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July 7, 2019

Global phylogenomic analysis of nonencapsulated Streptococcus pneumoniae reveals a deep-branching classic lineage that is distinct from multiple sporadic lineages.

Authors: Hilty, Markus and Wüthrich, Daniel and Salter, Susannah J and Engel, Hansjürg and Campbell, Samuel and Sá-Leão, Raquel and de Lencastre, Hermínia and Hermans, Peter and Sadowy, Ewa and Turner, Paul and Chewapreecha, Claire and Diggle, Mathew and Pluschke, Gerd and McGee, Lesley and Köseoglu Eser, Özgen and Low, Donald E and Smith-Vaughan, Heidi and Endimiani, Andrea and Küffer, Marianne and Dupasquier, Mélanie and Beaudoing, Emmanuel and Weber, Johann and Bruggmann, Rémy and Hanage, William P and Parkhill, Julian and Hathaway, Lucy J and Mühlemann, Kathrin and Bentley, Stephen D

The surrounding capsule of Streptococcus pneumoniae has been identified as a major virulence factor and is targeted by pneumococcal conjugate vaccines (PCV). However, nonencapsulated S. pneumoniae (non-Ec-Sp) have also been isolated globally, mainly in carriage studies. It is unknown if non-Ec-Sp evolve sporadically, if they have high antibiotic nonsusceptiblity rates and a unique, specific gene content. Here, whole-genome sequencing of 131 non-Ec-Sp isolates sourced from 17 different locations around the world was performed. Results revealed a deep-branching classic lineage that is distinct from multiple sporadic lineages. The sporadic lineages clustered with a previously sequenced, global collection of encapsulated S. pneumoniae (Ec-Sp) isolates while the classic lineage is comprised mainly of the frequently identified multilocus sequences types (STs) ST344 (n = 39) and ST448 (n = 40). All ST344 and nine ST448 isolates had high nonsusceptiblity rates to ß-lactams and other antimicrobials. Analysis of the accessory genome reveals that the classic non-Ec-Sp contained an increased number of mobile elements, than Ec-Sp and sporadic non-Ec-Sp. Performing adherence assays to human epithelial cells for selected classic and sporadic non-Ec-Sp revealed that the presence of a integrative conjugative element (ICE) results in increased adherence to human epithelial cells (P = 0.005). In contrast, sporadic non-Ec-Sp lacking the ICE had greater growth in vitro possibly resulting in improved fitness. In conclusion, non-Ec-Sp isolates from the classic lineage have evolved separately. They have spread globally, are well adapted to nasopharyngeal carriage and are able to coexist with Ec-Sp. Due to continued use of PCV, non-Ec-Sp may become more prevalent. © The Author(s) 2014. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

Journal: Genome biology and evolution
DOI: 10.1093/gbe/evu263
Year: 2014

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