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Radioactive source material for gamma radiation requires background checks for individuals and other security checks • Long exposure times • Some types of pathogens are resistant, including sporesb • Expensive • Sample size and radiation source affect the dose, complicating the inactivation process Chemical methods of inactivation Chemical inactivation Chemicals inactivate pathogens by (a) destroying the structure of proteins, (b) destroying the integrity of the nucleic acids, (c) negatively affecting the cell’s wall or disrupting the cell’s membrane, or (d) bonding the proteins during fixation of tissue samples. A wide range of chemicals are used for inactivation. • Varying concentrations of some chemicals can destroy a wide range of pathogens • Some chemicals act quickly • Flexibility to determine end product (e.g., proteins or nucleic acids) through chemical selection • Some chemicals can be irritating and toxic to humans • Some chemicals only work on specific pathogens • In certain circumstances, the pathogen can repair itself • Manufactured kits may not specify which chemicals are used. In these cases testing must be done to identify the effects of the chemical before research can start. Source: GAO analysis of information from peer-reviewed journal articles, experts, and agency documents. | GAO-16-642 a As an inactivation method, filtration works by filtering out the actual viable pathogenic materials from the sample (leaving viable material on the filter), as opposed to traditional inactivation methods, which render pathogens nonviable. b Spores are thick-walled cells produced by some bacteria and fungi that are capable of survival in unfavorable environments and are more resistant to antimicrobial agents. Page 10 GAO-16-642 Inactivation of Pathogens Following inactivation, researchers may test the viability of the material to ensure the pathogen was rendered nonviable. Different methods exist to test the viability of a pathogen, depending on the conditions under which the pathogen grows. For example, viability may be tested by attempting to grow inactivated material on cultured cells or by exposing animals to inactivated material to see if they become infected. Key Terms Related to Pathogen Inactivation • Decontamination: the removal or count reduction of contaminating pathogens present on an object. • Disinfection: the elimination of nearly all known pathogens but not necessarily all microbial forms, e.g., spores on inanimate objects. • High-containment laboratory: biosafety level (BSL)-3 or 4 facilities in which studies are conducted on a variety of dangerous pathogens and toxins. • Inactivation: a process to render infectious material (e.g., pathogens) unable to cause disease, but retain characteristics of interest for future use. • Irradiation: exposure to radiation (e.g., ultraviolet light, gamma rays, X-rays). • Kill curve: the results of a dose-response experiment where a pathogen is subjected to increasing amounts of the inactivating agent to determine the minimum conditions required to render it nonviable or noninfectious. • Nonviable: a pathogen that is no longer capable of growing, replicating, infecting, or causing disease. • Protocol: a detailed plan for a scientific procedure. • Select agent: in the United States, biological select agents (e.g., bacteria, viruses) and toxins have the potential to pose a severe threat to public, animal, or plant health, or to animal or plant products. • Validation: for the purpose of inactivation methods, the method must be scientifically sound and produce consistent results each time it is used such that the expected result can be ensured. Methods of validation may include (1) use of the exact conditions of a commonly accepted method that has been validated, (2) a published method with adherence to the exact published conditions, or (3) for in-house methods, validation testing should include the specific conditions used and appropriate controls (from the Select Agent Program). Source: GAO analysis of scientific literature and comments from our expert meeting. | GAO-16-642 Page 11 GAO-16-642 Inactivation of Pathogens Congress passed the Public Health Security and Bioterrorism Preparedness and Response Act of 2002 to improve the ability of the United States to prevent, prepare for, and respond to bioterrorism and other public health emergencies.16 This act was one of several acts passed in reaction to the September 11, 2001, terrorist attacks and subsequent anthrax incidents to combat terrorism and address increasing concerns about biological security.17 It expanded HHS’s authority to regulate select agents to include oversight of all laboratories that possess, use, and transfer select agents affecting public health and safety, and granted comparable authority to USDA for select agents posing a threat to plant or animal health, or animal or plant products. CDC’s Division of Select Agents and Toxins is responsible for the oversight and regulation of select agents that could pose a threat to public health and safety, such as the Ebola virus. APHIS’s Agriculture Select Agent Services is responsible for the oversight and regulation of select agents that could pose a threat to animal or plant health or animal or plant products, such as the virus that causes foot-and-mouth disease. Some select agents, such as Bacillus anthracis, are regulated by both agencies because they pose a threat to
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