Efficacy of Contact Lens Care Solutions Against Neutrophil Enhanced Biofilms
Hinojosa, Jorge A.
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PURPOSE: To evaluate currently available chemically preserved and peroxide-based lens care products (LCPs) antimicrobial efficacies against neutrophil enhanced biofilms in reference strains of S.auerus(SA), S. marcescens (SM), S. maltophilia(ST), and P.aeruginosa(PA). METHODS: Lotrafilcon B lenses were inoculated with 2.5 x 107 CFUs of American Type Culture Collection (ATCC) reference strains of either SA, SM, ST, or PA and 8.3x106 cells of human neutrophils harvested by whole blood centrifugation. Lenses were then incubated over night under conditions that facilitate biofilm formation. Lenses were then disinfected with either multipurpose contact lens solutions (MPS): Biotrue (BT), PureMoist (PM) or hydrogen peroxide-based lens care systems (HPB): ClearCare (CC), PeroxiClear (PC) according to specific manufacture guidelines. Antimicrobial activity was then quantified by quantitative culturing (colony-forming units) and by fluorescence confocal microscopy (FCM) using LIVE/DEAD BacLight Bacterial Viability Kit (Molecular Probes, Eugene, OR). RESULTS: Mean colony growth counts for each bacterial strain + neutrophils were: SA= 1.44 x 107 (CFU/ml), SM= 2.56x109 (CFU/ml), ST= 1.17x1010 (CFU/ml), PA= 3.43x109 (CFU/ml). After treatment, SA exhibited a 7-log reduction with all LCPs (P=0.609); SM exhibited 9-log reduction for all LCPs except BT, which showed a 7-log reduction (P < 0.001); ST exhibited a 9-log to 10-log reduction for all LCPs (P=0.040); PA showed a 9-log reduction for all LCPs (P=1.000). FCM with viability staining revealed the presence many unviable bacteria still adhered to the lens surface after treatment with LCPs. CONCLUSIONS: Although all LCPs meet FDA criterion of a 3-log reduction minimum even against neutrophil enhanced biofilms, FCM revealed that many remnants still remain adhered on the lens surface after just one use. Further deposition of bacterial products from continued used could enhance biofilm formation and promote a host inflammatory response, both of which could precipitate into a corneal infiltrative event (CIE). In addition, mean colony growth counts showed that SA exhibited the lowest growth on lens surfaces, which may explain why SA is more commonly associated with sterile CIEs.