The effects of contact lens wear on concentration of phospholipids in the tear film

Abstract

1% trypticase soy broth for 18–20h at 35 ◦C. Following washing with phosphate buffered saline (PBS), the biofilm was exposed to MPDS or PBS (control) for 6h at 22 ◦C and total viable bacteria counts (TVBC) performed. In the planktonic studies, MPDS or PBS (control) were challenged with bacteria and TVBC made after 6 hour’s incubation in accord with ISO:14729 protocol. Results: Bacteria under biofilm conditions were significantly more resistant to MPDS killing. For S. maltophilia, MPDS-1, MPDS2 and MPDS-4 gave >5 log kill in the planktonic state but only 3 log, 0 log and 2 log, respectively, when in biofilm (p 5 log for planktonic cells but only 2 log and 5 log kill of Delftia sp. in the planktonic state but <1 log kill in biofilm (p<0.001). MPDS-3 showed no activity against these bacteria (<1 log kill) in either the planktonic or biofilm state and 3% PER gave total kill for both. Conclusions: The bacteria strains studied herewere found to be susceptible to certainMPDSwhen tested in suspension but showed significantly greater resistance when grown under biofilm conditions. The ability of biofilm bacteria to survive within contact lens storage casesmay be significant as they: (a) are protected fromdisinfection; (b) produce inflammatory products such as endotoxins that may cause CIEs; and (c) provide a food source for the freeliving amoeba Acanthamoeba.