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Nonencapsulated Streptococcus pneumoniae resists extracellular human neutrophil elastase- and cathepsin G-mediated

Dieke van der Windt1, Hester J Bootsma, Peter Burghout

  • 1Laboratory of Pediatric Infectious Diseases, Radboud University Medical Centre, Nijmegen, The Netherlands.

FEMS Immunology and Medical Microbiology
|September 5, 2012
PubMed

Insights

Nonencapsulated Streptococcus pneumoniae show increased resistance to neutrophil proteases like elastase and cathepsin G. This enhanced survival is crucial for mucosal infections, impacting bacterial virulence.

Area of Science:

  • Microbiology
  • Immunology
  • Bacterial Pathogenesis

Background:

  • The polysaccharide capsule of Streptococcus pneumoniae is a key virulence factor.
  • Approximately 15% of S. pneumoniae carriage isolates are nonencapsulated and cause mucosal infections.
  • Neutrophils utilize proteases (elastase, cathepsin G) and antimicrobial peptides for bacterial killing.

Purpose of the Study:

  • To investigate the differential resistance of nonencapsulated and encapsulated S. pneumoniae to neutrophil-mediated killing.
  • To assess the role of extracellular neutrophil proteases in the survival of nonencapsulated pneumococci.

Main Methods:

  • Comparative analysis of nonencapsulated and encapsulated S. pneumoniae.
  • In vitro assays measuring bacterial killing by human neutrophil elastase and cathepsin G.
  • Evaluation of resistance to cationic antimicrobial peptides.

Main Results:

  • Nonencapsulated S. pneumoniae exhibit significantly greater resistance to killing by extracellular human neutrophil elastase and cathepsin G compared to encapsulated strains.
  • This enhanced protease resistance is a notable characteristic of nonencapsulated pneumococci.

Conclusions:

  • Nonencapsulated S. pneumoniae possess enhanced resistance to key extracellular neutrophil proteases.
  • This protease resistance is likely a critical factor for the survival and pathogenesis of nonencapsulated strains at mucosal surfaces.

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