Comparison of real-time polymerase chain reaction and conventional polymerase chain reaction methods for the rapid identification of Bacillus anthracis

Bacillus anthracis spores have been shown to be one of the most effective biological weapons. For the rapid detection of B. anthracis spores, several genetic markers, including chromosomal and plasmid-based sequences, were studied with polymerase chain reaction (PCR) methods. In the present study, a method using a primer/probe set based on the pXO1-encoded pag gene for the detection of B. anthracis was tested in addition to culture. Eight pathological samples (four blood-immersed cotton specimens, two spleen tissue specimens, and two blood smears) with confirmed positive results for anthrax were used. All samples were suspended in saline solution and fixed with Gram and Giemsa stains for examination of colony and capsule formation. Amplicons were analyzed on 2% agarose gels with the classic PCR method. For real-time PCR, a fluorescently labeled TaqMan probe was used with a Smartcycler. Positive smear and cotton samples were confirmed with the standard culture and real-time PCR methods, but the same samples were found to be negative with the classic PCR method. A spleen sample known to be positive for B. anthracis was found to be negative with the culture method because of possible contamination with Proteus-type bacteria.