Global phylogenomic analysis of nonencapsulated Streptococcus pneumoniae reveals a deep-branching classic lineage that is distinct from multiple sporadic lineages.
Genome Biol Evol, 2014/12/04;6(12):3281-94.
Hilty M[1], Wüthrich D[2], Salter SJ[3], Engel H[4], Campbell S[4], Sá-Leão R[5], de Lencastre H[6], Hermans P[7], Sadowy E[8], Turner P[9], Chewapreecha C[10], Diggle M[11], Pluschke G[12], McGee L[13], Eser ÖK[14], Low DE[15], Smith-Vaughan H[16], Endimiani A[4], Küffer M[4], Dupasquier M[17], Beaudoing E[17], Weber J[17], Bruggmann R[2], Hanage WP[18], Parkhill J[3], Hathaway LJ[4], Mühlemann K[19], Bentley SD[20]
Affiliations
PMID: 25480686DOI: 10.1093/gbe/evu263
Impact factor: 4.065
Abstract
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 β-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.
Keywords: antibiotic nonsusceptibility; comparative genomics; integrative conjugative elements; pneumococcal isolates; whole-genome sequencing
MeSH terms
Anti-Bacterial Agents; Bacterial Capsules; Cell Line; DNA Transposable Elements; Epithelial Cells; Genetic Loci; Genetic Speciation; Genome, Bacterial; Humans; Phylogeny; Streptococcus pneumoniae; beta-Lactams
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