Examination of Bacillus anthracis spores by multiparameter flow cytometry.

The ability to rapidly differentiate Bacillus anthracis spores from spores belonging to other Bacillus spp. is potentially useful for combating the intentional release of this biothreat agent. Furthermore, not all B. anthracis strains are fully virulent and the ability to determine the potential virulence of the endospore is also important. In this chapter, we describe a two-color flow cytometric assay capable of simultaneously identifying B. anthracis spores and the presence of spore-associated protective antigen, a virulence marker for strains harboring the pXO1 plasmid.