Evaluation of antibodies for immunomagnetic separation combined with flow cytometry detection of Listeria monocytogenes

Four polyclonal anti-Listeria antibodies were evaluated for the detection of Listeria monocytogenes in direct and indirect assays using immunomagnetic separation with flow cytometry. The efficiency of immunocapturing using magnetic beads was also determined. None of the tested antibodies exhibited sufficient specificity or avidity to allow sufficient separation and detection of L. monocytogenes for a useful test that differentiated between negative (without cell) and positive (with cell) samples. Plating results confirmed that cells were captured with Dynabeads anti-Listeria and magnetic beads coated with goat anti-Listeria antibody with recovery ranging from 7 to 23%. Fluorescent-labeled polyclonal antibodies used in this study were not sufficiently specific to allow the detection of L. monocytogenes cells captured by the beads.