Molecular assessment of invasive Streptococcus pneumoniae serotype 1 in Brazil: evidence of clonal replacement.

In Brazil, serotype 1 Streptococcus pneumoniae is one of the most prevalent causes of severe infection. This study investigated the genetic relatedness of 134 serotype 1 isolates obtained from invasive diseases during the period 1977-2005. Molecular typing by PFGE revealed two major lineages using visual inspection and computer analysis. Type A comprised 94 isolates (70.2 %) with four subtypes, whereas type B comprised 40 isolates (29.8 %) with eight subtypes. Subtype A3, the most frequent genotype, accounting for 65 % of the total isolates, was identified as a representative of clone Sweden(1)-40 (ST304). Type B was predominant in the period 1977-1988. In contrast, an increase in the type A lineage was detected from 1990 in Brazil, significantly associated with isolates recovered from pneumonia cases and from young patients. This study clearly established a temporal switch between two lineages of S. pneumoniae serotype 1 in Brazil, with a wide dispersion of clone Sweden(1)-40 in recent years.