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Category: Environmental Microbiology
Analysis of Bioaerosol Samples, Page 1 of 2
< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555815882/9781555813796_Chap75-1.gif /docserver/preview/fulltext/10.1128/9781555815882/9781555813796_Chap75-2.gifAbstract:
Respiratory exposure to certain pathogenic or toxigenic microorganisms and/or elevated concentrations of environmental organisms could result in health effects, such as allergic reactions, irritant responses, toxicosis, and respiratory illness. This chapter presents an overview of available methods for the analysis of bioaerosols. In addition, the potential use of enhanced monitoring of bioaerosols with PCR, biochemical, and immunological assays is discussed. Several conditions, such as pH, temperature, water activity, nutrients, antibiotics, light, and aeration, can be manipulated to favor the growth of a selected group of organisms. In contrast with culture techniques, microscopic analysis allows enumeration of both culturable and nonculturable microorganisms. However, identification of microorganisms to the species level is usually not possible without the aid of a taxon-specific technique, such as immunospecific fluorescence staining. Flow cytometry offers an alternative to microscopic enumeration of total cells. In a different application of flow cytometry, researchers coupled sandwich immunoassay utilizing microsphere beads with flow cytometry for the detection of biothreat agents. Fluorescence immunoassay consists of staining samples with a fluorescently labeled antibody that binds specifically to the antigens on the surfaces of the target organisms and enumeration by epifluorescence microscopy. Hybrid technologies are being developed that combine more than one analysis method to maximize the accuracy of the results obtained. One such system utilizes immunoassay, flow cytometry, and PCR analysis in various combinations for the continuous monitoring of airborne biological threat agents.
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Diagrams illustrating competitive PCR (cPCR) and QPCR. (A) In cPCR, the target template and the internal control DNA compete for the oligonucleotide primers during the PCR assay. Post-PCR manipulations are required to separate the target and competitor products and to determine the ratio between them (i.e., final product concentrations). (B) In QPCR, a fluorescent probe anneals to the target DNA between the specific primer binding sites. As new DNA is synthesized, the probe is cleaved by the Taq polymerase, causing it to fluoresce; the amount of fluorescence is used to measure the initial target DNA concentration.