Adherence and kinetics of biofilm formation of Staphylococcus epidermidis to different types of intraocular lenses under dynamic flow conditions

A review on antimicrobial strategies in mitigating biofilm-associated infections on medical implants

Biomedical implants are crucial in providing support and functionality to patients with missing or defective body parts. However, implants carry an inherent risk of bacterial infections that are biofilm-associated and lead to significant complications. These infections often result in implant failure, requiring replacement by surgical restoration. Given these complications, it is crucial to study the biofilm formation mechanism on various biomedical implants that will help prevent implant failures. Therefore, this comprehensive review explores various types of implants (e.g., dental implant, orthopedic implant, tracheal stent, breast implant, central venous catheter, cochlear implant, urinary catheter, intraocular lens, and heart valve) and medical devices (hemodialyzer and pacemaker) in use. In addition, the mechanism of biofilm formation on those implants, and their pathogenesis were discussed. Furthermore, this article critically reviews various approaches in combating implant-associated infections, with a special emphasis on novel non-antibiotic alternatives to mitigate biofilm infections.

Update on Current Microbiological Techniques for Pathogen Identification in Infectious Endophthalmitis

Infectious endophthalmitis is a vision-threatening medical emergency that requires prompt clinical diagnosis and the initiation of treatment. However, achieving precision in endophthalmitis management remains challenging. In this review, we provide an updated overview of recent studies that are representative of the current trends in clinical microbiological techniques for infectious endophthalmitis.

Chronic postoperative Cutibacterium acnes endophthalmitis with implantable collamer lens

Purpose

We report a case of chronic post-operative endophthalmitis secondary to Cutibacterium acnes (C. acnes) in a patient with an implantable collamer lens (ICL).

Observations

A 45-year-old male presented three months after ICL implantation of the right eye with blurry vision, redness, and ocular pain in the setting of prolonged post-operative anterior chamber (AC) cell. Reduced visual acuity (VA) at 20/30-1, keratic precipitates, 1+ AC cell, and white ICL precipitates were concerning for chronic post-operative endophthalmitis. Anaerobic cultures from a vitreous tap grew C. acnes. Multiple intravitreal and intracameral injections with topical steroids were required to maintain a stable VA at 20/30; however, inflammation persisted and removal of the ICL and his native lens was ultimately required.

Conclusions and importance

Chronic post-operative inflammation and white plaque after ICL implantation should raise high suspicion for endophthalmitis secondary to C. acnes. Anaerobic vitreous cultures can confirm the diagnosis. Removal of the ICL implant is often necessary for treatment. More research is needed to best manage this vision threatening condition.

Management and Microbiological Characteristics of Membrane Formation on a Hydrophilic Acrylic Intraocular Lens: A Clinical Case Series and Material Comparative Study of Different IOLs

Background/Aims. To report a case series of membrane formation on intraocular lenses (IOLs) after uneventful phacoemulsification and to evaluate the material characteristics and biofilm formation on different IOLs. Methods. Ten eyes implanted with the same type of IOLs were found to have membranes on their IOLs after uneventful phacoemulsification from May 2015 to May 2016. No other patients were found with the same phenomenon among 11236 patients who underwent cataract surgeries during this period. To further investigate the reasons for their formation, we assessed seven types of IOLs used in our hospital, including their material characteristics and the presence of microbes (Staphylococcus epidermidis) on the IOL surface by scanning electron microscopy (SEM). All IOLs were incubated under in vitro flow conditions (BioFlux 1000Z). After 36 h, the IOLs were taken from the system, and both the bound bacteria and biofilm formation were observed. Results. Five eyes underwent intravitreal injections of ceftazidime and norvancomycin with one positive culture obtained from the anterior chamber fluid. The other five eyes only received topical treatment of gatifloxacin/levofloxacin and tobramycin. At the last follow-up, all patients had best-corrected visual acuity (BCVA) of 20/50 or better. In the biofilm study on the IOL surface, Staphylococcus epidermidis biofilms formed more readily on hydrophilic acrylic IOLs than on hydrophobic acrylic IOLs. Conclusions. Bacterial adhesion and biofilm tend to develop on certain types of IOLs because of the characteristics of the biomaterial.

Bacterial and Fungal Endophthalmitis

Endophthalmitis is a severe eye infection that may result in permanent loss of useful vision in the affected eye. Most cases are exogenous and occur as a complication of cataract surgery, an intravitreal injection, or penetrating ocular trauma. Endogenous endophthalmitis results from hematogenous seeding of the eye by bacteria or fungi, but bacteremia or fungemia may be transient and patients may present without symptoms of systemic infection. Nearly all endophthalmitis patients present with decreased vision, and some also have eye pain. Eye examination usually reveals a hypopyon and intraocular inflammation. Diagnosis is clinical, supported by cultures of the vitreous and/or aqueous or by blood cultures in some endogenous cases. Molecular diagnostic techniques have been used in research laboratories for pathogen identification in endophthalmitis and offer the possibility of rapid diagnosis, including in culture-negative cases. Intravitreal injection of antibiotics is the most important component of treatment; some cases also benefit from surgical debridement of the vitreous by a vitrectomy. The visual outcome depends partly on the pathogen: coagulase-negative staphylococcal endophthalmitis has a better prognosis than does streptococcal endophthalmitis, for example. Endophthalmitis is a medical emergency, and prompt diagnosis and treatment are essential for saving vision.

Surface Modification of Intraocular Lenses

Objective:

This paper aimed to review the current literature on the surface modification of intraocular lenses (IOLs).

Data Sources:

All articles about surface modification of IOLs published up to 2015 were identified through a literature search on both PubMed and ScienceDirect.

Study Selection:

The articles on the surface modification of IOLs were included, but those on design modification and surface coating were excluded.

Results:

Technology of surface modification included plasma, ion beam, layer-by-layer self-assembly, ultraviolet radiation, and ozone. The main molecules introduced into IOLs surface were poly (ethylene glycol), polyhedral oligomeric silsesquioxane, 2-methacryloyloxyethyl phosphorylcholine, TiO₂, heparin, F-heparin, titanium, titanium nitride, vinyl pyrrolidone, and inhibitors of cytokines. The surface modification either resulted in a more hydrophobic lens, a more hydrophilic lens, or a lens with a hydrophilic anterior and hydrophobic posterior surface. Advances in research regarding surface modification of IOLs had led to a better biocompatibility in both in vitro and animal experiments.

Conclusion:

The surface modification is an efficient, convenient, economic and promising method to improve the biocompatibility of IOLs.

Analysis of Intraocular Lens Biofilms and Fluids After Long-Term Uncomplicated Cataract Surgery

PURPOSE

Postoperative endophthalmitis is a potentially sight-threatening complication of cataract surgery. However, the pathophysiological mechanisms are not completely understood. We sought to study and evaluate the intraocular environment (aqueous and vitreous humors), the capsular tissue, and the intraocular lens (IOL) surfaces of normal eyes after long-term uncomplicated cataract surgery.

DESIGN

Experimental laboratory investigation.

METHODS

We studied 69 eyes donated for transplantation that had previously undergone cataract surgery with posterior chamber IOL implantation and that had no recorded clinical history of postoperative inflammation. We assessed the intraocular environment (DNA traces and biofilm formation) by microbiological evaluation of intraocular fluids using conventional microbiology and molecular techniques, including assessment for the presence of microbes (biofilm formation) on the IOL surface by scanning electron microscopy and ultrastructural capsular remnants by transmission electron microscopy.

RESULTS

Isolated or aggregated cocci were probable in 18.8% of IOL optic surfaces (n = 13) studied by scanning electron microscopy, suggesting the presence of bacterial biofilm. In 3 intraocular fluid samples for IOLs with biofilm, we identified 16S rDNA by polymerase chain reaction and sequencing. No microbial contamination was found in intraocular fluids by conventional microbiological methods.

CONCLUSIONS

Our data suggest the possibility of bacterial biofilm formation on the optic surface of IOLs in normal eyes after long-term uncomplicated cataract surgery even in the absence of clinical or subclinical symptoms.

Staphylococcus aureus and its Bearing on Ophthalmic Disease

PURPOSE

To review antibiotic resistance associated with S. aureus endophthalmitis and the virulence of S. aureus.

METHODS

Review of the current and prospective approaches for treating S. aureus endophthalmitis.

RESULTS

Bacterial endophthalmitis remains to be a major threat for vision. S. aureus endophthalmitis specifically, carries a poor visual prognosis making early diagnosis and treatment crucial. Methicillin resistant Staphylococcus aureus (MRSA) endophthalmitis represents a significant number of S. aureus endophthalmitis cases. MRSA with reduced susceptibility to glycopeptide antibiotics such as vancomycin (vancomycin intermediate S. aureus, VISA) have also emerged in the ocular infections, and there has been a rise in S. aureus resistance to new and old generation fluoroquinolones that are commonly used for prophylaxis after intravitreal injections and intraocular surgeries.

CONCLUSIONS

With the rise in the number of penetrating procedures in the ophthalmology practice and the parallel rise in antibiotic resistance, prophylaxis and awareness of the antimicrobial resistance profiles remain crucial and the identification of novel antimicrobials is essential.

In vitro biofilm distribution on the intraocular lens surface of different biomaterials

PURPOSE

To study the disposition of bacterial adhesion to intraocular lens (IOL) biomaterials depending on the material and region of the optic IOL surface: center or peripheral edge.

SETTING

School of Medicine, University of Barcelona, Barcelona, Spain.

DESIGN

Experimental study.

METHODS

For the in vivo study, IOLs were explanted from donor ocular globes without clinical symptoms of endophthalmitis. Biofilm formation was qualitatively studied by scanning electron microscopy (SEM). For the in vitro study, 5 IOL biomaterials (hydrophilic acrylic, hydrophobic acrylic, poly[methyl methacrylate] [PMMA], heparinized PMMA, and silicone) were contaminated with a biofilm-producing strain of Staphylococcus epidermidis. Bacterial densities were quantitatively (colony-forming units per area) compared by SEM and direct counting of viable adherent bacteria, according to the biomaterial, region of the IOL optic surface, and time of incubation. For SEM, bacterial adhesion was also qualitatively classified according to the characteristics of biofilm observed: structure, cocci per cluster, homogeneity of cluster distribution, and extracellular matrix production.

RESULTS

At 3 hours of incubation, bacterial counts for hydrophilic acrylic and PMMA IOLs were significantly lower, but at 72 hours there were no statistically significant differences among biomaterials. A higher density of bacteria was observed at the periphery of the IOL's optic of assayed biomaterials for in vitro and in vivo studies. Biofilm formation and the presence of extracellular matrix were predominantly restricted to the edges of IOL optic surface.

CONCLUSION

Bacterial adhesion and biofilm development on the IOL optic surface depended on the region and biomaterial of the IOL.

FINANCIAL DISCLOSURE

Neither author has a financial or proprietary interest in any material or method mentioned.

Biofilms in infections of the eye

The ability to form biofilms in a variety of environments is a common trait of bacteria, and may represent one of the earliest defenses against predation. Biofilms are multicellular communities usually held together by a polymeric matrix, ranging from capsular material to cell lysate. In a structure that imposes diffusion limits, environmental microgradients arise to which individual bacteria adapt their physiologies, resulting in the gamut of physiological diversity. Additionally, the proximity of cells within the biofilm creates the opportunity for coordinated behaviors through cell–cell communication using diffusible signals, the most well documented being quorum sensing. Biofilms form on abiotic or biotic surfaces, and because of that are associated with a large proportion of human infections. Biofilm formation imposes a limitation on the uses and design of ocular devices, such as intraocular lenses, posterior contact lenses, scleral buckles, conjunctival plugs, lacrimal intubation devices and orbital implants. In the absence of abiotic materials, biofilms have been observed on the capsule, and in the corneal stroma. As the evidence for the involvement of microbial biofilms in many ocular infections has become compelling, developing new strategies to prevent their formation or to eradicate them at the site of infection, has become a priority.

Biofilm Formation by Staphylococcus epidermidis on Foldable and Rigid Intraocular Lenses

Background:

Biofilm formation of Staphylococcus epidermidis is a major etiological factor of inducing device-related infections.

Objectives:

The ability of biofilm formation by the S. epidermidis was assessed in vitro on two brands of foldable (hydrophilic) and two brands of rigid (hydrophobic) intraocular lens materials in order to investigate the role of lens material in postoperative endophthalmitis.

Materials and Methods:

To ensure reproducibility of biofilm formation on intraocular lenses, two strains of S. epidermidis and three quantification methods were performed. The S. epidermidis strains, DSMZ3270 (biofilm-producer) and ATCC12228 (non-biofilm-producer) were applied. Organisms were cultivated on disks of different brands of foldable hydrophilic Intra Ocular Lens (IOL) made of acrylic (Didar, Iran; (A) and Omni, India; (B)), and rigid hydrophobic IOL made of polymethyl methacrylate (PMMA; Didar, Iran; (C) and Hexavision, France; (D)). Biofilms were stained with crystal violet (CV) dye, which is an index of biofilm formation. The bacterial population was counted after biofilm homogenization. Scanning electron microscopy (SEM) was performed to examine the extent of biofilm formation.

Results:

Adherence of DSMZ3270 strain on both types of foldable and rigid IOLs, was significantly more than ATCC12228 (P < 0.001-0.05 and, P < 0.01-0.05, respectively). The bacterial populations between the lenses were significantly different (P < 0.05). Subsequent studies demonstrated significant differences between brands of foldable and PMMA IOLs. According to statistical analyses the incubation time influenced the biofilm formation on both types of IOLs which meant that by increasing incubation time, the biofilm formation increased. According to the SEM pictures, biofilm seems to be lysed at 72 hours.

Conclusions:

These data demonstrated that the attachment of bacteria to hydrophilic acrylic IOLs was more than hydrophobic PMMA ones independent of the brand. According to these results the bacterial strain might have more hydrophilic properties. Augmenting the biomass of biofilm by passing of time demonstrated the key role of time in biofilm formation on the IOL surfaces. The differences between IOL brands in the biofilm formation indicated the influence of design parameters for IOLs.

Calculation of intraocular lens surface free energy and its components from contact angle measurements

One of the most important biomaterial characteristics involved in bacterial adhesion on intraocular lenses (IOLs) is hydrophobicity. We calculated the hydrophobicity parameters of IOLs made of 6 different materials (polymethylmethacrylate, PMMA, heparin surface-modified PMMA, HSM-PMMA, silicone, hydrophilic and hydrophobic acrylics and collamer). Values of IOL surface free energy components were determined from contact angle measurements, using the Fowkes, Owens-Wendt and Good-van Oss calculations. Contact angles were higher for silicone and hydrophobic acrylic materials and lower for collamer and hydrophilic acrylic materials. The values of IOL surface free energy components obtained with the 3 different calculations were homogenous. According to the Owens-Wendt calculation, the IOLs could be separated into dispersive implants (hydrophobic acrylic, silicone and PMMA) and polar implants (collamer, hydrophilic acrylic and HSM-PMMA).

Staphylococcus epidermidis with the icaA⁻/icaD⁻/IS256⁻ genotype and protein or protein/extracellular-DNA biofilm is frequent in ocular infections

In ocular infections (OIs) caused by Staphylococcus epidermidis, biofilms composed mainly of poly-N-acetylglucosamine (PNAG) have been widely studied, but PNAG-independent biofilms have not. Therefore, we searched for a relationship between the ica operon (involved in PNAG-biofilm) and the biochemical composition of biofilms in isolates from OI. Isolates from OI (n = 62), from healthy conjunctiva (HC; n = 45) and from healthy skin (HS; n = 53), were used to detect icaA and icaD genes, and the insertion sequence 256 (IS256) using PCR. The compositions of the biofilms were determined by treatment with NaIO₄, proteinase K and DNase I. Multilocus sequence typing (MLST) was performed to characterize the isolates, and the expression of aap and embp genes was determined by real-time qPCR. A strong relationship between the icaA(-)/icaD(-)/IS256(-) genotype and protein- or protein/extracellular DNA (eDNA)-biofilm composition was found in the isolates from OI (53.6%), whereas the icaA(+)/icaD(+)/IS256(-) genotype and carbohydrate-biofilm was most prevalent in isolates from HC (25%) and HS (25%). Isolates with an icaA(-)/icaD(-)/IS256(-) genotype and protein-biofilm phenotype were predominantly of the ST2 lineage, while carbohydrate-biofilm-producing strains were mainly of the ST9 lineage. The protein-biofilm-producing strains had higher expression levels of aap gene than carbohydrate-biofilm-producing strains; while embp gene did not have the same pattern of expression. These results suggest that S. epidermidis strains with icaA(-)/icaD(-)/IS256(-) genotype and protein- or protein/eDNA-biofilms have a stronger ability to establish in the eye than S. epidermidis strains with icaA(+)/icaD(+)/IS256(-) genotype and PNAG-biofilms.

Staphylococcus epidermidis biofilm formation and structural organization on different types of intraocular lenses under in vitro flow conditions

AIM

To compare the adherence and structural organization of Staphylococcus epidermidis biofilm on intraocular lenses (IOLs).

METHODS

IOLs made of 3 different biomaterials [polymethyl methacrylate (PMMA), hydrophilic acrylic or hydrophobic acrylic] were incubated into an S. epidermidis bacterial solution. Scanning electron microscopy was used to count the bound bacteria and to analyze the structural biofilm architecture.

RESULTS

After 4-6 h of incubation, adherence was statistically weakest on the hydrophilic acrylic polymer. On the hydrophobic acrylic material, the bacterial cells tended to cover the substratum in a horizontal spread in a continuous monolayer. On the hydrophilic acrylic material or on the PMMA material bacterial cells tended to form only few, small scattered cell clusters.

CONCLUSIONS

The data suggest that the pattern of S. epidermidis adhesion varies with the IOL biomaterial. Hydrophobic IOLs seem to be more permissive to S. epidermidis adhesion.

Bacterial endophthalmitis in the age of outpatient intravitreal therapies and cataract surgeries: host-microbe interactions in intraocular infection

Bacterial endophthalmitis is a sight threatening infection of the interior structures of the eye. Incidence in the US has increased in recent years, which appears to be related to procedures being performed on an aging population. The advent of outpatient intravitreal therapy for management of age-related macular degeneration raises yet additional risks. Compounding the problem is the continuing progression of antibiotic resistance. Visual prognosis for endophthalmitis depends on the virulence of the causative organism, the severity of intraocular inflammation, and the timeliness of effective therapy. We review the current understanding of the pathogenesis of bacterial endophthalmitis, highlighting opportunities for the development of improved therapeutics and preventive strategies.

Cell adhesion and glistening formation in hybrid copolymer intraocular lenses

The purpose of this study is to investigate the cell adhesion and glistening formation properties of various foldable intraocular lenses (IOLs) in vitro. Three conventional hydrophobic methacrylate acrylic (MA) IOLs, a hydrophilic hydroxyethyl methacrylate (HEMA) IOL and a hybrid MA/HEMA copolymer IOL were investigated for immunologically activated cell adhesion and for formation of glistenings resulting from cavitation, by analysis of digital images using NIH Image J PC software. The MA IOLs exhibited a low level of adhering cells but a high level of glistening formation, the HEMA IOL exhibited the reverse tendency, and the MA/HEMA IOL exhibited a low level of both, thus indicating that hybrid MA/HEMA IOLs are less susceptible than HEMA IOLs to cell adhesion and less susceptible than MA IOLs to glistening formation.

[Intraocular lens and bacterial adhesion: influence of the environmental factors, the characteristics of the bacteria, and the target material surface]

Adhesion of bacteria to intraocular lenses is an important step in the pathogenesis of postoperative endophthalmitis. It can be described as a two-phase process including an initial, instantaneous, and reversible phase followed by a time-dependant and irreversible molecular and cellular phase. The binding of bacteria is affected by many factors including environmental factors such as medium composition, presence of proteins and flow conditions, the bacterial cell surface characteristics, and the material's surface properties. This article reviews all these factors affecting the adhesion of bacteria to intraocular lenses. A better understanding of these mechanisms would make it possible to reduce the bacterial adhesion process and thus could help decrease the incidence of postoperative endophthalmitis.

Increased resistance of contact lens-related bacterial biofilms to antimicrobial activity of soft contact lens care solutions

PURPOSE

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.

METHODS

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.

RESULTS

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.

CONCLUSION

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.

[Intraocular lens and cataract surgery: comparison between bacterial adhesion and risk of postoperative endophthalmitis according to intraocular lens biomaterial]

Cataract surgery is a usually successful procedure that restores vision by replacing the natural lens with an intraocular lens (IOL). Acute postoperative endophthalmitis is still one of the most serious complications of cataract surgery. Its incidence has been reported to be between 0.04% and 0.32%. Precisely why bacteria induce endophthalmitis is not entirely understood. Indeed the risk of its development may be influenced by several factors. Among them, bacterial adhesion to the IOL has been recently emphasized in the ophthalmology literature. Indeed, the ability of an organism to adhere to the IOL surface is believed to be associated with a risk of infection at the implantation site. Several studies have demonstrated that bacterial adhesion is influenced by IOL materials. Ever since, numerous studies have investigated the interactions between bacteria and different types of IOLs to determine which biomaterial would be most permissive to bacterial adherence. This article reviews all the epidemiological and experimental data relating to the study of the relationship between bacterial adhesion, IOL material, and risk of developing postoperative endophthalmitis. Even if discrepancies between these studies exist, mainly stemming from the use of different experimental conditions and protocols, it seems that bacterial adhesion is strongly influenced by IOL material. Epidemiological studies suggest that the implantation of silicone IOLs might be associated with increased rates of endophthalmitis. Experimental studies reach similar conclusions showing that hydrophobic IOLs such as silicone or acrylic hydrophobic IOLs are more permissive to bacterial adhesion and growth than hydrophilic IOLs such as acrylic hydrophilic IOLs. Among the interactions that govern bacterial attachment to the IOLs, it seems that hydrophilic-hydrophobic interactions have the greatest influence. Nevertheless, since bacterial adhesion is a complicated process affected by many factors, the conclusions drawn by these results have to be interpreted with care. Further investigations are still needed to understand the connections between IOL material and endophthalmitis.