Prevalence of Community Acquired Methicillin Resistant Staphylococcus aureus among Ocular MRSA Isolates

BACKGROUND/OBJECTIVES: Staphylococcus aureus is the most common ocular pathogen recovered from conjunctivitis, blepharitis, and surrounding soft skin infections. Isolation frequency ranges from 2% for endophthalmitis up to 90% for blepharitis. S. aureus may also be recovered as resident flora in 0-30% of normal eyes and in 1-2% of patients presenting for cataract surgery. Methicillin resistance among S. aureus ocular isolates is lower (5-30%) but may parallel trends in the surrounding community. The purpose of this study was to 1) determine the MRSA rate among select ocular sources and 2) correlate antibiograms, healthcare exposure and ocular sources to identify potential community acquired methicillin resistant Staphylococcus aureus (CA-MRSA) ocular infections. METHODS: Data on antibiograms, healthcare history, and ocular sources, were collected from laboratory and computer records during 2000-2005 for all MRSA isolates recovered from conjunctiva, lids, and orbit. Data was entered into SPSS for analysis. RESULTS: Four hundred and eighty-four S. aureus isolates were recovered during the 6 year period (conjunctiva, 375 (77.5%), lids 97 (20%) , orbit 12 (2.5%). The general MRSA recovery rate was 29.1% (141/484). Ocular source rates in descending order were: orbit, 33.0%, conjunctiva, 29.3% and lids 28.8%. Thirty-seven percent (53/141) of the ocular MRSA isolates were resistant to 2 or fewer antibiotics. Potential CA-MRSA isolates were recovered from lids (41%), conjunctiva (11%) and orbit (50%). Resistance to erythromycin was the most common resistance marker. No healthcare exposure was identified for 47% (25/53) of patients in this group. Resistance to the macrolides, clindamycin and the fluoroquinolones was the most common antibiogram profile among the 88 (62.5%) multidrug resistant MRSA isolates. Healthcare exposure was documented for all patients in this group. CONCLUSIONS: MRSA isolates consistent with CA-MRSA profiles can be isolated from ocular sources in the absence of an outbreak. Conjunctiva and lids could serve as potential reservoirs for CA-MRSA.