Abstract
Purpose:
Contact lens case bacterial biofilm formation has become a major cause of contact lens contamination. This is a serious problem since it has been found that bacteria grow even in the presence of contact lens cleaning solution. Silver as an antimicrobial has been incorporated into contact lens cases, however, silver has several drawbacks. Any patient with silver or metal allergies cannot use these cases and silver has minimal effects against Staphylococcus aureus (S. aureus), Stenotrophomonas maltophilia (S. maltophilia), and different fungi. In addition, silver is expensive and has to leach out of the case to be active. In contrast, selenium does not have to leach out of the material to be active since it kills by the catalytic formation of superoxide radicals and it is much less expensive. Thus, this project was carried out to test the ability of selenium, covalently incorporated into the polymer of contact lens case material, to inhibit biofilm formation by different bacteria.
Methods:
A polymer of polypropylene was produced that incorporated organo-selenium monomers into the final polymer. This material was then injection molded. The resulting material was tested for its ability to inhibit biofilm formation. with silver or metal allergies cannot use these cases and silver has minimal effects against S. aureus and S. maltophilia were tested since these bacteria are resistant to killing with silver. Pseudomonas aeruginosa and Serracia marcessans were also tested. The bacteria were allowed to grow in the presence of the polypropylene (with or without selenium) for 24 hours. The bacteria were then removed by vortexing and assayed. The bacterial concentration was determined by a colony forming unit assay (plating on agar). The biofilm was also imaged by confocal laser scanning spectroscopy and was then quantitated by COMSTAT analysis.
Results:
Selenium containing polypropylene showed over 7 logs (complete) inhibition against S. aureus, S. maltophilia and P. aeruginosa, and also was fully active after soaking in PBS for the equivalent of 8 weeks. S. marcessans showed 4 logs of killing.
Conclusions:
The results showed that selenium covalently incorporated into a polypropylene polymer could be injection molded yet showed total inhibition of S. aureus S. maltophilia and P. aeruginosa biofilm and was stable to soaking for 8 weeks.
Keywords: 477 contact lens •
433 bacterial disease