In vitro Staphylococcus epidermidis growth in some viscoelastic substances containing sodium hyaluronate

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). 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 degrees C, 100 microl 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 degrees 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.