Methicillin-resistant Staphylococcus aureus (MRSA) keratitis: An analysis of outcomes of cases treated initially with vancomycin versus cases treated with fluoroquinolone drops

Abstract

Purpose : Methicillin-resistant Staphylococcus aureus (MRSA) can cause fulminant keratitis that quickly threatens vision in patients with healthy corneas. Prompt recognition and appropriate antibiotic selection is required. Often these patients are treated with vancomycin, however, patients with MRSA keratitis can respond to fluoroquinolones. Given increasing concerns regarding antibiotic resistance, this study sought to determine if fluoroquinolone treatment was non-inferior to vancomycin treatment in cases of MRSA keratitis.

Methods : 52 culture-proven cases (48 subjects) of MRSA keratitis from 2008-2019 at the University of Pittsburgh Medical Center were identified and retrospectively reviewed for ocular and systemic risk factors, treatment modalities, outcomes, as well as antimicrobial sensitivity and resistance data.

Results : Two groups were identified: those treated initially with a fluoroquinolone (n=36 eyes) and those treated initially with vancomycin (n=16 eyes). Mean age in the fluoroquinolone group was 66.83±18.87 with mean follow-up time 370.72±531.59 days. Mean age in the vancomycin group was 63.56±21.25 with mean follow-up 239.56±267.09 days. Mean logmar visual acuity (VA) at presentation in the fluoroquinolone group was 1.59±0.68 compared to 1.94±0.93 in the vancomycin group (p=0.172). Final logmar VA was 1.16±0.97 in the fluoroquinolone group compared to 1.36±1.06 (p=.540). Mean treatment duration in the fluoroquinolone group was 89.26±85.93 compared to 117±176.90 in the vancomycin group. There was no statistically significant difference in the presence of hypopyon (p=0.356), need for adjunctive treatment (p=0.106), i.e. procedures such as tarsorrhaphy (p=0.662), debridement (p=1.00), penetrating keratoplasty (p=1.00), or enucleation (p=0.308).

Conclusions : Despite treatment with a fluoroquinolone in many cases, presenting characteristics and outcomes were comparable to those initially treated with vancomycin. This suggests the virulence of MRSA within ocular structures may be decreased as many cases of fluoroquinolone “resistant” MRSA by laboratory testing responded to fluoroquinolone therapy. Given the concern for antibiotic resistance as well as corneal toxicity from fortified vancomycin, fluoroquinolone therapy for MRSA keratitis may be a reasonable initial treatment option with close monitoring.

This is a 2020 ARVO Annual Meeting abstract.