On June 19, the Centers for Disease Control and Prevention revealed that scientists and staff working in three low-security CDC laboratories may have been exposed to anthrax after high security laboratories Bioterror Rapid Response and Advanced Technology Laboratory sent them anthrax bacteria for experimentation that were not inactivated.

In light of the ongoing investigation on the incident, CDC scientists are currently conducting tests to determine if the procedure that was used to kill the anthrax bacteria before they were sent to less secure laboratories may have actually killed the pathogen after all.

CDC's environmental health and safety compliance office director Paul Meechan said that scientists from the CDC bioterrorism response lab retrace the events between June 6 and June 13 that led to the possible exposure of 84 CDC employees to the potentially lethal anthrax.

Investigations suggest that the bacteria in question may have been immersed in acid for 24 hours before these were transferred to the low-security laboratories. Scientists are trying to determine if 24 hours were long enough to kill the pathogen with Meechan saying that they're conducting experiments to prove it.  An independent laboratory also conducts the same experiments to see if they get the same results which would add credence to the findings.

Meechan said that scientists in the bioterror lab were conducting a test on a new protocol for inactivating anthrax before sending samples to low security labs. The procedure, which has been used to inactivate other bacteria, involved taking some anthrax that have been soaked in a bath of acid for 10 minutes and placing them on a nutrient-rich plate and then in an incubator. Scientists then checked if any anthrax colonies have grown after 24 hours.

Finding that none had, the scientists put the anthrax that had been in the acid bath for 24 hours on slides and then sent it to low security laboratories.  Materials from the 10-minute sample, however, germinated overtime, divided and formed a colony, a process that usually takes 48 hours.

 Meechan said that they are currently investigating why the scientists did not wait for the standard 48 hours to ensure that the bacteria had been killed. Investigators also want to know what was happening to the anthrax samples that were left in the acid bath while those from the 10-minute sample were in the incubator.

"We want to know whether or not in the 24 hours when they were waiting for that plate to grow, they were actually killing more of the anthrax, and possibly all of it," Meechan said.