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A Mouse Model for the Transition of Streptococcus pneumoniae from Colonizer to Pathogen upon Viral Co-Infection Recapitulates Age-Exacerbated Illness
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Expression of the Streptococcus pneumoniae pilus-1 undergoes on and off switching during colonization in mice

Laura Pancotto1, Gabriella De Angelis, Esmeralda Bizzarri

  • 1Novartis Vaccines & Diagnostics, Research Center, Via Fiorentina 1, I-53100 Siena, Italy.

Scientific Reports
|June 21, 2013
PubMed

Insights

Streptococcus pneumoniae pilus-1 expression varies during mouse colonization. Expression is high during early stages for adhesion, then decreases later, suggesting in vitro rates may not reflect in vivo conditions.

Area of Science:

  • Microbiology
  • Bacterial Pathogenesis
  • Molecular Biology

Background:

  • Streptococcus pneumoniae utilizes pili for adherence and virulence.
  • Pilus-1 expression is bistable, leading to mixed populations of expressing and non-expressing bacteria.

Purpose of the Study:

  • To investigate changes in pilus-1 expression rates during S. pneumoniae colonization in a mouse model.
  • To determine if pilus-1 expression dynamics correlate with colonization stages.

Main Methods:

  • Mice were intranasally inoculated with S. pneumoniae strains exhibiting high, medium, or low pilus-1 expression.
  • Pilus-1 expressing bacteria were quantified in nasopharyngeal washes and pharyngeal tissues at different time points.

Main Results:

  • In nasopharyngeal washes, high expression decreased, while low/medium increased early on. Later, expression generally decreased.
  • Pharyngeal tissue showed similar trends, but maintained medium-high expression at late stages.
  • Pilus-1 expression is preferentially high during early colonization and reduced later.

Conclusions:

  • Pilus-1 expression is dynamically regulated during S. pneumoniae colonization, favoring early adherence.
  • Observed in vitro pilus-1 expression rates in clinical isolates may not accurately represent in vivo colonization dynamics.

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