Recent advances in the rapid detection of Bacillus anthracis

Bacillus anthracis is a Gram-positive, spore-forming rod that causes anthrax. Culture-based methods are the gold standard for the identification of virulent B. anthracis strains but these require days for completion. The experience from the anthrax attacks in September and October of 2001 revealed the urgent need for methods that can rapidly detect this pathogen with high reliability. Because of the extensive homology among non-anthrax Bacillus sp. at the chromosomal level, rapid detection of virulent B. anthracis strains depends on markers associated with the two plasmids, pXO1 and pXO2, responsible for its virulence. Genes encoding toxins and capsules have been used as markers for pXO1 and pXO2, respectively, in methods that are designed for rapid and sensitive detection of B. anthracis DNA, such as real-time polymerase chain reaction, direct liquid phase hybridization, and DNA microarrays. A variety of platforms can be modified to suit the needs for rapid detection of B. anthracis antigens, but little is known about plasmid-encoded antigens expressed in spores. Future studies should be aimed at detecting markers for pXO1 and pXO2in viable spores.