Researchers at NASA’s Jet Propulsion Laboratory (JPL), Pasadena,California, have demonstrated a prototype device that automatically and continuously monitors the air for the presence of bacterial spores. The result is a novel alarm system that is reminiscent of smoke detectors.
Current methods for detecting bacterial spores, such as anthrax, require a trained operator. The large number of trained monitors required, and associated costs, limits widespread implementation of these methods.
‘Having a technician continuously monitor the air for spores is like having the fire department live at your house to ensure there is no fire,’ said Dr. Adrian Ponce, a chemist and senior member of the technical staff at JPL. ‘What you want is a smoke detector, a device that continuously monitors the air for smoke, or in our case, bacterial spores,’ he said.
Ponce and Elizabeth D. Lester, a senior in microbiology at Baylor University, Waco, Texas, performed tests on the anthrax detector last summer. They got their results using harmless Bacillus subtilis spores that were aerosolised to simulate an anthrax attack. Bacillus subtilis is found worldwide in soils and on root vegetables.
During the tests, aerosolised spores were captured with an aerosol sampler and suspended in a solution. Suspended spores were ruptured with microwaves to release a chemical from inside the spores called dipicolinic acid, which is unique to bacterial spores. This dipicolinic acid instantaneously reacts with the chemical sensor in the solution.
The sensor is said to trigger an intense green luminescence when viewed under ultraviolet light. The intensity of the luminescence corresponds to the concentration of bacterial spores in the sample.
If an increase in spore concentration is detected, an alarm sounds. A technician would respond to confirm the presence of anthrax spores using traditional sampling and analysis, such as colony counting and polymerase chain reaction, which amplifies DNA to measurable concentrations. The instrument response time is 15 minutes, fast enough to help prevent widespread contamination.
JPL’s bacterial spore detection system is simple and robust, a prerequisite for continuous monitoring. The system is designed for constant and unattended monitoring of spaces such as public facilities and commercial buildings. Two features of the device prevent false alarms. JPL’s detection technology discriminates against detecting aerosol components, such as dust, and the device only sounds an alarm when it detects a significant increase in spore count.
In a related development, JPL recently entered into an agreement with the Californian company, Universal Detection Technology (UDT), to mutually develop a commercially available anthrax ‘smoke’ detector. The partnership will combine JPL spore detection technology with Universal’s aerosol capture device.
The system used by UDT cannot distinguish between inorganic particles or biological substances such as bacterial spores. For the next 12 months, JPL will work to incorporate bacterial spore detection technology to make the device sensitive enough for use by Universal as a bioterrorism warning monitor.