Identification of chromosomal markers for rapid detection of Bacillus anthracis is difficult because significant chromosomal homology exists among B. anthracis, Bacillus cereus, and Bacillus thuringiensis. We evaluated the bacterial gyrA gene as a potential chromosomal marker for B. anthracis. A real-time PCR assay was developed for the detection of B. anthracis. After analysis of the unique nucleotide sequence of the B. anthracis gyrA gene, a fluorescent 3' minor groove binding probe was tested with 171 organisms from 29 genera of bacteria, including 102 Bacillus strains. The assay was found to be specific for all 43 strains of B. anthracis tested. In addition, a test panel of 105 samples was analyzed to evaluate the potential diagnostic capability of the assay. The assay showed 100% specificity, demonstrating the usefulness of the gyrA gene as a specific chromosomal marker for B. anthracis.

Real-time PCR has become an important method for the rapid identification of Bacillus anthracis since the 2001 anthrax mailings. Most real-time PCR assays for B. anthracis have been developed to detect virulence genes located on the pXO1 and pXO2 plasmids. In contrast, only two published chromosomal targets exist, the rpoB gene and the gyrA gene. In the present study, subtraction-hybridization with a plasmid-cured B. anthracis tester strain and a Bacillus cereus driver was used to find a unique chromosomal sequence. By targeting this region, a real-time assay was developed with the Ruggedized Advanced Pathogen Identification Device. Further testing has revealed that the assay has 100% sensitivity and 100% specificity, with a limit of detection of 50 fg of DNA. The results of a search for sequences with homology with the BLAST program demonstrated significant alignment to the recently published B. anthracis Ames strain, while an inquiry for protein sequence similarities indicated homology with an abhydrolase from B. anthracis strain A2012. The importance of this chromosomal assay will be to verify the presence of B. anthracis independently of plasmid occurrence.Bacillus anthracis is a spore-forming gram-positive bacterium well known for its recent use as a bioterrorist agent. Identification of B. anthracis can be done clinically by Gram stain, colony morphology, and various biochemical tests (19). However, these methods are time-consuming, and more rapid tests, such as PCR, have been used to detect B. anthracis in clinical samples (20). Real-time PCR is preferred over conventional PCR methods for the identification of organisms because it is fast, is less labor-intensive, and adds the specificity of a probe. While real-time PCR assays have been used to identify B. anthracis on the basis of the virulence genes associated with the toxin-encoding plasmid (pXO1) and the capsule-encoding plasmid (pXO2) (11,20,22), a reliable chromosomal assay has not been developed. Chromosomal assays can be valuable tools when they are used in conjunction with virulence gene assays because they provide information on the genetic contexts of the pXO1 and pXO2 plasmids. While the chromosomal assays may not prove useful as initial screening assays, they can certainly have a significant role in confirmatory testing as part of an integrated diagnostic approach.Past attempts to develop a chromosomal real-time PCR assay have failed due to the close genetic relationship of Bacillus species. B. anthracis, Bacillus cereus, and Bacillus thuringiensis have very little variability and are genetically indistinguishable by multilocus enzyme electrophoresis (10). Recent work by repetitive PCR has shown that the previously listed species of Bacillus, as well as Bacillus mycoides, Bacillus pseudomycoides, and Bacillus weihenstephanensis, do have some genetic differences (3). Real-time PCR assays based on the chromosomal rpoB and gyrA genes of B. anthracis have been developed (5, 13, 25). However, these assays are based on single-nucleotide differences...

The implemented algorithm is available upon request.

Denaturing high-performance liquid chromatography (DHPLC) was evaluated as a method for identifying Bacillus anthracis by analyzing two chromosomal targets, the 16S-23S intergenic spacer region (ISR) and the gyrA gene. The 16S-23S ISR was analyzed by this method with 42 strains of B. anthracis, 36 strains of Bacillus cereus, and 12 strains of Bacillus thuringiensis; the gyrA gene was analyzed by this method with 33 strains of B. anthracis, 27 strains of B. cereus, and 9 strains of B. thuringiensis. Two blind panels of 45 samples each were analyzed to evaluate the potential diagnostic capability of this method. Our results show that DHPLC is an efficient method for the identification of B. anthracis.

Background: With multiple strains of various pathogens being sequenced, it is necessary to develop high-throughput methods that can simultaneously process multiple bacterial or viral genomes to find common fingerprints as well as fingerprints that are unique to each individual genome. We present algorithmic enhancements to an existing single-genome pipeline that allows for efficient design of microarray probes common to groups of target genomes. The enhanced pipeline takes advantage of the similarities in the input genomes to narrow the search to short, nonredundant regions of the target genomes and, thereby, significantly reduces the computation time. The pipeline also computes a three-state hybridization matrix, which gives the expected hybridization of each probe with each target.