Bacterial Isolates from Contact Lenses, Frames and Their Susceptibility to Disinfectants

A contact lens is a piece of glass or similar transparent material with curved surface(s), shaped for use in optical instrument (Nwaugo et al., 2008). Contact lenses are worn directly over the cornea mostly for correction of refractive error, improvement of visual acuity and enhancement of appearance for cosmetic or therapeutic reasons (Stern et al., 2004). The lens makes images appear clearer and better when looked through with defective eyes (Eisenhart, 1985; Stern et al., 2004; Nwaugo et al., 2008). In 2004, it was estimated that 125 million people (2%) use contact lenses worldwide, including 28 to 38 million in the United States and the continuous increase in the use of contact lens may be because of its optical, occupational and cosmetic advantages to individuals. Contact lens wearers have increased in Nigeria, where the climatic conditions and the environment favour the growth of microorganisms. There may be more problems associated with contact lens wear in the developing nations than in the industrialized nations (Emina and Idu, 2011). The environment, type of contact lens, duration of wear, and type of contact lenses cleansing solutions have been reported as determinants of the microbial load on the contact lenses (Iskeleli et al., 2002; Lee and Lim, 2003). Several authors have also reported that the introduction of contact lenses was associated with increase in ocular microbial complications (Devonshire et al., 2003; Fleiszig and Evans, 2003). The adhesion and colonization of contact lenses by microorganisms, particularly bacteria have been implicated in several adverse events such as microbial keratitis (Willcox and Holden, 2001); contact lens related acute red eye (Szczotka-Flynn et al., 2010); contact lens peripheral ulcer (Wu et al., 2003) and infiltrative keratitis (SzczotkaFlynn et al., 2010). Martins et al. (2002) also observed the presence of fungi, parasites and bacteria in contact lens swabs cultures. The occurrences of Staphylococcus, Citrobacter, Aeromonas, Enterobacter and Pseudomonas species on contact lenses have been reported (Sankaridurg et al. 2000; Brooks et al., 2001). Some of these pathogenic organisms may be transferred quite easily from the contact lens, especially a hydrogel one, to the eye (Gondi, 1992; Gopinathan et al., 1994; Wilhelmus et al., 1998). Thus, efficient disinfection of the lens is essential. Disinfection allows elimination or destruction of bacteria, fungi and the inactivation of undesirable viruses (Garrigue, 1996). This capability is necessary in order to avoid severe ocular infections such as microbial keratitis and contact lens peripheral ulcer (Ishibashi, 1997; Wu et al., 2003).

The chemical nature, application temperature and pH, concentration and quantity, contact time and tests method may determine the antimicrobial efficacy of the disinfectants (Russell and Hugo, 1987; Russell and Russell, 1995). Among the disinfectants used for cleaning contact lenses are hydrogen peroxides (H2O2), ELOC and Clear Care Cleaning Disinfecting Solution (CCCDS). Hydrogen peroxide is a lipid-soluble substance that produces highly reactive hydroxyl free-radical that attacks the lipid membrane, as well as the DNA, the mitochondria and other cell components. The toxicity of H2O2 to bacteria is mediated by this hydroxyl free-radical which is formed via the reaction of the oxidant with divalent iron (Russell and Hugo, 1987; Russell and Russell, 1995). Clear Care Cleaning Disinfecting Solution and Eye-Look Optical Lens Cleaner are peroxide-based clear care solutions that penetrate contact lenses and kills germs and bacteria. 

The aim of the study was to investigate the antibacterial activities of disinfectants (H2O2, ELOC and CCCDS) on the bacteria isolated from contact lenses and frames.