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Brien David, Denise Callahan, Julie Bair, Susan Norton; Evaluation of Biocidal Efficacy of Multipurpose Solutions Against Gram Negative Organisms in a Lens Case. Invest. Ophthalmol. Vis. Sci. 2013;54(15):522.
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Evaluating the biocidal efficacy of multipurpose solutions (MPS) against Gram - organisms associated with corneal infiltrative events (CIEs),Achromobacter xylosoxidans, Stenotrophomonas maltophilia, and Delftia acidovirans, in a lens case. Time points from 4 hrs to 7 days of exposure.
ISO Standard 14729 was used as a guideline to evaluate biocidal efficacy of 6 MPS: Biotrue, ReNu Fresh, RevitaLens, OptiFree Express,OptiFree Puremoist, OptiFree Replenish which included the preservatives PHMB/PQ; PHMB; PQ/alexidine; and 3 different PQ/aldox based MPS; to challenges of Gram - organisms, A.xylosoxidans, S. maltophilia, and D. acidovirans. Testing was performed in lens cases appropriate to each Manufacturer's solution. Each lens case was filled with 3 ml of MPS. Biocidal testing was performed on 3 lots of each MPS on 3 separate days, in the lens case, using ISO Standard 14729. Inoculum was prepared at ~5 x 10E5 colony forming units/mL. Biocidal testing was performed at 4, 6 and 24 hrs, and Day 7 after inoculation. .
Test results varied depending on organism and solution. 3 solutions, Biotrue, ReNu Fresh, and ReVitalens showed >3 log reduction for each organism at all time points. For OptiFree Express and OptiFree Puremoist, there was increasing efficacy at each time point, showing no microbial recovery by Day 7. However, OptiFree Replenish did not achieve a 1 log reduction, even after 7 days exposure. Overall, log reductions against these organisms ranged from >5.0 log reduction (no microbial recovery) to -0.9 log reduction (regrowth).
The ISO 14729 Stand Alone test is performed against "ISO organisms" in test tubes. The current testing was performed in contact lens cases using organisms associated with CIEs. In this study, the three MPS that contained PQ/aldox as their preservatives showed limited activity (<3 log reduction) against the three organisms when tested at recommended soak times. Although two of these solutions did show improvement with greater time of exposure, one PQ/aldox solution (OptiFree Replenish) did not improve with time of exposure. These studies show that ISO 14729 methodology can be adapted to distinguish differences in antimicrobial effects between various solutions. Further studies are needed to determine the significance of these in-vitro results.
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