Abstract
Purpose: :
To compare the adherence of clinically relevant bacteria, Staphylococcus epidermidis, to intraocular lenses of different commonly used materials.
Methods: :
Staphylococcus epidermidis with an ica, slime-forming, locus (ATCC 35984) was grown and colored with the cream agar method1. Nine IOLs of 3 materials (3 acrylic, 3 silicon, and 3 PMMA) were placed in culture slides containing bacterial suspension of known concentrations and were incubated at room temperature with gentle agitation for 30 minutes. The IOLs were then removed from the culture slides and rinsed in sterile saline. This procedure was to simulate the likely introduction of bacteria during surgery. The surface of the IOLs were then scanned with Olympus IX-70 Inverted System Microscope that allowed for automated scanning and counting of relatively large fields. 10 random areas of 17x17 microns were selected on each IOL and the colony-forming-units (cfu) were counted in these areas.A control of each IOL material was run through the same procedure without immersion into the bacterial suspension.
Results: :
The counting revealed that the bacteria number of bacteria adhering per unit area to the acrylic IOLs was approximately 10 times that of the silicon or the PMMA IOLs. The average count on the IOLs was approximately 40,000 cfu for the acrylic, 5,000 for the silicone, and 3,000 for the PMMA, per square millimeter. The Statistical analysis of the data yields a P-value of <0.01 when comparing the counts of bacteria on the acrylic IOLs to the silicone or PMMA IOLs. The counts on the silicone and the PMMA IOLs were not statistically different.
Conclusions: :
These data suggest that this particular bacterial strain is significantly more adherent to the surface of the acrylic IOLs than silicone or PMMA. This observation may have clinical correlation with the incidence of post-operative endophthalmitis after implantation of an IOL. Further investigation with other clinically relevant bacterial strains and other models of IOLs of various materials and surface-coatings may prove interesting and clinically useful.1. Brown, Richard W. Color of Cultures of Staphylococcus epidermidis Determined by Spectral Reflectance Colorimetry. J Bacteriol. 1966 March; 91(3): 911-918.
Keywords: intraocular lens • bacterial disease