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Updated: Feb 25, 2026
Development and Assessment of Intracellular Infection Models for Staphylococcus aureus
Published on: January 17, 2025
Investigating intracellular persistence of Staphylococcus aureus within a murine alveolar macrophage cell line
A Lacoma1,2, V Cano2,3, D Moranta2,3
1a Servei de Microbiologia , Hospital Universitari "Germans Trias i Pujol," Institut en Ciències de la Salut "Germans Trias i Pujol," Universitat Autònoma de Barcelona , Badalona , Spain.
Objective:
Staphylococcus aureus is a particularly difficult pathogen to eradicate from the respiratory tract. Previous studies have highlighted the intracellular capacity of S.aureus in several phagocytic and non-phagocytic cells. The aim of this study was to define S.aureus interaction within a murine alveolar macrophage cell line.
Methods:
Cell line MH-S was infected with Newman strain. Molecular mechanisms involved in phagocytosis were explored. To assess whether S.aureus survives intracellularly quantitative (gentamicin protection assays and bacterial plating) and qualitative analysis (immunofluorescence microscopy) were performed. Bacterial colocalization with different markers of the endocytic pathway was examined to characterize its intracellular trafficking.
Results:
We found that S.aureus uptake requires host actin polymerization, microtubule assembly and activation of phosphatidylinositol 3-kinase signaling. Time course experiments showed that Newman strain was able to persist within macrophages at least until 28.5 h post infection. We observed that intracellular bacteria are located inside an acidic subcellular compartment, which co-localizes with the late endosome/lysosome markers Lamp-1, Rab7 and RILP. Colocalization counts with TMR-dextran might reflect a balance between bacterial killing and intracellular survival.
Conclusions:
This study indicates that S.aureus persists and replicates inside murine alveolar macrophages, representing a privileged niche that can potentially offer protection from antimicrobial activity and immunological host defense mechanisms.
Insights
Staphylococcus aureus persists within murine alveolar macrophages, evading immune defenses. This intracellular survival highlights macrophages as a protective niche for the difficult-to-eradicate pathogen.
Area of Science:
- Microbiology
- Immunology
- Cell Biology
Background:
- Staphylococcus aureus is a resilient respiratory pathogen.
- S. aureus exhibits intracellular survival capabilities in various host cells.
- Understanding its interaction with alveolar macrophages is crucial for eradication strategies.
Purpose of the Study:
- To investigate the interaction between Staphylococcus aureus and a murine alveolar macrophage cell line.
- To elucidate the molecular mechanisms underlying S. aureus uptake and intracellular survival within macrophages.
Main Methods:
- Infection of MH-S cells with the Newman strain of S. aureus.
- Quantitative (gentamicin protection assays, bacterial plating) and qualitative (immunofluorescence microscopy) analyses.
- Examination of bacterial colocalization with endocytic pathway markers.
Main Results:
- S. aureus uptake necessitates host actin polymerization, microtubule assembly, and PI3K signaling.
- The Newman strain persisted intracellularly for at least 28.5 hours.
- Intracellular bacteria localized to acidic compartments co-localizing with late endosome/lysosome markers (Lamp-1, Rab7, RILP).
Conclusions:
- Staphylococcus aureus persists and replicates within murine alveolar macrophages.
- Macrophages serve as a privileged intracellular niche, potentially protecting S. aureus from host defenses and antimicrobial agents.
