All about Bacillus thuringiensis

1. What is Bacillus thuringiensis (Bt)?

Bacillus thuringiensis (Bt) are bacteria found naturally in the environments of every continent of the world. Some of the Bt strains are natural antagonists of some pests. A few Bt strains have been selected and commercialized as biological pest control products. These commercialized Bt strains are valuable to agriculture and public health because of their unique ability to naturally control certain destructive and disease-carrying insect pests while avoiding harm to non-target organisms (such as beneficial insects, people, other mammals, and fish). Biological insect control products based on Bt strains have been used safely and effectively in practical field conditions for more than 50 years, since its first commercial use in France in 1938.

2. Why do we need Bt?

The increasing use of biological pest control is reflective of a greater need for sustainable crop protection solutions, that meet the demands of consumers for food and environmental safety. Bt insect pest management is vital to producers of food, fiber and timber and in public health protection around the globe. Bt-based products are used widely in organic and conventional agriculture as well as forestry and public health, because they deliver consistent pest control while avoiding harm to beneficial insects, without negative impacts on the environment or people. Bt is a sustainable crop protection solution when used as part of effective integrated pest management and insecticide resistance management programs.

Bt safety and effectiveness are vital to ensure a sustainable food production and control of diseases in public health programs.

3. How does Bt work?

Commercial insect control products, based on specific Bt strains, are eaten by target pest insects. This prevents them from digesting food, causing them to die. The component of commercial Bt products that affects pest insects is a group of naturally produced proteins that have evolved to impact only the target insect’s gut.  For example: caterpillar control products based on Bt can only be activated in the caterpillar gut. This specificity is why they have little to no negative effects on non-target organisms such as other insects (e.g. pollinators like bees), animals, people, or fish.

4. Can people eat food treated with commercial Bt products?

People have been eating fresh food treated with commercial Bt products for more than 50 years without any evidence of adverse effects.  Bt strains used in pest control have evolved to survive best in the specific condition of the pests they target.  These conditions are so dramatically different from the human gut that Bt do not grow like they would in the targeted pest insects in the field.

5. What is Bacillus cereus (Bc) and why is it a concern?

Bacillus cereus (Bc) are members of the Bacillus bacteria family and found naturally in the environment. Some Bc strains produce certain toxins, like the emetic toxin and enterotoxins, which can be harmful to people. The emetic toxin is particularly of concern because it is not destroyed by cooking and causes vomiting. Although related to Bc it has been proven that commercial Bt strains do not have the ability to produce this toxin.

In addition to the emetic toxin, some Bc strains can produce large amounts of enterotoxins which can cause diarrhea. Research has shown that commercial Bt strains are unlikely to produce any of these toxins in the human digestive system.

6. What is the most likely source of pathogenic Bc in my food?

Bacillus cereus (Bc) are natural, common ubiquitous soil bacteria, so it is not unlikely to find them in food. The types of Bc that are most likely to adversely affect people are found in meats and starchy processed foods.  Fresh vegetables and fruits are highly unlikely sources of pathogenic Bc strains.

There is no evidence of a link between pathogenic Bc presence in food and the application of commercial Bt products. The Bt products do not contain pathogenic Bc.

7. What is the likelihood that a commercial Bt strain will produce enterotoxins?

Enterotoxins can only be produced when a microbe is actively growing.  Commercial Bt strains have been shown to have little to no growth on fruits and vegetables or in the human digestive system.

8. How is Bt differentiated from Bc?

Current methods to differentiate Bt products from potentially pathogenic Bacillus cereus (Bc) are generally based on the presence of insecticidal protein crystals or through whole genome sequencing.

Research organizations are developing new methods using PCR technology (a technology used to amplify  unique segments of the genetic code of the bacteria) or other modern tools to make this easier and faster.

There is a need for methods to rapidly differentiate Bt from Bc in food. Bt is necessary for sustainable food production because of its positive worker-safety profile, low impact on the environment and compatibility with beneficial insects; whereas Bc is not used in agriculture but is natural occurring.  

IBMA is open to opportunities for collaboration to fulfill this pressing need.

9. How are commercial Bt produced?

Commercial Bt are produced through fermentation in controlled, clean, conditions in fermenters, similar to those used to produce beer. Beginning with highly purified cultures, conditions are carefully controlled to favor the growth of only one organism: B. thuringiensis.  Because each bacterial strain can have slight variations in their optimal growth parameters, commercial Bt fermentation is carefully controlled to cover the specific needs of the single commercial strain being grown.  Commercial Bt products must conform to strict international guidelines of the OECD for microbial contamination, which is stricter than food safety requirements in some cases.  Commercial Bt strains themselves are identity-preserved through carefully maintained seed stock from the original isolates found in nature. This careful process makes sure it is the same pure strain every time a product is produced. Commercially produced Bt strains have been used effectively and safely for more than 50 years.

10. How are commercial Bt regulated?

To ensure the safety and effectiveness of products used in agriculture, the European Union has the most extensive and strict pesticide regulations in the world. Producers of Bt must submit detailed dossiers that include specific studies on human, animal, and non-target insect toxicology, long- and short-term environmental impact, and detailed assessments of the microorganism, among other requirements. These dossiers and studies are reviewed by regulators in all member states and by the European Food Safety Authority before the Bt products can be registered for use.  Bt products are currently registered in all European countries.  Regulatory agencies around the world, including the World Health Organization, have confirmed the value and safety of Bt products.  An outline of the extensive review process is available on the website of the European Food Safety Authority :

As with any crop protection product, Bt products should always be used according to label instructions, including the use of PPE.