In October of 2001, several letters containing Bacillus anthracis spores were sent through the U.S. Postal Service to recipients in government buildings in Washington, D.C., and in private office buildings (Atlas, 2002). Twenty-three cases of human anthrax infection occurred. Five of them were fatal. As a result of this terrorist act, several post offices, mailrooms in government buildings, and private office buildings were contaminated with B. anthracis spores.
The response to this incident highlighted the need for a reliable, rapid method of detecting Bacillus spores. Since it takes several days for laboratories to determine the existence of anthrax spores with typical culture-based analysis, anthrax hoaxes place a very heavy burden on public health laboratories. A simple and rapid screening procedure that could detect spores in an unidentified powder would reduce the workload of the laboratories significantly. Appropriate actions could be taken immediately upon detection of the spores.
anthracis is an aerobic, Gram-positive, spore-forming, nonmotile Bacillus species (Mock & Founet, 2001). Its spores germinate when they are in an environment rich in amino acids, nucleosides, and glucose, such as the blood or tissues of an animal or human host (Ireland & Hanna, 2002). By contrast, in harsh environmental conditions, such as boiling, freezing, desiccation, and nutrient exhaustion, vegetative Bacillus species will turn into spores; the spores can survive for decades in adverse ambient conditions (Titball, Turnball, & Hutson, 1991; Williams, 1986).
Current methods of bacterial-spore detection, such as colony counting or polymerase chain reaction (PCR), require more than a working day to provide results (Lester & Ponce, 2002). To prevent the spread of toxic spores from the environment to a human host, a test is needed that determines the existence of spores in a very short time so that corrective actions can be taken accordingly. An adenosine triphosphate (ATP) bioluminescence assay can satisfy the need to detect the presence of viable spores in near real time. The ATP bioluminescence assay allows estimation of viable bacterial cells within minutes (Deininger & Lee, 2001). Bacterial spores are, however, deficient in ATP and are almost undetectable by a regular bioluminescence technique. Therefore, they need to be germinated to a vegetative state by a nutrient addition (Stopa, Tieman, Coon, Milton, & Paterno, 1999). The purpose of this study was to find the best and fastest heat shock conditions that trigger the breakdown of endospore dormancy of Bacillus and give a higher luminescence signal. The variables include germination time, temperature, nutrient type, and nutrient concentration.
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