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Apoptosis observed in BALB/3T3 cells having ingested Staphylococcus aureus

M Murai1, J Sakurada, K Seki

  • 1Department of Microbiology, The Jikei University School of Medicine, Tokyo, Japan. murai-miyo@spu.ac.jp

Microbiology and Immunology
|October 21, 1999
PubMed

Insights

Internalized Staphylococcus aureus can escape host cells, multiply, and trigger apoptosis in fibroblasts. This study details the intracellular mechanisms of S. aureus infection in BALB/3T3 cells.

Area of Science:

  • Microbiology
  • Cell Biology
  • Immunology

Background:

  • Staphylococcus aureus is known to be internalized by murine fibroblasts.
  • The intracellular behavior of S. aureus within host cells remains incompletely understood.

Purpose of the Study:

  • To investigate the intracellular events following the ingestion of Staphylococcus aureus by BALB/3T3 fibroblast cells.
  • To elucidate the mechanisms by which S. aureus interacts with and affects host cells.

Main Methods:

  • BALB/3T3 cells were infected with S. aureus strains (A191, A151, Cowan I).
  • Cells were treated with lysostaphin to assess bacterial viability.
  • DNA fragmentation was analyzed using DNA laddering and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) assay.
  • Transmission electron microscopy (TEM) was used to visualize intracellular bacterial behavior and host cell morphology.

Main Results:

  • S. aureus strain A191 escaped the endosome, multiplied intracellularly, and induced apoptosis in BALB/3T3 cells within 4 hours.
  • Strain A151 remained largely contained within the endosome and showed limited intracellular multiplication.
  • The Cowan I strain also induced DNA fragmentation, indicating apoptosis, at a slower rate.
  • Apoptotic features observed included electron-dense nuclei and plasma membrane blebbing.

Conclusions:

  • Internalized Staphylococcus aureus can exhibit different intracellular fates depending on the strain.
  • Escape from the endosome, intracellular multiplication, and subsequent induction of apoptosis are key events in S. aureus-induced fibroblast cell death.
  • These findings provide insights into the pathogenesis of S. aureus infections at the cellular level.

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