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Let’s B. cereus about Emetic Toxin
July 12th 2022

Let’s B. cereus about Emetic Toxin


By Bill Adams

What is Bacillus cereus?

Per the FDA, Bacillus cereus is an aerobic spore-forming bacterium that is commonly found in soil, on vegetables, and in many raw and processed foods. B. cereus can quickly multiply at room temperature and has been known to cause food poisoning, broken down between enterotoxins and emetic toxins. The FDA estimates there are over 60,000 episodes of B. cereus related illnesses annually in the United States. These spores are quite resistant, even survive in extreme temperatures, and therefore are a major concern in food spoilage prevention.

Enterotoxins, divided into three distinct strains or types, specifically affect the intestinal mucosa, with an onset time of 6 to 15 hours after consumption of food left at room temperature for more than 2 hours. This poisoning can last up to 24 hours and will cause abdominal pain, diarrhea, and some nausea. The foodborne poison can frequently be found in meat products, soups, vegetables, puddings/sauces, and milk/milk products.

Emetic Toxin, also known as cereulide, has a shorter onset time of 1 to 6 hours after ingestion of foods left at room temperature, even after being reheated. While the effects can also last upwards of 24 hours, cereulide poisoning causes acute nausea and vomiting. Due to its stability, cereulide may still be present even when B. cereus can no longer be detected and is commonly found in starch-rich foods, such as rice and pasta.

B. cereus typically does not pose a long-term or severe health risk, but foodborne outbreak tends to occur when food is improperly cooked and/or stored. The most common source of treatment is symptomatic care with oral hydration. Additionally, sources of outbreaks can happen due to improper hygiene during food canning, or inadequate reheating of food in settings such as restaurants and schools.

Can B. cereus be tested for?

Most definitely!

B. cereus can be determined at a microbiological level using the aseptic technique. Plate count can be determined with Bacara or MYP agar plates after periods of incubation, where colonies are observed and confirmed. However, these methods may be inadequate for distinguishing B. cereus from culturally similar organisms.

While the immunoassay method testing for enterotoxins is not as reliable in quantifying the toxicity or detection of the strains, a method using liquid chromatography with mass spectrometry (LC-MS/MS) has been created for the detection and quantification for emetic toxin (cereulide). 

Known as ISO 18465:2017, this method focuses on the extraction of cereulide from the food matrix with acetonitrile. A synthetic cereulide is used as an internal standard. Using HPLC or UHPLC instrumentation and tandem mass spectrometry (using the electro spray ionization technique), cereulide is detected in positive mode. At least 18 cereulide variants were detected during the validation of this methodology.

The matrices subjected to the ISO 18465:2017 validation included: cooked rice, both spiked and naturally contaminated, fried rice, cream pastry with chocolate, hotdog sausage, mini pancakes, vanilla custard, and infant formula.

What Can Mérieux Nutrisciences Do For You? 

Mérieux NutriSciences has now validated the ISO 18465:2017 and can test for Quantitative Analysis for Cereulide in Food Products by LC/MS/MS, offering a Limit of Quantification (LOQ) of 1ng/g. Matrices validated at present are whole wheat flour, potato gnocchi, and corn masa, with additional matrices available to validate upon request.

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