This study analyzed clinical characteristics of Staphylococcus aureus keratitis according to methicillin-resistance.

The authors performed a retrospective chart review of 46 isolates in 46 eyes with Staphylococcus aureus keratitis that were followed up for more than 2 months between January 1998 and December 2014. Comparative analyses of the epidemiology, predisposing factors, initial clinical manifestations, antibiotics susceptibility and clinical outcome between methicillin-resistant Staphylococcus aureus (MRSA) keratitis and methicillin-sensitive Staphylococcus aureus (MSSA) keratitis were performed. Risk factors of poor visual outcome were analyzed using logistic regression analysis.

Among 46 eyes, MRSA was present in 15 eyes (33%) and MSSA in 31 eyes (67%). Male (61%) and older than 60 year-old group (48%) were common. Ocular surface disease/ocular surgery history and trauma were more common as a predisposing factor. Vancomycin was 100% sensitive to both the MRSA and MSSA groups. Antibiotics susceptibility to MRSA was significantly low in the oxacillin (0%), gentamicin (13.3%) and trimethoprim/sulfamethoxazole (53.3%) groups. Sensitivity to fluoroquinolone was 81.3% (MRSA 64.3% vs. MSSA 94.4%; p = 0.064). There were no differences in early corneal findings between the groups. The ratio of BCVA 0.5 or more was 24.4% initially and increased to 44.4% after treatment among all eyes ( p = 0.046). Risk factors for poor visual outcomes included a BCVA less than 0.1 at initial evaluation ( p = 0.033).

Among eyes with Staphylococcus aureus keratitis, 33% were MRSA. The ratio of BCVA 0.5 or more increased after treatment among all eyes. There were no differences between MRSA and MSSA eyes in terms of epidemiology, predisposing factors, initial clinical manifestations or clinical outcome, except for antibiotic susceptibility. For positive patient outcomes, a treatment approach considering methicillin-resistance as well as various factors affecting clinical course is recommended.