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Intravitreal Injection and Quantitation of Infection Parameters in a Mouse Model of Bacterial Endophthalmitis
Published on: February 6, 2021
Exogenous Methicillin-Resistant Staphylococcus aureus Endophthalmitis is Caused by Multidrug-Resistant Lineages that
Fatma Z A Ali1,2, Camille Andre1,2, Lucia Sobrin1,2
1Department of Ophthalmology, Massachusetts Eye and Ear, Harvard Medical School, Boston, Massachusetts, USA.
Purpose:
To investigate the genomic epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) endophthalmitis and correlate it with the presenting clinical features and outcomes.
Methods:
Nine patients presenting with MRSA endophthalmitis from 2014 to 2022 were included. Phenotypic and genomic tests were used for strain characterization. Demographics, clinical presentation, treatment and outcomes were reviewed.
Results:
The MRSA population was dominated by multidrug-resistant (MDR) strains within the clonal complex 5 (CC5) carrying an SCCmec type II genetic element (USA100-like strains). These strains carried genes that confer resistance to five antibiotic classes, in addition to mutations in topoisomerase genes (gyrA and parC) that resulted in resistance to all fluoroquinolones tested. Patients were mostly male (56%), with a median age of 82.7 years, and most had no recent history of extensive healthcare exposure. All cases were exogenous following ocular surgery (67%) or intravitreal injection (33%). The main exam findings were visual acuity ≤ hand motion, hypopyon (89%), and vitreous opacity (89%). Five patients (56%) showed improvement in visual acuity at 1 month following presentation, three (33%) at 3 months, and two (22%) at 6 months. Complications included evisceration (n = 1) and phthisis (n = 1). Patients who had pars plana vitrectomy within 48 hours of presentation had better clinical outcomes compared to those who did not.
Conclusion:
Exogenous MRSA endophthalmitis is caused by MDR strains that resemble the hospital-acquired lineage USA100. These strains cause severe endophthalmitis in patients with no recent hospital/healthcare exposure.
Insights
Methicillin-resistant Staphylococcus aureus (MRSA) endophthalmitis is often caused by multidrug-resistant strains similar to the USA100 lineage. Early surgical intervention may improve outcomes in these severe ocular infections.
Area of Science:
- Ophthalmology
- Infectious Diseases
- Genomics
- Microbiology
Background:
- Endophthalmitis is a severe intraocular inflammation, often leading to vision loss.
- Methicillin-resistant Staphylococcus aureus (MRSA) is a significant pathogen causing difficult-to-treat infections.
- Understanding the genomic characteristics and clinical impact of MRSA endophthalmitis is crucial for effective management.
Purpose of the Study:
- To investigate the genomic epidemiology of MRSA endophthalmitis.
- To correlate MRSA strain characteristics with clinical features and patient outcomes.
- To identify factors influencing the prognosis of MRSA endophthalmitis.
Main Methods:
- Retrospective case series of nine patients with MRSA endophthalmitis (2014-2022).
- Phenotypic and genomic testing for MRSA strain characterization.
- Review of patient demographics, clinical presentation, treatment, and outcomes.
Main Results:
- The MRSA strains were predominantly multidrug-resistant (MDR) CC5 (USA100-like) with fluoroquinolone resistance.
- Most patients were elderly males with exogenous endophthalmitis post-ocular surgery or injection, often without recent healthcare exposure.
- Visual acuity improved in 56% at 1 month; early pars plana vitrectomy (<48 hours) correlated with better outcomes.
Conclusions:
- Exogenous MRSA endophthalmitis is primarily caused by MDR strains of the USA100 lineage.
- These strains can cause severe infections even in patients without recent healthcare exposure.
- Timely surgical intervention, such as pars plana vitrectomy, appears beneficial for improving visual outcomes.
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