IMS

IMS: Method based on the specificity of an antibody coated on the surface of a magnetic polymer particle for an antigen (macromolecule, cell or micro-organism

Methods of detachment: Protein A covalently coupled to beads and incubated with IgG before isolation. IgG & cells released by addition of IgG with a higher affinity for Protein A or by mechanical agitation

Enzymatic detachment: after selective isolation --> 10 min treatment with Chymopapain --> 90% detachment of cells

Method of detecting bacteria: Super- paramagnetic particles modified with a variety of molecular groups. Coated with antibodies specific to the target bacteria. Bacteria will be captured and concentrated from a culture medium.

Magnetic Particles:Non-porous compact particles e.g. Dynabeads M-280. Macroporous magnetic particles e.g. MAP1 (pores accessible to large molecules)

Magnetic separation & detection of micro-organisms: Separates & isolates organisms from large volumes & removes inhibitors of growth, detection methods e.g. PCR

Detection methods: Conventional plating techniques, ELISA, Nucleic acid based methods (PCR, Probe hybridisation)

Advantages of IMS: Concentration of cells from sample, Removes inhibitors from sample (e.g. PCR), pre-concentration of the target bacteria into smaller volumes for further testing, reducing and simplifying the pre-enrichment step, eliminating the matrix effect of the food components

Examples of Application of IMS:E.Coli, Salmonella sp., Bacillus sp., Shigella