Ocular Microbiology and Immunology Group
Back to OMIG Main Page

< Previous | 2026 Agenda and Abstracts | Next >

2026 OMIG Abstract

Community Acquired MRSA USA300 Periorbital Infections: Clinical Features, Risk Factors, and Outcomes in a Comparative Cohort Study

Lisa Y. Lin¹, Annika G. Samuelson², Amee Azad², Camille Andre², Paulo J. M. Bispo²,
and Suzanne K. Freitag²

¹Wilmer Eye Institute, Johns Hopkins University, Baltimore, Maryland; ²Massachusetts Eye and Ear,
Harvard University, Boston, Massachusetts

Purpose: Methicillin-resistant Staphylococcus aureus (MRSA) infections are increasingly encountered in the broader community with the USA300 clone identified as the dominant strain in individuals without traditional risk factors. Although this pathogen has been associated with periorbital infections, its clinical manifestation remains poorly characterized. This study compares the clinical features, management, and outcomes of MRSA-USA300 periorbital infections to Methicillin-sensitive Staphylococcus aureus (MSSA) and MRSA-non-USA300 strains in the largest cohort reported to date.

Methods: Retrospective cohort study at a single institution from 2014 to 2021, including all patients with a culture-proven S. aureus periorbital infection. Using antimicrobial susceptibility and whole genome sequencing, cases were divided into cohorts: MSSA, MRSA-USA300, MRSA-non-USA300. Patient demographics, risk factors, clinical features, management, and outcomes were collected. Statistical analysis and univariate and multivariate multinominal regression analyses were performed.

Results: A total of 231 Staphylococcus aureus infections were identified: MSSA (n=118), MRSA USA300 (n=61), MRSA non-USA300 (n=52). MRSA occurred in younger patients vs. MSSA (46.1 vs 62.7 years, p<0.001), with MRSA USA300 affecting the youngest (40 years, p<0.001). MRSA USA300 most often presented as brow abscess (28%), whereas MSSA as nasolacrimal infections (53%). Polymicrobial infections were higher in MSSA (p=0.003). Risk factor burden was similar (p=0.057). Of risk factors identified, prior MRSA infection was most strongly associated with MRSA (p<0.001). Management, surgery rates, and visual outcomes were similar.

Conclusions: Community-acquired MRSA, specifically USA300, accounts for a substantial proportion of Staphylococcus aureus periorbital infections. These cases often occur in younger patients without traditional risk factors and have a predilection for brow abscess formation and preseptal cellulitis. Screening for prior MRSA history appears most useful. Treatment and visual outcomes remain favorable across all strains.