Abstract
Purpose::
A study was performed to determine the relative effect of contact lens disinfecting products on clinically collected isolates of Staphlococcus aureus and Fusarium solani.Six multipurpose contact lens care products were included in this study. Four products use the disinfecting agent known as polyhexamethylene biguanide (PHMB). Two products utilize the disinfecting agent known as Polyquaternium-1.
Methods::
Staph aureus, ATCC 6538 and Fusarium solani, ATCC 36031 were used as reference. Additional Staph aureus strains were clinically collected isolates obtained in a frozen state from Nelson Laboratories (Utah). The clinically collected strains of Fusarium solani were collected by the Bascom Palmer Eye Clinic, as cultures from contact lens-wearing patients’ eyes and lens cases. Solutions were tested using the ISO 14729 test methods for contact lens care products intended for stand alone disinfection efficacy. All strains were tested using this method with each solution tested at 100% of the manufacturers recommended disinfection time for that product.
Results::
In general, solutions containing PHMB demonstrate better overall activity against the battery of clinical isolates tested than the Polyquaternium-1 containing solutions. Although very good efficacy was seen for Fusarium solani by most of these products, certain clinical isolates appeared to be more difficult to kill. In ranking kill profiles, ReNu® MultiPlus performed best while products containing a combination of Polyquaternium-1 and an additional disinfecting agent, Aldox, demonstrated weaker activity against the clinical isolates of bacteria. The averaged kill for the OptiFree® Express® No Rub exceeded the minimum criteria of a 3 log reduction for the ISO standard strain of Staph aureus by 0.6 logs but against the clinical strains produced a 3.1 log reduction average with a range from 1.9 to 4.0 logs. Against the clinically collected strains, OptiFree® RepleniSHTM demonstrated an average 2.2 log reduction with a range of 1.6 to 3.1 logs
Conclusions::
Contact lenses and lens care products are exposed to many potential sources of microbial contamination. Microorganisms in found in or on water, air, soil, animals, and plants, as well as normal flora of the eye may, under the correct circumstances, result in infection. Published studies have implied that noncompliance including improper cleaning methods and infrequent solution change, can be contributing factors leading to contact lens-related microbial keratitis. For this reason, contact lens solutions must not only meet but should whenever possible strive to exceed standard guidelines