Prevalence of Staphylococcus epidermidis strains with biofilm-forming ability in isolates from conjunctiva and facial skin.

PURPOSE: To compare the prevalence of biofilm-forming strains of Staphylococcus epidermidis in the conjunctival and facial skin microflora.

DESIGN: Experimental study.

METHODS: The prevalence of biofilm-forming ability of 10 S epidermidis strains obtained from the conjunctival sac of healthy volunteers was compared with 40 strains obtained from the facial skin of healthy volunteers. The ability to form biofilm was determined by the presence of the icaA gene, and the production of biofilm was examined by qualitative (Congo red agar [CRA]) and quantitative (microtiter plate) assays. Additionally, the prevalence of 36 S epidermidis strains obtained from the conjunctival sac of precataract patients to form biofilm was investigated.

RESULTS: The icaA gene was detected in 60% of the isolates from the conjunctival sac of volunteers and 15% of those from the facial skin. Fifty percent of the isolates from the conjunctiva of volunteers and 5% from the facial skin were CRA positive. Biofilm production was significantly greater in isolates from the conjunctiva of volunteers. Of the nine pairs of isolates found in the same volunteers, six conjunctival sac isolates were positive for the icaA gene with biofilm-forming ability except one strain, whereas only one of the facial skin isolates was positive for the icaA gene and none exhibited biofilm-forming phenotype. Sixty-nine percent and 44% of the isolates from the conjunctival sac of precataract patients were positive for icaA gene and CRA test, respectively.

CONCLUSIONS: The prevalence of biofilm-forming S epidermidis isolates is higher in the conjunctival sac than the facial skin.