OnLine Journal of Biological Sciences

Development of an Immunomagnetic Separation Method for Viable Salmonella Typhimurium Detected by Flow Cytometry

Shakil Ahmed, Horst-Günter Rubahn and Helmut Erdmann

DOI : 10.3844/ojbsci.2016.165.174

OnLine Journal of Biological Sciences

Volume 16, Issue 4

Pages 165-174


A very small number of bacterial pathogens may have fatal effects on food safety. In spite of having great advancements in bioanalytical methods, most of the accepted detection methods are still cultivation based and thus time consuming. This leads to an intense need for efficient and rapid methods for detection of food-related bacteria. In this study, a flow cytometry based immunomagnetic separation (IMS) method for the isolation and enrichment of Salmonella Typhimurium from liquid samples was developed and optimized. Both polyclonal and monoclonal antibodies have been used to couple with 1 micron sized paramagnetic particles for the preparation of immunomagnetic beads (IMBs). The most suitable antibody was chosen by applying an enzyme linked immunosorbent assay (ELISA), whereas living bacteria were detected by flow cytometry. The parameters for both IMS and flow cytometry e.g., concentration of bead and bacteria, immunocapture time, staining and buffering conditions for the viability assays were optimized. The capture efficiency of IMS was>98% for a range of Salmonella Typhimurium cell concentrations from 103 to 105/mL using 108/mL bead concentration. The method proved to have high (98%) specificity towards Salmonella Typhimurium and very low (< 5%) binding with non-target bacterial strains.


© 2016 Shakil Ahmed, Horst-Günter Rubahn and Helmut Erdmann. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.