Expression of the Streptococcus pneumoniae pilus-1 undergoes on and off switching during colonization in mice

Sci Rep. 2013:3:2040. doi: 10.1038/srep02040.

Abstract

Streptococcus pneumoniae pili contribute to adherence and virulence. The regulation of pilus-1 expression is bistable, thus piliated strains contain a variable proportion of pilus-1-non-expressing bacteria. We investigated whether such proportion changes during colonization. Pilus-1-expressing bacteria were quantified in nasopharyngeal washes and pharyngeal tissues from mice that received intranasally bacterial populations with high (H), medium (M) or low (L) pilus-1 expression rates. In nasopharyngeal washes, at early colonization stages, pilus-1 expression rates decreased in H population, while increased in L and M; at later stages, expression rates decreased or remained low. Similar trends were observed in pharyngeal tissues, where, however, at late stages the expression rates were medium-high. In conclusion, pilus-1 is preferentially expressed at early colonization stages, consistently with its role in adhesion, while at later stages the expression is partially switched off. Pilus-1 expression rates observed in clinical isolates in vitro may not reflect the actual rates during colonization/infection.

MeSH terms

  • Animals
  • Antibodies, Bacterial / immunology
  • Bacterial Load
  • Female
  • Fimbriae Proteins / genetics*
  • Fimbriae, Bacterial / genetics*
  • Gene Expression Regulation, Bacterial*
  • Mice
  • Nasal Mucosa / immunology
  • Nasal Mucosa / microbiology
  • Nasopharynx / immunology
  • Nasopharynx / microbiology
  • Pneumococcal Infections / immunology
  • Pneumococcal Infections / microbiology
  • Streptococcus pneumoniae / genetics*
  • Streptococcus pneumoniae / growth & development
  • Streptococcus pneumoniae / immunology

Substances

  • Antibodies, Bacterial
  • Fimbriae Proteins