Multiplex polymerase chain reaction for detection and differentiation of the microbial insecticide Bacillus thuringiensis.

A rapid identification of Bacillus thuringiensis strains was established by using multiplex polymerase chain reaction (PCR). Primers of high homology specific to regions within genes encoding three major classes of B. thuringiensis crystal proteins were used to generate a PCR product profile characteristic of each strain of B. thuringiensis subsp. kurstaki. Differentiation among these strains was made on the basis of the electrophoretic pattern of the PCR products. Known B. thuringiensis subsp. kurstaki strains as well as unidentified strains isolated from insect cadavers were analyzed by PCR. Small amounts of crude sample lysates were assayed in a two-step PCR containing five primers capable of distinguishing between the strains giving products of 1,500, 858, and 653 bp for the CryIA(a) CryIA(b), and CryIA(c) genes, respectively. The method can be applied to rapidly detect the strains of B. thuringiensis subsp. kurstaki in commercial formulations and in the field.