Apply new tools to fight Bacillus cereus.

New and more efficient tools for use in detecting enterotoxins--diarrheal toxins--from Bacillus cereus have been developed in Europe. Investigators are also about to identify the genes responsible for the production of emetic toxins--vomiting toxins. Moreover, PCR methods for detecting and quantifying highly virulent strains will be available for use in the near future. PCR (polymerase chain reaction) techniques are analytical and enzyme-based methods used to detect very small quantities of DNA in a crop or sample.

As you may know, B. cereus is a spore-forming foodborne pathogen that causes gastroenteritis, diarrheal syndrome or emetic syndrome, by means of several enterotoxins and an emetic toxin. The virulence is highly dependent on the specific strains, and to date no methods exist to differentiate among these strains. The bacteria may be found in most foods. But products containing vegetables and milk, which may be contaminated from the soil, pose a particularly high risk for infection.

The goals of recent European research are to:

* Identify highly virulent food poisoning strains of B. cereus; and

* Propose methods and tools to reduce their incidence in foods.

The diversity of virulence among B. cereus strains and the ecology of the virulent ones will be investigated. The goal is to identify the contamination routes and to estimate the risk for the presence of these strains and their development in foods. Moreover, the dose response curve will be improved.

In the first six months of the project, the researchers have developed new and highly sensitive immunological ways to detect the diarrheal toxins. They have identified the genes responsible for production of emetic toxins, thus allowing the development of a PCR method to detect the emetic strains.

Next, investigators plan to search for mechanisms that could permit them to identify high enterotoxin producers. Future efforts aimed at developing immunological techniques for detecting enterotoxins will involve the production of new monoclonal antibodies as soon as pure toxins are obtained. Quantification of the impact of the gastrointestinal tract on the survival, growth and enterotoxin production by B. cereus will continue.

Concerning emetic toxins, researchers will search for emetic toxin genes that will quantify the effect of food conditions on emetic toxin production. A first set of 200 B. cereus nonredundant strains--representing various foods, environments and steps in the food chain and sourced from various countries--will be produced to described B. cereus biodiversity.

Further information. Christophe Nguyen, INRA, Mixte de Recherche A408, Securite et qualite des produits d'origine vegetale, Domaine St-Paul, Site Agroparc 84914 Avignon, Cedex 9, France; phone: [phone]; fax: [phone]; email: [e-mail].