Researchers from the National Institute of Standards and Technology (NIST) and the U.S. Army Dugway (Utah) Proving Ground have developed reliable methods, based on DNA analysis, to assess the concentration and viability of anthrax spores after prolonged storage. Because traditional methods to extract DNA from Bacillus anthracis spores - the bacterium responsible for anthrax - are too harsh to produce material suited for reliable measurements, the researchers developed an extraction technique using chemicals and enzymes to disrupt intact spores into releasing their DNA in a relatively pure state.
Working with samples that had been stored up to 2 1/2 years, the researchers team used two classic microbiological techniques to quantify Bacillus anthracis concentrations: counting spores under a microscope and counting the bacterial colonies that grow after the spores are spread on a nutrient surface and germinate. Scientists found that the better approach is to measure the amount of genetic material present in the sample. This method not only measures the DNA extracted from viable anthrax spores, but also DNA in solution from damaged spores, cell debris and spore fragments - yielding a truer measure of the source of DNA in the samples.
The study showed that laboratory-grade anthracis spores in suspension maintained their viability and did not clump when stored for up to 900 days. The results demonstrate that research-quality spores can be stored for long periods of time and still maintain their important properties. The findings could be good news for the Department of Homeland Security, which has been working with NIST to develop anthrax spore reference materials to calibrate spore detection equipment and to assess the efficiency of decontamination methods as part of its anti-terrorist efforts.
