Update on the detection of beta-exotoxin in Bacillus thuringiensis strains by HPLC analysis.

Aims: The current work aimed to study the presence of β-exotoxin by high-performance liquid chromatography (HPLC) in supernatant fluids from final whole cultures of the 69 type strains and 13 subtypes of Bacillus thuringiensis strains, as well as from some insecticidal strains. Methods and Results: Results from HPLC and bioassays with Ephestia kuhniella (Lepidoptera Pyralidae) were compared. Type I β-exotoxin was only detected in type strains representing serotypes H1, H9 and H10a,10b. Discrepancies between HPLC and bioassays were found in H8a,8b and some insecticidal strains, which suggests the occurrence of another soluble toxin different from type I β-exotoxin, possibly type II β-exotoxi…