Magnetic separation techniques in diagnostic microbiology

Abstract

The principles of magnetic separation aided by antibodies or other specific binding molecules have been used for isolation of specific viable whole organisms, antigens, or nucleic acids. Whereas growth on selective media may be helpful in isolation of a certain bacterial species, immunomagnetic separation (IMS) technology can isolate strains possessing specific and characteristic surface antigens. Further separation, cultivation, and identification of the isolate can be performed by traditional biochemical, immunologic, or molecular methods. PCR can be used for amplification and identification of genes of diagnostic importance for a target organism. The combination of IMS and PCR reduces the assay time to several hours while increasing both specificity and sensitivity. Use of streptavidin-coated magnetic beads for separation of amplified DNA fragments, containing both biotin and a signal molecule, has allowed for the conversion of the traditional PCR into an easy-to-read microtiter plate format. The bead-bound PCR amplicons can also easily be sequenced in an automated DNA sequencer. The latter technique makes it possible to obtain sequence data of 300 to 600 bases from 20 to 30 strains, starting with clinical samples, within 12 to 24 h. Sequence data can be used for both diagnostic and epidemiologic purposes. IMS has been demonstrated to be a useful method in diagnostic microbiology. Most recent publications describe IMS as a method for enhancing the specificity and sensitivity of other detection systems, such as PCR, and providing considerable savings in time compared with traditional diagnostic systems. The relevance to clinical diagnosis has, however, not yet been fully established for all of these new test principles. In the case of PCR, for example, the presence of specific DNA in a food sample does not demonstrate the presence of a live organism capable of inducing a disease. However, all tests offering increased sensitivity and specificity of detection, combined with reduced time of analysis, have to be seriously evaluated.

Use of immunomagnetic separation for the detection of Desulfovibrio vulgaris from environmental samples

“…Immunomagnetic separation (IMS) is a rapid, specific, efficient, and technically simple method that can be used for the separation and enrichment of a target organism directly from a consortium of non-target organisms or other particles. Magnetic separation based techniques are widespread in food and medical microbiology (Chapman et al, 2001;Foddai et al, 2010;Olsvik et al, 1994;Uyttendaele et al, 2000;Wadud et al, 2010), especially for Listeria spp. (Gasanov et al, 2005).…”

Automated Immunomagnetic Processing and Separation of Legionella Pneumophila with Manual Detection by Sandwich ELISA and PCR Amplification of the ompS Gene

“…After capturing the organisms with the beads, nearly all bioanalytical methods can be applied for detection, such as immunoassay, hybridization techniques, and PCR. 12,13 Furthermore, immunomagnetic cell sorting is also possible. For extracting mesenchymal stem cells from peripheral blood, an immunomagnetic cell sorter in combination with a mixer was developed by Inokuchi et al 14 In the first step, the cell suspension is mixed with antibody-coated paramagnetic beads.…”

Microstructure and Magnetic State of Fe3O4-SiO2Colloidal Particles

“…Magnetite nanoparticles have attracted a great deal of attention because of their unique physicochemical properties and great potential use in various biomedical applications, such as contrast agents in magnetic resonance imaging (MRI), carriers for targeted drug delivery, radio frequency hyperthermia, the magnetic separation in microbiology, biochemical sensing [1][2][3][4], etc.…”