A New Competitive Fluorescence Immune-Assay for Detection of Listeria Monocytogenes

Lacroix, Monique ;   D'Auria, Sabato

A new competitive immune assay has been designed using a specific monoclonal antibody (anti-p60 IgG) labeled with a fluorophore. A specific and highly conserved peptide of 11 amino acids from the protein p60 of L. monocytogenes has been synthesised and used for the production of a monoclonal anti-p60. This antibody was used in the conception of a detection test able to detect 1 CFU of L. monocytogenes after only 18 hours of incubation with a minimum of manipulation. The test is based on a competition principle between the recombinant p60 protein and the p60 from L. monocytogenes present in the sample. A column containing a sepharose matrix was used to immobilize the recombinant p60 protein and the labeled monoclonal antibody which is captured by the p60 from the sample when added to the column. An increase of the fluorescence signal in the eluate means a positive result. No cross-reactivity was observed with non-pathogenic Listeria species and each serotype of L. monocytogenes can be detected whereas some other immunological methods show cross-reactivity and false negative.