Chemical and Biological Terrorism Research and Development to Improve Civilian Medical Response (1999) / Chapter Skim
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6 Detection and Measurement of Biological Agents
6 Detection and Measurement of Biological Agents
Pages 78-96
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From page 78... ...
There will be no fire and rescue teams responding to a 911 call in an incident involving covert release of a biological agent, and thus little use for the sort of rapid detection devices that are so important in responding to chemical releases. Public health surveillance systems and the rapid analysis of information from those systems may in time provide an indication of when and where the biological agent was released, but unless there is a continuing source of agent, testing the release site at that point will probably be useful for forensic purposes only (testing may also be helpful in 78
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From page 79... ...
DETECTION OF BIOLOGICAL AGENTS IN CLINICAL SAMPLES (PATIENT DIAGNOSTICS) The classical approach to microbial detection involves the use of differential metabolic assays (monitored colormetrically)
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From page 80... ...
The design of the probe can be highly specific if there is a good fit to a pathogen-unique region of the target nucleic acid, or it can provide more generic identification if there is a fit with a region of nucleic acids conserved among several related pathogens. The sensitivity of these hybridization assays for bacteria is between 1,000 and 10,000 colony-forming units; improved sensitivity is an important area of research.
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From page 81... ...
A large array incorporating many more common pathogens as well might encourage everyday use in large medical labs and eliminate the bottleneck to rapid diagnosis identified in the previous chapter the need for a suspicious clinician to order an assay for a very rare disease. A similar but smaller microarray of gel-immobilized, fluorescencelabeled nucleic acids is being developed by Argonne National Laboratory (Yershov et al., 1996~.
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From page 82... ...
Until the recent development of combinatorial chemistry methods, ligand-based probes directed at specific receptors had been dyes that are structural analogs for ligands of microbial receptors and used in classical microbiological screening tests. More recently, scientists at Utah State University (Powers and Ellis, 1998)
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From page 83... ...
Electrochemical transducers utilize enzymes to generate an electrochemical signal, either amperometric or potentiometric (amperometric sensors are more sensitive)
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From page 84... ...
Specificity is derived from the probe material. Piezoelectricity is the basis for several chemical agent detectors using surface acoustic wave (SAW)
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From page 85... ...
Hybrid Technologies There are some detection devices in which there is no clear division of probe and transducer. Methods based on physical properties and separation are good examples: mass spectrometry and gas or liquid chromatography.
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From page 86... ...
DETECTION OF BIOLOGICAL AGENTS IN THE ENVIRONMENT Real-time detection and measurement of biological agents in the environment is daunting because of the number of potential agents to be distinguished, the complex nature of the agents themselves, and the myriad of similar microorganisms that are a constant presence in our environment and the minute quantities of pathogen that can initiate infection. Few, if any, civilian agencies at any level currently have even a rudimentary capability in this area.
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From page 87... ...
Therefore, positive results need to be confirmed with standard microbiology assays, conventional immunoassays, or genome detection via polymerase chain reaction (PCR) technology.
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From page 88... ...
Application to detection of biological agents in the environment differs from patient diagnostics primarily in the increased need for portability, ease of use by nonscientists, speed, and methods for collecting and preparing the sample. The following pages first describe the main approaches to sampling the environment for biological agents.
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From page 89... ...
By passing the collection probe airflow into successive virtual impactors, the particles can be concentrated to many times the original air concentration before collection. The final stage can then impact the particle stream into a liquid, resulting in a highly concentrated liquid sample (Boiarski et al., 1995~.
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From page 90... ...
Significant advances have been made with the use of lasers for the detection of aerosolized agents by light-scattering characteristics, infrared and Raman spectroscopy, and fluorescence, but these same methods can also be used to determine total microbial contamination on objects (Powers and Ellis, 1998) and in situations where effective sampling is impossible for reasons other than distance.
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From page 91... ...
Needs in this regard include not only investigation of suspected sources of contamination but also monitoring the air/water systems in buildings for general pathogen contamination or contamination by specific biological agents. A number of the embryonic microbe detectors described above in the section on patient diagnostics are being examined for utility in environmental detection as well.
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From page 92... ...
The sensitivity of detection of nucleic acids can thus be greatly improved by nucleic acid amplification. The polymerase chain reaction (PCR)
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From page 93... ...
are taking the last of these areas one step further, reducing the size of anthrax antibodies to that fragment of the light chain actually binding the antigen, identifying the relevant amino acids at the binding site, and making systematic substitutions to achieve higher affinity and selectivity. The previously described device under development at Utah State University for detection of total pathogenic microbes (including spores)
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From page 94... ...
The Department of Energy's Chemical Biological Nonproliferation Program is sponsoring a similar developmental effort at ORNL, where researchers are attempting to leverage hardware and software engineering currently under way in connection with the second generation CBMS to produce a man-portable, realtime system capable of identifying airborne bacteria or volatile organics as well as characteristic proteins of biowarfare viruses, toxins, and bacteria (McLuckey, 1998; McLuckey at al., 1998; Stephenson et al., 1998~. Although MS has the potential to identify infective agents and recent advances have significantly reduced the size of the device, libraries of unique signatures of agents have not been determined.
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From page 95... ...
The ability to determine total viable microbes present, total pathogenic microbes, and specific viable pathogens will likely cover the needs presented by both overt and covert "events" as well as provide monitoring and early warning. The ERDEC/EnViron virus detection system might prove to be a useful complement to a ligand probe system for detecting total pathogenic bacteria and handheld immunoassay tickets in a multistage approach beginning with the very general and progressing to the highly specific as required.
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From page 96... ...
The committee therefore has identified the following research and development needs: 6-1 In the area of patient diagnostics, the Public Health Service should encouragefederal research agencies to leverage burgeoning commercial development of faster, cheaper, easier assays of common pathogens rather than independently developing diagnostic technologyfor the less common pathogens thought to be good candidates for bioterrorism. 6-2 In the area of environmental detection, the Public Health Service should closely monitor military biodetection R&D effortsfor inexpensive or multipurpose biodetectors that might be appropriate for purchase or loan by civilian agencies rather than developing threat agent-specific assays)
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