Inhibitory Effects of 2,2′-Dipyridyl and 1,2,3,4,6-Penta-O-Galloyl-b-D-Glucopyranose on Biofilm Formation in Contact Lens Cases

PURPOSE. This study observed biofilm formation by Pseudomonas aeruginosa and Staphylococcus aureus in contact lens cases and investigated the inhibitory effects of 2,2'-dipyridyl (2DP) and 1,2,3,4,6-penta-O-galloyl-b-D-glucopyranose (PGG). METHODS. Biofilm formation of P. aeruginosa ATCC 9027 and S. aureus ATCC 25923 and ATCC 6538 in contact lens cases was determined for a range of initial inocula and incubation times using crystal violet staining. The effects of 2DP and PGG on biofilm were evaluated alone and in combination by their incorporation into the media at commencement of incubation. RESULTS. At 24 hours, biofilm production was related to initial concentration. However, with extended incubation, higher initial concentrations affected formation in S. aureus. Presence of 312 mu M 2DP significantly inhibited P. aeruginosa biofilm formation, but had little effect on that of S. aureus. In contrast, PGG (50 mu M) inhibited S. aureus biofilm formation, but had much less effect on that of P. aeruginosa. Combination of the agents effectively inhibited biofilm formation of all three organisms throughout a week-long incubation period with OD levels barely exceeding cell-free controls. CONCLUSIONS. Biofilm formation of P. aeruginosa could be prevented by 2DP, while biofilm formation of S. aureus was inhibited by PGG. However, combining these agents showed better inhibition of biofilm production than use of either agent alone on both species. This combination may be useful in prevention of biofilm in contact lens cases, thereby reducing infection risk due to poor compliance with lens case cleaning and replacement. Further work is needed to confirm compatibility with multipurpose solutions and investigate cytotoxicity to ocular tissues.