Abstract
Adhesion of pathogenic microbes, particularly bacteria, to contact lenses is implicated in contact lens related microbial adverse events. Various in vitro conditions such as type of bacteria, the size of initial inoculum, contact lens material, nutritional content of media, and incubation period can influence bacterial adhesion to contact lenses and the current study investigated the effect of these conditions on bacterial adhesion to contact lenses. There was no significant difference in numbers of bacteria that adhered to hydrogel etafilcon A or silicone hydrogel senofilcon A contact lenses. Pseudomonas aeruginosa adhered in higher numbers compared to Staphylococcus aureus. Within a genera/species, adhesion of different bacterial strains did not differ appreciably. The size of initial inoculum, nutritional content of media, and incubation period played significant roles in bacterial adhesion to lenses. A set of in vitro assay conditions to help standardize adhesion between studies have been recommended.
Highlights
Contact lenses provide several benefits over spectacles, but their wear has remained as a risk factor for the development of various adverse events, such as microbial keratitis (MK) [1], contact lens related acute red eye (CLARE) [2], contact lens peripheral ulcer (CLPU) [3] and infiltrative keratitis (IK) [4]
The reported inoculum sizes in bacterial adhesion assays have varied from 1 × 103 colony forming units (CFU) mLí1 up to 1 × 109 CFU mLí1 [10,21] and the incubation period for adhesion has ranged from 10 minutes to 72 hours [16,22]
Analysis of strain differences within a genera/species found that only P. aeruginosa ATCC 9027 showed higher adhesion to etafilcon A than senofilcon A (p < 0.01) and not for any other bacterial type
Summary
Contact lenses provide several benefits over spectacles, but their wear has remained as a risk factor for the development of various adverse events, such as microbial keratitis (MK) [1], contact lens related acute red eye (CLARE) [2], contact lens peripheral ulcer (CLPU) [3] and infiltrative keratitis (IK) [4]. Bacterial adhesion to contact lenses is a complex and multifactorial process and previous in vitro and ex vivo adhesion data differ widely between various studies [9]. This is mainly due to variety of methodology used to evaluate bacterial adhesion and there are a range of assay conditions that have been used to evaluate bacterial adhesion to lenses. These conditions have included different strains/types of bacteria, contact lenses types, inoculum sizes, the nutritional content of media and the incubation time for adhesion to occur [9]. As biofilm formation on contact lenses during wear is infrequent [23] the primary focus of this investigation was on initial steps in bacterial adhesion
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