19 March 1998
The aim of our study was to verify the in vitro growth of Staphylococcus epidermidis in various dilutions of some viscoelastic substances containing hyaluronic acid (Healon® and Healon GV, IAL®, Biolon<sup>TM</sup>). Serial twofold dilutions of each sterile viscoelastic substance, prepared so as to obtain a final concentration ranging from 50 to 0.78% of the product in sterile saline solution (0.85% NaCl), were taken out with a pipette that delivered 1.0 ml/tube. One hundred microliters of the S. epidermidis inocula, used for the evaluation of the positive control of the test organism, was dispensed into each tube. After 24 h of aerobic incubation at 37 °C, 100 μl of sample was taken out from each tube and plated into the specific medium for the growth of the test organism. After 24 h of incubation at 37 °C, these agar plates were examined and the colony-forming unit count of the test organism was compared to the corresponding total colony count, acting as a positive control, in order to determine the quantitative variation of the test organism grown in the presence of the viscoelastic compounds. For the lowest dilutions (from 1: 2 to 1: 8) statistically significant bacterial growth was detected in all tested viscoelastic substances. For the highest dilutions (1: 64 and 1: 128) Biolon and Healon GV showed a significant inhibition of S. epidermidis growth. A significant inhibition was also observed in the highest dilution (1: 128) of Healon. In every dilution of IAL a statistically significant increase in bacterial growth was observed. It remains to be carefully considered whether S. epidermidis, accidentally penetrating the eye via the intraocular lens, could find a culture medium in a small amount of sodium hyaluronate left in the capsular bag behind the optic.