Members of the genus Bacillus are aerobic, gram-positive, spore-forming, rod-shaped organisms. Some Bacillus species

are beneficial and are used in antibiotic or insecticide production; other species are implicated in food-poisoning or as agents of bioterrorism. Due to the large number of species and often incomplete descriptions of newly reported species, Bacillus species differentiation is difficult. 1 Additionally, a limited number of assays are available to distinguish between members of the “Bacillus cereus ” group, which includes B. cereus, B. thuringiensis, B. mycoides, and B. anthracis.2 Furthermore, studies have shown the only known difference between B. cereus and B. thuringiensis to be insecticidal toxin producing genes, which further complicates discrimination between these two species.3 Traditional identification has been based on Gram stain, colony morphology, motility, and biochemical testing, which are time-consuming, somewhat subjective, and labor intensive procedures. Both traditional and automated identification systems have difficulty identifying some Bacillus species and do not differentiate between strains. As the reality of bioterrorism attacks increase, such as the anthrax incident beginning in 2001, there is a need to develop systems to rapidly identify and differentiate biothreat agents. One possible solution is a commercial assay applying automated repetitive sequence-based PCR4 (rep-PCR), a method utilizing non-coding, interspersed repeat sequences as targets for oligonucleotide primers, which can be used to discriminate between species. This study explores the use and applicability of automated rep-PCR for the identification and strain differentiation of Bacillus species. RESULT