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Updated: May 28, 2026

Intravitreal Injection and Quantitation of Infection Parameters in a Mouse Model of Bacterial Endophthalmitis
07:24

Intravitreal Injection and Quantitation of Infection Parameters in a Mouse Model of Bacterial Endophthalmitis

Published on: February 6, 2021

Comparative Outcomes of Exogenous and Endogenous MRSA Vs MSSA Endophthalmitis

Kavya P Katragadda1, Alan G Palestine1

  • 1Department of Ophthalmology, University of Colorado School of Medicine, Aurora, Colorado, USA.

Ocular Immunology and Inflammation
|May 26, 2026
PubMed
Abstract

Insights

Methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive Staphylococcus aureus (MSSA) endophthalmitis show similar ocular outcomes. Exogenous cases had more enucleations, while endogenous MRSA cases had higher mortality, warranting further study.

Area of Science:

  • Ophthalmology
  • Infectious Diseases
  • Microbiology

Background:

  • Methicillin-resistant Staphylococcus aureus (MRSA) is linked to poorer systemic outcomes than methicillin-sensitive Staphylococcus aureus (MSSA).
  • Previous studies on MRSA and MSSA endophthalmitis often combined endogenous and exogenous cases.
  • This study provides the largest comparison of ocular outcomes in endogenous versus exogenous MRSA and MSSA endophthalmitis.

Purpose of the Study:

  • To compare ocular outcomes in endogenous and exogenous endophthalmitis caused by MRSA and MSSA.
  • To analyze visual acuity and complication rates in different endophthalmitis subtypes.
  • To identify factors influencing prognosis in MRSA and MSSA endophthalmitis.

Main Methods:

  • Retrospective cohort study of 46 eyes with culture-proven MRSA or MSSA endophthalmitis (October 2008-April 2025).
  • Cases were categorized as endogenous (30 eyes) or exogenous (7 eyes).
  • Visual acuity and complications were analyzed, with statistical comparisons using Fisher's t-test (p < 0.05).

Main Results:

  • No significant differences in vision outcomes between MRSA and MSSA were observed in either exogenous or endogenous groups.
  • The exogenous endophthalmitis cohort exhibited significantly higher rates of enucleation or evisceration compared to the endogenous group.
  • Endogenous MRSA infections were associated with increased intravenous drug use and mortality, though not statistically significant.

Conclusions:

  • MRSA and MSSA endophthalmitis demonstrate comparable ocular outcomes.
  • Higher enucleation/evisceration rates in exogenous cases may relate to direct inoculation and organism load.
  • The trend towards higher mortality in endogenous MRSA infections warrants further investigation.
Keywords:
EndophthalmitisMRSAMSSAStaphylococcus aureusexogenous endophthalmitis

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