MRSA Keratitis Often Cause By Antibiotic-Resistant Pathogens

Methicillin-resistant Staphylococcus aureus (MRSA) keratitis is associated with a high risk for poor visual outcomes even after treatment with the recommended antibiotic regimen, according to research presented at the Association for Research in Vision and Ophthalmology (ARVO) 2023 Annual Meeting, held in New Orleans from April 23 to April 27, 2023. 

Researcher Olivia Whitney Cummings, MD, ScM, and colleagues retrospectively reviewed culture-proven cases of MRSA keratitis between 2014 and 2022 at Massachusetts Eye and Ear and the University of British Columbia. The research team identified 61 culture-proven cases of MRSA keratitis in 58 patients. Among the cohort, the median age at diagnosis was 62 years, 37 patients were women (64%) and 50 patients (82%) presented with a best corrected visual acuity (BCVA) of greater than 20/60. 

Many patients with MRSA keratitis experienced pre-existing ocular surface disease (n=37; 61%), a history of ocular trauma (n=12; 20%), and at least 1 systemic comorbidity (n=52; 85%). The use of topical steroids and topical antibiotics immediately before presentation was common (31% and 38% respectively, with 13% on both). 

The researchers found that 13 patients with MRSA keratitis (21%) had extensive healthcare exposures in the year prior to presentation and 10 (16%) had a history of MRSA infection. The most common initial treatment was fortified vancomycin/tobramycin (n=45; 75%). A total of 15 cases (25%) underwent surgical management, including penetrating keratoplasty (n=5), tarsorrhaphy (n=15), and corneal gluing (n=8), the report shows. 

Post MRSA keratitis treatment BCVA was worse than 20/60 for 5 patients (15%) and 20/60 or better for 38 patients (62%; 23% of patients lost to follow-up). MRSA isolates were frequently multidrug-resistant (80%; MDR, resistant to ≥3 drug classes); demonstrating high levels of resistance to commonly used empiric antibiotics: ciprofloxacin (83%), moxifloxacin (76%) and tobramycin (70%). All MRSA isolates were susceptible to vancomycin in vitro, according to the report. 

“Even after treatment with the recommended medications, many patients with infections of the cornea caused by MRSA have persistent vision loss. We have discovered that many cases of this infection are caused by strains of MRSA that are resistant to many of the medications that we prescribe to treat corneal infections,” according to the researchers.

This study was limited by its retrospective nature.