Evidence of a clonal expansion of Streptococcus pneumoniae serotype 19A in adults as in children assessed by the DiversiLab® system.

Streptococcus pneumoniae serotype 19A was the main serotype responsible for invasive pneumococcal disease (IPD) in the Paris area in 2007 and 2009 in both adults and children. To verify if a particular clone is emerging, we determined the populational structure of S. pneumoniae isolates. Eighty-four S. pneumoniae strains responsible for invasive infections isolated from 52 adults and 32 children hospitalized in Parisian hospitals were analyzed. Capsular typing was performed by polymerase chain reaction (PCR) using the semi-automated repetitive sequence-based (rep-PCR) DiversiLab® System. Multilocus sequence typing (MLST) was also performed on 26 strains (ten selected strains after cluster analysis and 16 control strains). In 2007 and 2009, S. pneumoniae serotype 19A represented, respectively, 28.6 % and 25 % of the serotypes involved in IPDs in children and 13 % and 13.7 % in adults. The rep-PCR DiversiLab® analysis showed that the 84 S. pneumoniae serotype 19A isolates were distributed in five clusters and four unique rep-PCR types. Overall, 77/84 (91.6 %) S. pneumoniae 19A serotypes grouped into three main genetically related clusters (71/77 belonged to the cluster I). The five other strains exhibited different profiles. Using MLST, we demonstrated that most strains of the main cluster belonged to clonal complex (CC) 230, sequence type (ST) 276. However, for the other strains, the DiversiLab® method cannot be used to predict to which ST a strain belongs. The DiversiLab® method allowed us to identify the clonal expansion of S. pneumoniae serotype 19A strains isolated from both children and adults in 2007 and 2009.