A Better Anthrax Screener?

A speedier detector to thwart and deter terrorist attacks

4 min read

A newly marketed anthrax detector that originated in the U.S. space program promises to halve the detection time of the system currently used by the U.S. Postal Service. It was devised by Universal Detection Technology Inc., in Beverly Hills, Calif., building on work done by the Jet Propulsion Laboratory (JPL) at the California Institute of Technology, in Pasadena. If it proves its worth in the field, the system may offer the Postal Service a cheaper and more effective way of countering bioterrorist attacks [see photo, " "].

On 18 September 2001, exactly one week after the 9/11 attacks on the World Trade Center and Pentagon, letters containing anthrax, all with Trenton, N.J., postmarks, were mailed to ABC News, CBS News, NBC News, and the New York Post, all in New York City, and to the National Enquirer and the Sun at American Media Inc., in Boca Raton, Fla. Three weeks later, two more letters containing the deadly substance, also with the Trenton postmark, were discovered addressed to Democratic Senators Tom Daschle of South Dakota and Patrick Leahy of Vermont. In all, 22 people developed anthrax infections; 17 became severely ill and 5 died. The crimes are unsolved.

The anthrax spores in the deadly mailings contained millions of dried bacterial cells, which remain in suspended animation. If they are released into the air and then come into contact with moist surfaces such as nasal passages and lungs, they "wake up" and infect the host. Inside the lungs, the spores germinate just like plant seedlings and rapidly reproduce, causing fever, suffocation, and death. If about 3000 anthrax spores are breathed in within a half-hour, the dose is generally fatal. Rarely, anthrax can also be contracted through open cuts or sores on the skin, and this did occur in some of the postal attacks.

In 2002 the Postal Service received US $762 million from Congress to find and put into place an early-warning anthrax detection system. Ever since, research laboratories across the United States have been engaged in trying to develop new ways to detect the deadly spores. One of the first to succeed was a Sunnyvale, Calif., bioresearch laboratory, Cepheid Inc. It developed a genetic analysis system that could detect anthrax--and more.

In 2004, the Postal Service tested five Cepheid units, and it liked what it saw. The service installed 1700 units in 282 processing and distribution centers in 2005, at a cost of more than $250 million, or close to $150 000 per unit. This expense does not include an additional $100 million needed each year for operating costs, such as replacing the chemical cartridges that "sniff" for anthrax.

Named the GeneXpert, the Cepheid detector is simple enough to be maintained by anyone with minimal training. As mail whirs past the detector on sorting conveyors at up to 160 kilometers per hour, the air above the sorter is pumped into one of the chemical cartridges, which sounds an alarm within 30 minutes if it detects anthrax. Before, it would take a laboratory 24 hours or more for an anthrax analysis. What's more, GeneXpert can detect viruses that contain DNA, such as smallpox, or RNA, such as Ebola. It can also detect the poison ricin if it is in a crude extract containing DNA, says Kaye Chegwidden, the company's director of biothreat operations.

But now, the California company Universal Detection--which specializes in the manufacture of airborne particulate and pollutant detectors--has built a faster and cheaper device. "The time it takes for the machine to detect the presence of anthrax spores once the sample is collected is negligible--about 60 seconds--and the collection time is only 15 minutes," claims Amir Ettehadieh, the company's research director. While the device is still undergoing final calibrations, sales of individual units, for $45 000 each, have already begun.

Universal Detection's BSM-2000 continuously samples surrounding air for high concentrations of bacterial spores--there are others, mostly benign, besides anthrax. Normal room air contains naturally occurring bacterial spores in low concentrations of 0.01 to 0.50 spores per liter. The detector triggers an alarm only on registering a bacterial spore count of 50 or more per liter, on the assumption that a bioterrorist attack will release spores in much greater quantities than normally found.

In the detector, a microwave beam delivered by a fiber-optic system heats the outer shell of any bacterial spore and causes it to explode and release a particular chemical, dipicolinic acid (DPA), which is characteristic of all bacteria, including anthrax. The liberated DPA adheres to a tape strip within the device, and if enough collects on the strip, ultraviolet light causes a bright green luminescence to appear.

The GeneXpert system, in contrast, works on the principle that when cells divide, enzymes called polymerases are released that will prompt any contained DNA or RNA located in the chromosomes to start making copies. This is called a polymerase chain reaction.

So far, the GeneXpert detectors used by the Postal Service have detected no anthrax and have delivered no false positives. Given that solid performance, it's not a foregone conclusion that the BSM-2000 will be deemed superior and ultimately replace the GeneXpert, especially considering that the service has already invested heavily in the latter system. However, the Postal Service has compelling budgetary reasons for seriously considering alternatives in the longer term. The service requested $779 million for emergency preparedness for fiscal 2005 but obtained only $503 million from Congress. Unless there are additional appropriations, the Postal Service will have to cover biodefense expenditures out of its own revenues.

Besides being cheaper than the GeneXpert, the BSM-2000 requires little maintenance and does not require cartridge replacement, points out Ettehadieh. The Postal Service says that as new technologies emerge, it will evaluate them, working with the U.S. Department of Homeland Security.

The project that led to the invention of the BSM-2000 actually began in 2001, when NASA and JPL were looking for a new, efficient way to detect any bacterial spores clinging to spacecraft, to ensure that the planets and moons in our solar system do not become contaminated with germs from Earth. JPL created a device called the RapidSSEA (rapid single spore enumeration assay), and Universal Detection bought exclusive development rights in 2002. Last year the company won the Frost & Sullivan Technology Leadership Award for its work in biological detection technology. It is offering its new bacterial spore detector not only to the Postal Service but also to federal, state, and local government agencies.

Meanwhile, Universal Detection representatives have met with the Postal Service, which has expressed interest in learning more as results come in for the BSM-2000 on tests for interferents and false-positive rates.

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