Purpose: Biofilm formation caused by infrequent contact lens case replacement and the ineffectiveness of multi-purpose solutions (MPS) on biofilm removal is associated with high rates of bacterial keratitis infections. This study demonstrated biofilm elimination from the contact lens case by microwave irradiation. Methods: Staphylococcus aureus biofilms indicative of 3–9 months of contact wear were cultured in contact lens cases and visualized with crystal violet (CV) staining. Biofilms in contact cases were then exposed to four treatment regimens: No treatment (n = 8), 45 s microwave irradiation (n = 8), tap water (n = 6), and MPS (n = 9). Bacterial survival was assessed by colony forming unit (CFU) assay using streak dilutions. Results: Visualization of the biofilms through CV staining revealed that biofilms coalesce between ribs of the contact case. In 5/8 cases no CFU were cultivated from the case after treatment with microwave irradiation. In tap water and MPS the first dilution averaged 6 ± 2 and 31 ± 13 CFUs per plate, respectively, while microwave irradiation averaged < 1 CFU per plate. In Dilution 2, the average reduced to 0.7 ± 0.7 and 6 ± 5 CFUs per plate for tap water and MPS, respectively, while microwave irradiation had 0 CFUs in Dilution 2. Conclusion: Biofilms that coalesce between the ribs of the contact case pose a threat because this area is difficult to thoroughly scrub and could act as a basis for infection through fouling of contact lenses. Of the four treatment regimens, microwave irradiation displayed the most consistent and highest rate of bacterial eradication. Tap water was less effective compared to microwave irradiation, and poses other harmful side effects, but greatly reduced CFU count compared to no treatment. MPS displayed the poorest bacterial eradication of the treatments. Thus, microwave irradiation is worth further investigation as a viable in-home disinfecting option.
|Journal||Contact Lens and Anterior Eye|
|State||Published - Aug 2022|
Bibliographical noteFunding Information:
We gratefully acknowledge NIH funding under grant numbers P20GM130456 and R03DE029547 for completion of these experiments. The project described was supported by the NIH National Center for Advancing Translational Sciences through grant number UL1TR001998. Thank you to University of Kentucky Advanced Eye Care for the donation of contact lens cases. The sponsor had no role in design, conduct, analysis, or writing of this paper. The authors report no conflicts of interest and have no proprietary interest in any of the materials mentioned.
We gratefully acknowledge NIH funding under grant numbers P20GM130456 and R03DE029547 for completion of these experiments. The project described was supported by the NIH National Center for Advancing Translational Sciences through grant number UL1TR001998. Thank you to University of Kentucky Advanced Eye Care for the donation of contact lens cases.
© 2021 British Contact Lens Association
- Case disinfection
- Contact lens cases
- Microwave irradiation
- Multi-purpose solution
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