Anthrax testing: look to NASA?

Although federal administrators told Congress earlier this month that they didn't find all the anthrax that contaminated post offices in 2001 because no validated testing procedure existed at the time, a NASA researcher who helped create a highly accurate procedure that the agency has used to test spacecraft for bacteria since the 1970s said there's no reason it couldn't have been used to find anthrax in 2001. Similarly, three other methods are being tested by federal agencies, all of which require validation before they can be considered reliable.The NASA method—which was most recently used before the two Mars rovers left Earth—involves streaking a wet swab made of cotton or soft plastic over a 25-square-centimeter surface. "The NASA standard assay technique is a well defined and reproducible technique for the recovery of [bacterial] spores from solid surfaces," Larry Kirschner, a NASA researcher who did much of the 1970s work, told The Scientist. The technique should therefore work well for anthrax bacterial spores, although he recommended testing it on indoor surfaces first to make certain.Linda Stetzenbach, a professor at the University of Nevada at Las Vegas who testified before Congress earlier this month, told The Scientist that the NASA technique is now widely used outside the agency for other bacteria, over a standard area four times as large, 100 square centimeters. However, neither she nor Kirschner have ever seen a published validation of that change, and they agree that one is necessary.Tanja Popovic, acting associate director for science at the Centers for Disease Control and Prevention (CDC), testified at the hearing that no validated methods for sampling anthrax existed in 2001. She told The Scientist after the hearing that although the NASA technique is helpful, it cannot be considered validated for anthrax detection because "these studies have not been done on biothreat agents," just bacterial spores in general.Stetzenbach said that to her knowledge, only two sampling methods have ever been validated outside of NASA. The Army funded her lab to validate one, a technique called BiSKit which allows large surfaces to be tested using a tiny fraction of the samples that otherwise would be required. After she found serious initial accuracy problems, "we alerted the government to some of those issues, they corrected it, and it ended up being a really good sampler," she said.But more research is underway, some begun as long as 2 years ago. The Department of Homeland Security is paying for the CDC and the Environmental Protection Agency (EPA) to collaborate on validating three standard sampling methods at the Department of Energy's Sandia National Laboratories in Albuquerque, Popovic said. The CDC and EPA will validate the same three methods at the US Army's Dugway Proving Ground in Utah, she said, not only for anthrax, but also for additional biothreat agents.Stetzenbach said that while three procedures are a good start, they're not enough. "There are many other methods out there that may well be more useful for first responders and forensics and others, and they're not being studied," she said.Keith Rhodes, the chief technologist in the Government Accountability Office's Center for Technology and Engineering, agreed. If they're "not looking at everything, I'd have to ask why," he said.The CDC and EPA are also trying to standardize sampling methods across different labs by creating a national consortium of labs, according to Dana Tulis, the deputy director of the EPA's Office of Emergency Management, who testified at the hearing.Mike Mazza, of the Department of Defense's (DOD) Joint Program Executive Office for Chemical and Biological Defense, told The Scientist that the DOD's other labs are also involved in improving sampling techniques, in particular the US Army Medical Research Institute for Infectious Diseases in Frederick, Md., and the Naval Medical Research Center in Silver Spring, Md.Despite the new research, at least two problems remain unsolved. Although newer anthrax assays that use polymerase chain reaction can detect much lower levels of anthrax's two virulent plasmids, Stetzenbach said her research shows that dust on surfaces can lead to false negative results.Rhodes said the main remaining problem is a disagreement between scientists and some federal agencies about the necessity of performing "statistical" sampling when initial "targeted" sampling, the current method of testing only likely contaminated surfaces, gives negative results. According to a report by the Government Accountability Office released for the Congressional hearing, statistical sampling—in which all surfaces are divided into small grids and randomly sampled—is necessary to avoid a repeat of the 2001 false negative incident in a Wallingford, Conn., postal distribution center. But the US Postal Service and the CDC remain unconvinced, with Popovic agreeing only that statistical sampling "could be added as an additional tool."

Anthrax testing: look to NASA?

Space agency validated spore detection procedure in 1970s, but needs testing for biothreat agents

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