title: Characterization of invasive group B streptococcus strains from the greater Toronto area, Canada.
abstract: We determined the capsular polysaccharide (CPS) type of 600 group B Streptococcus (GBS) (also known as Streptococcus agalactiae) strains recovered from patients with invasive infections in the greater Toronto area, Canada, between 2009 and 2012. GBS strains of CPS type III were the most prevalent among infants (44% in those with early-onset disease, 75% in those with late-onset disease), while type V strains were most frequently isolated from adult patients (26% in patients≥19 years old). We next investigated the presence in our collection of GBS strains belonging to the hypervirulent multilocus sequence typing clonal complex 17 (CC17). We used a PCR test described as specific for the detection of CC17 strains, which targets the gene encoding the major virulence factor HvgA. We identified 91 hvgA-positive strains; of these, 88 were CPS type III, 2 were CPS type IV, and 1 was CPS type V. Using whole-genome sequencing, we showed that the two hvgA-positive CPS type IV strains are CC17 strains which underwent capsular switching. However, sequence analysis revealed that the hvgA-positive CPS type V strain does not belong to CC17 but instead is a bona fide CC1 strain which acquired hvgA, probably by recombination from a CC17 donor. Our findings underline the importance of recombination in GBS pathogenesis and caution against the use of single-gene-based PCR tests to detect CC17 GBS strains.
authors.affiliation: Public Health Ontario, Toronto, Ontario, Canada.
authors.forename: Sarah
authors.initials: S
authors.lastname: Teatero
authors.forename: Allison
authors.initials: A
authors.lastname: McGeer
authors.forename: Donald E
authors.initials: DE
authors.lastname: Low
authors.forename: Aimin
authors.initials: A
authors.lastname: Li
authors.forename: Walter
authors.initials: W
authors.lastname: Demczuk
authors.forename: Irene
authors.initials: I
authors.lastname: Martin
authors.forename: Nahuel
authors.initials: N
authors.lastname: Fittipaldi
mesh_terms: D018829:Adhesins, Bacterial / Q000235:genetics; D000293:Adolescent; D000328:Adult; D002170:Canada; D002648:Child; D002675:Child, Preschool; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008875:Middle Aged; D058885:Multilocus Sequence Typing / Q000379:methods; D013290:Streptococcal Infections / Q000382:microbiology*; D013292:Streptococcus agalactiae / Q000235:genetics / Q000302:isolation & purification*; D037521:Virulence Factors / Q000235:genetics; D055815:Young Adult
chemical_list: D018829:Adhesins, Bacterial; C559207:HvgA protein, Streptococcus agalactiae ST-17; D037521:Virulence Factors