The Centers for Disease Control and Prevention (CDC) conducted an internal review of an incident that involved an unintentional release of potentially viable anthrax within its Roybal Campus, in Atlanta, Georgia. On June 5, 2014, a laboratory scientist in the Bioterrorism Rapid Response and Advanced Technology (BRRAT) laboratory prepared extracts from a panel of eight bacterial select agents, including Bacillus anthracis (B. anthracis), under biosafety level (BSL) 3 containment conditions. These samples were being prepared for analysis using matrix-assisted laser desorption/ionization time-of-flight (MALDI- TOF) mass spectrometry, a technology that can be used for rapid bacterial species identification.

What Happened: This protein extraction procedure was being evaluated as part of a preliminary assessment of whether MALDI-TOF mass spectrometry could provide a faster way to detect anthrax compared to conventional methods and could be utilized by emergency response laboratories. After chemical treatment for 10 minutes and extraction, the samples were checked for sterility by plating portions of them on bacterial growth media. When no growth was observed on sterility plates after 24 hours, the remaining samples, which had been held in the chemical solution for 24 hours, were moved to CDC BSL-2 laboratories. On June 13, 2014, a laboratory scientist in the BRRAT laboratory BSL-3 lab observed unexpected growth on the anthrax sterility plate. While the specimens plated on this plate had only been treated for 10 minutes as opposed to the 24 hours of treatment of specimens sent outside of the BSL-3 lab, this nonetheless indicated that the B. anthracis sample extract may not have been sterile when transferred to BSL-2 laboratories.

Why the incident happened: The overriding factor contributing to this incident was the lack of an approved, written study plan reviewed by senior staff or scientific leadership to ensure that the research design was appropriate and met all laboratory safety requirements. Several additional factors contributed to the incident:Use of unapproved sterilization techniques; Transfer of material not confirmed to be inactive; Use of pathogenic B. anthracis when non-pathogenic strains would have been appropriate for this experiment; Inadequate knowledge of the peer-reviewed literature; Lack of a standard operating procedure or process on inactivation and transfer to cover all procedures done with select agents in the BRRAT laboratory.

What Has CDC Done Since the Incident Occurred: CDC’s initial response to the incident focused on ensuring that any potentially exposed staff were assessed and, if appropriate, provided preventive treatment to reduce the risk of illness if exposure had occurred. CDC also ceased operations of the BRRAT laboratory pending investigation, decontaminated potentially affected laboratory spaces, undertook research to refine understanding of potential exposures and optimize preventive treatment, and conducted a review of the event to identify key recommendations.

To evaluate potential risk, research studies were conducted at a CDC laboratory and at an external laboratory to evaluate the extent to which the chemical treatment used by the BRRAT laboratory inactivated B. anthracis. Two preparations were evaluated: vegetative cells and a high concentration of B. anthracis spores. Results indicated that this treatment was effective at inactivating vegetative cells of B. anthracis under the conditions tested. The treatment was also effective at inactivating a high percentage of, but not all B. anthracis spores from the concentrated spore preparation.

A moratorium is being put into effect on July 11, 2014, on any biological material leaving any CDC BSL-3 or BSL-4 laboratory in order to allow sufficient time to put adequate improvement measures in place.+++What's Next: Since the incident, CDC has put in place multiple steps to reduce the risk of a similar event happening in the future. Key recommendations will address the root causes of this incident and provide redundant safeguards across the agency, these include: The BRRAT laboratory has been closed since June 16, 2014, and will remain closed as it relates to work with any select agent until certain specific actions are taken; Appropriate personnel action will be taken with respect to individuals who contributed to or were in a position to prevent this incident; Protocols for inactivation and transfer of virulent pathogens throughout CDC laboratories will be reviewed; CDC will establish a CDC-wide single point of accountability for laboratory safety; CDC will establish an external advisory committee to provide ongoing advice and direction for laboratory safety; CDC response to future internal incidents will be improved by rapid establishment of an incident command structure; Broader implications for the use of select agents, across the United States will be examined.

This was a serious event that should not have happened. Though it now appears that the risk to any individual was either non-existent or very small, the issues raised by this event are important. CDC has concrete actions underway now to change processes that allowed this to happen, and we will do everything possible to prevent a future occurrence such as this in any CDC laboratory, and to apply the lessons learned to other laboratories across the United States.