931. Distribution of Multilocus Sequence Types among Invasive Group B Streptococcal Isolates from Adult, Elderly and Neonatal Populations in Canada
Session: Poster Abstract Session: Bacterial Pathogenesis
Saturday, October 22, 2011
Room: Poster Hall B1
Background: Group B Streptococcus (GBS), a leading cause of neonatal sepsis and meningitis, also causes invasive disease in non-pregnant adults and the elderly.  Adults can present with skin and osteoarticular infections as well as pneumonia and bacteremia.  While strains recovered from neonates have been studied extensively, less is known of the genetic diversity and population structure of GBS recovered from adults with invasive disease. Methods: Multilocus sequence typing (MLST) and serotyping were performed on 245 invasive GBS strains isolated from the blood of non-pregnant adults ages 17 to 96 years.  Cases were identified by population-based surveillance in Alberta, Canada between 1999 and 2003, and comparisons were made to 192 GBS strains collected from neonates and young children from the same region during the same time period. Results: Overall, capsular serotypes III, Ia and V accounted for 84% of neonatal and 68% of adult infections.  Neonatal GBS strains more frequently had capsular serotype III (OR, 7.7; P<0.0001), while capsular serotype V (OR, 3.0; P<0.0001) predominated in adult strains.  Phylogenetic analyses identified 57 sequence types (STs) that clustered into five distinct clonal complexes (CCs) and for the most part, correlated with the serotyping data.  Interestingly, the distribution of strains representing several CCs varied across populations.  Adults were 3.3 and 2.5 times more likely to have CC-1 and CC-12 infections, respectively, when compared to neonates (P<0.001).  Neonates, however, were 10.8 and 3.2 times more likely to have infections caused by strains of CC-17 and CC-19 (P<0.0001), the two lineages found to disproportionately affect neonates in prior studies. Conclusion: These data demonstrate that invasive GBS strains from adult and elderly cases have a similar population structure, as determined by MLST, when compared to neonates.  The frequency of the distinct GBS lineages, however, varies across populations and should be considered when developing vaccines and other prevention strategies.

Subject Category: B. Bacterial pathogenesis, studies in animal models, molecular pathogenicity

Rim Al Safadi, PhD1, Guangxi Wu1, A. Cody Springman1, Shannon D. Manning, PhD1 and H. Dele Davies, MD2, (1)Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI, (2)Pediatrics and Human Development, Michigan State University, East Lansing, MI


R. Al Safadi, None

G. Wu, None

A. C. Springman, None

S. D. Manning, None

H. D. Davies, None

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