Streptococcus pyogenes pili promote pharyngeal cell adhesion and biofilm formation

Andrea G.O. Manetti, Chiara Zingaretti, Fabiana Falugi, Sabrina Capo, Mauro Bombaci, Fabio Bagnoli, Gabriella Gambellini, Giuliano Bensi, Marirosa Mora, Andrew M. Edwards, James M. Musser, Edward A. Graviss, John L. Telford, Guido Grandi, Immaculada Margarit

Research output: Contribution to journalArticlepeer-review

191 Scopus citations


Group A Streptococcus (GAS, Streptococcus pyogenes) is a Gram-positive human pathogen responsible for several acute diseases and autoimmune sequelae that account for half a million deaths worldwide every year. GAS infections require the capacity of the pathogen to adhere to host tissues and assemble in cell aggregates. Furthermore, a role for biofilms in GAS pathogenesis has recently been proposed. Here we investigated the role of GAS pili in biofilm formation. We demonstrated that GAS pilus-negative mutants, in which the genes encoding either the pilus backbone structural protein or the sortase C1 have been deleted, showed an impaired capacity to attach to a pharyngeal cell line. The same mutants were much less efficient in forming cellular aggregates in liquid culture and microcolonies on human cells. Furthermore, mutant strains were incapable of producing the typical three-dimensional layer with bacterial microcolonies embedded in a carbohydrate polymeric matrix. Complemented mutants had an adhesion and aggregation phenotype similar to the wild-type strain. Finally, in vivo expression of pili was indirectly confirmed by demonstrating that most of the sera from human patients affected by GAS-mediated pharyngitis recognized recombinant pili proteins. These data support the role of pili in GAS adherence and colonization and suggest a general role of pili in all pathogenic streptococci.

Original languageEnglish (US)
Pages (from-to)968-983
Number of pages16
JournalMolecular Microbiology
Issue number4
StatePublished - May 2007

ASJC Scopus subject areas

  • Microbiology
  • Molecular Biology


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