Adherence of ocular isolates of Staphylococcus epidermidis to ACRYSOF intraocular lenses - A scanning electron microscopy and molecular biology study

Purpose: To investigate the adherence of two clinically relevant ocular iso lates of Staphylococcus epidermidis to ACRYSOF intraocular lenses (IOLs) (A lcon Surgical, Fort Worth, Texas) and to determine whether the strains unde r study carried the intercellular adhesion (ica) locus, which encodes produ ction of S. epidermidis antigens mediating adherence to biomaterials. Design: Experimental study. Participants: The authors examined the in vitro adherence of two clinically relevant ocular isolates of S. epidermidis (S. epidermidis I and S. epider midis 2). Adherence was tested on six ACRYSOF IOLs. Methods: Three IOLs were placed in three separate test tubes containing 5 m i of S. epidermidis I suspension, and three other IOLs were placed in three test tubes containing 5 mi of S. epidermidis 2 suspension. At different ti mes (3, 30, and 90 minutes), the IOLs were removed from the test tubes and rinsed in sterile phosphate buffered solution. The lenses were then fixed i n glutaraldehyde, postfixed in osmium tetroxide, and serially dehydrated in ethyl alcohol. After critical point drying, they were sputter-coated with gold and then examined with a scanning electron microscope. In addition, po lymerase chain reaction amplification was used to investigate whether the i solates under study carried the ica locus. Main Outcome Measures: The number of adhered bacteria per area (square mill imeters) of IOL optic was calculated. Statistical analysis included calcula tion of arithmetic means and 95% confidence intervals (t test). Polymerase chain reaction amplification products were visualized in ethidium bromide-s tained agarose gel. Results: Direct counting of adherent bacteria in scanning electron microsco py photographs revealed that the total amount of adhered bacteria per area of IOL optic after 3, 30, and 90 minutes of incubation in bacterial suspens ion was 1306/mm(2), 3389/mm(2), and 7195/mm(2) (S. epidermidis I) and 778/m m(2), 1056/mm(2), and 3861/mm(2) (S. epidermidis 2). Differences at 30 and 90 minutes were statistically significant (P = 0.01 and 0.02, respectively) . Polymerase chain reaction amplification revealed that S. epidermidis I co ntained the ica locus, whereas S. epidermidis 2 was ica negative. Conclusions Different ocular isolates of S. epidermidis may differ signific antly with regard to adherence to ACRYSOF IOLs. Adherence appeared to be gr eater when the bacterial DNA contained the ica locus. Strains of S. epiderm idis carrying the ica locus may play an important role in the pathogenesis of some forms of endophthalmitis occurring after cataract surgery. (C) 2000 by the American Academy of Ophthalmology.