That's the implication of what New Scientist has learned about the latest attempts to distinguish between the anthrax cultures held by different labs. But astonishingly, it appears that federal investigators have not yet collected all the samples that could tell them where the attacker got the bacteria in the first place.
Distinguishing between different labs' holdings, or accessions, of the Ames strain used in the attacks is extremely difficult. There's very little genetic difference even between different strains of anthrax, so spotting differences within a strain is harder still.
Paul Keim of Northern Arizona University at Flagstaff, who has been leading the genetic analysis of the anthrax since the first victim was diagnosed, has been focusing on regions in the bacterial genome where there are varying numbers of repeats. This at first turned up no differences between the Ames lineages (New Scientist, 9 February p 8). But Keim told a conference on microbial genomes in Las Vegas last month that he has discovered a repeat region that does vary. "We can distinguish among different Ames accessions," Keim told New Scientist.
Keim is not allowed to say what labs are involved. But his collection includes samples from the US Army Medical Research Institute for Infectious Diseases in Fort Detrick, Maryland, and from Dugway. Keim's team has been unable to distinguish between the attacker's bacteria and a sample that came from the British biodefence laboratory at Porton Down, which in turn acquired the bacteria from USAMRIID.
That suggests that differences have emerged between the attacker's anthrax and samples from Dugway-the only lab known to have recently produced the kind of fine, floating spore powder used in the attack. So if Dugway's bacteria are genetically different from the attacker's, it seems likely that he or she acquired a culture, possibly from USAMRIID, and weaponised it. That narrows the field to someone with access to fairly specialised equipment.
It will be impossible to home in on the source, however, until Keim's team has been able to compare samples from the over 20 labs known to have acquired the Ames strain from USAMRIID. But so far, the team has analysed only bacteria from the victims of the attack-which have all been identical-and from the few labs that had provided samples for Keim's collection before the attacks.
"No one knows of anyone who has been subpoenaed by the FBI to provide copies of cultures in their care," says Martin Hugh-Jones of Louisiana State University at Baton Rouge, who helped compile the collection of cultures used by Keim. Various labs have received subpoenas for records of cultures and people who had access to them. But the FBI has not demanded actual bacteria for analysis.
Author: Debora MacKenzie
New Scientist issue: 2nd March 2002
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