At least seven people in an Oakland, Calif., research laboratory have been inadvertently exposed to live anthrax bacteria that had twice been tested to be dead, once by the vendor company that shipped it and once in the lab.

The seven work at Children's Hospital and Research Center at Oakland in a building located 1 mile from the hospital, and no one at the hospital itself was exposed. Three researchers were trying to create an anthrax vaccine using Bacillus anthracis that had supposedly been heat inactivated, while the other four people, and perhaps a few others yet to be determined, worked in the lab but not on the project, according to Ann Petru, an infectious disease specialist at the hospital.

Nasal swabs were taken, Petru said, "but they aren't processed yet." All seven have been put on a 60-day regimen of ciprofloxacin, she said, because they might develop anthrax even if their cultures show they are not carriers of the disease.

The problem was discovered this week after 49 of 50 mice inoculated with the B. anthracis last week quickly died. Subsequent attempts to culture both the material and a sample from one of the dead mice both showed the bacteria was alive. The Federal Bureau of Investigation removed the remaining material from the lab last Wednesday night (June 9).

At a press conference at the hospital yesterday, California Department of Health Services officials said they feel confident that there is no risk to anyone else in the research building or the surrounding community, according to Ken August, a departmental spokesperson. A 2-hour inspection convinced them that the lab had handled the bacteria properly, he said. Researchers had been wearing masks and proper clothing, and the lab's air is filtered both entering and leaving. According to Petru, the lab is a Biosafety Laboratory 2 (BSL-2) facility, appropriate for research with inactivated B. anthracis. All seven are still working in the lab, August said.

The focus of the ongoing investigation by the Centers for Disease Control and Prevention (CDC) is on the vendor, Southern Research Institute (SRI), which shipped the B. anthracis from its facility in Frederick, Md., about 3 months ago. "What happened there in this heat process that failed to kill the bacteria?" August asked. "What checks and balances do they have, and how did it pass through that?"

Thomas Voss, vice president of the Homeland Security and Emerging Infectious Disease Research Division at SRI, told The Scientist that his company tested the B. anthracis it shipped by trying to grow the material in a culture medium for 48 hours. The culture didn't grow, so SRI concluded that it was totally inactivated.

Petru said that when the samples arrived in the Oakland lab, workers there also tried to grow it in culture for 48 hours but failed, so they too concluded it was dead. When asked how material that had twice been tested as inactivated 3 months ago could now be alive, Voss said, "This is biology. It doesn't always work they way you expect it to work every time. You want to validate these procedures as fully as you possibly can, and that's what we're doing right now," to see if they are sensitive enough to ensure inactivity.

Voss said the sample sent to the Oakland lab is the only heat-inactivated B. anthracis sample SRI has ever shipped to any lab. The bacteria can also be killed with formaldehyde, UV light, and gamma radiation, he said. While Petru said the Oakland lab had only received one shipment, Voss said, "We've done two [shipments to the Oakland lab]. The ones we've done with these folks are probably the only ones we've done with Bacillus anthracis that's been heat killed. Outside of that, that's all."

Petru speculated that the SRI material is a heat-resistant mutant strain of B. anthracis: "If the material was properly processed, I think you have to presume it must be mutant, because heat didn't kill it, that's how you define it, right?" Voss said no one knows at this point.

Although both SRI and the Oakland lab cultured the shipment of B. anthracis, the Oakland lab did not subculture it by taking a sample of the first culture and transferring it to a fresh culture dish. Voss said he doubts SRI subcultured it either, although he has not yet verified that fact. With some bacteria, subculturing is important because it won't grow otherwise, according to a prominent bioterrorism researcher, who spoke on condition of anonymity because his organization competes with SRI. "We didn't subculture it prior to inoculating it," Petru said. "If we had, perhaps we would have discovered that."

Both August and Voss said the incident illustrates the heightened awareness and cooperation among government agencies fostered by the federal government's efforts to strengthen the US public health system in the wake of September 11. August said that from the time his department was notified, it inspected the lab, wrote a report, and held a press conference in a little more than 24 hours. "I've been with the department for about 16 years," he said. Of the cooperation among CDC, SRI, and state and local authorities, he said, "You wouldn't have seen that 3 years ago."

Richard Ebright, a professor at Rutgers University, said he thinks the extraordinary increases in the National Institutes of Allergy and Infectious Diseases budget, which is sponsoring the Oakland anthrax research, make accidents like this much more likely than they were before. "I think events like this are inevitable with the expansion of effort in this area," Ebright said. "I think that additional accidents of all flavors and descriptions as well as deliberate releases are inevitable with this expansion."