Characterization and application of a Listeria monocytogenes reactive monoclonal antibody C11E9 in a resonant mirror biosensor

Abstract

Typical detection of Listeria monocytogenes involves selective enrichment, isolation and biochemical testing. Development of antibodies to Listeria species has improved detection; however, most antibodies detect all species of Listeria. A previously developed monoclonal antibody (MAb)-C11E9 was examined for its reaction to 13 L. innocua and 40 L. monocytogenes strains representing all 13 serotypes by ELISA. Absorbance values for L. monocytogenes strains were 0.44–3.58 and for L. innocua 0.22–1.44. ELISA reactions were divided into three arbitrary groups of high (Abs 1.0 or higher), intermediate (0.6–0.99) and low (0.18–0.59). Most L. monocytogenes strains (32/41, 78%) were in the high group while only 23% (3/13) of L. innocua were in the same group. In the Western blot assay, antibody reacted with phosphate-buffered saline (PBS) extracted protein preparations of 52, 66 and 97 kDa. Ribopattern of all strains was analyzed and no clear relationship was observed for antibody reaction and ribotype of a given strain. MAb C11E9 was used in a resonant mirror biosensor (IAsys sensor), but failed to detect any viable intact L. monocytogenes cells at levels as high as 10 8 cells/ml; however, it showed binding (85–150 arc/s) with the surface protein preparations containing the 97-, 66- and 52-kDa proteins at 208 μg/ml. Binding kinetics of L. monocytogenes and L. innocua surface protein extracts showed significantly ( p<0.05) higher responses than the three other Listeria species ( L. ivanovii, L. welshimeri and L. grayi), which could be detected in 10–20 min. These data corroborate with ELISA results. In summary, this study suggest that MAb-C11E9 is suitable for detection of all serotypes of L. monocytogenes despite cross-reaction with L. innocua and could be used for detection of soluble protein extracts in the resonant mirror (IAsys) biosensor.