Screening and Characterization of Staphylococcus aureus from Ophthalmology Clinic Surfaces: A Proposed Surveillance Tool

Abstract

To screen environmental surfaces of an outpatient ophthalmic clinic for methicillin-susceptible and methicillin-resistant Staphylococcus aureus (MSSA and MRSA); to identify the most commonly contaminated surfaces and to phenotype and genotype all collected isolates. A single institution, 1-year prospective environmental study. Commonly touched surfaces in examination rooms and common areas were targeted and sampled on a quarterly basis for 1 year. Samples were collected using electrostatic cloths and swabs. S. aureus was isolated using nonselective and selective media. Morphologic characteristics and standard biologic testing were used to confirm staphylococcal species. S. aureus isolates were phenotypically (Kirby-Bauer method) and genotypically characterized (mecA confirmation, SCCmec typing and pulsed-field gel electrophoresis). Dendrogram analysis was used to establish genetic relatedness between the isolates. Of 112 total samples, 27 (24%) and 5 (4%) were MSSA- and MRSA-positive, respectively. Both community-associated (SCCmec IV, USA300) and hospital-associated (SCCmec II, USA100) MRSA isolates were found. No single surface remained consistently positive with the same isolate over time, and molecular analysis demonstrated high levels of diversity among isolates. Doorknobs, slit-lamp headrests and chinrests, and computer keyboards were commonly found to be contaminated. The proposed surveillance protocol successfully allowed the detection of both MSSA and MRSA contaminating important high-touch surfaces in a representative ophthalmology clinic. Frequently contaminated surfaces must be targeted for routine cleaning and disinfection because there is a constant introduction of clones over time. Hence, other clinics may consider implementing and adapting surveillance tools, like the one described here, to help them control these important nosocomial pathogens.