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Enterotoxin expression of Bacillus thuringiensis strains used as pesticides and biocidal products
Project
Project code: BfR-BIOS-08-1322-650
Contract period: 01.01.2016
- 31.12.2016
Purpose of research: Applied research
B. thuringiensis strains are used as microbiological agents in plant protection products and biocidal products (specially in organic farming and for vector control in water reservoirs). Thus these strains have a great economic importance. Studies made with Bacillus (B.) thuringiensis strains used in Germany in plant protection and biocidal products have shown that these strains harbour the genetic information for all subunits of the enterotoxins NHE and HBL (Frederiksen et al., 2006). The producers of plant protection and biocidal products emphasize that the strains used, produce enterotoxins only in very small amounts. This statement was confirmed in one study by comparison of the enterotoxin expression levels between a strain from a plant protection product and a human pathogenic Bacillus cereus strain. However, it was not the subject of the investigation, to define or optimize the culture conditions under which higher toxin amounts maybe occur (Damgaard, 1995). The first report in Germany about an outbreak, in which the suspected food was contaminated with high concentrations of B. thuringiensis, occurs in autumn 2012. This was understood as first evidence that B. thuringiensis strains used in plant protection products could have a human pathogenic potential. The persons affected developed diarrhoea after eating salad, which had been treated with a B. thuringiensis containing product shortly before harvest (BfR, 2013). A risk assessment of products containing B. thuringiensis regarding to human health has not been done by EFSA until now. This is probably because of the limited data about: (a) the toxin forming ability of the strains used, (b) conditions that affect the enterotoxins production, and (c) the toxin amount required to trigger a diarrheal disease. However, according to the present state of knowledge, it is not possible to carry out investigations to (c). The following questions about the B. thuringiensis strains used in plant protection and biocidal products concerning the human health still open: 1. Do the B. thuringiensis strains used in plant protection and biocidal products have the potential for expression of human pathogenic toxins, and if so, under which (cultural) conditions? 2. How long can spores or vegetative cells survive and under which conditions? 3. Are there appropriate risk mitigation procedures, such as waiting periods between treatment and harvest, to avoid or reduce exposure of consumers to the spores or vegetative cells of B. thuringiensis?
Section overview
Subjects
- Biotechnology
- Toxicology
