Widely used Listeria monocytogenes strains EGD, 10403S and EGD-e are genetically and phenotypically different.. Listeria monocytogenes EGD isolate:EGD

For nearly three decades, listeriologists have been using a restricted number of strains to analyze the virulence of the facultative intracellular pathogen Listeria monocytogenes. It is assumed that the three main model strains, EGD, EGD-e and 10403S are derived from the same “parent” strain isolated in 1926 by E.G.D. Murray. However, despite their common origin, these strains exhibit significant phenotypic differences including different invasiveness in tissue cultured cells. Moreover, although these three strains are of serotype 1/2a, as the original strain from 1926, EGD-e appears phylogenetically closer to serotype 1/2c strains. EGD-e was sequenced twelve years ago and 10403S five years ago, but no report has been made concerning genomic differences between these two strains and strain EGD. Here we report the genome sequence of the third reference strain, EGD, and a comparison of the 3 strains strikingly. In the genome of strain EGD, we discovered a relevant point mutation in PrfA, the major transcriptional activator of virulence genes. We report in addition a series of genomic and phenotypic differences of interest to listeriologists and immunologists who use or may have used Listeria as a tool to study various aspects of the immune response in mammals.