Quantifying the Dynamics of Bacterial Biofilm Formation on the Surface of Soft Contact Lens Materials Using Digital Holographic Tomography to Advance Biofilm Research.

The increase in bacterial resistance to antibiotics in recent years demands innovative strategies for the detection and combating of biofilms, which are notoriously resilient. Biofilms, particularly those on contact lenses, can lead to biofilm-related infections (e.g., conjunctivitis and keratitis), posing a significant risk to patients. Non-destructive and non-contact sensing techniques are essential in addressing this threat. Digital holographic tomography emerges as a promising solution. This allows for the 3D reconstruction of the refractive index distribution in biological samples, enabling label-free visualization and the quantitative analysis of biofilms. This tool provides insight into the dynamics of biofilm formation and maturation on the surface of transparent materials. Applying digital holographic tomography for biofilm examination has the potential to advance our ability to combat the antibiotic bacterial resistance crisis. A recent study focused on characterizing biofilm formation and maturation on six soft contact lens materials (three silicone hydrogels, three hydrogels), with a particular emphasis on Staphylococcus epidermis and Pseudomonas aeruginosa, both common culprits in ocular infections. The results revealed species- and time-dependent variations in the refractive indexes and volumes of biofilms, shedding light on cell dynamics, cell death, and contact lens material-related factors. The use of digital holographic tomography enables the quantitative analysis of biofilm dynamics, providing us with a better understanding and characterization of bacterial biofilms.

Conjunctival microbiome changes in soft contact lens users and contact lens discomfort patients.

INTRODUCTION: Contact lens discomfort (CLD) acts as a challenging problem, and the associated conjunctival microbiome changes were unclear. MATERIAL AND METHODS: Conjunctival sac swab samples were collected from 12 eyes of nonwearers (NW), 12 eyes of asymptomatic contact lens (ACL) wearers, and 11 eyes of CLD. The V3-V4 region of the 16S rRNA gene sequencing was used to investigate differences among three groups. RESULTS: No differences in alpha diversity were observed among the three groups. The beta diversity showed a distinct microbiome composition between ACL and CLD group (P = 0.018) with principal coordinate analysis. The relative abundance of Firmicutes was significantly higher in CLD (48.18%) than in ACL (13.21%) group (P = 0.018). The abundance of Bacillus in patients with ACL (0.05%) or with CLD (0.02%) were significantly lower than that in the NW (1.27%) group (P = 0.024, 0.028, respectively). Moreover, the abundance of Firmicutes was positively correlated with the OSDI scores in CLD patients (r = 0.817, P < 0. 01, Spearman). DISCUSSIONS: Patients with CLD have various degrees of bacterial microbiota imbalance in the conjunctival sac, compared with NW and ACL groups. CONCLUSION: Firmicutes may serve as a potential biomarker for the CLD patients.

In the current study, we investigated the conjunctival microbiome changes among nonwearers (NW), asymptomatic contact lens (ACL) wearers, and contact lens discomfort (CLD) patients using high-throughput 16S rRNA gene sequencing, and correlated relative abundances of the microbiota with clinical parameters.The relative abundance of Firmicutes was higher in CLD than that in ACL group. The abundance of Bacillus was lower in ACL or CLD group than that in NW group. The abundance of Firmicutes was positively correlated with the OSDI scores in CLD patients.Firmicutes may serve as a potential biomarker for the CLD patients.

Factors Affecting Microbial Contamination on the Back Surface of Worn Soft Contact Lenses.

SIGNIFICANCE: The results of this study demonstrate that Smart Touch Technology packaging, which is designed to reduce and simplify contact lens handling before insertion, is effective in reducing the frequency of bacterial contamination of the back surface of contact lenses after short-term wear. PURPOSE: The purpose of this study was to investigate the effect of lens packaging type, chelating agent, and finger contamination on microbial contamination on the back surface of worn soft contact lenses. METHODS: Twenty-five subjects completed each contralateral lens wear comparison in this randomized study: Smart Touch Technology versus conventional blister packaging for (1) silicone hydrogel lenses with ethylenediaminetetraacetic acid (EDTA) and (2) hydrogel lenses without EDTA in the packaging, and (3) silicone hydrogel lenses without EDTA versus hydrogel lenses with EDTA both in Smart Touch Technology packaging. Participants washed hands, underwent finger swabs, and inserted the lenses. After 45 minutes, lenses were removed aseptically and the posterior lens surfaces cultured. RESULTS: Thirty-eight subjects (average age, 30.9 ± 12.5 years) participated in this study. Overall, the level of back surface contamination was low for both lens materials, ranging from 0 to 43 colony-forming unit (CFU)/lens for the silicone hydrogel and 0 to 17 CFU/lens for the hydrogel lenses. The proportion of lenses with zero back surface contamination ranged from 16 to 64% for silicone hydrogel lenses and 28 to 64% for hydrogel lenses. Contact lenses from conventional packaging containing EDTA had 3.38 times increased risk (95% confidence interval [CI], 1.02 to 11.11; P = .05) of contamination being present compared with lenses from Smart Touch packaging with EDTA. Contact lenses from conventional packaging without EDTA had 3.4 times increased risk (95% CI, 1.02 to 11.36; P = .05) of contamination being present compared with Smart Touch packaging without EDTA, and silicone hydrogel lenses had a 6.28 times increased risk (95% CI, 1.65 to 23.81; P = .007) of contamination being present compared with hydrogels. The median (interquartile range) number of bacteria isolated from fingers used to perform lens insertion after handwashing but before lens insertion was not significantly different between the silicone hydrogel and hydrogel lenses (63.7 [204.2] vs. 59 [84.5], P = .09). Finger contamination was not significantly associated with lens contamination in the presence or absence of EDTA. CONCLUSIONS: Smart Touch Technology packaging was effective in reducing the proportion of contaminated lenses. Although silicone hydrogel lenses were more likely to be contaminated, the presence of EDTA ameliorated this effect. Finger contamination was not associated with lens contamination.

Technical Report: Guidelines for Handling of Multipatient Contact Lenses in the Clinical Setting.

SIGNIFICANCE: Standardized guidelines that are clinically practical are needed to assist the prescriber in minimizing the risk of conveying infection through multiuse diagnostic contact lens use and reuse.Contact lens prescribers face the specter of transferring potential pathogens from one patient to another when reusing diagnostic (trial) contact lenses on multiple patients because infectious organisms have been recovered from worn contact lenses, although there is no evidence of transmission through this mechanism. These pathogens can be introduced into the system from one patient to another, or they may be introduced by clinician lens handling, storage, or both. These pathogens can cause acute or chronic systemic or ocular infection that can lead to significant morbidity (temporary or permanent) that includes vision loss.

Chronic Conjunctivitis From a Retained Contact Lens.

PURPOSE: To help clinicians diagnose and manage unilateral recalcitrant chronic bacterial conjunctivitis secondary to a retained soft contact lens and describe the first report of Gram-negative bacteria causing this condition. METHODS: Chart review of successive cases presenting with unilateral chronic conjunctivitis with positive cultures and a retained contact lens. RESULTS: Three cases were identified and described. Culturing of the retained contact lenses grew Pseudomonas aeruginosa in the first case, Achromobacter xylosoxidans in the second, and Staphylococcus epidermidis in the third. All three patients were successfully treated with removal of the retained lens and targeted antibiotic eyedrop therapy. CONCLUSIONS: Unilateral chronic recurrent or recalcitrant purulent papillary conjunctivitis is rare, and a retained contact lens should be suspected in patients with a history of wearing contact lenses. Careful examination with double eversion of the upper eyelid and sweeping of the fornices can recover the offending lens. Although only Gram-positive organisms have been isolated in previous reports, two of our three cultures grew Gram-negative organisms, highlighting the importance of broad-spectrum antibiotic usage for these cases.

A Case of Nocardia farcinica Keratitis in a Pediatric Contact Lens Wearer.

PURPOSE: To report a case of Nocardia farcinica keratitis in a pediatric contact lens wearer. METHODS: Case report and literature review. RESULTS: A pediatric contact lens wearer was initially misdiagnosed with a poorly healing corneal abrasion after swimming with his contact lenses. On examination at our center, he was found to have a 2.5 by 2.5 mm corneal infiltrate with feathery margins. Microbiology revealed N. farcinica keratitis, which was treated with topical amikacin. The patient returned to his baseline visual acuity after treatment. CONCLUSIONS: Nocardia keratitis can be misdiagnosed because of its low prevalence, especially in young patients. Prompt diagnosis is important for proper management in these cases. The infection resolved in our patient with prompt diagnosis and treatment with topical amikacin eye drops.

Evaluation of prevention and disruption of biofilm in contact lens cases.

PURPOSE: The presence of biofilm in the lens case has been shown to be a risk factor for contamination of lenses and consequently microbial keratitis. This study aimed to evaluate effectiveness of solutions for rigid contact lenses in prevention and disruption of biofilm in lens cases and methods for biofilm detection. METHOD: This study adopted a stepwise approach to evaluate effectiveness of four rigid lens disinfecting solutions against biofilm. These included two polyhexamethylene bigiuanide (PHMB) solutions and a chlorhexidine/PHMB-based solution, as well as a novel povidone-iodine formulation. The presence of biofilm following exposure to the solutions was assessed using both crystal violet (CV) staining and MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) viability assay, taking into account the effect of lens case design. Three lens case designs, conventional flat, large bucket type, and cylindrical cases, were investigated for the ability to trap stain and allow biofilm formation. RESULTS: Considerable differences were noted between solutions in their ability to prevent and disrupt biofilm (p < 0.001). Lens case design greatly influenced optical density (OD) measurements even in negative controls, as cylindrical cases trapped more stain, increasing OD readings. Correcting for this factor reduced variations, but could not differentiate between residues and biofilm. MTT assay revealed that both povidone-iodine and chlorhexidine-containing solutions could effectively kill > 95% of organisms, whilst PHMB-based solutions were less effective with up to 55% of staphylococci and 41% of Pseudomonas surviving at 24 h. CONCLUSION: Biofilm can rapidly form in lens cases and may not be killed by disinfecting solutions. Of the solutions tested, none were able to prevent biofilm formation or disrupt established biofilm, but those containing chlorhexidine or povidone iodine were able to penetrate the biofilm and kill organisms. Assessment of biofilm by CV assay may be confounded by lens case design. Whilst CV assay can demonstrate presence of biofilm, this technique should be accompanied by viability assay to determine bactericidal activity.

Diversity of Ocular Surface Bacterial Microbiome Adherent to Worn Contact Lenses and Bacterial Communities Associated With Care Solution Use.

PURPOSE: This study assessed microbiome adherent to contact lenses and defined the bacterial communities associated with use of lens care solutions. METHODS: Among 84 lenses screened for adherent ocular surface bacterial microbiome using 16S rRNA molecular amplification, 63 (75%) generated bacterial-specific amplicons processed using the Ion Torrent Personal Genome Machine workflow. Data were stratified by solution use (peroxide vs. polyhexamethylene biguanide [PHMB]-preserved multipurpose solution [MPS]). Diversity of lens-adherent microbiome was characterized using Shannon diversity index and richness index. Data were analyzed using principal components analysis and Kruskal-Wallis tests. RESULTS: We identified 19 phyla and 167 genera of bacteria adherent to the lenses. Proteobacteria was the most abundant phyla, followed by Firmicutes and Actinobacteria. The most abundant bacterial genera (>1% abundance) were Ralstonia, Enterococcus, Streptococcus, Halomonas, Corynebacterium, Staphylococcus, Acinetobacter, Shewanella, Rhodococcus, and Cobetia. Sixteen of 20 lenses (80%) negative for bacterial DNA were worn by participants using peroxide solutions while only 4 (20%) were MPS-treated lenses (P=0.004). Genera diversity of lens-adherent microbiome showed a significant increase in MPS-treated lenses compared with peroxide (P=0.038). Abundance of Corynebacterium, Haemophilus, and Streptococcus were increased 4.3-, 12.3-, and 2.7-fold, respectively, in the MPS group compared with peroxide (P=0.014, 0.006, 0.047, respectively). CONCLUSIONS: Commensal, environmental, and pathogenic bacteria known to be present in the conjunctival microbiome can be detected on worn contact lenses. Although most contact lenses worn by asymptomatic wearers harbor bacterial DNA, compared with peroxide, lenses stored in a PHMB-preserved MPS have more quantifiable, abundant, and diverse bacterial communities adherent to them.

Stenotrophomonas maltophilia-A Case Series of a Rare Keratitis Affecting Patients With Bandage Contact Lens.

OBJECTIVES: Stenotrophomonas maltophilia is an opportunistic pathogen known to form biofilms on contact lens and case surfaces that may result in permanent visual loss in cases of microbial keratitis. Because of its multiple drug resistance and extremely low incidence, there is little consensus on treatment. We investigated the predisposing factors, management, and visual outcomes in a small case series of patients to better inform the management of this rarely reported keratitis. METHODS: Retrospective analysis of medical records was performed at a single tertiary referral center between 2011 and 2017. The case notes of each microbiology confirmed S. maltophilia keratitis were examined. RESULTS: Six cases were identified (four men) with a median age of 62 years (range 1 month-90 years) and pre-existing ocular surface disease in all cases. At presentation, four patients were using bandage contact lenses and three were on topical antibiotic and steroid medications. Initial antibiotic treatment was intensive topical 0.3% ofloxacin and 5% cefuroxime, which was modified based on corneal scrape culture and sensitivity and clinical findings. One patient chose not to complete the treatment course. The 5 remaining patients had complete resolution of ulceration over a mean of 2.9 months (SD 0.8 months). CONCLUSIONS: Contact lens in the context of ocular surface problems, prolonged topical antibiotic and steroid treatments may predispose to S. maltophilia, a rare cause of keratitis. We report successful treatment with case-specific combinations of topical antibiotics such as fluoroquinolone, cotrimoxazole, and/or cephalosporin agents, although visual outcomes remain poor due to corneal scar.

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.

Acceleration of the formation of biofilms on contact lens surfaces in the presence of neutrophil-derived cellular debris is conserved across multiple genera.

Purpose: We have previously shown that invasive strains of Pseudomonas aeruginosa exploit the robust neutrophil response to form biofilms on contact lens surfaces and invade the corneal epithelium. The present study investigated the ability of multiple bacterial genera, all commonly recovered during contact lens-related infectious events, to adhere to and form biofilms on contact lens surfaces in the presence of neutrophils. Methods: Five reference strains from the American Type Culture Collection were used: P. aeruginosa, Serratia marcescens, Stenotrophomonas maltophilia, Staphylococcus aureus, and Staphylococcus epidermidis. Each bacterial strain was incubated overnight with or without stimulated human neutrophils in the presence of an unworn contact lens. Standard colony counts and laser scanning confocal microscopy of BacLight-stained contact lenses were used to assess bacterial viability. Three-dimensional modeling of lens-associated biofilms with Imaris software was used to determine the biofilm volume. Lenses were further examined using scanning electron microscopy. Results: Less than 1% of the starting inoculum adhered to the contact lens surface incubated with bacteria alone. There were no differences in adhesion rates to contact lens surfaces between bacteria in the absence of neutrophils for either the Gram-negative or Gram-positive test strains. Bacterial adhesion to contact lens surfaces was accelerated in the presence of human neutrophils for all test strains. This effect was least evident with S. epidermidis. There was also an increase in the number of viable bacteria recovered from contact lens surfaces (p<0.001 for the Gram-negative and Gram-positive test strains, respectively) and in biofilm volume (p<0.001 for the Gram-negative test strains, p = 0.005 for S. aureus). Conclusions: These results show that in addition to P. aeruginosa, other bacteria commonly encountered during contact lens wear possess the capacity to utilize neutrophil-derived cellular debris to facilitate colonization of the lens surface. These data suggest that this phenomenon is conserved among multiple genera. Thus, during contact lens wear, the presence of inflammation and the accumulation of neutrophil debris under the posterior lens surface likely contribute to colonization of the lens. Further studies are needed to correlate these findings with risk for infection in an animal model.

Development of Silicone Hydrogel Antimicrobial Contact Lenses with Mel4 Peptide Coating.

SIGNIFICANCE: This study investigated the development of an antimicrobial coating on silicone hydrogel contact lenses that may have the capacity to reduce contact lens-related infection and inflammatory events. PURPOSE: The purpose of this study was to develop an effective antimicrobial coating for silicone hydrogel contact lenses by attachment of Mel4 peptide. METHODS: Lotrafilcon A, comfilcon A, somofilcon A, senofilcon A, and lotrafilcon B silicone hydrogel contact lenses were plasma coated with acrylic acid followed by Mel4 antimicrobial peptide immobilization by covalent coupling. Peptide immobilization was quantified by x-ray electron spectroscopy. Contact lens diameter, base curve, center thickness, and lens surface wettability were measured by captive-bubble contact-angle technique. Antimicrobial activity of the lenses was determined against Pseudomonas aeruginosa and Staphylococcus aureus by viable plate count and also after soaking with artificial tears solution for 1 day. In vivo safety and biocompatibility were determined in an animal model for 1 week. RESULTS: Mel4 peptide-coated silicone hydrogel contact lenses were associated with high antimicrobial inhibition (>2 log), except for lotrafilcon B and senofilcon A. Lotrafilcon B did not exhibit any activity, whereas senofilcon A showed 1.4- and 0.7-log inhibition against P. aeruginosa and S. aureus, respectively. X-ray electron spectroscopy revealed significant increases in the lens surface-bound amide nitrogen in all contact lenses except for lotrafilcon B. All contact lens parameters remained unchanged except for the base curve and center thickness for senofilcon A. Mel4 immobilization was associated with a decrease in contact angle. Mel4-coated contact lens wear was not associated with any signs or symptoms of ocular irritation in a rabbit model study. Reduced antimicrobial activity was observed with all the lenses after soaking with artificial tears solution or rabbit wear. CONCLUSIONS: Mel4 antimicrobial coating may be an effective option for development of antimicrobial silicone hydrogel contact lenses.

In Vitro Evaluation of Adhesion of Two Acanthamoeba Strains to Cosmetic Contact Lenses.

PURPOSE: To evaluate the factors affecting the adhesion of Acanthamoeba trophozoites to the surface of cosmetic contact lenses (CCLs). METHODS: Acanthamoeba castellanii and A. hatchetti trophozoites were inoculated onto CCLs (hema copolymer [HM] [38.5% H2O], phemfilcon [PF] [55% H2O], polymacon [PM] [38% H2O], polyhema [PH] [%42 H2O], and hema [HM55] [55% H2O]), and the number of trophozoites adhered to the lens surfaces was assessed over time, that is, at 15 min, 1, and 24 hr. In addition, scanning electron microscopy (SEM) analysis of the lens surfaces was performed to evaluate the effect of lens surface topology on adhesion. RESULTS: The number of amoeba adhered to the contact lens surface was found lower with PF and PH production materials, than lenses with HM, PM, and HM55 production materials (P<0.05). No significant difference was detected in amoebic strains adhered in all the contact lens types (P>0.05). No significant difference was found on average amoeba adhesion between contact lenses with hema production material but with different water contents (45%, 55%), to see the effect of water content on amoebic adhesion (P>0.05). As a result of SEM analysis, surface topology showed no effect on adhesion. CONCLUSION: (1) Chemical composition of lenses seemed to be mostly responsible for the adhesion of Acanthamoeba. (2) Different numbers of trophozoites, obtained after the adhesion experiment, could also indicate that adherence capacity can also differ among Acanthamoeba species.

Adhesion of Stenotrophomonas maltophilia, Delftia acidovorans, and Achromobacter xylosoxidans to Contact Lenses.

PURPOSE: Contact lens cases become contaminated with microbes during use. We wished to compare the adhesion of uncommon bacterial contaminants isolated from lens cases to contact lenses with and without organic soil. METHODS: Strains of Delftia acidovorans (001), Stenotrophomonas maltophilia (002 and 006), and Achromobacter xylosoxidans (001) isolated from contact lens cases (test strains) and Pseudomonas aeruginosa (Paer1) isolated from eyes at the time of infiltrative response (control strain) were used. Bacteria were grown and resuspended in phosphate-buffered saline (PBS) or 10% organic soil (heat-killed Saccharomyces cerevisiae resuspended in complement inactivated bovine serum). Two silicone hydrogel (senofilcon A and comfilcon A) and one hydrogel lens (etafilcon A) lens materials were used. Bacteria (1.0×10 and 1.0×10 colony-forming units/mL; CFU/mL) adhered to lenses for 24 hr and the numbers of bacteria adherent to each lens type (with and without organic soil) were estimated by culture. RESULTS: All the four test strains adhered in significantly greater numbers to contact lenses after incubation in inoculum prepared with organic soil compared with PBS-D. acidovorans 001 (0.7 log10 CFU; P<0.05), S. maltophilia 002 (1.7 log10 CFU; P<0.05), S. maltophilia 006 (0.9 log10 CFU; P<0.05), and A. xylosoxidans 001 (0.4 log10 CFU; P<0.05). However, the presence of organic soil did not increase adhesion of P. aeruginosa Paer1 (-0.1 log10 CFU; P>0.05). Achromobacter xylosoxidans 001 (P<0.01), D. acidovorans 001 (P<0.01), and S. maltophilia 002 (P<0.01) significantly differed in their adhesion to the three contact lens materials. CONCLUSION: Bacteria that are commonly found in contact lens cases adhered to contact lenses in relatively high numbers in the presence of organic soil. This might indicate that a similar phenomenon occurs in the presence of tears. This may facilitate their transfer from the lens to the cornea and the production of corneal infiltrates.

Clinical Outcomes and Contact Lens Case Contamination Using a Povidone-Iodine Disinfection System.

OBJECTIVE: To assess the incidence of adverse events during the use of a povidone-iodine disinfecting solution (cleadew) and the microbial contamination in contact lens cases. METHODS: A prospective, single-center, open-label, controlled study evaluating the use of cleadew cleaning and disinfecting system in existing daily wear soft contact lens wearers over a 3-month period was conducted. Ocular signs and symptoms during lens wear were assessed at baseline and after 1 and 3 months of using cleadew. Contact lens cases were assessed for the frequency of microbial contamination and the types of microbes, using traditional microbial culture, followed by identification of bacteria using 16S rRNA sequencing. RESULTS: Use of cleadew was well tolerated. There was reduction in corneal staining (0.5±0.5 at 3 months of use) compared with the participant's habitual multipurpose disinfecting system (1.1±1.0); all other clinical signs were not significantly different. There were no cases of solution-induced corneal staining. There was a low adverse event rate of 0.8% per 100 participant-months. Contact lens case contamination was low, with 30% of cases having no culturable microbes. Comparison with previously published data showed that use of cleadew resulted in low frequencies of Gram-positive (49%) and fungal (8%) contamination and a low, but higher than some other disinfecting solutions, level of Gram-negative bacteria. CONCLUSIONS: Cleadew cleaning and disinfecting system was associated with low levels of adverse events during use. Contact lens cases were significantly less frequently contaminated than for some other types of disinfecting solutions.

Paecilomyces lilacinus Keratitis in a Soft Contact Lens Wearer.

We describe a case of keratitis caused by Paecilomyces lilacinus in a contact lens wearer with a history of diabetes.

Biofilm Formation on Bandage Contact Lenses Worn by Patients with the Boston Type 1 Keratoprosthesis: A Pilot Comparison Study of Prophylactic Topical Vancomycin 15 mg/mL and Linezolid 0.2.

OBJECTIVES: To determine the rate of biofilm formation on bandage contact lenses worn by patients with the Boston type 1 keratoprosthesis (K-Pro) while on prophylactic topical vancomycin versus linezolid. METHODS: Patients wearing a bandage contact lens (BCL) with a K-Pro were eligible for enrollment. After irrigation of the ocular surface with 5% povidone-iodine solution, each patient was placed on either topical vancomycin 15 mg/mL or linezolid 0.2% BID for one month. At the one-month visit, the BCL was collected and stored in fixative solution. Standard photographs were taken of each lens at high magnification using scanning electron microscopy (SEM), which were subsequently analyzed for evidence of biofilm. RESULTS: Nineteen contact lenses were obtained from 12 K-Pro patients at the Illinois Eye and Ear Infirmary. Zero of eight (0%; 95% CI=0 to 37%) contact lenses from patients treated with topical vancomycin, and 1 of 11 (9%; 95% CI=0 to 41%; P-value=1.00) contact lenses from patients treated with topical linezolid were found to have biofilm formation at one month as detected by SEM. None of the patients developed a clinically significant infection while on either prophylactic vancomycin or linezolid during the study period. CONCLUSIONS: Overall, the rate of biofilm formation as detected by SEM on the surface of bandage contact lenses was low. These results suggest that vancomycin and linezolid are both relatively effective in reducing biofilm-forming bacterial growth at one month. Accordingly, linezolid may be an effective alternative to vancomycin in patients with allergy or intolerance. However, further investigation is required to develop evidence-based antibiotic prophylaxis regimens.

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.

Study of the Effectiveness of Multipurpose Solutions on the Bacterial Disinfection of Silicone Hydrogel Contact Lenses In Vitro.

OBJECTIVES: To assess the antimicrobial effectiveness of multipurpose solutions in regard to the disinfection of silicone hydrogel contact lenses (CL) using a study of clinical bacterial isolates from ocular material. METHODS: Three multipurpose solutions (solution A: polyhexamethylene biguanide 0.00025 g/100 mL; solution B: polyquaternary-1 0.001% and myristamidopropyl dimethylamine 0.0006%; and solution C: polyaminopropyl biguanide 0.00013% and polyquaternary 0.0001%) were used as a 3-phase disinfection on silicone hydrogel CL contaminated with bacteria from clinical isolates that were divided into five groups (group 1: Pseudomonas aeruginosa; group 2: Staphylococcus aureus; group 3: Staphylococcus epidermidis; group 4: Streptococcus spp; and group 5: enterobacteria). RESULTS: No differences were observed between the 24- and 48-hr measurements in any of the samples, and the positivity of microorganisms in T0 was 100% for all solutions; it was 0% in T3. Therefore, only steps T1 (rubbing followed by rinsing) and T2 (rubbing followed by rinsing and immersion of CL into solution) were considered for analysis at the 24-hr measurement time. Throughout the phases, a decrease in the number of bacteria was observed, culminating in the elimination (no recovery) of all microorganisms in the three solutions. CONCLUSIONS: At the end of the proposed process, the tested solutions were effective.

The Antibiofilm efficacy of nitric oxide on soft contact lenses.

BACKGROUND: To investigate the antibiofilm efficacy of nitric oxide (NO) on soft contact lenses. METHODS: Nitrite (NO precursor) release from various concentrations (0-1000 µM) of sodium nitrite (NaNO2, NO donor) was measured by Griess Assay. Cell viability assay was performed using human corneal epithelial cell under various concentration (0-1000 µM) of NaNO2. Biofilm formation on soft contact lenses was achieved by adding Staphylococcus aureus or Pseudomonas aeruginosa to the culture media. Various concentrations of NaNO2 (0-1000 µM) were added to the culture media, each containing soft contact lens. After incubation in NaNO2 containing culture media for 1, 3, or 7 days, each contact lens was transferred to a fresh, bacteria-free media without NaNO2. The bacteria in the biofilm were dispersed in the culture media for planktonic growth. After reculturing the lenses in the fresh media for 24 h, optical density (OD) of media was measured at 600 nm and colony forming unit (CFU) was counted by spreading media on tryptic soy agar plate for additional 18 h. RESULTS: Nitrite release from NaNO2 showed dose-dependent suppressive effect on biofilm formation. Most nitrite release from NaNO2 tended to occur within 30 min. The viability of human corneal epithelial cells was well maintained at tested NaNO2 concentrations. The bacterial CFU and OD showed dose-dependent decrease in the NaNO2 treated samples on days 1, 3 and 7 for both Staphylococcus aureus and Pseudomonas aeruginosa. CONCLUSIONS: NO successfully inhibited the biofilm formation by Staphylococcus aureus or Pseudomonas aeruginosa on soft contact lenses in dose-dependent manner.