title: Expression of the Streptococcus pneumoniae pilus-1 undergoes on and off switching during colonization in mice.
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.
authors.affiliation: Novartis Vaccines & Diagnostics, Research Center, Via Fiorentina 1, I-53100 Siena, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Pancotto
authors.forename: Gabriella
authors.initials: G
authors.lastname: De Angelis
authors.forename: Esmeralda
authors.initials: E
authors.lastname: Bizzarri
authors.forename: Michèle A
authors.initials: MA
authors.lastname: Barocchi
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Del Giudice
authors.forename: Monica
authors.initials: M
authors.lastname: Moschioni
authors.forename: Paolo
authors.initials: P
authors.lastname: Ruggiero
mesh_terms: D000818:Animals; D000907:Antibodies, Bacterial / Q000276:immunology; D058491:Bacterial Load; D005260:Female; D036781:Fimbriae Proteins / Q000235:genetics*; D010861:Fimbriae, Bacterial / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial; D051379:Mice; D009297:Nasal Mucosa / Q000276:immunology / Q000382:microbiology; D009305:Nasopharynx / Q000276:immunology / Q000382:microbiology; D011008:Pneumococcal Infections / Q000276:immunology / Q000382:microbiology; D013296:Streptococcus pneumoniae / Q000235:genetics* / Q000254:growth & development / Q000276:immunology
chemical_list: D000907:Antibodies, Bacterial; D036781:Fimbriae Proteins