Molecular Bioburden of the Lens Storage Case for Contact Lens-Related Keratitis

Activity of multipurpose contact lens solutions against Staphylococcus aureus, Pseudomonas aeruginosa, Serratia marcescens and Candida albicans biofilms

INTRODUCTION

The use of contact lenses has progressively increased around the world, thereby increasing the risk of complications. The most serious complication is microbial keratitis (corneal infection) that can progress to a corneal ulcer.

METHODS

Fourteen multipurpose contact lens solutions were tested on mature biofilms comprising Staphylococcus aureus, Pseudomonas aeruginosa, Serratia marcescens and Candida albicans, using the minimum disinfection times recommended by the manufacturers. The biofilm was induced in the lens case, and 24 h later, the solutions were added. Activity against planktonic and sessile cells was evaluated and quantified as colony forming units per millilitre. The minimum concentration for biofilm eradication was defined as a 99.9% reduction in viable cells.

RESULTS

Although most solutions exhibited activity against planktonic cells, only five of the 14 solutions produced a significant reduction in the S. marcescens biofilm. No solution achieved the minimal biofilm eradication of S. aureus, P. aeruginosa and C. albicans.

CONCLUSION

Multipurpose contact lens solutions provide greater bactericidal and/or fungicidal activity on planktonic cells than biofilms. The minimal eradication biofilm concentration was only achieved for S. marcescens.

TFOS Lifestyle: Impact of contact lenses on the ocular surface

Several lifestyle choices made by contact lens wearers can have adverse consequences on ocular health. These include being non-adherent to contact lens care, sleeping in lenses, ill-advised purchasing options, not seeing an eyecare professional for regular aftercare visits, wearing lenses when feeling unwell, wearing lenses too soon after various forms of ophthalmic surgery, and wearing lenses when engaged in risky behaviors (e.g., when using tobacco, alcohol or recreational drugs). Those with a pre-existing compromised ocular surface may find that contact lens wear exacerbates ocular disease morbidity. Conversely, contact lenses may have various therapeutic benefits. The coronavirus disease-2019 (COVID-19) pandemic impinged upon the lifestyle of contact lens wearers, introducing challenges such as mask-associated dry eye, contact lens discomfort with increased use of digital devices, inadvertent exposure to hand sanitizers, and reduced use of lenses. Wearing contact lenses in challenging environments, such as in the presence of dust and noxious chemicals, or where there is the possibility of ocular trauma (e.g., sport or working with tools) can be problematic, although in some instances lenses can be protective. Contact lenses can be worn for sport, theatre, at high altitude, driving at night, in the military and in space, and special considerations are required when prescribing in such situations to ensure successful outcomes. A systematic review and meta-analysis, incorporated within the review, identified that the influence of lifestyle factors on soft contact lens dropout remains poorly understood, and is an area in need of further research. Overall, this report investigated lifestyle-related choices made by clinicians and contact lens wearers and discovered that when appropriate lifestyle choices are made, contact lens wear can enhance the quality of life of wearers.

Comparative Evaluation of Pseudomonas aeruginosa Adhesion to a Poly-(2-Methacryloyloxyethyl Phosphorylcholine)-Modified Silicone Hydrogel Contact Lens

Pseudomonas aeruginosa is the most common causative agent associated with microbial keratitis. During contact lens wear, pathogens may be introduced into the ocular environment, which might cause adverse events. Lehfilcon A is a recently developed contact lens with a water gradient surface composed of polymeric 2-methacryloyloxyethyl phosphorylcholine (MPC). MPC is re-ported to impart anti-biofouling properties onto modified substrates. Therefore, in this in vitro experimental study, we tested the capability of lehfilcon A to resist adhesion by P. aeruginosa. Quantitative bacterial adhesion assays using five strains of P. aeruginosa were conducted to compare the adherence properties of lehfilcon A to five currently marketed silicone hydrogel (SiHy) contact lenses (comfilcon A, fanfilcon A, senofilcon A, senofilcon C, and samfilcon A). Compared to lehfilcon A, we observed 26.7 ± 8.8 times (p = 0.0028) more P. aeruginosa binding to comfilcon A, 30.0 ± 10.8 times (p = 0.0038) more binding to fanfilcon A, 18.2 ± 6.2 times (p = 0.0034) more binding to senofilcon A, 13.6 ± 3.9 times (p = 0.0019) more binding to senofilcon C, and 29.5 ± 11.8 times (p = 0.0057) more binding to samfilcon A. These results demonstrate that, for various strains of P. aeruginosa, lehfilcon A reduces bacterial adhesion compared to other contact lens materials.

Evaluation of Serratia marcescens Adherence to Contact Lens Materials

Bacterial keratitis is a risk associated with the use of contact lenses for cosmetic purposes or vision correction. In this in vitro experimental study, we examined the ability of the ocular pathogen Serratia marcescens to adhere to monthly or biweekly replacement contact lenses. We performed quantitative adhesion assays to evaluate the adherence of S. marcescens to seven contact lens materials: comfilcon A, senofilcon A, omafilcon B, fanfilcon A, balafilcon A, senofilcon C, and lehfilcon A. Lehfilcon A is a newly marketed silicon hydrogel contact lens with a surface modification of poly-(2-methacryloyloxyethyl phosphorylcholine) (PMPC). PMPC has previously been demonstrated to be an effective anti-biofouling treatment for numerous surfaces. We observed low S. marcescens adherence to lehfilcon A compared to other materials. We demonstrate the use of the fluorescent dye 5(6)-Carboxytetramethylrhodamine succinimidyl ester to covalently stain live cells prior to material adhesion studies.

Deep Learning Approach in Image Diagnosis of Pseudomonas Keratitis

This investigation aimed to explore deep learning (DL) models' potential for diagnosing Pseudomonas keratitis using external eye images. In the retrospective research, the images of bacterial keratitis (BK, n = 929), classified as Pseudomonas (n = 618) and non-Pseudomonas (n = 311) keratitis, were collected. Eight DL algorithms, including ResNet50, DenseNet121, ResNeXt50, SE-ResNet50, and EfficientNets B0 to B3, were adopted as backbone models to train and obtain the best ensemble 2-, 3-, 4-, and 5-DL models. Five-fold cross-validation was used to determine the ability of single and ensemble models to diagnose Pseudomonas keratitis. The EfficientNet B2 model had the highest accuracy (71.2%) of the eight single-DL models, while the best ensemble 4-DL model showed the highest accuracy (72.1%) among the ensemble models. However, no statistical difference was shown in the area under the receiver operating characteristic curve and diagnostic accuracy among these single-DL models and among the four best ensemble models. As a proof of concept, the DL approach, via external eye photos, could assist in identifying Pseudomonas keratitis from BK patients. All the best ensemble models can enhance the performance of constituent DL models in diagnosing Pseudomonas keratitis, but the enhancement effect appears to be limited.

Compliance versus Risk Awareness with Contact Lens Storage Case Hygiene and Replacement

SIGNIFICANCE

Compliance with hygiene and replacement of contact lens (CL) storage cases is key to avoid CL contamination and anterior ocular surface complications. However, compliance levels with these accessories remain low, even in patients with awareness of the risk associated with noncompliance.

PURPOSE

This study aimed to determine level of compliance with common practices regarding CL storage case hygiene and replacement, type of information provided by practitioners, and risk perception.

METHODS

An ad hoc self-reported survey was used to collect demographic and CL wear details, compliance with storage case care, type of received information, and risk perception (in a 1-to-5 scale). Inferential statistics explored the relationship of demographic details and type of received information with compliance and risk perception.

RESULTS

Nondaily disposable wearing participants returned 299 completed surveys, with a median age of 24 years (76.9% females). Monthly replacement silicone hydrogel CLs and multipurpose solutions were predominant. Self-reported compliance with storage case care was poor, with 19.1% of respondents never cleaning their cases, 68.6% exposing them to tap water, and 26.4% failing to replace them within 6 months of acquisition. Two-thirds of respondents received specific information on case maintenance, mainly in oral form. Perceived risk associated with poor-compliance practices was high (median values of 4 and 5), and increased with educational level (P = .02, regarding handwashing; P = .03, regarding case hygiene), with years of CL wear experience (P < .001, regarding handwashing), in those patients provided with specific information on CL case care (P = .01, regarding case replacement).

CONCLUSIONS

Compliance with CL storage case hygiene and replacement was generally poor, although awareness of risk associated with noncompliance was high and influenced by factors related to demographic details, CL experience, and patient-practitioner communication. Strategies must be explored to increase risk awareness through education because this may lead to better compliance practices.

Mechanisms Underlying Contact Lens-Related Keratitis Caused by Pseudomonas aeruginosa

ABSTRACT

Infectious keratitis is a severe complication associated with contact lens (CL) wear, and can progress rapidly with suppurative infiltration, resulting in the loss of vision. Contact lens wearers with poor and improper care are susceptible to develop infectious keratitis. Gram-negative bacilli such as Pseudomonas aeruginosa, have an ability to form biofilms on CL cases and CLs. Moreover, P. aeruginosa has various virulence factors such as type III secretion system (TTSS) which is an important factor for pathogenicity in keratitis. The effector proteins of TTSS have been identified, namely ExoU, ExoS, ExoT, and ExoY. Pseudomonas aeruginosa strains with ExoU show resistance to disinfection. The strains isolated from CL-related keratitis have higher ExoU gene positivity. Expression of elastase and swarming motility of P. aeruginosa isolates significantly correlates with focus size of keratitis. In addition to education of lens care for the CL wearer, development of CL cleaning solutions targeting suppression of virulence factors are needed for prevention of CL-related keratitis in the future.

The role of Acanthamoeba spp. in biofilm communities: a systematic review

Acanthamoeba spp. have always caused disease in immunosuppressed patients, but since 1986, they have become a worldwide public health issue by causing infection in healthy contact lens wearers. Amoebae of the Acanthamoeba genus are broadly distributed in nature, living either freely or as parasites, and are frequently associated with biofilms throughout the environment. These biofilms provide the parasite with protection against external aggression, thus favoring its increased pathogeny. This review aims to assess observational studies on the association between Acanthamoeba spp. and biofilms, opening potential lines of research on this severe ocular infection. A systematic literature search was conducted in May 2020 in the following databases: PubMed Central^®/Medline, LILACS, The Cochrane Library, and EMBASE^®. The studies were selected following the inclusion and exclusion criteria specifically defined for this review. Electronic research recovered 353 publications in the literature. However, none of the studies met the inclusion criterion of biofilm-producing Acanthamoeba spp., inferring that the parasite does not produce biofilms. Nonetheless, 78 studies were classified as potentially included regarding any association of Acanthamoeba spp. and biofilms. These studies were allocated across six different locations (hospital, aquatic, ophthalmic and dental environments, biofilms produced by bacteria, and other places). Acanthamoeba species use biofilms produced by other microorganisms for their benefit, in addition to them providing protection to and facilitating the dissemination of pathogens residing in them.

Effect of Hygiene Procedures on Lens Case Contamination with Povidone-Iodine or Multipurpose Disinfecting Solutions

SIGNIFICANCE

A multipurpose disinfecting solution (MPDS), which contains povidone-iodine (PI) as a disinfectant, has high disinfecting efficacy not only on planktonic bacterium but also on the case biofilms. The addition of case hygiene practice removed more bacteria from cases than MPDS alone.

PURPOSE

This study compared the ability of two MPDSs, one containing PI and another containing polyaminopropyl biguanide and polyquaternium, to reduce bacterial numbers in solution or adhered to the cases following case hygiene procedures.

METHODS

Bacterial strains (Delftia acidovorans, Pseudomonas aeruginosa, Stenotrophomonas maltophilia, Serratia marcescens, Staphylococcus aureus, and Staphylococcus epidermidis) were exposed to the MPDSs for the recommended disinfection times, and the viable number evaluated according to ISO 14729. Cases were inoculated with bacterial strains and incubated for 24 hours to allow for biofilm formation. Cases were disinfected with both disinfecting solutions for 4 hours and rinsed, followed by recapping or air-drying, or tissue-wiping and air-drying for 18 hours. The number of survivors was counted using standard culture techniques.

RESULTS

Both products exceeded the recommended 3-log reduction against planktonic bacteria. Regarding biofilm, after rinsing and recapping wet, the numbers of D. acidovorans (mean difference [95% confidence interval] log10 colony-forming units per case, -2.9 [0.8 to -4.6], P < .01), P. aeruginosa (-2.0 [0.5 to -3.1], P < .01), S. marcescens (-1.7 [0.8 to -3.5], P < .05), and S. epidermidis (-2.1 [0.6 to -3.5], P < .05) in PI cases were significantly lower than in the dual-disinfectant MPDS storage cases. After air-drying, the PI storage cases had significantly lower numbers of S. maltophilia (-2.6 [0.6 to -4.0], P < .01), D. acidovorans (-1.6 [0.7 to -3.3], P < .05), and S. aureus (-1.6 [0.7 to -3.1], P < .05). The addition of tissue-wiping reduced the bacterial numbers in the MPDS storage cases to levels in the PI storage cases.

CONCLUSIONS

Contact lens users should be recommended to tissue-wipe and air-dry their lens storage cases after disinfection with regular MPDS.

Corneal Infection Models: Tools to Investigate the Role of Biofilms in Bacterial Keratitis

Bacterial keratitis is a corneal infection which may cause visual impairment or even loss of the infected eye. It remains a major cause of blindness in the developing world. Staphylococcus aureus and Pseudomonas aeruginosa are common causative agents and these bacterial species are known to colonise the corneal surface as biofilm populations. Biofilms are complex bacterial communities encased in an extracellular polymeric matrix and are notoriously difficult to eradicate once established. Biofilm bacteria exhibit different phenotypic characteristics from their planktonic counterparts, including an increased resistance to antibiotics and the host immune response. Therefore, understanding the role of biofilms will be essential in the development of new ophthalmic antimicrobials. A brief overview of biofilm-specific resistance mechanisms is provided, but this is a highly multifactorial and rapidly expanding field that warrants further research. Progression in this field is dependent on the development of suitable biofilm models that acknowledge the complexity of the ocular environment. Abiotic models of biofilm formation (where biofilms are studied on non-living surfaces) currently dominate the literature, but co-culture infection models are beginning to emerge. In vitro, ex vivo and in vivo corneal infection models have now been reported which use a variety of different experimental techniques and animal models. In this review, we will discuss existing corneal infection models and their application in the study of biofilms and host-pathogen interactions at the corneal surface.

A Genomic Approach to Investigating Ocular Surface Microorganisms: Monitoring Core Microbiota on Eyelid Margin with a Dot hybridization Assay

A sound ocular surface microbiota has been recognized as a part of ocular surface health following a growing body of evidence from next-generation sequencing technique and metagenomic analysis. However, even from the perspective of contemporary precision medicine, it is difficult to directly apply these new technologies to clinical practice. Therefore, we proposed a model based on dot hybridization assay (DHA) to bridge conventional culture with a metagenomic approach in investigating and monitoring ocular surface microbiota. Endophthalmitis, mostly caused by bacterial infection, is the most severe complication of many intraocular surgeries, such as cataract surgery. Hazardous microorganisms hiding and proliferating in the ocular surface microbiota not only increase the risk of endophthalmitis but also jeopardize the effectiveness of the preoperative aseptic procedure and postoperative topical antibiotics. The DHA model enables the simultaneous assessment of bacterial bioburden, detection of target pathogens and microorganisms, and surveillance of methicillin/oxacillin resistance gene mecA in the ocular surface microbiota. This assay revealed heavier bacterial bioburden in men, compatible with a higher risk of endophthalmitis in male patients who underwent cataract surgery. No occurrence of endophthalmitis for these patients was compatible with non-hazardous microorganisms identified by specific dots for target pathogens. Moreover, the mecA dot detected oxacillin-resistant strains, of which culture failed to isolate. Therefore, the DHA model could provide an alternative genomic approach to investigate and monitor ocular surface microorganisms in clinical practice nowadays.

Silicone hydrogel daily disposable benefits: The evidence

Daily disposable (DD) contact lenses first came to the market approximately 25 years ago and eye care professionals (ECPs) started prescribing silicone hydrogel (SiH) contact lenses, primarily for extended or continuous wear, approximately 20 years ago. It has now been over ten years since SiH DD contact lenses have been available, and while SiH materials are routinely prescribed by ECPs for reusable daily wear, hydrogel materials are still frequently selected for the DD modality of contact lens wear. This article reviews the evidence to support the benefits of both a DD modality and SiH materials and how patients' needs may be met with SiH DD contact lenses, with respect to clinical performance, health outcomes, satisfaction, compliance and convenience. Factors which may enable or constrain ECPs from prescribing SiH DD contact lenses, as opposed to hydrogel DD and reusable contact lenses, for more of their patients are discussed with the objective of providing ECPs with a greater understanding of the advantages that can be afforded by prescribing SiH DD contact lenses to both their new and existing contact lens wearers.

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.