Paul Jackson of Los Alamos National Laboratory, New Mexico, says some strains of B. cereus are more different from each other genetically than they are from B. anthracis. Bt, B. cereus and B. anthracis were considered different species because they favour different hosts and carry different plasmids. Two plasmids in B. anthracis code for toxins that cause anthrax in mammals. Bt has one that makes insect poisons. And although its plasmids seem innocuous, the main part of Bt's genetic material codes for toxins that can cause diarrhoea, vomiting, muscle and kidney damage and liver failure .
Manufacturers insist their commercial strains are safe.
Abbott refused to make any further comment on any aspect of Bt safety. But recent research in Canada suggests that commercial strains of Bt do make B. cereus toxins. Vern Seligy and colleagues at the Canadian federal health ministry told the American Society for Microbiology in Chicago in June that, at concentrations similar to those in aerial sprays, two commercial strains of Bt killed human cells in culture, by producing toxins that behaved like those from B. cereus . There are also reports of health damage with Bt. Their symptoms included diarrhoea, vomiting and respiratory problems.