AvirulentBacillus anthracisStrain with Molecular Assay Targets as Surrogate for Irradiation-Inactivated Virulent Spores

The revelation in May 2015 of the shipment of γ irradiation-inactivated wild-type Bacillus anthracis spore preparations containing a small number of live spores raised concern about the safety and security of these materials.The finding also raised doubts about the validity of the protocols and procedures used to prepare them.Such inactivated reference materials were used as positive controls in assays to detect suspected B. anthracis in samples because live agent cannot be shipped for use in field settings, in improvement of currently deployed detection methods or development of new methods, or for quality assurance and training activities.Hence, risk-mitigated B. anthracis strains are needed to fulfill these requirements.We constructed a genetically inactivated or attenuated strain containing relevant molecular assay targets and tested to compare assay performance using this strain to the historical data obtained using irradiation-inactivated virulent spores.A n effective and constant real-time surveillance capabil- ity is crucial for protecting the public from biological threats.Biological threats can be intentional (e.g., resulting from biowarfare or bioterrorism) or unintentional (e.g., resulting from accidental release or emerging infectious diseases) (1,2).Early detection of a biological threat is critical not only for identifying the threat organism but also for implementing appropriate countermeasures to save and protect the victims and prevent further infection and for decontaminating and reclamating the affected environment and infrastructures.The bedrock of successful biodetection platforms and sensors is use of well-characterized molecular assays, immunoassays, or other types of detection assays.Any assay development effort requires testing, evaluation, and validation of the assays with live or inactivated spiking materials in appropriate matrices relevant to the environments in which the assays are intended to be used (e.g., aerosol collection filters, soils, or clinical matrices).Distribution and use of select agents and toxins are restricted to facilities that have appropriate approval for storage and use of such materials in containment suites and are regulated by the Federal Select Agent Program of the Centers for Disease Control and Prevention (CDC; Atlanta, GA, USA) and the US Department of Agriculture Animal and Plant Health Inspection Service (Riverdale, MD, USA).For other facilities, inactivated select agents, including inactivated spores, historically were the source of reference materials.Many private and academic organizations, government agencies, and foreign government partners have used these materials for various activities, including quality control exercises and medical countermeasure research.In May 2015, previously shipped irradiation-inactivated B. anthracis spore reference materials were found to contain a small number of live spores (3,4).The incomplete inactivation of the spores raised concern about the safety and security of these materials and doubts about the Avirulent Bacillus anthracis Strain with Molecular Assay Targets as Surrogate for Irradiation-Inactivated Virulent Spores