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Ashkan M. Abbey, Darlene Miller, Harry W. Flynn, Jr.; Staphylococcus aureus Endophthalmitis: Antibiotic Susceptibilities, Methicillin Resistance, and Clinical Outcomes. Invest. Ophthalmol. Vis. Sci. 2012;53(14):1689.
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To investigate the antibiotic susceptibility and clinical outcomes of endophthalmitis caused by methicillin-sensitive (MSSA) versus methicillin-resistant (MRSA) Staphylococcus aureus.
A consecutive case series of 7 patients with culture-proven S. aureus endophthalmitis seen at the Bascom Palmer Eye Institute from January 1, 2008, through October 1, 2011, was performed. Antibiotic susceptibility profiles, identified using standard microbiologic protocols, and visual acuity at 1 and 3 months were the main outcome measures. Historical published outcomes (1995-2007) were also compared.
MSSA was recovered from 4/7 patients (57%) and MRSA was recovered from 3/7 patients (43%). The etiologies included the following: cataract surgery in 3/7 (43%), intravitreal injection in 2/7 (29%), endogenous in 1/7 (14%), and trauma/open globe injury in 1/7 (14%). All isolates were sensitive to vancomycin. Fluoroquinolone (FQ) resistance was 2/4 (50%) in the MSSA group, and 3/3 (100%) in the MRSA group. The median presenting visual acuity was hand movements for both MSSA and MRSA eyes. All eyes received intravitreal antibiotics. Pars plana vitrectomy was performed on 25% of MSSA and 33% of MRSA patients. At 3 months, a visual acuity of 20/400 or better was achieved in 3/7 (43%). In a previously published case series from the same institution evaluating 32 cases of S. aureus endophthalmitis from 1995 to 2007, 41% of cases involved MRSA. In the previous study, all MSSA and MRSA isolates were sensitive to vancomycin. However, MRSA isolates from the current study exhibited 100% FQ resistance (38% resistant in previous study), and 50% of the MSSA isolates demonstrated FQ resistance (5% resistant in previous study). A visual acuity of 20/400 or better at 3 months was achieved in 43% of the current series versus 51% of the previous series.
The frequency of MRSA has remained stable in the current study compared to a previous study. All isolates were sensitive to Vancomycin, but a higher percentage of isolates was resistant to fluoroquinolones in the current study. A similar percentage of these patients achieved 20/400 or better visual acuity in both studies.
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