An investigation of bacillus thuringiensis in rectal-collected fecal samples of cows.

In order to better understand the range and role of Bacillus thuringiensis (Bt) and its toxins in nature, we have undertaken a study of Bt taken directly from the rectum of 117 cows from 37 farms on the Caribbean island of Trinidad. Thirty-seven fecal samples (32%) were found to contain at least one Bt. Generally only one or two isolates with a particular crystal morphology were isolated from any one sample, however, a few samples contained more, up to 11 isolates, suggesting post-ingestion amplification.