A Listeria monocytogenes-specific phage-displayed antibody fragment recognizes a cell surface protein whose expression is regulated by physiological conditions

We recently selected a phage-displayed single-chain antibody that detects several strains of Listeria monocytogenes and does not cross-react with any of the other five species of Listeria. The efficacy of a phage-displayed anti-L. monocytogenes single-chain antibody as a detection reagent was examined by enzyme-linked immunosorbent assay using L. monocytogenes grown at different temperatures and in a variety of media commonly used for the isolation of L. monocytogenes from food. The best results were observed when cells were grown in supplemented Fraser enrichment broth. The antigen detected by the phage-displayed antibody was present on the surface of the cells grown between 20 and 42C, but was not present on the cell surface when cells were grown at or below 15C. As determined by Western blot analysis, the antibody bound to a protein with apparent molecular mass of approximately 90 kD. Identification of the protein antigen would allow a more rational approach to the development of an antibody-based method for the specific detection of L. monocytogenes.