First report of Streptococcus pneumoniae serotype 6D isolates from invasive infections.

We report the first invasive Streptococcus pneumoniae isolates of serotype 6D and the first occurrence of this serotype in Europe. Till now, the appearance of serotype 6D pneumococci in nasopharyngeal carriage has been speculated to be associated with a selective pressure from vaccination with the conjugated 7-valent antipneumococcal vaccine. Our observations indicate that this serotype is present also among unvaccinated individuals in the population where mass infant vaccination has not yet been introduced. Importantly, these strains were isolated from invasive infections, indicating the full virulence potential of pneumococci belonging to serotype 6D and its importance for future vaccine formulations.