Rapid identification of Listeria monocytogenes by cell surface protein based indirect ELISA

An indirect plate ELISA was clef eloped using polyclonal antibodies directed against crude cell surface protein (CSP) extract. 68 kDa CSP. 64 kDa CSP. 43 kDa CSP and whole formalin killed cells (WFC) of Listeria monocytogenes 4b (MTCC 1143). Minimum detection levels of heat killed L. monocytogenes cells by the standardized test were 10(5), 10(6), 10(7), 10(6) and 10(8) cells/ml for anti-crude CSR anti 68, anti 64, anti 43 and anti WFC sera, respectively, The cross reactivity of these sera was assessed with 39 Cultures comprising L. monocytogenes-11, other Listeria spp.-9 and other Gram positive and negative organisms-19. The results repealed that antibodies directed against 64 kDa CSP were more specific for L. monocytogenes than the other sera. These antibodies identified all L. monocytogenes isolates and did not cross react with an other bacteria except one positive and a weak positive reaction with L. seeligeri and L. innocua, respectively. Anti 43 kDa, anti crude CSP and anti WFC sera showed cross-reactions with many bacteria including other Listeria spp, Antibodies against 68 kDa CSP crossreacted only with L. ivanovii. L. innocua and L. welshimeri. The indirect plate ELISA using antibodies directed against 64 kDa CSP in conjunction with PI-PLC assay can be used for rapid identification of L. monocytogenes.