The Art and Science of Biological Detection

It is no secret to anyone in the hazardous-materials response field that the detection of biological agents is a complicated process. The detectors themselves are complicated, at least in terms of the sciences and operating principles involved. The biological agents that may or may not be present also are complicated, as is the determination that a suspicious white powder or other substance poses a credible health threat. Finally, the processes of sampling a biological agent and running a reliable and trustworthy test, or series of tests, add a completely different set of complications. Practically speaking, therefore, everything must go exactly right in order to run a dependable test and feel confident about the results. Moreover, even when everything is done right, a negative reading does not always mean that a biological agent is completely absent; on the other hand, a positive reading does not absolutely guarantee that the suspected agent is present.  

From a broad perspective, responders should look at effective biological detection as a multi-faceted operation, not reliant on a single test or detection technology. Monitoring for radiation hazards, flammability, corrosivity, and the presence of volatile organic compounds should be automatic, of course. In addition, any suspected biological agent should initially be tested against a protein screen and/or other “rule out” systems or devices. Determining whether or not a sample contains a protein (which may indicate the presence of a microbe) is a good first step. Basically, if a sample turns up negative for proteins, and the overall situation does not appear to be a credible threat, there usually is a low probability that the substance poses a significant health hazard.  

The next step should include an attempt to identify the substance. This is where the selection of current biological-detection systems comes into play. There are a number of detectors on the market, each employing a slightly different testing methodology. Regardless of what technology – PCR or immunoassay, for example – is selected, a few basic features of the machine should be understood.   

Polymerase chain reaction (PCR) technology involves genetic-based detection, which identifies the specific DNA or RNA of a suspected biological agent.

Immunoassay tests are based on an antigen-antibody response. Antigens are molecules present on the surface of foreign microbes; antibodies of various types form strong and specific interactions with antigens. The use of known antibodies to determine the presence of specific antigens is one of the most effective detection tools available to the scientific community.    

The user of the machine should understand two things from the beginning: First, that each monitor is unique in terms of sensitivity—sensitivity refers to the detector’s ability to determine the presence of even a small amount of biological agent in a sample.

Second, the monitor should not only be sensitive enough to pick up a biological agent below what is considered an “infective dose,” but also specific enough to rule out so-called neighbor organisms (thereby reducing the instances of false positive readings). If an assay is not sensitive enough, or if there are not enough microorganisms in the sample, a false negative reading may occur. If a detector is not specific enough to identify a particular agent, a false positive reading is likely. 

Prerequisites to Understanding

The sampling aspect of the operation can be thought of as the Achilles’ heel of biological detection. In many situations, if the responder does not completely understand the particular parameters the machine requires to run a test, the test may not be valid. There may be too much powder put into a buffered solution, for example, thereby making the machine incapable of processing the sample. On the other hand, if the sample is too diluted – i.e., there are not enough organisms present – the test may come up negative, leading the responder to believe there is no agent present. Either way, the results may be questionable, causing additional stress at the incident scene. It is important, therefore, to ensure that all samples are taken in strict accordance with the guidelines established by the manufacturer of the biological detector.  

If a suspected substance comes up positive for the presence of protein and is specifically identified by a reliable detector, the testing process should move toward confirmation by a public health laboratory, the commonly accepted “gold standard” of biological detection. Anthrax, to cite but one example of several biological agents now in the news, is not considered to have been truly identified as anthrax until a high-level public health lab has confirmed it by culturing. The process of culturing includes: (a) growing a colony of spores on a nutrient surface such as blood agar; and (b) visually observing the results through a microscope. In this instance, identifying a biological agent is considered by many to be as much of an art form – based on the observations and experience of the microbiologist running the test – as it is a science.  

Most biological agents, even those at or above lethal concentrations, would be invisible to the naked eye and therefore might require a responder to sample numerous areas of potential presence – e.g., any and all surfaces, liquids, and/or airborne environments – to obtain a sufficient quantity of the agent to run a test. This requirement adds a few additional complications. A slight breeze or air current created by a ventilation system, for example, may push or pull an aerosolized biological agent throughout a building, forcing responders to sample air-handling systems and secondary locations far removed from the original release location.  

A Simple Enough Challenge

Essentially, the accuracy of a biological-detection operation depends first on taking a sample in the right place with the right tools, and then on using a machine with a proven track record of reliability – i.e., sensitive enough to detect the suspected agent, but not prone to false positives. “To run a reliable test for a bio agent,” said Rick Thomas, Vice President of Government Programs for Sceptor Industries Inc., “you need to collect enough material to run a test. That may seem simple enough, but in reality, especially with an aerosolized release, collecting enough agent is a challenge.”  

Thomas, who has over 25 years of experience in the chemical and biological instrumentation field, recommends that responders adopt a “collect to detect” philosophy when it comes to positively identifying a biological agent. In situations where responders suspect an airborne release of a biological agent, or where powders may have become airborne, Thomas recommends the use of a concentrator and collector as an adjunct to a biological detector. “Our machine helps to concentrate air samples,” Thomas said. “We manufacture high-volume air samplers, intended to draw in and collect larger quantities of a suspected material and concentrate those substances in a solution. A responder can then remove that vial of solution, withdraw whatever amount the detector requires, and run a test.”  

Sceptor Industries, the manufacturer of the Omni 3000, a rugged and portable air sampler, has supplied aerosol sampling equipment for such major public venues as the Super Bowl and World Series, various Mardi Gras festivities, and other high-profile events. It is important to understand, Thomas said, that a sampler such as the Omni “is not a biological detector–it is designed to expand the ability of a responder to detect an aerosolized biological release by providing a highly concentrated sample of the ambient air. At events like the Super Bowl, for example, these air samplers can be strategically placed throughout the venue, and run for specific periods of time. The sample vials can be removed at certain intervals, and responders can use whatever amount of the solution they need to run a test with their own bio detector. It provides a unique opportunity to do biological detection at a large venue.”  

When it comes to sampling a suspect powder, Thomas said he believes that responders often neglect to consider the potential for an airborne hazard. “Responders should keep in mind that powders like anthrax are very easily blown around. If an agent happens to be dispersed into the ventilation system of a building, or otherwise released or blown into the air, the only way to retrieve those particles is by using an air sampler like the Omni. The way I see it, if you don’t sample the aerosol component, you may be missing something critical.”  

Differences and Distinctions in Detection

To a large degree, biological detection is a unique science – considerably different from the standard principles and practices of gas detection that most hazardous-materials responders are accustomed to. The primary difference is that biological detectors do not, as the typical gas detector does, sample the suspected environment and provide the user with real-time results. Similarly, in the field of chemical detection, if the proper detector is used and the released substance is within the detectable range of the machine, the user will receive an immediate reading that does not require validation by a laboratory or a public health agency.  

Another critical distinction lies in the fact that chemical substances (gases and vapors) do not need to be prepared or handled in any way in order to detect them. If a gas is present, and the detector is capable of “seeing” it, a reading will be obtained. In contrast, biological detection, because of the nature of the agents themselves and the limitations as well as capabilities of current detection technologies, will be effective only when all facets of the sampling and detection processes are performed correctly. To that end, it is incumbent on all responders both to understand the operational principles of their particular machines and to be fully trained to sample all potential environments with a wide array of tools and equipment.  

It is in that context that Thomas again cautions responders to consider the entire environment when sampling for a biological agent: “If you swab a desk, for example, and get a negative test result, you may not really have a ‘clean’ room,” he noted. For that reason alone it is “imperative,” he added, “to look not only at the surfaces, but also at the air. If you don’t know what’s in the air you may not be truly safe.”

Rob Schnepp

Rob Schnepp is division chief of special operations (ret.) for Alameda County (CA) Fire Department. His incident response career spans 30 years as a special operations fire chief, incident commander, consultant, and published author. He commanded numerous large-scale emergencies for the Alameda County (CA) Fire Department, protecting 500 square miles and two national laboratories in the East Bay of the San Francisco Bay Area. He twice planned and directed Red Command at Urban Shield, the largest Homeland Security exercise in the United States. He served on the curriculum development team and instructed Special Operations Program Management at the U.S. Fire Administration’s National Fire Academy. He is the author of “Hazardous Materials: Awareness and Operations.” He has developed risk assessment, incident management, and incident command training for Fortune 500 companies, foreign governments, and U.S. national laboratories.



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