To Investigate the Role of Staphylococcus Aureus Polysaccharide Intercellular Adhesin (Pia) in the Cases in Addition to Biofilm Formation

Project: National Science and Technology CouncilNational Science and Technology Council Academic Grants

Project Details


Staphylococcus aureus which has long been recognized as a major cause of nosocomial infections and the development of a biofilm of this pathogen can provide an extracellular barrier to antimicrobial agents or host immune defenses. Maturation of biofilms is mediated by the production of extracellular factors, such as the polysaccharide intercellular adhesin (PIA), which is regulated by genes in the icaRADBC locus. PIA plays a fundamental role in intercellular adhesion of staphylococci within a biofilm, and it is also an important structural component of the biofilm matrix architecture. We recently found that PIA was continued expressed and released to the culture broth under planktonic growth condition whereas an environment is not suitable for the biofilm formation. We propose that PIA may act as a virulence factor or a regulator for gene expression in S. aureus. Results from our pilot study show that a significant difference of the expression profiles of both intracellular and extracellular proteins was observed between PIA wild-type and deficient strains. Notably, a decreased expression of protein A (encoded by spa), an important virulence factor for immune evasion, was observed in PIA-deficient strain. PIA-contained broth showed a higher cytotoxicity to epithelial cells but a lower cytotoxicity to macrophages than PIA-free broth. Strikingly, hemolytic activity was significantly enhanced in PIA-deficient strains. We aim to study the role of PIA in the gene regulation in S. aureus, pathogenesis to hosts, and host immune response to PIA. Deletion of icaA in different S. aureus strains and their cytotoxicity on different cell lines will be analyzed to rule out the effect of genetic background on the cytotoxicity. The purified PIA is employed in the same experiment and the apoptotic activities are studied to investigate mechanisms underlying the cytotoxicity. A comparative proteomic approach is employed to identify and characterize PIA-regulated proteins. A promoter trapping method is used for identifying factors controlling spa expression. Activation of hemolysins, particular β-hemolysin, will be investigated to study mechanisms underlying PIA-suppressed hemolysis. Expression level of pro-inflammatory cytokines is determined to study the immune response to PIA challenge in macrophages. The potential receptors and signaling pathways activated by PIA per se in macrophages is investigated through a PCR array assay. A murine systemic infection model is used for evaluating the pathogenesis of PIA infection in vivo. Pathogenesis is evaluated according to mouse viability, physiological status, bacterial load in blood and different organs, and histopathological examination. The effect of PIA on the in vivo immune response is evaluated through the determination of the expression level of pro-inflammatory cytokines in mice challenged with purified PIA, wild-type S. aureus strain and its PIA-deficient counterpart. A matched-paired study is employed to investigate the clinical significance of PIA through the comparison of the cytotoxicity between PIA-producing and non-producing S. aureus clinical isolates. Less has been known about the PIA behind its fundamental role in biofilm matrix architecture. Our study will get more insight into the clinical significance of PIA per se and its interaction with hosts.

Project IDs

Project ID:PC10607-0352
External Project ID:MOST106-2320-B182-020
Effective start/end date01/08/1731/07/18


  • Staphylococcus aureus
  • Polysaccharide intercellular adhesin (PIA)
  • pathogenesis
  • hemolysis


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