Multipurpose Contact Lens Care Solutions Research Articles

Poly-Gamma-Glutamic Acid Functions as an Eective Lubricant with Antimicrobial Activity in Multipurpose Contact Lens Care Solutions.

In order to perform the multiple functions of disinfection, cleansing, and storage, preservatives are often added to contact lens care solutions. The disadvantage of adding preservatives is that this often causes various eye conditions. However, lens care solutions would not be able to disinfect in the absence of such preservatives. In addition, comfort is an important issue for contact lens wearers due to the long periods of time they are worn. It has been shown that lower friction coefficients are correlated with increased comfort. We have previously developed a multipurpose contact lens care solution in which poly-gamma-glutamic acid (γ-PGA) was the main ingredient. In this study, we investigated the antimicrobial activity and lubricating property of our care solution. We showed that there was a synergetic effect of γ-PGA and chlorine dioxide on antimicrobial activity. We also demonstrated that γ-PGA functioned as a lubricating agent. Our results provided evidence of γ-PGA acting as a multi-functional polymer that could be applied in contact lens care solutions.

Comparison of the Antimicrobial Efficacy of Various Contact Lens Solutions to Inhibit the Growth of Pseudomonas aeruginosa and Staphylococcus aureus.

Soft contact lenses provide perfect conditions for the breeding of pathogens. The study is a prospective, experimental study, conducted to know the antimicrobial ability of multipurpose contact lens solution against standard strains of Staphylococcus aureus and Pseudomonas aeruginosa by the stand-alone test. The test method is based on the procedures in the ISO 14729 standard primary stand-alone test. Three multipurpose contact lens care solutions commercially available in Mangalore markets, namely, Biotrue (Bausch & Lomb), Opti-Free Replenish (Alcon), and Aquasoft (Stericon Pharma), were tested for its antimicrobial effect in the microbiology lab at Kasturba Medical College, Mangalore. According to this study, the solutions named “Biotrue” and “Aquasoft” met the primary stand-alone and reached the 3log reduction and 5log reduction criteria in the manufacturer recommended time, respectively. No conclusion could be drawn for Opti-Free Replenish since the minimum recommended disinfection time was overnight, whereas it was noted for 6 hr only, and it should have been experimented further. The effectiveness of multipurpose solutions varies against different bacterial species. We have observed that the antimicrobial activity of different solutions varies with respect to time of incubation, and also there was a marked difference in the activity of some solutions against S. aureus and P. aeruginosa. So, it is necessary for the contact lens users to store their lenses in solutions for longer duration of hours. It is also recommended to use solutions that clear the ISO 14729 standards for better health conditions of the eye.

Antimicrobial efficacies of four multi-purpose contact lens care solutions

Amac: Kontakt lens ile iliskili enfeksiyonlarin onlenmesi ve goz sagliginin korunmasi icin kontakt lenslerin uygun bakimi cok onemlidir. Cok amacli solusyonlar, yumusak kontakt lenslerin temizlenmesi, durulanmasi, dezenfekte edilmesi ve saklanmasi gibi cesitli amaclar icin kullanilmaktadir. Gerec ve Yontem: Calismamizda ticari olarak satilan cok amacli dort kontakt lens bakim solusyonunun (CAKLBS) etkinlikleri arastirilmistir. Bu amacla, bes bakteri ve bir maya olmak uzere alti mikroorganizma kullanilmis ve dort adet cok amacli kontakt lens bakim solusyonu; ReNu® MultiPlus, Opti-Free® Express, All in One Light, Biotrue ™ degerlendirilmistir. Test mikroorganizmasi olarak S. epidermidis ATCC 35948 (biyofilm olusturan), S. epidermidis ATCC 12228 (biyofilm olusturmayan), Pseudomonas aeruginosa ATCC 9027, Staphylococcus aureus ATCC 25923, S. aureus ATCC 43300 (metisilin direncli) ve Candida albicans ATCC 10231 kullanilmistir. Kantitatif suspansiyon testi yapilmis ve sonuclar EN ISO 14729 bagimsiz test birincil kriterlerine gore degerlendirilmistir. 6 saatlik temas suresi sonunda ortalama log indirgeme degerlerine gore, tum CAKLBS’ ler test mikroorganizmalarina karsi etkili bulunmustur. Sonuc ve Tartisma: Piyasada cesitli ticari CAKLBS tipleri bulunmaktadir. Bu urunlerin antimikrobiyal etkinlikleri, iceriklerinde bulunan antimikrobiyal maddelerin tipine ve konsantrasyonlarina baglidir. Bu calismada, tum CAKLBS' ler, ureticinin tavsiye ettigi temas suresinde test mikroorganizmalarina karsi etkili bulunmustur.

Effects of multipurpose solutions on the adhesion of Acanthamoeba to rigid gas permeable contact lenses.

To evaluate the effect of multipurpose contact lens care solutions (MPSs) on the adhesion of Acanthamoeba to rigid gas permeable (RGP) contact lenses. Acanthamoeba castellanii (AC) trophozoites were inoculated onto untreated RGP contact lenses (FP, Extra, or Menicon Z), and numbers of trophozoites adhering to lenses were counted under a phase contrast microscope at 18h post-inoculation (controls). Similarly, adhering trophozoites were counted at 6h post-inoculation on each of the three RGP lens types with one of three MPSs (Boston Simplus, Menicare Plus, and O2 Care). Scanning electron microscopic examinations were performed to compare lens surfaces. Adhesion of AC trophozoites to untreated FP was greater than to untreated Extra or Menicon Z. Surfaces of Extra and Menicon Z lenses were waxier, smoother, and more homogeneous than those of FP lenses. After treatment with Boston Simplus, adhesion of AC trophozoites was significantly reduced for all lens types as compared with controls (p<0.0001). Treatments with Menicare Plus or O2 Care reduced the number of adherent AC trophozoites significantly on FP lenses only as compared with controls (p<0.0001). The adhesion rates of AC trophozoites to RGP lenses depended on lens surfaces. Boston Simplus reduced the adhesion rate of AC trophozoites more than Menicare Plus or O2 Care. Appropriate RGP lens and MPS selection could decrease the prevalence of Acanthamoeba keratitis.

Disinfectant efficacy of soft contact lens care system containing povidone iodine

Disinfectant efficacy of soft contact lens care system containing povidone iodine

Bacteria biofilms provide protection from disinfection by multipurpose contact lens care solutions

Bacteria biofilms provide protection from disinfection by multipurpose contact lens care solutions

In vitro effects of selected contact lens care solutions on Acanthamoeba castellanii strains in Poland

Free-living, cosmopolitan amoebae of the Acanthamoeba genus may be the causative agents of Acanthamoeba keratitis (AK) – a progressive, vision-threatening infection of the human cornea described particularly among contact lens wearers. Use of contact lens care solutions, effective against these organisms, is important in preventing AK infections. 3 different strains of Acanthamoeba castellanii of the T4 genotype (Neff strain and two others, isolated from patients with AK) were exposed to 4 selected multipurpose contact lens care solutions available in Poland: Ciba Vision AoSept Plus, Bausch & Lomb ReNu MultiPlus, Alcon Opti-Free, Ciba Vision Solo Care Aqua. No amoebicidal effect was observed. The strongest amoebostatic effect was visible after 24h of exposition to Opti-Free and ReNu solution and associated with percentage increase of rounded, motionless forms. This is significantly longer than minimum disinfection time recommended by manufacturers of all tested multipurpose solutions. Surprisingly, no clear induction of the encystation process was observed.

Multipurpose care solution-induced corneal surface disruption and Pseudomonas aeruginosa internalization in the rabbit corneal epithelium.

To evaluate the effects of a chemically preserved multipurpose contact lens care solution (MPS) on the corneal epithelial surface and Pseudomonas aeruginosa (PA) internalization in the rabbit corneal epithelium. Rabbits were fit in one eye with a silicone hydrogel lens (balafilcon A) soaked overnight in a borate-buffered MPS (BioTrue). The contralateral eye was fit with a lens removed directly from the blister pack containing borate-buffered saline (control). Lenses were worn for 2 hours. Upon lens removal, corneas were challenged ex vivo with invasive PA strain 6487 and assessed for PA internalization. Ultrastructural changes were assessed using scanning electron (SEM) and transmission electron microscopy (TEM). Scanning electron microscopy showed frank loss of surface epithelium in MPS-exposed eyes, while control eyes exhibited occasional loss of surface membranes but retention of intact junctional borders. Transmission electron microscopy data supported and extended SEM findings, demonstrating the presence of epithelial edema in MPS-treated eyes. There was a 12-fold increase in PA uptake into the corneal epithelium following wear of the MPS-treated lens compared to control (P = 0.008). These data demonstrate that corneal exposure to MPS during lens wear damages the surface epithelium and are consistent with our previous clinical data showing an increase in bacterial binding to exfoliated epithelial cells following MPS use with resultant increased risk for lens-mediated infection. These findings also demonstrate that the PA invasion assay may provide a highly sensitive quantitative metric for assessing the physiological impact of lens-solution biocompatibility on the corneal epithelium.

BCLA Pioneers Lecture – Evidence basis for patient selection: How to predict contact lens success

A prediction (Latin præ-, “before,” and dicere, “to say”) or forecast can be defined as “a statement about the way things will happen in the future, often but not always based on experience or knowledge. Although guaranteed information about the future is in many cases impossible, prediction is necessary to allow plans to be made about possible developments” (Wikipedia). Some predictions in the field of contact lenses have been very high profile and controversial, such as the predicted demise in rigid gas permeable contact lenses (RGPs) by Nathan Efron [1], whereas others, such as the presumed safety of multipurpose contact lens care solutions that have met specified regulatory criteria, have proved disastrously wrong (resulting in the Fusarium outbreak) [2].

Contact Lens Care Solutions Downregulate Membrane-Associated Mucins 1 and 16 in Cultured Human Corneal Epithelial Cells and at the Rat Corneal Surface In Vivo

The purpose of this study was first to evaluate the effect of multipurpose contact lens care solutions (MPSs) on the expression of membrane-associated mucins (MUC1 and MUC16) in SV40-transformed human corneal epithelial (HCE-T) cells and in vivo rat cornea. The second aim of this study was to determine the role of the common MPS additive boric acid in reducing mucin expression and release. The HCE-T cells were exposed to different concentrations of MPS-F, MPS-G, MPS-H, MPS-I, and MPS-J with 100% treatment for 30 minutes and 10% treatment for 24 hours. MUC1 and MUC16 expressions were subsequently analyzed by Western blotting. Wister rats were also subjected to MPS-A, MPS-B, MPS-C, MPS-D, and MPS-E and received phosphate-buffered saline exposure (1 drop in the right eye every 10 minutes for 1 hour). The left eye was used as control. Cornea sections and lysates were used for the immunohistochemical assay of MUC1 and MUC16 expressions. Conditioned media from treated HCE-T cells were also analyzed using Western blotting. The MPSs containing boric acid downregulated MUC1 and MUC16 in the rat cornea, whereas MPSs without boric acid had no effect as demonstrated by the Western blotting and immunohistochemical analysis. Conditioned media from MPS-containing boric acid revealed some trace of MUC16. The clinical use of MPSs containing boric acid that reduce MUC1 and MUC16 availability should be avoided. Additionally, the presence of MUC16 in the conditioned media suggests that boric acid may have enhanced cleavage of MUC16 at the cell membrane surface.

Effects of Multipurpose Solutions on the Viability and Encystment of Acanthamoeba Determined by Flow Cytometry

To evaluate simultaneously the effects of multipurpose contact lens care solution (MPS) on the viability and encystment of Acanthamoeba using flow cytometry. Viability and encystment rate were evaluated using Acanthamoeba castellanii (ATCC 50514 and ATCC 50370) and three clinical strains of Acanthamoeba spp. isolated from patients with Acanthamoeba keratitis. Acanthamoeba trophozoites (1.0 × 10(5) cells/mL) were exposed to four kinds of commercially available MPSs for 24 hours. After dispensing the cell suspension into two portions, one portion was stained with 0.004% Congo Red (CR), a fluorescence dye to stain the inner cell wall of cysts, and the other portion was stained with a mixture of Congo Red and 3% sarkosyl (CRS), a detergent to lyse the trophozoites and pseudocysts. Flow cytometric analysis of the treated portions was then carried out on an EPICS ALTRA flow cytometer. The encystment rate and disinfecting efficacies (percentage of rounded trophozoites, "pseudocyst") were calculated by the rates of CR-stained, CR-nonstained, and CRS-stained populations, respectively. Ultrastructural features of resistant (mature or immature) cysts and pseudocysts were observed by transmission electron microscopy. Resistant cysts and rounded trophozoites (pseudocysts) were stained with CR, whereas native (unrounded) trophozoites were not. Resistant cysts were also stained with CRS unlike pseudocysts. Three clinical isolates showed higher resistance and higher encystment rates than two ATCC strains when treated with encystment-positive control solution. Disinfecting efficacy of each MPS was not directly related to each encystment rate. Transmission electron microscopy observations showed basic differences in the ultrastructure of pseudocysts produced by MPSs and resistant cysts. These results suggest that viability and encystment of Acanthamoeba are independent phenomena, and therefore disinfecting efficacy of MPS and encystment rates of Acanthamoeba should be evaluated, respectively. Thus, it is important to evaluate simultaneously the disinfecting efficacies and encystment rates of newly developed premarket MPS using the authors' novel flow cytometric methods.

Effects of Multipurpose Contact Lens Care Solutions on the Adhesion of Acanthamoeba to Silicone Hydrogel Contact Lenses

To evaluate the effect of 7 multipurpose contact lens care solutions (MPSs) on the adhesion of Acanthamoeba (AC) to 5 silicone hydrogel contact lenses (SHCLs). Acanthamoeba castellanii (ATCC50370) trophozoites were inoculated onto disks trimmed from SHCLs, Asmofilcon A, Galyfilcon A, Senofilcon A, Lotrafilcon B, and Balafilcon A. After 4-hour incubation, the number of adherent AC trophozoites on SHCL was counted under phase contrast microscopy. AC trophozoites mixed with 7 MPSs were inoculated onto Balafilcon A and incubated for 24 hours followed by direct counting, phase contrast microscopy, and scanning electron microscopy. AC cysts were also inoculated onto Balafilcon A followed by counting using phase contrast microscopy. Adhesion of AC trophozoites to Lotrafilcon B and Balafilcon A was 10 times higher in comparison with the other 3 SHCLs. Twenty four-hour treatment of AC trophozoites with Epica Cold, Epica Cold Aquamore, ReNu MultiPlus, OptiFree Plus, and Complete DoubleMoist reduced the numbers of adherent AC to less than 25% of control, whereas the numbers of AC treated with Complete AminoMoist and C3 SoftOne Moist was about 50% and 75% of control, respectively. Normal AC trophozoites without any treatments showed 25 times higher adhesion rates compared with normal AC cysts. The adhesion rates of AC trophozoites to SHCL varied depending on the type of MPSs used. Appropriate uses of MPS could reduce adhesion rates of AC to SHCL and potentially decrease clinical rates of Acanthamoeba keratitis.

Efficacy of Care Solutions Against Contact Lens-Associated Fusarium Biofilms

The aim of this study is to assess the effect of lens wear on the formation of soft contact lens-associated Fusarium biofilms and to determine the efficacy of marketed contact lens care products against such biofilms. Using an established in vitro soft contact lens-Fusarium biofilm model, two clinical Fusarium isolates (F. solani B6914 and F. oxysporum B8996) were incubated with three different types (lotrafilcon A, etafilcon A, and balafilcon A) of worn contact lenses under conditions that facilitate biofilm formation. Unworn lenses were used as internal controls for biofilm formation. Biofilm was quantified using a tetrazolium XTT (2,3-bis[2-methoxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxanilide) assay. In addition, susceptibilities of the fungal biofilm growth phases to the five most common multipurpose contact lens care solutions available at the time of study (three polymeric biguanide-preserved and two polyquaternium-preserved) and two hydrogen peroxide care solutions were assessed. Both Fusarium strains formed dense biofilms on each of the contact lens types tested. Worn lenses showed no differences in the ability of biofilm to form compared with unworn lenses except worn etafilcon A lenses which formed more biofilm with F. oxyspourm B8996 compared with unworn controls. Lens material did not influence biofilm formation. The biofilms of F. solani on all three lens types were consistently susceptible to both hydrogen peroxide care systems (growth reduction of 84 to 97%, p ≤ 0.001) and two of the five multipurpose solutions (MPSs) (growth reduction of 62 to 85% for a biguanide-preserved MPS, p ≤ 0.05; growth reduction of 92 to 96% for a polyquaternium-myristamidopropyl dimethylamine preserved MPS, p < 0.001). The biofilms of F. oxysporum on all three lens types were consistently susceptible to both hydrogen peroxide care systems (growth reduction of 79 to 99%, p ≤ 0.001) and one of the five MPSs (growth reduction of 93 to 96% for a polyquaternium-myristamidopropyl dimethylamine preserved MPS, p ≤ 0.001). F. solani and F. oxysporum form biofilms on lotrafilcon A, etafilcon A, and balafilcon A worn contact lenses, which are resistant to the antifungal activity of several soft contact lens care products. Only the hydrogen peroxide care systems and one polyquaternium-myristamidopropyl dimethylamine-preserved solution consistently demonstrated effective antifungal activity against both Fusarium strains on all three lens types.

57 Relationship between disinfecting efficacy of multi-purpose contact lens care solutions and encystment rate of Acanthamoeba

Purpose: To evaluate the efficacy of a new contact lens disinfecting solution. Method: The efficacy of a new contact lens disinfecting solution with a dual disinfection system was assessed against standard challenge microorganisms and clinical isolates of Acanthamoeba castellanii, Acanthamoeba polyphaga, Staphylococcus aureus, Pseudomonas aeruginosa, Serratia marcescens, Candida albicans, and Fusarium solani using stand-alone microbiological test methodology. Additionally, the efficacy of recently marketed contact lens care solutions, including Revitalens and Biotrue, was tested against standard challenge microorganisms. The stand-alone test is a time kill study designed to qualify individual solutions with a suitable level of antimicrobial activity as contact lens disinfection products. Results: After six hours of disinfection time, the OPTI-FREE EverMoist showed ∼2 logs kill against cysts of A. castellanii ATCC30234 and A. polyphaga ATCC 30871. OPTI-Free EverMoist met the primary Stand-alone criteria with efficacies of more than 4 log reductions for each of the three standard bacteria and each standard yeast and mold. All tested marketed contact lens care solutions showed efficacy against standard challenge microorganisms. Clinical isolates of Staphylococcus aureus, Pseudomonas aeruginosa, Serratia marcescens, and Candida albicans were reduced by approximately 4 logs or greater after six hours of exposure to OPTI-FREE EverMoist. Conclusions: OPTI-FREE EverMoist MPDS provides broad spectrum antimicrobial activity against a variety of challenge ATCC and clinical microorganisms. OPTI-FREE EverMoist leverages the proven PolyQuad® and Aldox® dual disinfection system to provide excellent antimicrobial efficacy.

In Vitro Interactions ofFusariumandAcanthamoebawith Drying Residues of Multipurpose Contact Lens Solutions

To examine in vitro effects of evaporation and drying of multipurpose contact lens solutions on survival of Fusarium and Acanthamoeba. Conidia of representative Fusarium from the 2004-2006 keratitis outbreak and trophozoites of Acanthamoeba castellanii were inoculated into commercially available multipurpose contact lens care solutions. These solutions were inoculated with 10(2)-10(6) microbial propagules/mL and were evaporated for at least 24 hours. After drying, nutrient media for recovery of surviving organisms were added to the residues formed in the lids of 38 mm polystyrene Petri dishes. General morphologic patterns of the solution residuals and the distribution and morphologies of the microorganisms were recorded with microscopic imaging. Various multipurpose contact lens disinfection solutions formed distinctive dried residual patterns. Both Fusarium and Acanthamoeba at concentrations tested above 10(3) per mL of disinfection solution were recovered from dried films with replicate testing. Mature cysts of Acanthamoeba not evident in the inocula were observed in sparse numbers in all dried solutions except one (Complete Moisture Plus; Advanced Medical Optics) and control salines where precysts and mature cysts were common. Both fusaria and amoeba tended to be observed in discrete regions of the dried residues. Regions of drying films of multipurpose contact lens disinfection solutions on contact lens cases may induce and harbor dormant-resistant stages of Fusarium and Acanthamoeba. It is hypothesized that the evaporation and drying of multipurpose contact lens disinfection solutions may have been an added risk factor for case contamination among Fusarium and Acanthamoeba keratitis patients. The need for frequent replacement of contact lens cases is enforced.

Antimicrobial efficacy of multi-purpose contact lens disinfectant solutions following evaporation

Non-compliance is a significant factor in contact lens related microbial keratitis and includes solution reuse and failure to recap the lens storage case resulting in evaporation effects. To address this, impact of partial evaporation on the antimicrobial efficacy of multipurpose contact lens care solutions was investigated. Solutions were evaporated under a stream of air to 2× and 4× concentration and challenged with Fusarium solani (ATCC 36031), Candida albicans (ATCC 10231) and Acanthamoeba castellanii (ATCC 50370). The level of organism kill at 6h was compared to the non-evaporated product. ReNu with MoistureLoc(®) (RML) lost 90-100% of biocidal activity against C. albicans on evaporation, 75-99% for F. solani and 29-33% with A. castellanii at 2× or 4× concentration, respectively. OPTI-FREE(®) RepleniSH(®) lost 72-90% efficacy against C. albicans and F. solani, and 61% at 2× and 10% at 4× concentration with A. castellanii. ReNu(®) MultiPlus, AQuify(®) Multi-Purpose and Biotrue™ showed only loss in efficacy with C. albicans at 4× concentration giving 79%, 34.5% and 48% reduction, respectively. No loss in biocidal activity on evaporation was obtained with Complete(®) Revitalens for all organisms. Partial evaporation can affect biocidal efficacy of multi-purpose solutions and may have been a significant factor in an outbreak of Fusarium keratitis cases associated with RML. Evaporation results in increased binding of cationic disinfectants to counter-ions in the formulation, reducing ability to attach and rupture anionic microbial cell walls. Interaction may also occur between the biocidal ingredient and other components, such as surfactants, resulting in sequestration of activity through micelle formation.

Effects of Multipurpose Contact Lens Care Solutions and Their Ingredients on Membrane-Associated Mucins of Human Corneal Epithelial Cells

Membrane-associated mucins play an important role for protecting epithelial cells at the ocular surface from microbial invasion. The purpose of this study was to determine whether multipurpose solutions (MPSs) for contact lens care and their ingredients alter the expression of membrane-associated mucins in human corneal epithelial (HCE-T) cells. SV40-immortalized HCE-T cells were cultured in Dulbecco's modified Eagle medium/F12 medium with 5% fetal bovine serum to confluence and were then exposed to 10% dilutions of five different MPSs, or to their representative ingredients, 0.1% macrogolglycerol hydroxystearate, 0.1% poloxamer, 0.1% poloxamine, 1 and 5 ppm polyhexamethylene biguanide, or 0.05% and 0.1% boric acid for 24 hr. Quantitative real-time polymerase chain reaction was used to investigate the gene expression of MUC1, MUC4, and MUC16. Immunofluorescence staining of MUC16 protein on the surface of the HCE-T cells exposed to 10% diluted MPSs for 24 hr or undiluted MPSs for 30 min was observed by laser confocal scanning microscopy followed by quantitative image analysis. Three MPSs containing boric acid significantly reduced gene expressions of MUC1 from 20.2% to 56.7% (P<0.01). Gene expressions of MUC4 and MUC16 were also reduced by these MPSs; however, there were no significant differences. Among ingredients, 0.1% boric acid significantly reduced gene expressions of MUC1 and MUC16 by 7.4% and 18.9%, respectively (P<0.01). Immunofluorescence microscopy also demonstrated that in undiluted form, three MPSs containing boric acid significantly reduced the expression of MUC16 protein. The MPSs containing boric acid downregulate membrane-associated mucins as compared with MPSs that do not contain boric acid. There may be some subtle membrane or other interactions between ingredients in lens-care solutions that adversely alter corneal cell mucins.

Effects of Multipurpose Contact Lens Care Solutions on the Adhesiveness of Acanthamoeba to Corneal Epithelial Cells

To study the adhesion of Acanthamoeba castellanii treated with multipurpose contact lens care solutions (MPSs) to human corneal epithelial cells. Cell suspensions of A. castellanii (ATCC50514) trophozoites were mixed with six MPSs: MPS-A (polyhexamethylene biguanide [PHMB], macrogolglycerol hydroxystearate, propylene glycol), MPS-B (PHMB, poloxamine, boric acid), MPS-C (polyquad, poloxamine, boric acid), MPS-D (PHMB, poloxamer, propylene glycol), MPS-E (PHMB, poloxamer), or MPS-F (PHMB, poloxamer) for 4 hr. Morphologic changes of A. castellanii after exposure with MPSs were observed with scanning electron microscopy. A. castellanii cells treated with MPS for 4 hr were inoculated onto cultured SV40-immortalized human corneal epithelial cells. After 2-hr incubation, the number of adherent A. castellanii was assessed by 18S-rDNA quantification using real-time polymer chain reaction. After 4-hr incubation, MPS-A- and MPS-B-treated A. castellanii have changed from trophozoite morphology into cyst form; however, MPS-E- and MPS-F-treated A. castellanii maintained trophozoite morphology. In contrast, both cyst and trophozoite forms were observed in MPS-C- and MPS-D-treated A. castellanii. The adherence rate of A. castellanii was approximately two times higher in MPS-E (not significant), and more than three times higher in MPS-F (P<0.05) compared with MPS-A, which produced the lowest adhesiveness as estimated by real-time polymer chain reaction. Taken together, these results support the possibility that chronic use of MPS with the lowest efficacies on promoting encystment of A. castellanii (MPS-E and MPS-F) by hydrogel contact lens wearers may increase adhesiveness of A. castellanii to corneal epithelial cells.

Increased Resistance of Contact Lens-Related Bacterial Biofilms to Antimicrobial Activity of Soft Contact Lens Care Solutions

To determine if clinical and reference strains of Pseudomonas aeruginosa, Serratia marcescens, and Staphylococcus aureus form biofilms on silicone hydrogel contact lenses and ascertain antimicrobial activities of contact lens care solutions. Clinical and American Type Culture Collection reference strains of P. aeruginosa, S. marcescens, and S. aureus were incubated with lotrafilcon A lenses under conditions that facilitate biofilm formation. Biofilms were quantified by quantitative culturing (colony-forming units, CFUs), and gross morphology and architecture were evaluated using scanning electron microscopy and confocal microscopy. Susceptibilities of the planktonic and biofilm growth phases of the bacteria to 5 common multipurpose contact lens care solutions and 1 hydrogen peroxide care solution were assessed. Pseudomonas aeruginosa, S. marcescens, and S. aureus reference and clinical strains formed biofilms on lotrafilcon A silicone hydrogel contact lenses, as dense networks of cells arranged in multiple layers with visible extracellular matrix. The biofilms were resistant to commonly used biguanide-preserved multipurpose care solutions. Pseudomonas aeruginosa and S. aureus biofilms were susceptible to a hydrogen peroxide and a polyquaternium-preserved care solution, whereas S. marcescens biofilm was resistant to a polyquaternium-preserved care solution but susceptible to hydrogen peroxide disinfection. In contrast, the planktonic forms were always susceptible. Pseudomonas aeruginosa, S. marcescens, and S. aureus form biofilms on lotrafilcon A contact lenses, which in contrast to planktonic cells are resistant to the antimicrobial activity of several soft contact lens care products.

Using a Meta-Analysis to Determine Relationships Between Various Safety Parameters and Lens Care Solutions

Free-living, cosmopolitan amoebae of the Acanthamoeba genus may be the causative agents of Acanthamoeba keratitis (AK) – a progressive, vision-threatening infection of the human cornea described particularly among contact lens wearers. Use of contact lens care solutions, effective against these organisms, is important in preventing AK infections. 3 different strains of Acanthamoeba castellanii of the T4 genotype (Neff strain and two others, isolated from patients with AK) were exposed to 4 selected multipurpose contact lens care solutions available in Poland: Ciba Vision AoSept Plus, Bausch & Lomb ReNu MultiPlus, Alcon Opti-Free, Ciba Vision Solo Care Aqua. No amoebicidal effect was observed. The strongest amoebostatic effect was visible after 24 h of exposition to Opti-Free and ReNu solution and associated with percentage increase of rounded, motionless forms. This is significantly longer than minimum disinfection time recommended by manufacturers of all tested multipurpose solutions. Surprisingly, no clear induction of the encystation process was observed.