Gene flow and Bayesian phylogeography of serogroup C meningococci circulating in Italy.

Hyperinvasive strains of Neisseria meningitidis serogroup C have caused outbreaks of severe disease in Italy. Here, we report the analysis of the migration patterns of C:P1.5-1,10-8:F3-6:ST-11(cc11) meningococcal strains from different Italian regions collected between 2012 and 2017. N. meningitidis genomes were sequenced through the whole genome sequencing (WGS) method and were analyzed using the BIGSdb Genome Comparator tool. The phylogeography was performed using BEAST. The gene flows in Italy were tested by using MacClade. The C:P1.5-1,10-8:F3-6:ST-11(cc11) hyperinvasive meningococcal strain, for the data available at the time of the analysis, from UK reached at first Emilia Romagna region, and then, in 2012, was detected in the outbreak occurred in the port of Livorno. The "Tuscany-outbreak strain" was likely introduced in Italy between 2013 and 2014. Most of the observed gene flow events occurred from the Center to Northern part of Italy. The phylogeographic analysis allowed to track the dissemination of C:P1.5-1,10-8:F3-6:ST-11(cc11) strains in the country.