Carriage-associated Streptocccus pneumoniae serotype 1 in Brussels, Belgium.

Streptococcus pneumoniae serotype 1 presents a high invasiveness index and is seldom isolated from its niche, the nasopharynx. We report an unusual serotype 1 carriage in a healthy pediatric population at the time of the heptavalent pneumococcal vaccine adoption in Belgium. Our sampling period coincides with an epidemic wave of serotype 1 invasive pneumococcal infections. Invasive and colonizing isolates were characterized by both antibiotic resistance profile and multilocus sequence typing and were shown to share the same backbone (ST306 and ST350).