REACTIVITIES OF GENUS-SPECIFIC MONOCLONAL-ANTIBODY EM-6E11 AGAINST LISTERIA SPECIES AND SEROTYPES OF LISTERIA-MONOCYTOGENES GROWN IN NONSELECTIVE AND SELECTIVE ENRICHMENT BROTH MEDIA

Depending on the growth medium used for enrichment of bacterial cells prior to assay, the monoclonal antibody (MAb) EM-6E11 recognizing List eria genus-specific epitope on 43 and 94 to 97 kDa cell-surface antige ns (A. K. Bhunia and M. G. Johnson, Appl. Environ. Microbiol. 58:1924- 1929, 1992) exhibited extensive variability in the detection of Lister ia species. MAb EM-6E11 strongly detected live cells of all Listeria s pecies and all serotypes of L. monocytogenes by ELISA when cells were grown in nonselective brain heart infusion (BHI) broth, in selective L isteria enrichment broth (LEB), or in Listeria repair broth (LRB). In contrast, EM-6E11 detected only four of the thirteen serotypes of L. m onocytogenes (serotypes 1/2c, 3b, 4ab, and 7) when cells were grown in the UVM1 formulation of Listeria enrichment broth (UVM1) or Fraser br oth (FRB). This MAb failed to react with live cells of four other List eria species, including L. ivanovii, L, welshimeri, L. grayi, and L. m urrayi cells grown in UVM1 or FRB. Heating of Listeria cells at 100 de grees C for 20 min, irrespective of the enrichment media used, led to large losses of MAb EM-6E11 reactivity in ELISA, suggesting that the s pecific cell-surface epitopes involved may not be heat stable. Our res ults confirm that MAb EM-6E11 is suitable for detection of Live cells but not heat-killed cells of Listeria spp. and can be used in conjunct ion with an enrichment step in BHI, LEE, or LRB but not in UVM1 or FRB .