A microevolution study on the highly clonal monophasic Salmonella Typhimurium circulating massively in Europe since 2010 have been progressed on 300 genomes of Salmonella Typhimurium and its monophasic variant isolated from 1992 to 2018 from 5 countries (UK, FR, IT, DE, and DK). The phylogeny and presence of specific genomic regions (i.e. Salmonella pathogenic island, fljB region, …), of genes associated to antimicrobial and heavy metals resistance and of plasmids have been investigated to understand the fast spreading of this hazardous Salmonella. Comparatives phylogeny and Bayesian evolutionary analyses have been conduced to investigate the possible co-evolution between these regions and determine the timeframe of their acquisition.