Reduction of disinfection efficacy of contact lens care products on the global market in the presence of contact lenses and cases.

OBJECTIVE: Sight-threatening infections can be caused by pathogenic micro-organisms colonising the cornea, leading to microbial keratitis (MK). These micro-organisms can be introduced to the eye via improper contact lens use and care. MK can also result from ineffective contact lens care solutions (CLCs), even if the patient is following best practice guidelines. Therefore, it is critical to understand the differences between the effectiveness of popular CLCs on the global market. METHODS AND ANALYSIS: Following the International Standards Organisation standards 14 729 and 18259, bacteria (Pseudomonas aeruginosa, Serratia marcescens, Staphylococcus aureus), fungi (Candida albicans, Fusarium strains) and Acanthamoeba strains were inoculated into each CLC with and without contact lenses, and held for the manufacturer's stated disinfection time. Plate counts were conducted to determine the number of surviving micro-organisms. RESULTS: All CLCs examined met the primary log reduction criteria during stand-alone testing for Pseudomonas, Staphylococcus, Candida and Fusarium. renu Multiplus, All Clean Soft, and Kombilösung Super did not meet the primary criteria when challenged with Serratia. Only OPTI-FREE Express exceeded 4 log reduction for both strains of Acanthamoeba tested. We noted a substantial reduction in disinfection efficacy when CLCs were challenged with Fusarium in the presence of lenses and cases versus stand-alone testing. OPTI-FREE Express demonstrated significantly less net log reduction loss than the other four CLCs tested. CONCLUSION: Of the popular CLCs on the global market, the product which relies on dual biocides polyquaternium-1 and myristamidopropyl dimethylamine demonstrated the highest disinfection efficacy in microbial disinfection challenges in the absence and presence of contact lenses.

Differential Antimicrobial Efficacy of Multipurpose Solutions against Acanthamoeba Trophozoites.

SIGNIFICANCE: This investigation examines the effectiveness of several common contact lens solutions in the disinfection of Acanthamoeba, which causes a serious eye infection most often resulting from dysfunctional or improper use of contact lens products. PURPOSE: Acanthamoeba keratitis is an eye infection caused by a free-living amoeba, which can lead to extensive corneal damage and frequently blindness. Acanthamoeba keratitis is linked with contact lens use combined with noncompliance with contact lens care cleaning regimens. The patient's choice and use of multipurpose solutions (MPSs) continue to be a risk factor for Acanthamoeba keratitis. Thus, it is critical that the Acanthamoeba disinfection efficacy of the popular MPSs be determined. Here we compare the efficacy of seven major MPSs on the global market. METHODS: Using standard methods of Acanthamoeba disinfection and quantification, Acanthamoeba ATCC 30461, 30868, 50370, and 50676 trophozoites were inoculated into each MPS and held for the manufacturer's recommended disinfection time. Acanthamoeba recovery plates were incubated for 14 days, after which positive wells were identified and cell concentrations determined using the 50% endpoint method. RESULTS: Members of the OPTI-FREE products (Express, Replenish, and Puremoist [Alcon, Fort Worth, TX]) demonstrated significantly higher percentages of antimicrobial activity compared with the renu Advanced Formula (Bausch + Lomb, Rochester, NY), Biotrue (Bausch + Lomb), Acuvue RevitaLens (Johnson & Johnson, Santa Ana, CA), and Lite products (Cooper Vision, Scottsville, NY) for four of the trophozoite strains tested. CONCLUSIONS: Many of the popular MPS biocides maintain little or no antimicrobial activity against Acanthamoeba trophozoites, and the number of biocides in an MPS does not necessarily indicate its antimicrobial activity.

Antimicrobial Efficacy of Contact Lens Solutions Assessed by ISO Standards.

Microbial keratitis (MK) is an eye infection caused by opportunistic bacteria or fungi, which may lead to sight-threatening corneal ulcers. These microorganisms can be introduced to the eye via improper contact lens usage or hygiene, or ineffective multipurpose solutions (MPSs) to disinfect daily wear contact lenses. Thus, the patient's choice and use of these MPSs is a known risk factor for the development of MK. It is then critical to determine the efficacy of popular MPSs against ubiquitous ocular microorganisms. Therefore, we compare the efficacy of nine major MPSs on the global market against four different microorganism species, and with four different common contact lenses. In accordance with International Standards Organization protocol 14729 and 18259, the microorganisms were inoculated into each MPS with and without contact lenses, and held for the manufacturer's disinfection time, 24 h, and 7 days after challenge with Serratia marcescens or Fusarium spp. Plates were incubated for 2-7 days and plate counts were conducted to determine the number of surviving microorganisms. The majority of MPSs demonstrated significantly higher disinfection efficacies without contact lenses. Broadly, among the microorganisms tested, the OPTI-FREE products (Puremoist, Express, and Replenish) maintained the highest disinfection efficacies at the manufacturer's stated disinfection time when paired with any contact lens, compared with other MPSs. These were followed closely by RevitaLens and renu Advanced. MPSs containing dual biocides polyquaternium-1 and myristamidopropyl dimethylamine possessed the highest disinfection efficacy against multiple ocular pathogens.

Variables Affecting the Recovery of Acanthamoeba Trophozoites.

While the results of Acanthamoeba testing have been extensively published, laboratories conducting such testing are left to develop their own methods in the absence of a standardized methodology. The wide disparity of methods has resulted in equally inconsistent reported results for contact lens care (CLC) products. This study's objective was to determine the source of these discrepancies by evaluating basic Acanthamoeba biology and their impact on antimicrobial efficacy testing, including the ability of a recovery method to stimulate a single trophozoite to proliferate. Antimicrobial efficacy testing was conducted using well-published Acanthamoeba strains, storage conditions, and growth-based recovery methods. To identify variables that influence results, test solutions with low Acanthamoeba disinfection rates were utilized to prevent differences from being masked by high log reductions. In addition, single-cell proliferation assays were executed to understand the growth requirements to stimulate trophozoite propagation in two recovery methods. These studies indicated that both nutrient density (>106 CFU) and the length of plate incubation (at least 14 days) could significantly influence the accurate recovery of trophozoites. Together, this study emphasizes the need to understand how Acanthamoeba trophozoites biology can impact test methods to create divergent results.

Hydrogen Peroxide Disinfecting Solution for Gas Permeable Contact Lenses: A Review of the Antimicrobial Efficacy, Compatibility, and Safety Performance of a One-Step Lens Care System.

CLEAR CARE PLUS (CCP), also known as AOSEPT PLUS with HydraGlyde, is approved for use with gas permeable (GP) lenses, and the indication is supported by the scientific evidence that is reviewed in this article. Antimicrobial efficacy testing of CCP both as a stand-alone disinfectant and as part of a regimen shows that CCP exceeds the ISO 14729 criteria against bacteria, yeast, and mold. In real-world conditions, it is effective against clinically relevant bacterial strains isolated from adverse events and against the two forms, trophozoites and cysts, of resilient Acanthamoeba species. Compatibility tests of CCP with two types of GP lenses indicate that the physical and/or optical parameters of lenses are unaffected through 30 cycles of simulated use with CCP, and a clinical trial shows substantial equivalence of clinical performance with a commonly used GP multipurpose solution. These results indicate that CCP is well suited for cleaning and disinfection of GP contact lenses.

Biocidal Efficacy of a Hydrogen Peroxide Lens Care Solution Incorporating a Novel Wetting Agent.

PURPOSE: To compare the antimicrobial effects of CLEAR CARE, a 3% hydrogen peroxide (H2O2) solution formulated for simultaneous cleaning, daily protein removal, disinfection, and storage of soft (hydrophilic) hydrogel, silicone hydrogel, and gas-permeable contact lenses, and CLEAR CARE PLUS, consisting of the 3% H2O2 solution plus a novel wetting agent, polyoxyethylene-polyoxybutylene (EOBO-21). METHODS: Three lots each of the 2 solutions were incubated with 5 compendial microorganisms required by the Food and Drug Administration (FDA) 510(k) and International Organization for Standardization (ISO) 14729 stand-alone procedures, 4 clinical isolates of Gram-positive and Gram-negative bacteria, and trophozoites and cysts of 2 Acanthamoeba strains that are associated with microbial keratitis. Microbial loads were evaluated after disinfection and neutralization. RESULTS: Both solutions exceeded the FDA/ISO stand-alone primary criteria against Gram-positive and Gram-negative compendial bacteria, yeast, and mold after only 1.5-hr disinfection/neutralization. At the recommended minimum disinfection time, bacteria were reduced by 4.4 to 5.1 logs, yeast by 4.4 to 4.9 logs, and mold by 2.9 to 3.5 logs with and without organic soil. In addition, both solutions eliminated or effectively reduced populations of clinically relevant ocular bacterial isolates (4.5-5.0 logs), Acanthamoeba trophozoites (3.4-4.2 logs), and cysts (1.5-2.1 logs). CONCLUSION: Both solutions eliminated or reduced populations of FDA/ISO compendial bacteria and fungi as well as clinically relevant microorganisms and Acanthamoeba trophozoites and cysts. The addition of EOBO-21 to the 3% H2O2 lens care solution had no impact on antimicrobial activity.

Antimicrobial Efficacy of Multipurpose Disinfecting Solutions in the Presence of Contact Lenses and Lens Cases.

OBJECTIVE: The aim of this study was to use antimicrobial efficacy endpoint methodology to determine compatibility of multipurpose disinfecting solutions (MPSs), lens cases, and hydrogel lenses for disinfection (AEEMC) against International Organization for Standardization (ISO)-specified microorganisms and clinical ocular isolates of Stenotrophomonas maltophilia. METHODS: Six MPSs (PQ/Aldox 1, 2, and 3; PQ/Alexidine; PQ/PHMB; and PHMB) were challenged against ISO-specified microorganisms and S. maltophilia using the AEEMC test. AEEMC tests were performed with and without balafilcon A, etafilcon A, and senofilcon A lenses in lens cases with organic soil. Exposure times included disinfection time (DT) and 24 hr. Additionally, all six MPSs were challenged with two strains of S. maltophilia, based on the ISO Stand-alone test. RESULTS: The efficacy against bacteria for PQ/Aldox and PQ/Alexidine MPSs was not diminished by the presence of lenses. The efficacy of PQ/PHMB and PHMB MPSs against Serratia marcescens was significantly reduced compared with the no-lens control at DT for at least one lens type. The PHMB MPS with lenses present also demonstrated reduced efficacy against Staphylococcus aureus at DT versus the control. PQ/Aldox MPSs retained activity against Fusarium solani with lenses present; however, all other test MPSs demonstrated reduced F. solani efficacy at DT with lenses present. With lenses, all MPSs showed reduced efficacy against Candida albicans. CONCLUSIONS: AEEMC antimicrobial efficacy test results vary based on challenge microorganism, contact lenses, and MPS biocide systems. This study highlights the importance of evaluating MPSs for compatibility with lenses and lens cases.

Pseudomonas aeruginosa Outer Membrane Vesicles Triggered by Human Mucosal Fluid and Lysozyme Can Prime Host Tissue Surfaces for Bacterial Adhesion.

Pseudomonas aeruginosa is a leading cause of human morbidity and mortality that often targets epithelial surfaces. Host immunocompromise, or the presence of indwelling medical devices, including contact lenses, can predispose to infection. While medical devices are known to accumulate bacterial biofilms, it is not well understood why resistant epithelial surfaces become susceptible to P. aeruginosa. Many bacteria, including P. aeruginosa, release outer membrane vesicles (OMVs) in response to stress that can fuse with host cells to alter their function. Here, we tested the hypothesis that mucosal fluid can trigger OMV release to compromise an epithelial barrier. This was tested using tear fluid and corneal epithelial cells in vitro and in vivo. After 1 h both human tear fluid, and the tear component lysozyme, greatly enhanced OMV release from P. aeruginosa strain PAO1 compared to phosphate buffered saline (PBS) controls (∼100-fold). Transmission electron microscopy (TEM) and SDS-PAGE showed tear fluid and lysozyme-induced OMVs were similar in size and protein composition, but differed from biofilm-harvested OMVs, the latter smaller with fewer proteins. Lysozyme-induced OMVs were cytotoxic to human corneal epithelial cells in vitro and murine corneal epithelium in vivo. OMV exposure in vivo enhanced Ly6G/C expression at the corneal surface, suggesting myeloid cell recruitment, and primed the cornea for bacterial adhesion (∼4-fold, P < 0.01). Sonication disrupted OMVs retained cytotoxic activity, but did not promote adhesion, suggesting the latter required OMV-mediated events beyond cell killing. These data suggest that mucosal fluid induced P. aeruginosa OMVs could contribute to loss of epithelial barrier function during medical device-related infections.

Ex vivo analysis of cholesterol deposition for commercially available silicone hydrogel contact lenses using a fluorometric enzymatic assay.

OBJECTIVE: Lipid deposition on silicone hydrogel (SiHy) lenses, which are believed to be caused by their hydrophobic surface, can lead to discomfort, reduced vision, and inflammatory reactions. This study used a highly specific and sensitive fluorometric enzymatic assay for ex vivo cholesterol analysis of seven types of SiHy lenses: balafilcon A, comfilcon A, enfilcon A, enhanced-lotrafilcon A, enhanced-lotrafilcon B, galyfilcon A, and senofilcon A. METHODS: Cholesterol sorption was assessed in 140 previously worn SiHy lenses from 8 clinical trials conducted in the United States and Australia between 2006 and 2008. Patients wore the lenses for 2 to 4 weeks. Unworn negative control lenses for each lens material were obtained directly from the manufacturer. Lipids were isolated from the lenses using a two-step chloroform: methanol extraction method, and total cholesterol was quantified using a fluorometric enzymatic assay. Nonparametric Mann Whitney statistical analysis was performed to determine the differences in total cholesterol sorption between lens-specific data sets. RESULTS: Enhanced-lotrafilcon A and enhanced-lotrafilcon B contact lenses showed significantly lower median total cholesterol sorption (median±quartile, 0.30±0.2 µg/lens and 0.09±0.1 µg/lens, respectively) than all other types of lenses that were tested (P<0.0001). By contrast, enfilcon A (3.96±0.8 µg/lens) and galyfilcon A (3.75±1.1 µg/lens) showed the highest median total cholesterol sorption of all tested lenses. CONCLUSIONS: Cholesterol deposition in SiHy contact lenses seems to be lens polymer dependent. Enhanced-lotrafilcon A and enhanced-lotrafilcon B both sorbed the lowest amount of cholesterol compared with the other five types of SiHy lenses that were tested in this study.

Rat silicone hydrogel contact lens model: effects of high- versus low-Dk lens wear.

OBJECTIVES: This study used a rat contact lens (CL) model to test if high- versus low-Dk lens wear caused changes in (1) conjunctival Langerhans cell (LC) number or location; (2) Bcl-2 expression; and (3) infection risk. METHODS: Female, Lewis rats wore a high- or low-Dk CL continuously for 2 weeks. Afterward, corneas were harvested and processed for ADPase activity to identify LCs, for immunostaining and for real time-polymerase chain reaction. Contact lens-wearing rats also were challenged with Pseudomonas aeruginosa by placing a bacterial-soaked CL on the eye followed by topical delivery of bacteria. After 48 hrs, slit lamp examination and real time-polymerase chain reaction were used to evaluate the corneal response. RESULTS: Conjunctival LC were significantly increased after low- versus high-Dk CL wear (P<0.0001). In contrast, conjunctival LC in non-lens wearing rats was not significantly different from the high-Dk lens wearing group. Bcl-2 mRNA levels were significantly decreased in low- versus high-Dk CL wearing rats, while Bax, FasL, caspase 3, and caspase 9 levels were unchanged. Immunostaining for Bcl-2 showed fewer positively stained epithelial cells in the low- versus high-Dk lens wearing group. After bacterial challenge, 30% of low- versus none of the high-Dk CL wearing corneas became infected and showed increased mRNA levels for several proinflammatory cytokines/chemokines, inducible nitric oxide synthase and matrix metalloproteinase-9. CONCLUSION: Low- versus high-Dk or non-CL wear led to an increased number of conjunctival LC, decreased Bcl-2 levels, and increased the risk of bacterial infection.

Creating antimicrobial surfaces and materials for contact lenses and lens cases.

Contact lenses are a safe and effective mode of vision correction used by more than 100 million people worldwide, yet some adverse responses to microbial contamination of contact lenses still occur. Various medical devices, including contact lens cases, currently use antimicrobial agents to eliminate or reduce microbial contamination at the surface. The application of antimicrobial surface technologies to contact lenses and lens cases is being explored. This article describes agents that hold promise for antimicrobial surfaces for contact lenses or lens cases.

Pseudomonas aeruginosa-induced inflammation in the rat extended-wear contact lens model.

PURPOSE: To examine the early host response to Pseudomonas aeruginosa challenge in the extended contact lens-wearing rat model. METHODS: Lewis rats were fitted with extended-wear lotrafilcon A hydrogel lenses in the left eye, and the right eye served as the control. Bacterial challenge was initiated in the experimental eye by fitting a bacteria-soaked contact lens and by topical delivery of the bacteria. On first detection of corneal opacity, slitlamp examination, histopathologic examination, viable bacteria counts, enzyme-linked immunosorbent assay, myeloperoxidase, Langerhans cell detection, and multiprobe ribonuclease protection assays were used to evaluate the early corneal response. RESULTS: Analysis of bacterially challenged contact lens-wearing versus control rats showed Langerhans cells and polymorphonuclear neutrophils only in the experimentally challenged cornea. In addition, in the experimentally challenged cornea, ribonuclease protection and enzyme-linked immunosorbent analyses showed an upregulation of proinflammatory cytokines, including interleukins 1beta and 6, suggesting that with contact lens wear, these cytokines contribute to the early corneal response and, potentially, disease. CONCLUSIONS: The contact lens-wearing rat model allows a unique analysis of the early effects of bacterial challenge in extended-wear contact lenses in the absence of corneal scarring, used in most rodent models. The rat model should be valuable to delineate further the effects of contact lens wear, including the testing of additional contact lens-related complications.

Development of a new extended-wear contact lens model in the rat.

PURPOSE: To develop a rat model to experimentally monitor the potential inflammatory effects of soft contact lens (CL) usage on the cornea during extended wear (EW). METHODS: Lewis rats were fitted with EW lotrafilcon A (CIBA Vision, Duluth, GA) hydrogel lenses (Dk/t 175 barrers/cm) in the left eye, the right eye serving as a control. After 12 days (n = 5 rats) and 30 days (n = 8 rats) of continuous extended wear, corneas were removed and total RNA was extracted from both CL-wearing and non-lens-wearing eyes. Multiprobe ribonuclease protection assays (RPA) were used to detect and compare cytokine and chemokine gene expression in corneas from both groups. RESULTS: Cytokine-chemokine mRNA expression levels were similar for interleukin (IL)-1alpha, IL-1 receptor antagonist (RA), IL- 18, transforming growth factor (TGF)-beta1, TGF-beta2, TGF-beta3, and macrophage migration inhibitory factor (MIF) levels in CL-wearing and non-lens-wearing corneas after 12 or 30 days of EW. CONCLUSION: This in vivo rat model for extended contact lens wear allows analysis and comparison of mRNA levels of cytokines and chemokines in the cornea with and without EW soft CL use. Remarkably, after 12 or 30 days of continuous CL wear, there was no significant up-regulation in lens wearing corneas for any of the cytokines-chemokines tested.