, CA, United States of America.
Plos One
|September 30, 2020
Summary
A new low-cost luminometer and cell-based assay can detect active non-hemolytic enterotoxin (Nhe) from Bacillus cereus. This method offers a viable alternative to animal testing for food safety applications.
Area of Science:
- Food Microbiology
- Biotechnology
- Analytical Chemistry
Background:
- Bacillus cereus is a foodborne pathogen linked to diarrhea.
- Non-hemolytic enterotoxin (Nhe) is implicated in B. cereus-induced diarrhea.
- Current Nhe detection methods lack activity differentiation and ethical alternatives.
Purpose of the Study:
- To develop a novel, low-cost method for detecting active Nhe.
- To provide an ethically sound alternative to animal-based bioassays.
- To enhance food safety by enabling accurate Nhe activity tracing.
Main Methods:
- Development of a custom, low-cost CCD-based luminometer.
- Utilization of a cell-based assay with luciferase-expressing Vero cells.
- Measurement of Nhe activity via inhibition of luciferase synthesis (light reduction).
Main Results:
- The assay successfully quantified Nhe activity by measuring light emission reduction.
- A concentration-dependent inverse relationship was observed between Nhe concentration and light intensity.
- The method achieved a limit of detection of 7 ng/ml Nhe for concentrations ranging from 7 to 125 ng/ml.
Conclusions:
- A novel, cost-effective, and ethically preferable method for detecting active Nhe has been established.
- This assay provides a sensitive tool for monitoring Nhe activity in food safety contexts.
- The developed system offers a promising alternative to traditional, animal-reliant bioassays.
