title: Serotype IV Streptococcus agalactiae ST-452 has arisen from large genomic recombination events between CC23 and the hypervirulent CC17 lineages.
abstract: Streptococcus agalactiae (Group B Streptococcus, GBS) causes life-threatening infections in newborns and adults with chronic medical conditions. Serotype IV strains are emerging both among carriers and as cause of invasive disease and recent studies revealed two main Sequence Types (STs), ST-452 and ST-459 assigned to Clonal Complexes CC23 and CC1, respectively. Whole genome sequencing of 70 type IV GBS and subsequent phylogenetic analysis elucidated the localization of type IV isolates in a SNP-based phylogenetic tree and suggested that ST-452 could have originated through genetic recombination. SNPs density analysis of the core genome confirmed that the founder strain of this lineage originated from a single large horizontal gene transfer event between CC23 and the hypervirulent CC17. Indeed, ST-452 genomes are composed by two parts that are nearly identical to corresponding regions in ST-24 (CC23) and ST-291 (CC17). Chromosome mapping of the major GBS virulence factors showed that ST-452 strains have an intermediate yet unique profile among CC23 and CC17 strains. We described unreported large recombination events, involving the cps IV operon and resulting in the expansion of serotype IV to CC23. This work sheds further light on the evolution of GBS providing new insights on the recent emergence of serotype IV.
authors.affiliation: GSK Vaccines s.r.l., Siena, Italy.|Sapienza, Università di Roma, Rome, Italy.
authors.forename: Edmondo
authors.initials: E
authors.lastname: Campisi
authors.affiliation: GSK Vaccines s.r.l., Siena, Italy.
authors.forename: C Daniela
authors.initials: CD
authors.lastname: Rinaudo
authors.affiliation: Department of Computational Biology, Research and Innovation Centre, Fondazione Edmund Mach, San Michele all'Adige, Italy.
authors.forename: Claudio
authors.initials: C
authors.lastname: Donati
authors.affiliation: GSK Vaccines s.r.l., Siena, Italy.|Department of physics "Enrico Fermi", University of Pisa, Pisa, Italy.
authors.forename: Mara
authors.initials: M
authors.lastname: Barucco
authors.affiliation: GSK Vaccines s.r.l., Siena, Italy.
authors.forename: Giulia
authors.initials: G
authors.lastname: Torricelli
authors.affiliation: Department of Pediatrics, Baylor College of Medicine, Houston, Texas, USA.
authors.forename: Morven S
authors.initials: MS
authors.lastname: Edwards
authors.affiliation: Department of Pediatrics, Baylor College of Medicine, Houston, Texas, USA.|Department Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas, USA.
authors.forename: Carol J
authors.initials: CJ
authors.lastname: Baker
authors.affiliation: GSK Vaccines s.r.l., Siena, Italy.
authors.forename: Imma
authors.initials: I
authors.lastname: Margarit
authors.affiliation: GSK Vaccines s.r.l., Siena, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Rosini
mesh_terms: D000328:Adult; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D016680:Genome, Bacterial / Q000235:genetics*; D023281:Genomics / Q000379:methods*; D006801:Humans; D007231:Infant, Newborn; D010802:Phylogeny; D020641:Polymorphism, Single Nucleotide; D011995:Recombination, Genetic; D012703:Serotyping; D013045:Species Specificity; D013290:Streptococcal Infections / Q000382:microbiology; D013292:Streptococcus agalactiae / Q000145:classification / Q000235:genetics* / Q000472:pathogenicity; D014774:Virulence / Q000235:genetics; D000073336:Whole Genome Sequencing / Q000379:methods*
chemical_list: D004269:DNA, Bacterial