Castillo-Ramirez, Santiago2; Corander, Jukka2; Marttinen, Pekka2; Aldeljawi, Mona2; Hanage, William P2; Westh, Henrik1; Boye, Kit1; Gulay, Zeynep2; Bentley, Stephen D2; Parkhill, Julian2; Holden, Matthew T2; Feil, Edward J2
1 Department of Clinical Microbiology, Amager and Hvidovre Hospital, The Capital Region of Denmark2 unknown
ABSTRACT: BACKGROUND: Next-generation sequencing (NGS) is a powerful tool for understanding both patterns of descent over time and space (phylogeography) and the molecular processes underpinning genome divergence in pathogenic bacteria. Here, we describe a synthesis between these perspectives by employing a recently developed Bayesian approach, BRATNextGen, for detecting recombination on an expanded NGS dataset of the globally disseminated methicillin-resistant Staphylococcus aureus (MRSA) clone ST239. RESULTS: The data confirm strong geographical clustering at continental, national and city scales and demonstrate that the rate of recombination varies significantly between phylogeographic sub-groups representing independent introductions from Europe. These differences are most striking when mobile non-core genes are included, but remain apparent even when only considering the stable core genome. The monophyletic ST239 sub-group corresponding to isolates from South America shows heightened recombination, the sub-group predominantly from Asia shows an intermediate level, and a very low level of recombination is noted in a third sub-group representing a large collection from Turkey. CONCLUSIONS: We show that the rapid global dissemination of a single pathogenic bacterial clone results in local variation in measured recombination rates. Possible explanatory variables include the size and time since emergence of each defined sub-population (as determined by the sampling frame), variation in transmission dynamics due to host movement, and changes in the bacterial genome affecting the propensity for recombination.