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Updated: Nov 18, 2025
Intravitreal Injection and Quantitation of Infection Parameters in a Mouse Model of Bacterial Endophthalmitis
Published on: February 6, 2021
Difference in Host Immune response to Methicillin-Resistant and Methicillin Sensitive Staphylococcus aureus (MRSA and
Poonam Naik1,2, Joveeta Joseph1
1Jhaveri Microbiology Centre, Brien Holden Eye Research Centre, L. V. Prasad Eye Institute, Hyderabad, Telangana, India.
Purpose:
The study aimed to understand the differential immune response of methicillin susceptible Staphylococcus aureus (MSSA) and methicillin-resistant S. aureus (MRSA) strains in in vitro models of endophthalmitis.
Methods:
Retinal pigment epithelium (RPE) and microglia cells (CHME-3) were exposed to MRSA and MSSA strains and analyzed for expression of inflammatory mediators by real-time quantitative PCR and validated by ELISA or immunofluorescence assay. Heatmap and STRING analysis was used to assess the differential immune expression.
Results:
Both microglia and RPE expressed TLR-2, TLR-1, TLR-6, and TLR -9 after challenge with MRSA and MSSA strains though the expression varied. MRSA-infected cells induced higher expression of IL-1β, IL-8, 1 L-10, IL-6, and GM-CSF, while TNF-α and IFN-ϒ were downregulated in comparison to MSSA-infected cells. We also demonstrate that MRSA infection leads to increased activation of MMP-9 and MMP-2 in RPE cells, while microglia expressed only MMP-9 in MRSA-infected cells.
Conclusions:
MRSA strain can induce an exacerbated immune response in retinal cells. Giving clues for potential targets in immunomodulatory therapies.
Insights
Methicillin-resistant Staphylococcus aureus (MRSA) triggers a stronger immune response in retinal cells than methicillin-susceptible S. aureus (MSSA). This suggests MRSA may be a target for new immunomodulatory therapies for endophthalmitis.
Area of Science:
- Ophthalmology
- Immunology
- Microbiology
Background:
- Endophthalmitis is a serious eye inflammation often caused by Staphylococcus aureus.
- Differentiating the immune response to methicillin-susceptible S. aureus (MSSA) and methicillin-resistant S. aureus (MRSA) is crucial for effective treatment.
Purpose of the Study:
- To investigate the differential immune responses of retinal pigment epithelium (RPE) and microglia cells to MSSA and MRSA strains in vitro.
- To identify potential therapeutic targets for MRSA-induced endophthalmitis.
Main Methods:
- RPE and microglia cells (CHME-3) were exposed to MRSA and MSSA.
- Expression of inflammatory mediators was analyzed using real-time quantitative PCR, ELISA, and immunofluorescence.
- Heatmap and STRING analysis were employed to assess differential immune expression.
Main Results:
- Both RPE and microglia cells expressed Toll-like receptors (TLRs) upon challenge with MRSA and MSSA, with varying expression levels.
- MRSA infection led to higher expression of IL-1β, IL-8, IL-10, IL-6, and GM-CSF, and downregulation of TNF-α and IFN-γ compared to MSSA.
- MRSA increased MMP-9 and MMP-2 activation in RPE cells, and MMP-9 in microglia.
Conclusions:
- MRSA induces a more severe immune response in retinal cells than MSSA.
- These findings highlight potential targets for immunomodulatory therapies in MRSA-related endophthalmitis.
