Fluoroquinolone Effective Initial Treatment for MRSA Keratitis

Sarah Atta, BS

New study findings showed that fluoroquinolone therapy for methicillin-resistant Staphylococcus aureus (MRSA) keratitis may be a reasonable initial treatment option.

The study was presented by Sarah Atta, BS, on ARVOLearn due to the cancellation of the 2020 Association for Research in Vision and Ophthalmology (ARVO) annual meeting. The findings relayed that despite treatment with a fluoroquinolone, presenting characteristics and outcomes were comparable to those initially treated with vancomycin.

Atta, a first-year medical student at the University of Pittsburgh School of Medicine, and a team of investigators aimed to determine if fluoroquinolone treatment was non-inferior to vancomycin treatment in cases of MRSA keratitis. Typically, patients are treated with vancomycin, but patients with MRSA keratitis could respond to fluoroquinolones.

The team identified 52 culture-proven cases from 48 subjects of MRSA keratitis from 2008-2019 at the University of Pittsburgh Medical Center. The investigators retrospectively reviewed the electronic health record for demographic data, ocular and systemic risk factors, symptom duration prior to presentation, initial and final visual acuity, and infiltrate size, shape, and location. What’s more, the team extracted duration of treatment, follow-up length, time to epithelial defect closure, medical and adjunctive management, presence of hypopyon and hyphema, and presence of polymicrobial infection and/or concurrent herpes simplex virus infection.

There were 2 groups identified by Atta and the team: patients who were initially treated with a fluoroquinolone (36 eyes) and those treated initially with vancomycin (16 eyes). In the fluoroquinolone group, the mean age was 66.83±18.87 with a mean follow-up time 370.72±531.59 days. For the vancomycin group, the mean age was 63.56±21.25 with a mean follow-up 239.56±267.09 days.

The mean logmar visual acuity at baseline in the fluoroquinolone group was 1.59±.68 and 1.94±.93 in the vancomycin group (P=.172). The final logmar visual acuity was 1.16±.97 in the fluoroquinolone group and 1.36±1.06 in the vancomycin cohort (P=.54). Treatment duration in the fluoroquinolone group was 89.26± 85.93 compared to 117±176.90 in the vancomycin group.

There were no statistically significant differences in the presence of hypopyon (P=.356), need for adjunctive treatment (P=.106), i.e. procedures such as tarsorrhaphy (P=.662), debridement (P=1), penetrating keratoplasty (P=1), or enucleation (P=.308). Among the patients, 20.8% received moxifloxacin alone, 20.8% had fortified cefazolin and fortified tobramycin together, and 12.5% had fortified vancomycin and fortified tobramycin.

Although fluoroquinolone was used as a treatment in many cases, presenting characteristics and outcomes were comparable to those who were 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,” Atta and the investigators said.

Because of antibiotic resistance and corneal toxicity caused by fortified vancomycin, treatment with fluoroquinolone therapy could be a reasonable initial treatment option for MRSA keratitis.

The study, “Methicillin-resistant Staphylococcus aureus (MRSA) keratitis: An analysis of outcomes: An analysis of outcomes of cases treated initially with vancomycin versus cases treated with fluoroquinolone drops,” was published online on ARVOLearn.