Comparative antimicrobial activity of no-rub multipurpose lens care solutions in the presence of organic soil

This study reports the effect of organic soil on the antimicrobial activity of four commercially available multipurpose contact lens care solutions used in no-rub regimens as determined by a modified International Organization for Standardization 14729 (ophthalmic optics-contact lens care products-microbiological requirements for products and regimens for hygienic management of contact lenses) Stand Alone Test procedure.

Testing was performed with organic soil consisting of a mixture of heat-killed yeast cells and heat-inactivated bovine serum or these components added separately. The organic soil was mixed with the challenge microorganisms before addition to the solution, added to the solution after addition of the challenge microorganisms, or added to the solution before addition of the challenge microorganisms. A final concentration of 0.4% v/v organic soil and 1 x 105 to 1 x 106 cfu/mL challenge microorganisms was realized in all test cases.

The antimicrobial activity of no-rub multipurpose lens care solutions was reduced in the presence of added organic soil. The extent of reduction varied with the type of organic soil, the method of addition of the organic soil to the solution, the challenge organism, and the solution tested.

The type of organic soil used and the method of addition of organic soil to the lens care solution may affect antimicrobial activity as determined by the primary criteria of the International Organization for Standardization Stand Alone Test procedure. The overall reduction in antimicrobial activity depends on the solution and organism.