Identification and classification of Listeria by two-dimensional protein mapping

The cellular proteins of 29 Listeria strains belonging to different species and serotypes were analysed by two-dimensional (2-D) electrophoresis with the help of a computerized 2-D gel analysis system. The protein patterns were similar among strains within a Listeria species, but were different from one species to another. The comparative analysis of these protein maps enabled us to find specific proteins and to determine the genetic relatedness among Listeria spp. strains. The cluster analysis based on protein mapping showed a division between species and a clear separation of L. monocytogenes from other Listeria species. Inside L. monocytogenes the strains were divided into two main clusters in correlation with flagellar antigenic structures; this is in concordance with the results that have been found on the basis of multilocus enzyme electromorphs or DNA-restriction patterns. This technique enabled us to subtype the strains sharing the same serovar or the same lysovar. Because of its independence and high discriminating capacity, the 2-D protein mapping technique might provide a powerful tool for the identification and classification of Listeria strains.