Purpose:
To compare the antibiotic susceptibilities and final visual acuity of endophthalmitis caused by methicillin-resistant S. aureus (MRSA) versus methicillin-sensitive S. aureus (MSSA).
Methods:
Microbiological and clinical records of 35 eyes of 35 patients with S. aureus endophthalmitis treated at The New York Eye and Ear Infirmary since Jan. 1st, 1998 were reviewed. Data collected included antibiotic susceptibilities and visual acuity (VA) at presentation, and 3, 6, and ≥12 months after treatment. All eyes received intravitreal antibiotic treatment as a "tap and inject" or following a pars plana vitrectomy (PPV). Eyes were divided into two groups based on methicillin resistance and Fisher’s exact test was used to compare the MSSA and MRSA groups.
Results:
Of the 35 eyes, 15 (43%) were in the MRSA group and 20 (57%) were in the MSSA group. Mean age in years was 70 in the MRSA group and 69 in the MSSA group. There were 40% men in the MRSA group compared to 35% in the MSSA group (p=1.0). Antibiotic susceptibilities for both groups are shown in Table 1. The known sources of endophthalmitis (n=34) were cataract surgery in 18 (53%), intravitreal injection in 4 (12%), penetrating keratoplasty in 3 (9%), retinal surgery in 2 (6%), trauma in 2 (6%), endogenous in 2 (6%), bleb associated in 2 (6%) and glaucoma surgery in 1 (3%). PPV was performed on 12/15 (80%) of the MRSA and 16/19 (84%) of the MSSA eyes (p=1.0). Median presenting VA was hand motions for both the MRSA and MSSA groups. Mean LogMAR VA at presentation was 3.9 in the MRSA group and 3.5 in the MSSA group (p=0.40). There was no significant difference in VA between the MRSA and MSSA groups at any time point. A final VA of better than 20/200 at ≥ 12 months was achieved in 7/11 (64%) MRSA eyes compared to 6/12 (50%) MSSA eyes (p=0.68). A final VA of 20/50 or better at ≥ 12 months was achieved in 7/11 (64%) MRSA eyes compared to 4/12 (33%) MSSA eyes (p=0.22).
Conclusions:
There was no significant difference in presenting or final VA between the MRSA and MSSA groups. Resistance to fourth generation fluoroquinolones was present in over 85% of MRSA isolates and in no MSSA isolates. Resistance to the third generation fluoroquinolone levofloxacin was seen in 69% of MRSA strains and in only one MSSA strain. No strains were resistant to vancomycin or gentamicin.
Keywords: endophthalmitis • Staphylococcus • antibiotics/antifungals/antiparasitics