Foundational concepts in the biology of bacterial keratitis

Research progress on the correlation between corneal neovascularization and lymphangiogenesis (Review)

The cornea is a clear connective tissue membrane at the front of the outer layer of the eyeball wall. It plays a crucial role in the refractive system of the eyeball, making it essential to maintain its transparency. Neovascularization and lymphangiogenesis in the cornea significantly impact corneal transparency and immune privilege. The growth of corneal neovascularization (CNV) and corneal lymphangiogenesis (CL) vessels is interconnected yet independent. Currently, there is a substantial amount of clinical and experimental research on CNV and CL vessels. However, due to the relatively recent focus on CL vessel research compared with CNV research, most scholars tend to concentrate on CNV, with few articles offering a comprehensive comparison and discussion of the two processes. The present review emphasizes the similarities and differences between CNV and CL and summarizes recent research progress on their correlation in animal models, growth characteristics, cytokine effects and related diseases.

Predisposing factors, clinical and microbiological insights of bacterial keratitis: analysis of 354 cases from a leading French academic centre

AIMS

To report an epidemiological update of bacterial keratitis (BK) in a tertiary ophthalmology centre over 20 months compared with a previous study on the same timeframe from 1998 to 1999.

METHODS

354 patients with BK documented by microbiological corneal scraping or resolutive under antibiotics treatment from January 2020 to September 2021 were analysed retrospectively.

RESULTS

One or several risk factors were found in 95.2% of patients: contact lens wear (45.2%), ocular surface disease (25.0%), systemic disease (21.8%), ocular trauma (11.9%) and ocular surgery (8.8%). The positivity rate of corneal scrapings was 82.5%, with 18.2% polybacterial. One hundred seventy-five (59.9%) bacteria were Gram-negative, and 117 (40.1%) were Gram-positive. The most common bacteria were Pseudomonas aeruginosa (32.5%), Moraxella spp (18.1%) and Staphylococcus aureus (8.2%). Final visual acuity (logarithm of the minimum angle of resolution) was associated with age (r=+0.48; p=0.0001), infiltrate size (r=+0.32; p<0.0001), ocular surface disease (r=+0.13; p=0.03), ocular trauma (r=-0.14; p=0.02) and contact lens wear (r=-0.26; p<0.0001). Gram-negative bacteria were responsible for deeper (r=+0.18; p=0.004) and more extensive infiltrates (r=+0.18; p=0.004) in younger patients (r=-0.19; p=0.003). Compared with the previous period, the positivity rate of corneal scrapings and the proportion of Gram-negative bacteria, especially Moraxella spp, increased. All P. aeruginosa and Moraxella spp were sensitive to quinolones, and all S. aureus were sensitive to both quinolones and methicillin.

CONCLUSION

Contact lens wear remained the leading risk factor. The bacteria distribution was reversed, with a predominance of Gram-negative bacteria and increased Moraxella spp.

[Bacterial keratitis: Retrospective and prospective 2024]

Bacterial keratitis (BK) is an infection of the cornea caused by one or more bacteria. Contact lens wear is the main risk factor. Staphylococcus and Pseudomonas are the most frequently isolated pathogens in developed countries. BK requires a standardized work-up to avoid diagnostic and therapeutic delays that may negatively affect visual prognosis. Corneal signs, the speed at which lesions progress and the presence of risk factors allow the clinician to presume an empirical microbiological diagnosis, but corneal scraping, which allows the isolation and identification of the bacteria involved in the infection, is the only way to confirm the diagnosis. The type of antibiotic treatment depends on the severity of the lesions, the risk factors involved, and the bacteria identified. Corticosteroids have been shown to be effective as adjuvant therapy and may be used under certain well-defined circumstances. Surgical treatment is sometimes necessary.

Engineered PVA-tamarind gum-based biocomposite for sustained ophthalmic delivery of moxifloxacin: Effect of nanocellulose on physicochemical, mechanoelectrical and permeation kinetics

Widely used polysaccharide-based films in ophthalmic drug delivery have major limitations of inadequate mechanical strength, poor electrical conductivity, and insufficient ocular drug permeability. Moxifloxacin (MFX) biocomposite film of adequate mechanoelectrical properties was developed for sustained ophthalmic drug delivery. Nanocellulose (NC) incorporated (2.5, 5.0, 7.5, and 10.0 %) PVA-tamarind gum-based moxifloxacin composite was prepared using solvent casting method. The addition of NC improved the mechanical properties of the film, demonstrating its ability to strengthen the structure. Stress relaxation (SR) of the film has been augmented (64.67±7.55 to 73.15±0.34 %) due to increased content of NC (0 to 10 %) respectively. Film containing 5 % NC showed the critical edge of tensile strength (11.9±0.39 MPa), and also the threshold limit of electrical conductivity (4.5*107 Ω). The same film exhibited continued drug release as well as erosion-controlled sustained ocular permeation (pH 7.4) and revealed the highest antibacterial activity (ZOI of disc diffusion, cm) with Pseudomonas aeruginosa (4.63±0.15) and Staphylococcus aureus (4.30±0.26) of MFX (≈224 μg). Notably, incorporating NC produced non-irritating and safe for corneal delivery as confirmed by the Draize model test. Our findings suggested that the NC-containing PVA-tamarind gum-based composite film holds a promising approach for sustained ophthalmic delivery of MFX.

Advancements in Hydrogels for Corneal Healing and Tissue Engineering

Hydrogels have garnered significant attention for their versatile applications across various fields, including biomedical engineering. This review delves into the fundamentals of hydrogels, exploring their definition, properties, and classification. Hydrogels, as three-dimensional networks of crosslinked polymers, possess tunable properties such as biocompatibility, mechanical strength, and hydrophilicity, making them ideal for medical applications. Uniquely, this article offers original insights into the application of hydrogels specifically for corneal tissue engineering, bridging a gap in current research. The review further examines the anatomical and functional complexities of the cornea, highlighting the challenges associated with corneal pathologies and the current reliance on donor corneas for transplantation. Considering the global shortage of donor corneas, this review discusses the potential of hydrogel-based materials in corneal tissue engineering. Emphasis is placed on the synthesis processes, including physical and chemical crosslinking, and the integration of bioactive molecules. Stimuli-responsive hydrogels, which react to environmental triggers, are identified as promising tools for drug delivery and tissue repair. Additionally, clinical applications of hydrogels in corneal pathologies are explored, showcasing their efficacy in various trials. Finally, the review addresses the challenges of regulatory approval and the need for further research to fully realize the potential of hydrogels in corneal tissue engineering, offering a promising outlook for future developments in this field.

Liquiritin Alleviates Inflammation in Lipopolysaccharide-Induced Human Corneal Epithelial Cells

PURPOSE

This research was designed to elucidate the anti-inflammatory impacts of liquiritin on lipopolysaccharide (LPS)-activated human corneal epithelial cells (HCECs).

METHODS

The Cell Counting kit-8 (CCK-8) assay was adopted to assess cell viability. The enzyme-linked immunosorbent assay (ELISA) was used to detect the secretion levels of the proinflammatory cytokines IL-6, IL-8, and TNF-α. Transcriptome analysis was conducted to identify the genes that exhibited differential expression between different treatment. The model group included cells treated with LPS (10 µg/mL), the treatment group comprised cells treated with liquiritin (80 µM) and LPS (10 µg/mL), and the control group consisted of untreated cells. To further validate the expression levels of the selected genes, including CSF2, CXCL1, CXCL2, CXCL8, IL1A, IL1B, IL24, IL6, and LTB, quantitative real-time PCR was performed. The expression of proteins related to the Akt/NF-κB signaling pathway was assessed through western blot analysis. NF-κB nuclear translocation was evaluated through immunofluorescence staining.

RESULTS

The secretion of IL-6, IL-8, and TNF-α in LPS-induced HCECs was significantly downregulated by liquiritin. Based on the transcriptome analysis, the mRNA expression of pro-inflammatory cytokines, namely IL-6, IL-8, IL-1β, IL-24, TNF-α, and IL-1α was overproduced by LPS stimulation, and suppressed after liquiritin treatment. Furthermore, the Western blot results revealed a remarkable reduction in the phosphorylation degrees of NF-κB p65, IκB, and Akt upon treatment with liquiritin. Additionally, immunofluorescence analysis confirmed liquiritin's inhibition of LPS-induced p65 nuclear translocation.

CONCLUSIONS

Collectively, these findings imply that liquiritin suppresses the expression of proinflammatory cytokines, and the anti-inflammatory impacts of liquiritin may be caused by its repression of the Akt/NF-κB signaling pathway in LPS-induced HCECs. These data indicate that liquiritin could provide a potential therapeutic application for inflammation-associated corneal diseases.

Frequency and Outcome of Emergency Penetrating Keratoplasty in Infectious Keratitis in Sweden During the 21st Century

PURPOSE

To study the frequency over time and outcome of penetrating keratoplasty (PK), "keratoplasty à chaud," in patients with infectious keratitis with 2-year follow-up data.

METHODS

This register-based study included keratitis cases that had undergone PK in Sweden between 2001 and 2020 and reported to the Swedish Corneal Transplant Register.

RESULTS

During the study period, 69 eyes were subjected to acute PK due to progressive infectious keratitis. The number increased from 2 annual procedures in the first half of the study period to 5 in the second half (P = 0.01). Preoperative corneal perforation was present in 43.5% (n = 30) of the eyes. Two years after surgery, follow-up data were completed in the register for 53 eyes; of these, 62.3% (n = 33) were considered to have functioning grafts, and 20.8% (n = 11) had experienced a rejection episode. The visual acuity improved from hand motion to counting fingers (P = 0.002), and the proportion of eyes with a visual acuity of ≤1.0 logMAR increased from 5.7% (n = 3) before the surgery to 45.3% (n = 24) at the 2-year follow-up (P < 0.001).

CONCLUSIONS

The number of active infectious keratitis cases undergoing keratoplasty à chaud increased in Sweden during the 21st century. Most of the cases were successful regarding the structural integrity of the bulb, that is, "had a saved eye" and even a functioning graft 2 years after corneal transplantation. The visual gain was distinct, albeit modest. In cases with severe infectious keratitis, and even a concomitant perforation in the cornea due to the infection, corneal transplantation should continue to be an option.

Thermosensitive Polyhedral Oligomeric Silsesquioxane Hybrid Hydrogel Enhances the Antibacterial Efficiency of Erythromycin in Bacterial Keratitis

Bacterial keratitis is a serious ocular infection that can impair vision or even cause blindness. The clinical use of antibiotics is limited due to their low bioavailability and drug resistance. Hence, there is a need to develop a novel drug delivery system for this infectious disease. In this study, erythromycin (EM) was encapsulated into a bifunctional polyhedral oligomeric silsesquioxane (BPOSS) with the backbone of the poly-PEG/PPG urethane (BPEP) hydrogel with the aim of improving the drug efficiency in treating bacterial keratitis. A comprehensive characterization of the BPEP hydrogel was performed, and its biocompatibility was assessed. Furthermore, we carried out the evaluation of the antimicrobial effect of the BPEP-EM hydrogel in S. aureus keratitis using in vivo mouse model. The BPEP hydrogel exhibited self-assembling and thermogelling properties, which assisted the drug loading of drug EM and improved its water solubility. Furthermore, the BPEP hydrogel could effectively bind with mucin on the ocular surface, thereby markedly prolonging the ocular residence time of EM. In vivo testing confirmed that the BPEP-EM hydrogel exerted a potent therapeutic action in the mouse model of bacterial keratitis. In addition, the hydrogel also exhibited an excellent biocompatibility. Our findings demonstrate that the BPEP-EM hydrogel showed a superior therapeutic effect in bacterial keratitis and demonstrated its potential as an ophthalmic formulation.

Nitroreductase-responsive nanoparticles for in situ fluorescence imaging and synergistic antibacterial therapy of bacterial keratitis

As bacterial keratitis progresses rapidly, prompt intervention is necessary. Current diagnostic processes are time-consuming and invasive, leading to improper antibiotics for treatment. Therefore, innovative strategies for diagnosing and treating bacterial keratitis are urgently needed. In this study, Cu2-xSe@BSA@NTRP nanoparticles were developed by loading nitroreductase-responsive probes (NTRPs) onto Cu2-xSe@BSA. These nanoparticles exhibited integrated fluorescence imaging and antibacterial capabilities. In vitro and in vivo experiments showed that the nanoparticles produced responsive fluorescence signals in bacteria within 30 min due to an interaction between the released NTRP and bacterial endogenous nitroreductase (NTR). When combined with low-temperature photothermal therapy (PTT), the nanoparticles effectively eliminated E. coli and S. aureus, achieved antibacterial efficacy above 95% and facilitated the re-epithelialization process at the corneal wound site in vivo. Overall, the Cu2-xSe@BSA@NTRP nanoparticles demonstrated potential for rapid, noninvasive in situ diagnosis, treatment, and visualization assessment of therapy effectiveness in bacterial keratitis.

Iron-doped nanozymes with spontaneous peroxidase-mimic activity as a promising antibacterial therapy for bacterial keratitis

The development of non-antibiotic pharmaceuticals with biocompatible and efficient antibacterial properties is of great significance for the treatment of bacterial keratitis. In this study, we have developed antibacterial iron-doped nanozymes (Fe3+-doped nanozymes, FNEs) with distinguished capacity to fight against bacterial infections. The iron-doped nanozymes are composed of Fe3+ doped zeolitic imidazolate framework-8 (Fe/ZIF-8) and polyethylene imide (PEI), which were functionally coated on the surface of Fe/ZIF-8 and imparted the FNEs with improved water dispersibility and biocompatibility. FNEs possess a significant spontaneous peroxidase-mimic activity without the need for external stimulation, thus elevating cellular reactive oxygen species level by catalyzing local H2O2 at the infection site and resulting in bacteria damaged to death. FNEs eliminated 100% of Staphylococcus aureus within 6 h, and significantly relieved inflammation and bacterial infection levels in mice bacterial keratitis, exhibiting higher bioavailability and a superior therapeutic effect compared to conventional antibiotic eye drops. In addition, the FNEs would not generate drug resistance, suggesting that FNEs have great potential in overcoming infectious diseases caused by antimicrobial resistant bacteria.

Spectrum and antibiotic sensitivity of bacterial keratitis: a retrospective analysis of eight years in a Tertiary Referral Hospital in Southwest China

Purpose

The objective of this study was to investigate the epidemiological characteristics, distribution of isolates, prevailing patterns, and antibiotic susceptibility of bacterial keratitis (BK) in a Tertiary Referral Hospital located in Southwest China.

Methods

A retrospective analysis was conducted on 660 cases of bacterial keratitis occurring between January 2015 and December 2022. The demographic data, predisposing factors, microbial findings, and antibiotic sensitivity profiles were examined.

Results

Corneal trauma emerged as the most prevalent predisposing factor, accounting for 37.1% of cases. Among these cases, bacterial culture results were positive in 318 cases, 68 species of bacteria were identified. The most common Gram-Positive bacteria isolated overall was the staphylococcus epidermis and the most common Gram-Negative bacteria isolated was Pseudomonas aeruginosa. Methicillin-Resistant Staphylococci accounted for 18.1% of all Gram-Positive bacteria. The detection rate of P. aeruginosa showed an increasing trend over time (Rs=0.738, P=0.037). There was a significant decrease in the percentage of Gram-Negative microorganisms over time (Rs=0.743, P=0.035). The sensitivity of Gram-Positive bacteria to linezolid, vancomycin, tigecycline, quinupristin/dalfopristin, and rifampicin was over 98%. The sensitivity rates of Gram-Negative bacteria to amikacin, meropenem, piperacillin/tazobactam, cefoperazone sodium/sulbactam, ceftazidime, and cefepime were all above 85%. In patients with a history of vegetative trauma, the possibility of BK should be taken into account in addition to the focus on fungal keratitis.

Conclusion

The microbial composition primarily consists of Gram-Positive cocci and Gram-Negative bacilli. Among the Gram-Positive bacteria, S. epidermidis and Streptococcus pneumoniae are the most frequently encountered, while P. aeruginosa is the predominant Gram-Negative bacteria. To combat Gram-Positive bacteria, vancomycin, linezolid, and rifampicin are considered excellent antimicrobial agents. When targeting Gram-Negative pathogens, third-generation cephalosporins exhibit superior sensitivity compared to first and second-generation counterparts. As an initial empirical treatment for severe cases of bacterial keratitis and those unresponsive to fourth-generation fluoroquinolones in community settings, the combination therapy of vancomycin and tobramycin is a justifiable approach. Bacterial keratitis can be better managed by understanding the local etiology and antibacterial drug susceptibility patterns.

Fulminant Eye Infection in a Patient With Nephrotic Syndrome: A Case Report

This case report presents the clinical course of a 53-year-old male farmer with nephrotic syndrome, specifically focal segmental glomerulosclerosis, who developed a fulminant eye infection. While receiving maintenance hemodialysis and immunosuppressive therapy, the patient presented with sudden onset redness, discharge, and decreased vision in his right eye. Initial management with topical antibiotics and steroids failed to halt the progression of the infection, leading to corneal perforation and iris prolapse within a few days. Despite the discontinuation of immunosuppressive medications and initiation of broad-spectrum antimicrobial therapy, the patient's compromised renal function and anaemia precluded surgical intervention. This case underscores the challenges in managing severe ocular infections in immunocompromised patients. It highlights the importance of early recognition, aggressive antimicrobial therapy, and close ophthalmologic monitoring in preventing sight-threatening complications. Despite intensive management, the prognosis for visual recovery in such cases may be poor, emphasizing the need for preventive strategies and careful surveillance in high-risk patient populations.

Ferroptosis as a Potential Therapeutic Target for Reducing Inflammation and Corneal Scarring in Bacterial Keratitis

Purpose

Bacterial keratitis (BK) is a serious ocular infection that can cause severe inflammation and corneal scarring, leading to vision loss. In this study, we aimed to investigate the involvement of ferroptosis in the pathogenesis of BK.

Methods

Transcriptome analysis was performed to evaluate ferroptosis-related gene expression in human BK corneas. Subsequently, the ferroptosis in mouse models of Pseudomonas aeruginosa keratitis and corneal stromal stem cells (CSSCs) were validated. The mice were treated with levofloxacin (LEV) or levofloxacin combined with ferrostatin-1 (LEV+Fer-1). CSSCs were treated with lipopolysaccharide (LPS) or LPS combined Fer-1. Inflammatory cytokines, α-SMA, and ferroptosis-related regulators were evaluated by RT-qPCR, immunostaining, and Western blot. Iron and reactive oxygen species (ROS) were measured.

Results

Transcriptome analysis revealed significant alterations in ferroptosis-related genes in human BK corneas. In the BK mouse models, the group treated with LEV+Fer-1 exhibited reduced inflammatory cytokines (MPO, TNF-α, and IFN-γ), decreased corneal scarring and α-SMA expression, and lower Fe3+ compared to the BK and LEV groups. Notably, the LEV+Fer-1 group showed elevated GPX4 and SLC7A11 in contrast to the BK and LEV group. In vitro, Fer-1 treatment effectively restored the alterations of ROS, Fe2+, GPX4, and SLC7A11 induced by LPS in CSSCs.

Conclusions

Ferroptosis plays a crucial role in the pathogenesis of BK. The inhibition of ferroptosis holds promise for mitigating inflammation, reducing corneal scarring, and ultimately enhancing the prognosis of BK. Consequently, this study provides a potential target for innovative therapeutic strategies for BK, which holds immense potential to transform the treatment of BK.

Carboxylated nanofibrillated cellulose empowers moxifloxacin to overcome Staphylococcus aureus biofilm in bacterial keratitis

Bacterial keratitis is one of the vision-threatening ocular diseases that is increasing at an alarming rate due to antimicrobial resistance. One of the primary causes of antimicrobial resistance could be biofilm formation, which alters the mechanism and physiology of the microorganisms. Even a potent drug fails to inhibit biofilm due to the extracellular polysaccharide matrix surrounding the bacteria, inhibiting the permeation of drugs. Therefore, we aimed to develop carboxylated nanocellulose fibers loaded with moxifloxacin (Mox-cNFC) as a novel drug delivery system to treat bacterial corneal infection. Nanocellulose fibers were fabricated using a two-step method involving citric acid hydrolysis followed by TEMPO oxidation to introduce carboxylated groups (1.12 mmol/g). The Mox-cNFC particles showed controlled drug release till 40 h through diffusion. In vitro biofilm inhibition studies showed the particle's ability to disrupt the biofilm matrix and enhance the drug penetration to achieve optimal concentrations that inhibit the persister cells (without increasing minimum inhibitory concentration), thereby reducing the bacterial drug-resistant property. In vivo studies revealed the therapeutic potential of Mox-cNFC to treat Staphylococcus aureus-induced bacterial keratitis with once-a-day treatment, unlike neat moxifloxacin. Mox-cNFC could improve patient compliance by reducing the frequency of instillation and a controlled drug release to prevent toxicity.

Transcriptional profiling specifies the pathogen-specific human host response to infectious keratitis

Purpose

Corneal infections are a leading cause of visual impairment and blindness worldwide. Here we applied high-resolution transcriptomic profiling to assess the general and pathogen-specific molecular and cellular mechanisms during human corneal infection.

Methods

Clinical diagnoses of herpes simplex virus (HSV) (n=5) and bacterial/fungal (n=5) keratitis were confirmed by histology. Healthy corneas (n=7) and keratoconus (n=4) samples served as controls. Formalin-fixed, paraffin-embedded (FFPE) human corneal specimens were analyzed using the 3' RNA sequencing method Massive Analysis of cDNA Ends (MACE RNA-seq). The cellular host response was investigated using comprehensive bioinformatic deconvolution (xCell and CYBERSORTx) analyses and by integration with published single cell RNA-seq data of the human cornea.

Results

Our analysis identified 216 and 561 genes, that were specifically overexpressed in viral or bacterial/fungal keratitis, respectively, and allowed to distinguish the two etiologies. The virus-specific host response was driven by adaptive immunity and associated molecular signaling pathways, whereas the bacterial/fungal-specific host response mainly involved innate immunity signaling pathways and cell types. We identified several genes and pathways involved in the host response to infectious keratitis, including CXCL9, CXCR3, and MMP9 for viral, and S100A8/A9, MMP9, and the IL17 pathway for bacterial/fungal keratitis.

Conclusions

High-resolution molecular profiling provides new insights into the human corneal host response to viral and bacterial/fungal infection. Pathogen-specific molecular profiles may provide the foundation for novel diagnostic biomarker and therapeutic approaches that target inflammation-induced damage to corneal host cells with the goal to improve the outcome of infectious keratitis.

Depth, size of infiltrate, and the microbe - The trio that prognosticates the outcome of infective keratitis

PURPOSE

To analyze the influence of infiltrate size, depth, and organism on the outcome of microbial keratitis.

DESIGN

Retrospective comparative study.

METHODS

Medical records of patients with infective keratitis, who reported from January 2015 to December 2019 to a tertiary eye care center, were analyzed. Size and depth of ulcer at presentation were the factors used to group patients, and the influence on the outcome of the organism causing it was analyzed. Grouping was as follows: group A: ulcer size <6 mm/anterior to midstromal infiltrate, group B: ulcer < 6 mm/full-thickness infiltrate, group C: ulcer >6 mm/anterior to midstromal infiltrate, group D: ulcer > 6 mm/full-thickness infiltrate. Patients with viral keratitis or unidentified organism were excluded. Response to treatment and best-corrected visual acuity (BCVA) at the final follow-up were the outcome measures.

RESULTS

In the study, 1117/6276 patients were included, with 60.8% patients in group A. A significant improvement in visual acuity was noted in groups A/B compared to groups C/D. Group A had the best response to medical management, irrespective of the organism. Higher risk for surgery was noted in group C compared to group B, with group A as the reference. Overall resolution with medical treatment was noted in 70% miscellaneous keratitis, 64.8% bacterial keratitis, 64.3% mixed keratitis, 62.5% acanthamoeba keratitis, 52.6% fungal keratitis, and 12.1% Pythium keratitis. Bacteria and acanthamoeba responded better to medical management than fungal keratitis, whereas Pythium had the highest risk for surgery.

CONCLUSION

An interplay between virulence of the organism along with depth and size of the infiltrate determines the outcome of microbial keratitis.

Targeted Bacterial Keratitis Treatment with Polyethylene Glycol-Dithiothreitol-Boric Acid Hydrogel and Gatifloxacin

INTRODUCTION/OBJECTIVE

To prolong the ocular residence time of gatifloxacin and enhance its efficacy against bacterial keratitis, this study developed a velocity-controlled polyethylene glycol-dithiothreitol-boric acid (PDB) hydrogel loaded with gatifloxacin.

METHODS

First, the basic properties of the synthesized PDB hydrogel and the gatifloxacin-loaded PDB hydrogel were assessed. Secondly, the in vitro degradation rate of the drug-loaded PDB was measured in a simulated body fluid environment with pH 7.4/5.5. The release behavior of the drug-loaded PDB was studied using a dialysis method with PBS solution of pH 7.4/5.5 as the release medium. Finally, a mouse model of bacterial keratitis was established, and tissue morphology was observed using hematoxylin-eosin staining. Additionally, mouse tear fluid was extracted to observe the antibacterial effect of the gatifloxacin-loaded PDB hydrogel.

RESULTS

The results showed that the PDB hydrogel had a particle size of 124.9 nm and a zeta potential of -23.3 mV, with good porosity, thermosensitivity, viscosity distribution, rheological properties, and high cell compatibility. The encapsulation of gatifloxacin did not alter the physical properties of the PDB hydrogel and maintained appropriate swelling and stability, with a high drug release rate in acidic conditions. Furthermore, animal experiments demonstrated that the gatifloxacin- loaded PDB hydrogel exhibited superior therapeutic effects compared to gatifloxacin eye drops and displayed strong antibacterial capabilities against bacterial keratitis.

CONCLUSION

This study successfully synthesized PDB hydrogel and developed a gatifloxacin drug release system. The hydrogel exhibited good thermosensitivity, pH responsiveness, stability, and excellent biocompatibility, which can enhance drug retention, utilization, and therapeutic effects on the ocular surface.

Tacrolimus Ointment in Periorbital Atopic Dermatitis

Periorbital atopic dermatitis (AD) is a common sign in ophthalmological practice and usually has a persistent and relapsing course. Treatment with topical corticosteroids has various side effects associated with their usage. Tacrolimus topical ointment has unique immunomodulatory properties that decrease skin inflammation and pruritus in AD. In this case series, we present a prospective case series of five patients (three males and two females) who received topical application of tacrolimus ointment 0.1-0.03% in the periorbital area twice daily for one to four weeks. The pre- and post-treatment images of all patients were recorded to compare the effects of the treatment. The cases were selected from patients attending the outpatient clinics of East Jeddah Hospital, Saudi Arabia. All patients were suffering from AD. Patients underwent a clinical assessment by tactile inspection (location, size, color, and surface condition) in the first week, secondweek, third month, and first year. We may conclude from this study that tacrolimus showed promising outcomes and is safe and effective for the treatment of flares or resistant periorbital AD in both adults and children.

Design of phenothiazine-based cationic amphiphilic derivatives incorporating arginine residues: Potential membrane-active broad-spectrum antimicrobials combating pathogenic bacteria in vitro and in vivo

Multidrug-resistant bacteria infections pose an increasingly serious threat to human health, and the development of antimicrobials is far from meeting the clinical demand. It is urgent to discover and develop novel antibiotics to combat bacterial resistance. Currently, the development of membrane active antimicrobial agents is an attractive strategy to cope with antimicrobial resistance issues. In this study, the synthesis and biological evaluation of cationic amphiphilic phenothiazine-based derivatives were reported. Among them, the most promising compound 30 bearing a n-heptyl group and two arginine residues displayed potent bactericidal activity against both Gram-positive (MICs = 1.56 μg/mL) and Gram-negative bacteria (MICs = 3.125-6.25 μg/mL). Compound 30 showed low hemolysis activity (HC50 = 281.4 ± 1.6 μg/mL) and low cytotoxicity (CC50 ＞ 50 μg/mL) toward mammalian cells, as well as excellent salt resistance. Compound 30 rapidly killed bacteria by acting on the bacterial cell membrane and appeared less prone to resistance. Importantly, compound 30 showed potent in vivo efficacy in a murine model of bacterial keratitis. Hence, the results suggested compound 30 has a promising prospect as a broad-spectrum antibacterial agent for the treatment of drug-resistant bacterial infections.

Nanomedicine for the Detection and Treatment of Ocular Bacterial Infections

Ocular bacterial infection is a prevalent cause of blindness worldwide, with substantial consequences for normal human life. Traditional treatments for ocular bacterial infections areless effective, necessitating the development of novel techniques to enable accurate diagnosis, precise drug delivery, and effective treatment alternatives. With the rapid advancement of nanoscience and biomedicine, increasing emphasis has been placed on multifunctional nanosystems to overcome the challenges posed by ocular bacterial infections. Given the advantages of nanotechnology in the biomedical industry, it can be utilized to diagnose ocular bacterial infections, administer medications, and treat them. In this review, the recent advancements in nanosystems for the detection and treatment of ocular bacterial infections are discussed; this includes the latest application scenarios of nanomaterials for ocular bacterial infections, in addition to the impact of their essential characteristics on bioavailability, tissue permeability, and inflammatory microenvironment. Through an in-depth investigation into the effect of sophisticated ocular barriers, antibacterial drug formulations, and ocular metabolism on drug delivery systems, this review highlights the challenges faced by ophthalmic medicine and encourages basic research and future clinical transformation based on ophthalmic antibacterial nanomedicine.

A rise in the frequency of lasR mutant Pseudomonas aeruginosa among keratitis isolates between 1993 and 2021

Introduction

Pseudomonas aeruginosa causes vision threatening keratitis. The LasR transcription factor regulates virulence factors in response to the quorum sensing molecule N-3-oxo-dodecanoyl-L-homoserine lactone. P. aeruginosa isolates with lasR mutations are characterized by an iridescent high sheen phenotype caused by a build-up of 2-heptyl-4-quinolone. A previous study demonstrated 22% (n=101) of P. aeruginosa keratitis isolates from India between 2010 and 2016 were sheen positive lasR mutants, and the sheen phenotype correlated with worse clinical outcomes for patients. In this study, a longitudinal collection of P. aeruginosa keratitis isolates from Eastern North America were screened for lasR mutations by the sheen phenotype and sequencing of the lasR gene.

Methods

Keratitis isolates (n=399) were classified by sheen phenotype. The lasR gene was cloned from a subset of isolates, sequenced, and tested for loss of function or dominant-negative status based on an azocasein protease assay. A retrospective chart review compared outcomes of keratitis patients infected by sheen positive and negative isolates.

Results

A significant increase in sheen positive isolates was observed between 1993 and 2021. Extracellular protease activity was reduced among the sheen positive isolates and a defined lasR mutant. Cloned lasR alleles from the sheen positive isolates were loss of function or dominant negative and differed in sequence from previously reported ocular lasR mutant alleles. Retrospective analysis of patient information suggested significantly better visual outcomes for patients infected by sheen positive isolates.

Discussion

These results indicate an increase in lasR mutations among keratitis isolates in the United States and suggest that endemic lasR mutants can cause keratitis.

The role of matrix metalloproteinases in infectious corneal ulcers

During infectious keratitis, the production of collagenolytic and inflammatory substances, along with increased corneal matrix metalloproteinase (MMP) activity, induces the degradation of corneal collagen and may cause postkeratitis complications, such as opacity, thinning, and corneal perforation. MMPs, especially MMP-2 and MMP-9, are overexpressed in infectious keratitis and sustained over time by inflammatory and nonmicrobial mechanisms. The high MMP levels are correlated with excessive corneal destruction in bacterial, herpetic, fungal, and acanthamoeba infections. Nonspecific treatments, such as tetracyclines, particularly doxycycline, or corticosteroids, are used as adjuvants to antimicrobials to alleviate the disproportionate degradation and inflammation of the corneal layers caused by corneal MMPs and decrease the recruitment and infiltration of inflammatory cells. Treatments showing inhibition of specific MMPs (Galardin, ZHAWOC7726), interfering with pro-MMP activation (EDTA, ascorbic acid), or showing anticytokine effect (epigallocatechin-2-gallate, TRAM-34) have been reported. Other treatments show a direct action over corneal collagen structure such as corneal cross-linking or have been associated with reduction of MMP levels such as amniotic membrane grafting. Although the use of these drugs has been shown in studies to be effective in controlling inflammation, especially in experimental ones, robust studies are still needed based on randomized and randomized clinical trials to demonstrate their potential effect as adjuvants in the management of infectious keratitis.

Corneal regeneration strategies: From stem cell therapy to tissue engineered stem cell scaffolds

Corneal epithelial defects and excessive wound healing might lead to severe complications. As stem cells can self-renew infinitely, they are a promising solution for regenerating the corneal epithelium and treating severe corneal epithelial injury. The chemical and biophysical properties of biological scaffolds, such as the amniotic membrane, fibrin, and hydrogels, can provide the necessary signals for stem cell proliferation and differentiation. Multiple researchers have conducted investigations on these scaffolds and evaluated them as potential therapeutic interventions for corneal disorders. These studies have identified various inherent benefits and drawbacks associated with these scaffolds. In this study, we provided a comprehensive overview of the history and use of various stem cells in corneal repair. We mainly discussed biological scaffolds that are used in stem cell transplantation and innovative materials that are under investigation.

Ocular Bacterial Infections: A Ten-Year Survey and Review of Causative Organisms Based on the Oklahoma Experience

Ocular infections can be medical emergencies that result in permanent visual impairment or blindness and loss of quality of life. Bacteria are a major cause of ocular infections. Effective treatment of ocular infections requires knowledge of which bacteria are the likely cause of the infection. This survey of ocular bacterial isolates and review of ocular pathogens is based on a survey of a collection of isolates banked over a ten-year span at the Dean McGee Eye Institute in Oklahoma. These findings illustrate the diversity of bacteria isolated from the eye, ranging from common species to rare and unique species. At all sampled sites, staphylococci were the predominant bacteria isolated. Pseudomonads were the most common Gram-negative bacterial isolate, except in vitreous, where Serratia was the most common Gram-negative bacterial isolate. Here, we discuss the range of ocular infections that these species have been documented to cause and treatment options for these infections. Although a highly diverse spectrum of species has been isolated from the eye, the majority of infections are caused by Gram-positive species, and in most infections, empiric treatments are effective.

Recent advancements in nanotechnology-based bacteriophage delivery strategies against bacterial ocular infections

Antibiotic resistance is growing as a critical challenge in a variety of disease conditions including ocular infections leading to disastrous effects on the human eyes. Staphylococcus aureus (S. aureus) mediated ocular infections are very common affecting different parts of the eye viz. vitreous chamber, conjunctiva, cornea, anterior and posterior chambers, tear duct, and eyelids. Blepharitis, dacryocystitis, conjunctivitis, keratitis, endophthalmitis, and orbital cellulitis are some of the commonly known ocular infections caused by S. aureus. Some of these infections are so fatal that they could cause bilateral blindness like panophthalmitis and orbital cellulitis, which is caused by methicillin-resistant S. aureus (MRSA) and vancomycin-resistance S. aureus (VRSA). The treatment of S. aureus infections with known antibiotics is becoming gradually difficult because of the development of resistance against multiple antibiotics. Apart from the different combinations and formulation strategies, bacteriophage therapy is growing as an effective alternative to treat such infections. Although the superiority of bacteriophage therapy is well established, yet physical factors (high temperatures, acidic pH, UV-rays, and ionic strength) and pharmaceutical barriers (poor stability, low in-vivo retention, controlled and targeted delivery, immune system neutralization, etc.) have the greatest influence on the viability of phage virions (also phage proteins). A variety of Nanotechnology based formulations such as polymeric nanoparticles, liposomes, dendrimers, nanoemulsions, and nanofibres have been recently reported to overcome the above-mentioned obstacles. In this review, we have compiled all these recent reports and discussed bacteriophage-based nanoformulations techniques for the successful treatment of ocular infections caused by multidrug-resistant S. aureus and other bacteria.

Establishing an Experimental Pseudomonas aeruginosa Keratitis Model in Mice - Challenges and Solutions

BACKGROUND

With the ongoing increase in antimicrobial resistances seen in bacterial isolates causing a keratitis in humans, animal models have become an important tool to study new antimicrobial therapies. Nevertheless, the establishment of experimental keratitis is difficult. Here, we discuss the impact of different arrangements, including animal age, bacterial strain and dose as well as epithelium removal on the outcome of experimental keratitis. We therefore present the methods and results of our establishing experiments.

METHODS

Bacterial load determination and flow cytometry were performed using eye homogenate gained from a 72hours lasting murine Pseudomonas aeruginosa keratitis model. Additionally, the intensity of the infection was scored from 0 to 5, the mice weighed, and blood immune cells counted.

RESULTS

We found that older C57BL/6N mice (8-11 months) are more susceptible to develop a keratitis than younger mice (5-6 weeks). Epithelium removal has no major impact on infectivity and disease progression in aged mice. P. aeruginosa exoU⁺ strains, such as PA54, should preferentially be used and highly concentrated (∼ 5×10⁷ CFU). Establishing an infection with the exoU^- PAO1 derivative DSM 19880 was not possible.

CONCLUSIONS

We present a replicable method to achieve a successful experimental P. aeruginosa keratitis in C57BL/6N mice that is sustained or aggravated over the observation period of 3 days in 80% of all animals tested. Our work is of particular interest to all researchers planning the establishment of such experimental models. We show some key aspects that can simplify and quicken the procedure, ultimately saving costs and animal life.

Urgent unmet needs in the care of bacterial keratitis: An evidence-based synthesis

Bacterial corneal infections, or bacterial keratitis (BK), are ophthalmic emergencies that frequently lead to irreversible visual impairment. Though increasingly recognized as a major cause of global blindness, modern paradigms of evidence-based care in BK have remained at a diagnostic and therapeutic impasse for over half a century. Current standards of management - based on the collection of corneal cultures and the application of broad-spectrum topical antibiotics - are beset by important yet widely underrecognized limitations, including approximately 30% of all patients who will develop moderate to severe vision loss in the affected eye. Though recent advances have involved a more clearly defined role for adjunctive topical corticosteroids, and novel therapies such as corneal crosslinking, overall progress to improve patient and population-based outcomes remains incommensurate to the chronic morbidity caused by this disease. Recognizing that the care of BK is guided by the clinical axiom, "time equals vision", this chapter offers an evidence-based synthesis for the clinical management of these infections, underscoring critical unmet needs in disease prevention, diagnosis, and treatment.

Galectin-8 Downmodulates TLR4 Activation and Impairs Bacterial Clearance in a Mouse Model of Pseudomonas aeruginosa Keratitis

Pseudomonas aeruginosa provokes a painful, sight-threatening corneal infection. It progresses rapidly and is difficult to treat. In this study, using a mouse model of P. aeruginosa keratitis, we demonstrate the importance of a carbohydrate-binding protein, galectin-8 (Gal-8), in regulation of the innate immune response. First, using two distinct strains of P. aeruginosa, we established that Gal-8-/- mice are resistant to P. aeruginosa keratitis. In contrast, mice deficient in Gal-1, Gal-3, and Gal-9 were fully susceptible. Second, the addition of exogenous rGal-8 to LPS (TLR4 ligand)-stimulated bone marrow-derived macrophages suppressed 1) the activation of the NF-κB pathway, and 2) formation of the MD-2/TLR4 complex. Additionally, the expression level of reactive oxygen species was substantially higher in infected Gal-8-/- bone marrow neutrophils (BMNs) compared with the Gal-8+/+ BMNs, and the P. aeruginosa killing capacity of Gal-8-/- BMNs was considerably higher compared with that of Gal-8+/+ BMNs. In the bacterial killing assays, the addition of exogenous rGal-8 almost completely rescued the phenotype of Gal-8-/- BMNs. Finally, we demonstrate that a subconjunctival injection of a Gal-8 inhibitor markedly reduces the severity of infection in the mouse model of P. aeruginosa keratitis. These data lead us to conclude that Gal-8 downmodulates the innate immune response by suppressing activation of the TLR4 pathway and clearance of P. aeruginosa by neutrophils. These findings have broad implications for developing novel therapeutic strategies for treatment of conditions resulting from the hyperactive immune response both in ocular as well as nonocular tissues.

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.

Antibacterial Activity of Antibiotic-Releasing Polydopamine-Coated Nephrite Composites for Application in Drug-Eluting Contact Lens

The aim of this study is to prepare ciprofloxacin (CIP) or levofloxacin (LEVO)-incorporated and polydopamine (PDA)-coated nephrite composites for application in drug-eluting contact lenses. PDA was coated onto the surface of nephrite to improve antibacterial activity and to payload antibiotics. CIP or LEVO was incorporated into the PDA layer on the surface of nephrite. Furthermore, CIP-incorporated/PDA-coated nephrite composites were embedded into the contact lenses. PDA-coated nephrite composites showed dull and smooth surfaces according to the dopamine concentration while nephrite itself has sharp surface morphology. CIP- or LEVO-loaded/PDA-coated nephrite composites also have dull and smooth surface properties. Nano and/or sub-micron clusters were observed in field emission-scanning electron microscopy (FE-SEM) observation, indicating that PDA nanoparticles were accumulated and coated onto the surface of nephrite. Furthermore, CIP- or LEVO-incorporated/PDA-coated nephrite composites showed the sustained release of CIP or LEVO in vitro and these properties contributed to the enhanced antibacterial activity of composites compared to nephrite or PDA-coated nephrite composites. CIP-incorporated/PDA-coated nephrite composites were embedded in the contact lenses and then, in an antibacterial study, they showed higher bactericidal effect against Staphylococcus aureus (S. aureus) compared to nephrite itself or PDA-coated nephrite composites. We suggest that CIP- or LEVO-loaded/PDA-coated nephrite composite-embedded contact lenses are a promising candidate for therapeutic application.

Infectious keratitis: A review

Globally, infectious keratitis is the fifth leading cause of blindness. The main predisposing factors include contact lens wear, ocular injury and ocular surface disease. Staphylococcus species, Pseudomonas aeruginosa, Fusarium species, Candida species and Acanthamoeba species are the most common causal organisms. Culture of corneal scrapes is the preferred initial test to identify the culprit organism. Polymerase chain reaction (PCR) tests and in vivo confocal microscopy can complement the diagnosis. Empiric therapy is typically commenced with fluoroquinolones, or fortified antibiotics for bacterial keratitis; topical natamycin for fungal keratitis; and polyhexamethylene biguanide or chlorhexidine for acanthamoeba keratitis. Herpes simplex keratitis is mainly diagnosed clinically; however, PCR can also be used to confirm the initial diagnosis and in atypical cases. Antivirals and topical corticosteroids are indicated depending on the corneal layer infected. Vision impairment, blindness and even loss of the eye can occur with a delay in diagnosis and inappropriate antimicrobial therapy.

Host Defense Peptides at the Ocular Surface: Roles in Health and Major Diseases, and Therapeutic Potentials

Sight is arguably the most important sense in human. Being constantly exposed to the environmental stress, irritants and pathogens, the ocular surface – a specialized functional and anatomical unit composed of tear film, conjunctival and corneal epithelium, lacrimal glands, meibomian glands, and nasolacrimal drainage apparatus – serves as a crucial front-line defense of the eye. Host defense peptides (HDPs), also known as antimicrobial peptides, are evolutionarily conserved molecular components of innate immunity that are found in all classes of life. Since the first discovery of lysozyme in 1922, a wide range of HDPs have been identified at the ocular surface. In addition to their antimicrobial activity, HDPs are increasingly recognized for their wide array of biological functions, including anti-biofilm, immunomodulation, wound healing, and anti-cancer properties. In this review, we provide an updated review on: (1) spectrum and expression of HDPs at the ocular surface; (2) participation of HDPs in ocular surface diseases/conditions such as infectious keratitis, conjunctivitis, dry eye disease, keratoconus, allergic eye disease, rosacea keratitis, and post-ocular surgery; (3) HDPs that are currently in the development pipeline for treatment of ocular diseases and infections; and (4) future potential of HDP-based clinical pharmacotherapy for ocular diseases.

COVID-19 and the eye: alternative facts The 2022 Bowman Club, David L. Easty lecture

In addition to catastrophic loss of life, and dramatic and unwanted alterations to the daily lives of those left behind, the COVID-19 pandemic has fostered the publication and dissemination of an unprecedented quantity of peer-reviewed medical and scientific publications on a single subject. In particular, the ophthalmic literature is now replete with clinical and laboratory studies on putative eye involvement by SARS-CoV-2, the aetiologic agent of COVID-19. In this review, we critically appraise the published literature on COVID-19, and suggest that the quality of scientific peer review and editorial decision-making also suffered during the COVID-19 pandemic.

Paradox of complex diversity: Challenges in the diagnosis and management of bacterial keratitis

Bacterial keratitis continues to be one of the leading causes of corneal blindness in the developed as well as the developing world, despite swift progress since the dawn of the "anti-biotic era". Although, we are expeditiously developing our understanding about the different causative organisms and associated pathology leading to keratitis, extensive gaps in knowledge continue to dampen the efforts for early and accurate diagnosis, and management in these patients, resulting in poor clinical outcomes. The ability of the causative bacteria to subdue the therapeutic challenge stems from their large genome encoding complex regulatory networks, variety of unique virulence factors, and rapid secretion of tissue damaging proteases and toxins. In this review article, we have provided an overview of the established classical diagnostic techniques and therapeutics for keratitis caused by various bacteria. We have extensively reported our recent in-roads through novel tools for accurate diagnosis of mono- and poly-bacterial corneal infections. Furthermore, we outlined the recent progress by our group and others in understanding the sub-cellular genomic changes that lead to antibiotic resistance in these organisms. Finally, we discussed in detail, the novel therapies and drug delivery systems in development for the efficacious management of bacterial keratitis.

Pivotal Role of Corneal Fibroblasts in Progression to Corneal Ulcer in Bacterial Keratitis

The shape and transparency of the cornea are essential for clear vision. However, its location at the ocular surface renders the cornea vulnerable to pathogenic microorganisms in the external environment. Pseudomonas aeruginosa and Staphylococcus aureus are two such microorganisms and are responsible for most cases of bacterial keratitis. The development of antimicrobial agents has allowed the successful treatment of bacterial keratitis if the infection is diagnosed promptly. However, no effective medical treatment is available after progression to corneal ulcer, which is characterized by excessive degradation of collagen in the corneal stroma and can lead to corneal perforation and corneal blindness. This collagen degradation is mediated by both infecting bacteria and corneal fibroblasts themselves, with a urokinase-type plasminogen activator (uPA)-plasmin-matrix metalloproteinase (MMP) cascade playing a central role in collagen destruction by the host cells. Bacterial factors stimulate the production by corneal fibroblasts of both uPA and pro-MMPs, released uPA mediates the conversion of plasminogen in the extracellular environment to plasmin, and plasmin mediates the conversion of secreted pro-MMPs to the active form of these enzymes, which then degrade stromal collagen. Bacterial factors also stimulate expression by corneal fibroblasts of the chemokine interleukin-8 and the adhesion molecule ICAM-1, both of which contribute to recruitment and activation of polymorphonuclear neutrophils, and these cells then further stimulate corneal fibroblasts via the secretion of interleukin-1. At this stage of the disease, bacteria are no longer necessary for collagen degradation. In this review, we discuss the pivotal role of corneal fibroblasts in corneal ulcer associated with infection by P. aeruginosa or S. aureus as well as the development of potential new modes of treatment for this condition.