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Updated: May 8, 2026

Characterization of Inflammatory Responses During Intranasal Colonization with Streptococcus pneumoniae
Published on: January 17, 2014
Intraclonal variations among Streptococcus pneumoniae isolates influence the likelihood of invasive disease in
Sarah Browall1, Martin Norman, Jeanette Tångrot
1Department of Microbiology, Tumor, and Cell Biology.
Background:
Pneumococcal serotypes are represented by a varying number of clonal lineages with different genetic contents, potentially affecting invasiveness. However, genetic variation within the same genetic lineage may be larger than anticipated.
Methods:
A total of 715 invasive and carriage isolates from children in the same region and during the same period were compared using pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing. Bacterial genome sequencing, functional assays, and in vivo virulence mice studies were performed.
Results:
Clonal types of the same serotype but also intraclonal variants within clonal complexes (CCs) showed differences in invasive-disease potential. CC138, a common CC, was divided into several PFGE patterns, partly explained by number, location, and type of temperate bacteriophages. Whole-genome sequencing of 4 CC138 isolates representing PFGE clones with different invasive-disease potentials revealed intraclonal sequence variations of the virulence-associated proteins pneumococcal surface protein A (PspA) and pneumococcal choline-binding protein C (PspC). A carrier isolate lacking PcpA exhibited decreased virulence in mice, and there was a differential binding of human factor H, depending on invasiveness.
Conclusions:
Pneumococcal clonal types but also intraclonal variants exhibited different invasive-disease potentials in children. Intraclonal variants, reflecting different prophage contents, showed differences in major surface antigens. This suggests ongoing immune selection, such as that due to PspC-mediated complement resistance through varied human factor H binding, that may affect invasiveness in children.
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