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Published on: January 7, 2019

The role of the capsule of the Streptococcus milleri group in its pathogenicity

Shuzo Kanamori1, Nobuchika Kusano, Takashi Shinzato

  • 1Division of Internal Medicine, Department of Infectious Diseases Control, Graduate School and Faculty of Medicine, University of the Ryukyus, 207 Uehara, Nishihara, Okinawa 903-0215, Japan. s-kanamori@par.odn.ne.jp

Journal of Infection and Chemotherapy : Official Journal of the Japan Society of Chemotherapy
|May 26, 2004
PubMed

Insights

Encapsulated Streptococcus milleri group (SMG) strains are pathogenic, causing abscesses in mice and inhibiting human immune cell activity. Their capsular material appears to be a key virulence factor.

Area of Science:

  • Microbiology
  • Immunology
  • Pathogenesis

Background:

  • The Streptococcus milleri group (SMG) comprises bacteria implicated in various infections.
  • Understanding the virulence factors of SMG is crucial for developing effective treatments.

Purpose of the Study:

  • To investigate the pathogenicity of encapsulated SMG strains.
  • To determine the role of capsular material in SMG virulence.

Main Methods:

  • Assessing subcutaneous abscess formation in mice by encapsulated and unencapsulated SMG isolates.
  • Evaluating the phagocytosis and phagocytic killing of SMG by human polymorphonuclear neutrophils (PMNs).
  • Testing the inhibitory effect of purified capsular material from Streptococcus constellatus on PMN activity.

Main Results:

  • Encapsulated SMG strains induced abscesses in mice, unlike most unencapsulated strains.
  • Encapsulated strains demonstrated greater inhibition of PMN phagocytosis and killing compared to unencapsulated strains.
  • Separated encapsular material from Streptococcus constellatus inhibited PMN activity in a dose-dependent manner.

Conclusions:

  • Capsular material produced by SMG is a significant pathogenic factor.
  • Encapsulation enhances the virulence of SMG by evading host immune defenses.

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