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

Authors

Abstract

Introduction

Neisseria meningitidis is a bacterial pathogen that can cause sporadic cases, small outbreaks and large epidemics. Serogroup C and B meningococci are the most common in Italy. In particular, hyperinvasive strains of serogroup C meningococci have caused outbreaks of severe disease in our country. In a previous study we tracked the pattern of dispersal of hyperinvasive strains, focusing the attention on their introduction routes. In the present paper we report the results of 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.

Methods

N. meningitidis genomes of isolates collected between January 2012 and December 2017 were sequenced using the Illumina MiSeq platform, through the whole genome sequencing (WGS) method and were analyzed using the BIGSdb Genome Comparator tool implemented within the PubMLST website. The phylogeography was performed using the software package BEAST. The gene out/in flows in Italy were tested by a modified version of the Slatkin and Maddison test using MacClade.

Results

The majority of the Italian C:P1.5-1,10-8:F3-6:ST-11(cc11) strains clustered together and segregated into two main  sub-clades. In particular, the hyperinvasive strain, starting from UK reached at first Emilia Romagna region and by 2012 the port of Livorno, causing a small outbreak. Subsequently a wave of migrations involved different Italian regions. 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.

Discussion

The phylogeographic analysis allowed to track the dissemination of this strain belonging to the hypervirulent C:P1.5-1,10-8:F3-6:ST-11(cc11) clone. In particular, Central Italy was identified as a major source of dissemination, with a 54.5% of gene flows to the North and, to a lesser extent, to the South of the country. The information gathered through the application of phylogenetic and evolutionary methods appears consistent with the epidemiological data derived from the national surveillance system. 

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Authors

Alessandra Lo Presti - Department of Infectious Diseases, Istituto Superiore di Sanità, Rome, Italy

Giovanni Rezza - Department of Infectious Diseases, Istituto Superiore di Sanità, Rome, Italy

Arianna Neri - Department of Infectious Diseases, Istituto Superiore di Sanità, Rome, Italy

Cecilia Fazio - Department of Infectious Diseases, Istituto Superiore di Sanità, Rome, Italy

Luigina Ambrosio - Department of Infectious Diseases, Istituto Superiore di Sanità, Rome, Italy

Annapina Palmieri - Department of Infectious Diseases, Istituto Superiore di Sanità, Rome, Italy

Paola Vacca - Department of Infectious Diseases, Istituto Superiore di Sanità, Rome, Italy

Paola Stefanelli - Department of Infectious Diseases, Istituto Superiore di Sanità, Rome, Italy

How to Cite
Lo Presti, A., Rezza, G., Neri, A., Fazio, C., Ambrosio, L., Palmieri, A., Vacca, P., & Stefanelli, P. (2020). Gene flow and Bayesian phylogeography of serogroup C meningococci circulating in Italy. Annali dell’Istituto Superiore Di Sanità, 56(4), 403-408. Retrieved from https://annali.iss.it/index.php/anna/article/view/1015
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