Bacillus thuringiensis in grain elevator dusts

Abstract

Grain dust from four large grain elevators along the Mississippi River near New Orleans, Louisiana, were analyzed for the presence of Bacillus thuringiensis, a pathogen of lepidopterous insects. Both settled grain dust and respirable grain dust samples were taken. A total of 20 settled and 53 respirable dust samples were assayed. No insects, alive or dead, insect parts, webbing, or feces were observed. Of the settled dust samples, 55.0% contained Bacillus thuringiensis, while 16.9% of the respirable dust samples were positive for this organism. Two hundred and fifty-five Bacillus colonies were studied, with 30.9% being Bacillus thuringiensis. Serological and biochemical tests showed 94.9% of them to be variety aizawai. Other varieties present were morrisoni, canadensis, indiana, and kurstaki.