Abstract
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.
Keywords
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Article info
Publication history
Published online: October 09, 2021
Accepted:
September 28,
2021
Received in revised form:
August 24,
2021
Received:
February 17,
2021
Identification
Copyright
© 2021 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.
