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  • Title: Expression of the Streptococcus pneumoniae pilus-1 undergoes on and off switching during colonization in mice.
    Author: Pancotto L, De Angelis G, Bizzarri E, Barocchi MA, Del Giudice G, Moschioni M, Ruggiero P.
    Journal: Sci Rep; 2013; 3():2040. PubMed ID: 23784148.
    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.
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