Abstract
Purpose: :
Proteins in the tear film are deposited on and within soft contact lenses during wear. We have previously shown that proteins recovered from lenses retain their antimicrobial function, and that treatment of worn lenses with different care solutions denatures tear proteins and reduces this activity. In the present study we investigated whether the activity of ex vivo lens protein extracts is affected by the solution in which the antimicrobial assays take place. Moreover, we tested whether the potency of the tear protein antimicrobial activity is sufficient to enable it to be detected during disinfection with standard contact lens care solutions, i.e. over and above the antimicrobial activity of the biocides within those solutions.
Methods: :
Tear proteins were extracted from worn and unworn 1-day Acuvue contact lenses with ACN/TFA. In order to assess the activity of extracted lens proteins in the presence of contact lens cleaning solutions, suspensions of Pseudomonas aeruginosa (ATCC 9027) and Staphylococcus aureus (ATCC 6538) were challenged with or without tear protein extracts in the presence of various MPS, stand-alone MPS solution components and PBS. The numbers of viable bacteria after treatment were assessed by colony counting.
Results: :
Incubation of S. aureus and P. aeruginosa with tear proteins solubilised in PBS resulted in decreased bacterial growth. However this effect was stronger in partial MPS formulations lacking disinfectants, relative to that found in PBS. The tear protein activity was also readily detectible in the presence of fully formulated MPS, and the activity was once again stronger in full formulation MPS than that found when assays were conducted with tear proteins in PBS alone.
Conclusions: :
These data show that tear proteins absorbed to soft contact lenses possess potent antimicrobial activity which functions synergistically with MPS and their ingredients, and which is demonstrable above and beyond the activity of fully formulated MPS. These data suggest that tear protein antimicrobial activity is important during lens disinfection and may be clinically significant.
Keywords: contact lens • protein structure/function • bacterial disease