Microbial Forensics: A Scientific Assessment, 2003

Executive Summary

Microorganisms have been used as weapons in criminal acts, most recently highlighted by the terrorist attack using anthrax in the fall of 2001. Although such “biocrimes” are few compared with other crimes, these acts raise questions about the ability to provide forensic evidence for criminal prosecution that can be used to identify the source of the microorganisms used as a weapon and, more importantly, the perpetrator of the crime. Microbiologists traditionally investigate the sources of microorganisms in epidemiological investigations, but rarely have been asked to assist in criminal investigations. This colloquium examined the application of microbial forensics to assist in resolving biocrimes, with a focus on research and education needs to facilitate the use of microbial forensics in criminal investigations and the subsequent prosecution of biocrimes, including acts of bioterrorism.

A colloquium was convened by the American Academy of Microbiology and held in Burlington, Vermont on June 7-9, 2002. The purpose was to consider issues relating to microbial forensics, which included a detailed identification of a microorganism used in a bioattack and analysis of such a microorganism and related materials to identify its forensically meaningful source—the perpetrators of the bioattack.

Developing systems and methods to detect and track bioattacks will lead to greater safety and security for our nation against international terrorists. But it will also benefit the investigation of all biocrimes, including those carried out in a personal manner. In a very fundamental way, biocrimes are a public health concern and, as such, involve the public health infrastructure. Biocrimes against agriculture and the food supply system, in addition to impacting economic and political stability, have had and will continue to have consequences for human health. Partnerships among the law enforcement, public health, and agricultural communities could lead to long-term programs that will enhance efforts.

First responders to any suspected terrorist bioattack or other biocrime face a number of issues, beginning with their own safety and the safety of the public. After the primary issues of health and safety are addressed, they must consider forensic issues, such as proper collection of samples to allow for optimal laboratory testing, which is paramount, along with maintaining a chain of custody that will support eventual prosecution. Because a biocrime may not be immediately apparent, a linkage must be made between routine diagnosis, epidemiological investigation, and criminal investigation. There is a need for establishing standard operating procedures and training of first responders to meet these initial challenges, or, at a minimum, to be aware of them to minimize disturbance of the evidence.

While epidemiology and forensics are similar sciences with similar goals when applied to biocrimes, forensics has additional and more stringent requirements. Maintaining a chain of custody on evidentiary samples is one example of an extra requirement imposed on an investigation of a biocrime. Another issue is the intent in microbial forensics to identify a bioattack organism in greatest detail. If possible, forensic investigations will strive to identify the precise strain and substrain, rather than just to the species level, which might be sufficient in an epidemiological investigation. Some pathogen attributes that are unimportant in protecting public health may provide clues in a forensic investigation.

Although multiple national and international groups have developed lists of bioterrorism target pathogens, these lists are too narrow. An expansion of microorganisms relevant to food and water threats should be considered. Potential pathogens that could be used in a biocrime should be periodically reviewed to keep target lists current with scientific and political realities. Pathogenic potential, degree of protection (e.g., vaccination, effective therapy), and accessibility are a few of the characteristics that could be used to prioritize pathogen lists.

Computerized networks should be established to track infectious disease outbreaks in real time. Such systems do exist to some degree but better connectivity or communication is needed. These systems could alert public health and agricultural officials to the existence of a potential bioattack earlier than simply waiting for a report of a suspicious cluster of similar patients. Indeed, bioattacks might go undetected altogether if dispersed cases are not linked via such a system.

Once a biocrime is suspected, a wide variety of methods are available to identify the microorganism used in the bioattack and to analyze features that might lead to the source of the event (e. g., strain typing). A multipronged approach to such an investigation may be preferable, using many available methods—ranging from genomics to sequencing to physiology to analysis of substances in the sample. Infective samples are comprised of more than just the pathogen; analysis of contaminating spores or pollen, growth medium constituents, or even the water in the sample could be informative. Unfortunately, unique and possibly engineered pathogen attributes that enhance pathogenicity have to be considered for biocrimes. The needs of each case will dictate what tests may be needed.

Microbial forensics will be most effective if there is sufficient basic scientific information concerning microbial genetics, evolution, physiology, and ecology. Simply studying the pathogen without understanding biotic and abiotic environmental backgrounds will lead to false confidence in our ability to detect it. Strain subtyping analysis will be difficult to interpret if we do not understand some of the basic evolutionary mechanisms and population diversity of pathogens. Phenotypic features associated with evidentiary pathogens also may provide investigative leads, but full exploitation of these features can only be accomplished if we understand basic principles that control microbial physiology. Novel technologies and basic research support are needed for many microbial forensic endeavors.

Additional microbial forensics information may be gained through analysis of the host response. This may be as simple as testing for humoral immune response by temporal IGM and IGG responses to the epitopes of the offending microbe, which may lead to a differentiating perpetrator from a victim profile. Assays may evolve to validated cellular responses and possibly microarrays.

High quality assurance and quality control standards for microbial forensics will ensure highly reliable results and those results that will stand up in a court of law. More importantly, the Quality Assurance/Quality Control practices will provide the public a degree of confidence. Standard operating procedures, training of technologists, proficiency testing, enhanced databases, and multiple analyses are some of the steps that will meet this need. Setting up a multi-tiered laboratory system, analogous to or building upon the Laboratory Response Network, would be a great help in the microbial forensic area.

Finally, the more precise and refined a microbial forensic system becomes, the more proper guidelines for handling and storage will be defined. Thus, improper dissemination or use of the pathogens will be reduced and inadvertent release will be minimized. An additional outcome of establishing these guidelines or rules is that the legitimate investigator will be protected to pursue research without unnecessary intrusion.

Colloquium participants identified a variety of needs and directions in the following areas: sample handling and collection, detection, research direction, data access, QA/QC, and education. General recommendations are provided for direction or insight for the scientific community, law enforcement community, legal community, and the public.

 

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