Bacterial keratitis: identifying the areas of clinical uncertainty

Whole Genome Sequencing-Based Prediction of Antibiotic-Resistance of Ocular Staphylococcus aureus Across Six Continents

Staphylococcus aureus is a leading cause of ocular infections, resulting in vision loss in severe cases. Understanding the antibiotic resistance profiles of ocular S. aureus can help customize treatments. However, there is a lack of global data on the resistance patterns of ocular isolates and comparative regional analyses. Hence, WGS data from 195 ocular S. aureus isolates across six continents were analysed to identify antibiotic resistance genes (ARGs) and predict antibiotic resistance phenotypes in this study. A total of 40 ARGs were detected, involving resistance mechanisms against aminoglycosides, beta-lactams, macrolide-lacosamide-streptogramin B (MLSB), glycopeptides, tetracyclines, other antibiotic classes, and efflux pump regulators. Notably, the prevalences of ARGs associated with efflux pump regulators and beta-lactams were particularly high (>80%). Resistance to 45 antibiotics was predicted across the isolates, with 51% identified as multidrug-resistant (MDR), while only 8% were predicted to be fully susceptible to all predicted antibiotics. Regional data varied, with isolates from North America and Asia exhibiting the most extensive resistance patterns, showing predicted resistance to 45 and 41 antibiotics, respectively. In contrast, Oceanian isolates were predicted to be resistant to only 14 antibiotics. Beta-lactams showed the highest predicted resistance prevalence among all antibiotic classes. Notably, North American isolates showed markedly higher resistance to MLSB antibiotics. A high proportion of cloud genes highlights the need for monitoring regional resistance. This study provides antibiotic resistance profiles among ocular S. aureus using WGS prediction, emphasizing the importance of regional surveillance and antimicrobial stewardship to suggest effective treatment strategies. It is recommended that WGS of more strains be deposited to overcome limited data, and laboratory tests be performed to analyse the consistency between genetic predicted and phenotypic resistance.

Dextran guanidinylated carbon dots with antibacterial and immunomodulatory activities as eye drops for the topical treatment of MRSA-induced infectious keratitis

Bacterial keratitis (BK) develops rapidly and can cause serious consequences, requiring timely and efficient treatment. As the main treatment strategy, antibiotic eye drops are still plagued by bacterial resistance by biofilms and failure to modulate immunity. Herein, dextran guanidinylated carbon dots (DG-CDs) with antimicrobial and immunomodulatory properties were developed. DG-CDs with the graphitized core-like structure with the ordered arrangement of carbon atoms and surface groups of CN, COC, and -OH were thoroughly characterized and modeled as a graphene-like sheet. DG-CDs exhibited strong antimicrobial and anti-biofilm activities with a minimum inhibitory concentration (MIC) of 5 μg/mL against methicillin-resistant Staphylococcus aureus (MRSA). Molecular docking based on well-characterized structures of DG-CDs revealed that DG-CDs had strong affinity for key bacterial proteins including FtsA, IcaA and ArgA, which were confirmed by corresponding RT-qPCR and transcriptomics. Furthermore, DG-CDs regulated macrophage polarization by inhibiting the M1 subtype and promoting the transition to the M2 subtype. In vivo experiments illustrated that DG-CDs used as eye drops significantly attenuated corneal infection, enhanced the expression of anti-inflammatory factors, and effectively promoted corneal repair in MRSA-infected BK. Overall, this study provides a promising antibacterial nanomaterial with clarified properties and acting mechanism for treating BK as eye drops. STATEMENT OF SIGNIFICANCE: Besides bacterial invasion, bacterial keratitis (BK) also suffers from immune imbalance, which further impairs corneal healing. Current antibiotic eye drops are plagued by bacterial resistance and their inability to modulate immunity. Herein, dextran guanidinylated carbon dots (DG-CDs) with dual functions of antimicrobial and immunomodulatory were developed for treating MRSA infected BK. DG-CDs, with clarified structure and surface groups, exhibited strong antimicrobial activity and no detectable resistance. Molecular docking, based on well-characterized structures of DG-CDs, was achieved to reveal the antibacterial mechanism, which was subsequently confirmed by RT-qPCR and transcriptomics. In addition, DG-CDs exhibited an effective healing ability in an MRSA-infected rat keratitis model by exerting antibacterial activity and regulating macrophage polarization from M1 type to M2 type. DG-CDs represent a promising antibacterial nanomedicine with clarified properties and acting mechanism for treating bacterial infection.

Evaluating Medical Therapy Failure in Microbial Keratitis: Risk Factors and Management Alternatives

PURPOSE

To describe the treatments used in cases of infectious keratitis and determine the risk factors associated with treatment failure, including prolonged infection duration, treatment modifications, and the need for surgical intervention.

PATIENTS AND METHODS

This retrospective case series includes culture-proven microbial keratitis cases treated in nine hospitals in the region of Galicia, Spain, between 2010 and 2020.

RESULTS

A total of 654 patients were included. Prolonged infection duration was associated with factors such as advanced age, deep infiltrates, corneal thinning, and large epithelial defects. Initial empirical treatment was modified in 204 cases (31.2%), with 113 cases requiring changes due to antibiotic resistance and 88 cases due to clinical deterioration. Polymicrobial infections, contact with vegetable matter, previous herpetic keratitis, and topical steroid use were identified as risk factors for treatment modification. Surgical intervention was required in 142 cases (21.7%). Among these, 50 patients (7.6%) underwent evisceration, 43 (6.6%) received amniotic membrane transplantation, and 37 (5.7%) underwent tectonic penetrating keratoplasty. Previous keratoplasty, prior herpetic keratitis, topical steroid use, and large epithelial defects were also significant risk factors for surgical intervention.

CONCLUSIONS

Treatment failure in cases of microbial keratitis (MK) may be influenced by systemic factors, such as advanced age, and ocular factors, including large epithelial defects, deep infiltrates, polymicrobial infections, contact with vegetable matter, and previous topical steroid use. Identifying these risk factors is essential for guiding empirical treatment and recognizing refractory ulcers that may require more intensive management, including surgical intervention.

Synchronous Sterilization and Immunoreaction Termination for Corneal Transparency Protection in Treating Pseudomonas aeruginosa Induced Bacterial Keratitis

In the treatment of infectious keratitis, therapeutic strategies often prioritize enhancing bactericidal efficacy. However, endotoxins released from Gram-negative bacteria cause inflammatory reaction, leading to corneal structural damage and scar formation. Given that polymyxin B (PMB) can bind and neutralize lipopolysaccharide (LPS), this study employs large-pore mesoporous silica nanoparticles (lMSNs) grafted with PMB as carriers for cationic antibacterial carbon quantum dots (CQDs) to prepare CQD@lMSN-PMB, which enables synchronous sterilization and endotoxin neutralization. In the acidic infectious microenvironment, the accelerated release of CQDs eliminates 99.88% bacteria within 2 h, effectively substituting immune mediated sterilization. Notably, CQD@lMSN-PMB exhibits exceptional LPS neutralization performance (2.22 µg LPS/mg CQD@lMSN-PMB) due to its high specific surface area. In an infectious keratitis model, inflammation subsides significantly within the first day of CQD@lMSN-PMB intervention and is completely resolved by day 3. By day 2, interleukin-1β, interleukin-6 and tumor necrosis factor-α in CQD@lMSN-PMB group decrease by 86.99%, 91.15%, and 77.56%, respectively, compared to the CQDs-only sterilization group. Ultimately, corneal integrity and transparency are preserved, with suppressed expressions of fibrosis-related factors including matrix metalloproteinase 9, transforming growth factor-β and α-smooth muscle actin. Therefore, this synchronous sterilization and endotoxin neutralization strategy outperforms monotherapy strategies focused solely on sterilization or endotoxin neutralization.

Stable topical application of antimicrobials using plumbing rings in an ex vivo porcine corneal infection model

Microbial keratitis (MK) is a substantial cause of clinical blindness worldwide. Pseudomonas aeruginosa is an opportunistic Gram-negative bacterium and is the leading cause of MK. Infection models are vital tools in understanding host-pathogen interactions and the development of novel therapies. As well as ethical and practical advantages, ex vivo infection models enable researchers to study host-pathogen interactions with greater accuracy and physiological relevance compared to traditional cell culture systems. The versatility of porcine corneal ex vivo models have been employed to study various pathogens (for example Staphylococcus aureus and Acanthamoeba) and has enabled innovation of novel MK therapies. Here, we describe an improved porcine corneal ex vivo protocol, which uses plumbing rings and medical adhesive to circumvent several distinct limitations and challenges. The application of a 10 mm plumbing ring to the center of the cornea allows localized inoculation of pathogens of interest, maintaining them at the site of infection, rather than running the risk of "run off" of topically added aqueous solutions. The second important advantage is that topically applied therapeutic agents can be properly maintained on the cornea within the plumbing ring reservoir, allowing more accurate study of antimicrobial effects. In this contextualized protocol, we infected porcine corneas with the P. aeruginosa strain PA103 with topical treatments of moxifloxacin. PA103 colony-forming unit (CFU) quantification, spectrophotometric measurement of corneal opacity, and histological analysis of stromal edema using hematoxylin and eosin staining were employed to assess infection over 48 hours. Moxifloxacin treatment demonstrated a dose-dependent reduction in infection and corneal damage. These findings have contributed to the development of an improved and standardized ex vivo infection model for evaluating therapeutic interventions, potentially supporting clinical translation to alleviate the burden of microbial keratitis.

Recent in vitro advances in the ocular antimicrobial agents against Acanthamoeba

This review examines the advancements in antimicrobial drug discovery with in vitro assays for Acanthamoeba, highlighting the efficacy of current topical antimicrobial agents. In recent decades, the treatment and diagnosis of Acanthamoeba keratitis (AK) have presented clinical challenges. Clinicians often rely on clinical judgment, risk factors, and patient travel history to guide initial treatment decisions. The clinical presentation of AK frequently coincides with bacterial and fungal keratitis, leading to delays in diagnostic confirmation. This review compiles a list of commonly used antimicrobial agents that may be useful in controlling and preventing Acanthamoeba and other microbial infections during the diagnostic waiting period. Due to their unique life cycle, consisting of both trophozoite and cyst stages, amoebae exhibit resistance to various clinical drugs. Current research efforts are focused on identifying alternative and effective treatment options. Despite the ongoing characterization of various cytocidal agents from natural and synthetic sources, chlorhexidine gluconate (CHG) and polyhexamethylene biguanide (PHMB) have emerged as the most effective therapies for AK. Drawing from previous studies, we catalog several commonly used antimicrobial agents that may enhance the efficacy of PHMB and CHG while also preventing other microbial infections. These alternative agents present promising options for treating AK cases. This review evaluates progress in anti-amoebic drug discovery, focusing on antibiotics and cataloging their activity at different stages of Acanthamoeba.

Unlocking the Potential of Antimicrobial Peptides: Cutting-Edge Advances and Therapeutic Potential in Combating Bacterial Keratitis

Bacterial keratitis is a prevalent, and severe corneal illness resulting from bacterial pathogens. Failure to administer a timely and suitable therapy may lead to corneal opacity, ulceration, significant vision impairment, or potential blindness. Current clinical interventions for bacterial keratitis involve the administration of topical antimicrobial agents and systemic antibiotics. However, the misuse and overuse of antibiotics have led to the rapid emergence of antibiotic-resistant bacteria. Additionally, the restricted antibacterial spectrum and possible adverse effects of antibiotics have provided considerable obstacles to traditional therapies. This highlights the urgent need for novel and highly effective antimicrobial agents. Antimicrobial peptides (AMPs) are a class of naturally occurring or synthetically designed small molecules that have gained significant attention due to their unique antimicrobial mechanisms and low risk of resistance development. AMPs exhibit promising potential in treating bacterial keratitis through direct antibacterial mechanisms, such as inhibiting cell wall synthesis, disrupting cell membranes, and interfering with nucleic acid metabolism, as well as indirect mechanisms, including modulation of the host immune response. This review provides a comprehensive overview of the antibacterial mechanisms of AMPs and their advancements in the treatment of bacterial keratitis. It emphasizes the role of various modification strategies and artificial-intelligence-assisted design in enhancing the antibacterial efficacy, stability, and biocompatibility of AMPs. Furthermore, this review discusses the latest progress in combining AMPs with delivery systems for improved therapeutic outcomes. Finally, the review highlights the current challenges and future perspectives of AMPs in bacterial keratitis treatment, providing valuable insights for developing novel AMPs with high antibacterial efficacy, stability, and safety for bacterial keratitis therapies.

Responsive Microneedles for Diagnostic and Therapeutic Applications of Ocular Diseases

Traditional ophthalmic formulations are characterized by low bioavailability, short intraocular retention time, strong irritation, and failure to achieve the expected therapeutic effect due to the special physiological structure of the eye and the existence of many barriers. Microneedle drug delivery is a novel transdermal drug delivery modality. Responsive microneedles are defined as controllably releasing the drug payloads in response to physiological stimuli, including pH levels, temperature, enzymes, and reactive oxygen species (ROS), as well as external stimuli such as magnetic fields and light. In addition to inheriting the advantages of traditional microneedles, which include enhanced targeting and permeability, non-invasiveness, and painless application, the integration with stimulus-responsive materials enables responsive microneedles to achieve a personalized precision drug delivery process, which further increases the accuracy and efficiency of ocular treatments, making on-demand drug delivery possible. This article systematically reviews the classification, mechanisms, and characteristics of responsive microneedles and provides a detailed introduction to their diagnostic and therapeutic applications as well as real-time monitoring potential in ocular diseases, aiming to offer insights for the precision treatment of ocular diseases in the future.

An exploration of the ocular mysteries linking nanoparticles to the patho-therapeutic effects against keratitis

Microbial keratitis, a sight-threatening corneal infection, remains a significant global health concern. Conventional therapies using antimicrobial agents often suffers from limitations such as poor drug penetration, side effects, and occurrence of drug resistance, with poor prognosis. Novel treatment techniques, with their unique properties and targeted delivery capabilities, offers a promising solution to overcome these challenges. This review delves into timely update of the state-of-the-art advance therapeutics for keratitis treatment. The diverse microbial origins of keratitis, including viral, bacterial, and fungal infections, exploring their complex pathogenic mechanisms, followed by the drug resistance mechanisms in keratitis pathogens are reviewed briefly. Importantly, the emerging therapeutic techniques for keratitis treatment including piezodynamic therapy, photothermal therapy, photodynamic therapy, nanoenzyme therapy, and metal ion therapy are summarized in this review showcasing their potential to overcome the limitations of traditional treatments. The challenges and future directions for advance therapies and nanotechnology-based approaches are discussed, focusing on safety, targeting strategies, drug resistance, and combination therapies. This review aims to inspire researchers to revolutionize and accelerate the development of functional materials using different therapies for keratitis treatment.

Factors Associated with Vision Outcomes in Microbial Keratitis: A Multisite Prospective Cohort Study

PURPOSE

To investigate factors associated with 90-day vision in patients with microbial keratitis (MK).

DESIGN

Multicenter prospective cohort study recruited patients with MK from the United States and India from July 23, 2020, through May 1, 2024, and followed them for 90 days.

PARTICIPANTS

Individuals ≥ 15 years of age with MK of > 2 mm2 in stromal infiltrate area without prior corneal surgery or gluing, impending corneal perforation or keratoplasty, no light perception vision, current pregnancy, or incarceration.

METHODS

Data on sociodemographics, history, symptoms, clinical measures, and best-corrected visual acuity (BCVA) (as logarithm of the minimum angle of resolution (logMAR) units) at initial and 90-day visits were gathered, with BCVA carried forward for those healed before 90 days. Features were summarized overall and by site. Site-stratified multivariable linear regression models were investigated for associations with 90-day BCVA.

MAIN OUTCOME MEASURES

Ninety-day logMAR BCVA.

RESULTS

Of 479 participants analyzed, after exclusions (n = 31) and participants without a 90-day BCVA (n = 52), participants had an average 90-day BCVA of 1.36 ± 1.40 logMAR in the United States (US) and 0.70 ± 0.99 logMAR in India (P < 0.0001). For the US, worse 90-day BCVA was associated with worse presenting BCVA (β = 0.05-logMAR per 0.1-logMAR unit increase in presenting BCVA; P < 0.0001), longer time until presentation (β = 0.01 per day; P < 0.0001), no contact lens use (β = 0.46; P = 0.0131), and larger stromal infiltrate area (bacterial: β = 0.02 per 1-mm2 [P = 0.0082]; fungal: β = 0.10 per 1-mm2 increase in area [P = 0.0002]; P = 0.0017 for interaction). For the India, worse 90-day BCVA was associated with worse presenting BCVA (β = 0.04 logMAR; P < 0.0001), longer delays to presentation (β = 0.03 per day; P = 0.0004), diabetes mellitus (β = 0.41; P = 0.0019), hypopyon (β = 0.27; P = 0.0083), no recent ocular trauma (β = 0.21; P = 0.0370), and larger stromal infiltrate area (fungal: β = 0.03 per 1-mm2 [P < 0.0001]; bacterial: nonsignificant β [P = 0.07]; P = 0.0001 for interaction).

CONCLUSIONS

Initial vision, longer time until presentation, and larger infiltrate size conferred risk for worse 90-day BCVA, whereas other factors were unique. Systems to mitigate care delays and to support access care are needed would support clinicians and improve vision outcomes.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Inactivation of antibiotic resistant bacteria by nitrogen-doped carbon quantum dots through spontaneous generation of intracellular and extracellular reactive oxygen species

The widespread antibiotic resistance has called for alternative antimicrobial agents. Carbon nanomaterials, especially carbon quantum dots (CQDs), may be promising alternatives due to their desirable physicochemical properties and potential antimicrobial activity, but their antimicrobial mechanism remains to be investigated. In this study, nitrogen-doped carbon quantum dots (N-CQDs) were synthesized to inactivate antibiotic-resistant bacteria and treat bacterial keratitis. N-CQDs synthesized via a facile hydrothermal approach displayed a uniform particle size of less than 10 nm, featuring a graphitic carbon structure and functional groups including -OH and -NH2. The N-CQDs demonstrated antimicrobial activity against Staphylococcus aureus (S. aureus) and methicillin-resistant S. aureus, which was both dose- and time-dependent, reducing the survival rate to below 1 %. The antimicrobial activity was confirmed by live/dead staining. In in vivo studies, the N-CQDs were more efficient in treating drug-resistant bacterial keratitis and reducing corneal damage compared to the common antibiotic levofloxacin. The N-CQDs were shown to generate intracellular and extracellular ROS, which potentially caused oxidative stress, membrane disruption, and cell death. This antimicrobial mechanism was supported by scanning and transmission electron microscopy, significant regulation of genes related to oxidative stress, and increased protein and lactate dehydrogenase leakage. This study has provided insight into the development, application, and mechanism of N-CQDs in antimicrobial applications.

Drug in Drug: Quorum Sensing Inhibitor in Star-Shaped Antibacterial Polypeptides for Inhibiting and Eradicating Corneal Bacterial Biofilms

Biofilm-related bacterial keratitis is a severe ocular infection that can result in drastic vision impairment and even blindness. However, the therapeutic efficiency of clinical antibiotic eyedrops is often compromised because the bacteria in the biofilms resist bactericide via the community genetic regulation, namely, bacterial quorum sensing. Herein, quercetin (QCT)-loaded star-shaped antibacterial peptide polymer (SAPP), QCT@SAPP, is developed based on a "drug" in a "drug" strategy for inhibiting and eradicating Pseudomonas aeruginosa biofilms on the cornea. The natural antibacterial peptide-mimic SAPP with the positively charged amphipathic structure not only enables QCT@SAPP to penetrate the biofilms readily but also selectively adheres to the highly negatively charged P. aeruginosa, releasing the loaded QCT into the bacteria to regulate quorum sensing by inhibiting lasI, lasR, rhlR, and rhlI. Thanks to its robust bactericidal ability from SAPP, QCT@SAPP can eliminate more than 99.99% of biofilms. Additionally, QCT@SAPP displayed outstanding performance in relieving ocular inflammation by significantly downregulating pro-inflammatory cytokines and profiting from scavenging reactive oxygen species by releasing QCT, which finally helps to restore visual function. In conclusion, QCT@SAPP, with good compatibility, exerts excellent therapeutic effects in a bacterial keratitis mice model, making it a promising candidate for controlling bacterial biofilm-induced infections, including bacterial keratitis.

Reply to Troisi et al. Comment on "Cabrera-Aguas, M.; Watson, S.L. Updates in Diagnostic Imaging for Infectious Keratitis: A Review. Diagnostics 2023, 13, 3358"

We appreciate the interest of Troisi and his colleagues [...].

Microbial keratitis in north-western Spain: a review of risk factors, microbiological profile and resistance patterns

PURPOSE

To review the risk factors, clinical characteristics, and microbiological profiles of microbial keratitis cases, as well as the antibiotic resistance patterns of bacterial isolates in the region of Galicia, Spain.

METHODS

This retrospective case series includes patients with culture-positive non-viral microbial keratitis between 2010 and 2020, treated at nine hospitals within the region of Galicia, North-West Spain. The standard protocol involved Gram staining for bacterial infections and calcofluor white staining for fungal or amoebal infections, identification by MALDI-TOF mass spectrometry or microscopy, and antimicrobial susceptibility interpreted according to EUCAST or CLSI guidelines.

RESULTS

780 microorganisms were isolated from corneal scraping cultures from 654 patients. 36.9% resided in urban areas, and 63.1% in rural areas. Isolates were more frequently collected in spring and summer. The median time to corneal scraping was 0 days (IQR 0-2), and the median time to epithelialisation was 24.0 days (IQR 11-49). Most cases had a single corneal infiltrate (509 cases; 77.8%) and affected the stroma (432; 66.1%), with small (< 3 mm) epithelial defects (347; 53.1%). Significant risk factors included contact lens wear (24.2%) and exposure to organic matter (4.9%). The most frequent bacteria was CoNS (207; 26.4). Fungi (77; 9.9%) and amoebae (6; 0.8%) were less common. Steroid use and eyelid disease increased resistance in CoNS species. An increase in the percentage of MRSA (compared to MSSA) was detected over the study period (p = 0.045).

CONCLUSIONS

In Galicia (Spain), microbial keratitis was mostly attributed to CoNS. An increase in MRSA keratitis was observed. Analysis of risk factors may help in suspecting antibiotic resistance. Surveillance programs for detecting the development of antimicrobial resistance are necessary to provide treatment guidelines based on local data.

Severe Microbial Keratitis in Virgin and Transplanted Cornea-Probability of Visual Acuity Improvement

Purpose: To evaluate visual acuity improvement and identify contributing factors in patients with severe keratitis affecting both virgin and transplanted corneas, treated at a hospital. Methods: A retrospective analysis was conducted on 497 patients with unilateral corneal ulcers treated at a tertiary referral center between 2008 and 2023. Data included distance (BCVA) and near best-corrected visual acuity at initial presentation and at discharge, treatments before hospital admission, demographic details, risk factors, clinical signs and symptoms, ancillary test results, and management strategies. Patients were categorized into two groups: Group A (naïve corneal ulcers, 379 patients) and Group B (post-keratoplasty infectious keratitis, 118 patients). Additional analysis focused on patients with presenting visual acuity of at least 1.0 logMAR (≤5/50 Snellen charts = legal blindness) to predict final visual outcomes. Results: The median BCVA at presentation for the entire cohort was 1.9 logMAR, advancing to 1.5 logMAR at discharge (p < 0.001). At least one line improvement in BCVA was observed in 47% of patients (52% of naïve cornea and 33% of transplanted cornea patients). Significantly worse results were observed in Group B were observed for BCVA at presentation, BCVA improvement, and distance and near vision improvement. Among patients with legal blindness at presentation, vision status improved for 52/379 (14%) in Group A and 6/118 (5%) in Group B during hospital admission (p < 0.001), while 67% of the cohort was discharged with VA equal or worse than 5/50. The average hospital stay was 9 days. Near visual acuity got better in 23% of patients (27% in Group A vs. 9% in Group B). A multivariate regression model showed that older age and worse distance BCVA on admission were independent negative predictors of improvement (p < 0.001, p < 0.001, respectively) while midperiphery ulcers were associated with better visual outcomes. Conclusions: Hospital admission leads to BCVA improvement in 47% of the patients with severe corneal ulcer, though the prognosis is significantly worse for those with post-keratoplasty microbial keratitis. At discharge, 67% of patients remained at the legal blindness level. Older age and lower BCVA at first presentation are associated with worse prognosis, while ulcers located in the corneal midperiphery are linked to better visual outcomes.

[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.

Antimicrobial and antifouling hyaluronic acid-cobalt nanogel coatings built sonochemically on contact lenses

The wearing of contact lenses (CLs) may cause bacterial infections, leading in turn to more serious complications and ultimately vision impairment. In this scenario, the first step is the adhesion of tear proteins, which provide anchoring points for bacterial colonization. A possible solution is the functionalization with an antimicrobial coating, though the latter may also lead to sight obstruction and user discomfort. In this study, adipic acid dihydrazide-modified hyaluronic acid-cobalt (II) (HA-ADH-Co) nanogels (NGs) were synthesized and deposited onto commercial CLs in a single-step sonochemical process. The coating hindered up to 60 % the protein adsorption and endowed the CLs with strong antibacterial activity against major ocular pathogens like Staphylococcus aureus and Pseudomonas aeruginosa, reducing their concentration by around 3 logs. Cytotoxicity assessment with human corneal cells demonstrated viabilities above 95 %. The nanocomposite coating did not affect the optical power and the light transmission of the CLs and provided enhanced wettability, important for the wearer comfort.

Sodium butyrate alleviates lipopolysaccharide-induced inflammation through JAK/STAT signalling in primary human corneal fibroblasts

BACKGROUND

Bacterial keratitis is a common cause of blindness. Antibiotic treatment leads to the rapid release of lipopolysaccharide (LPS), which can activate corneal fibroblasts and cause persistent and excessive inflammatory responses. The anti-inflammatory drugs currently used to treat keratitis have serious side effects. Therefore, the ability of sodium butyrate (NaB), which can suppress the production of proinflammatory cytokines and promote the production of anti-inflammatory cytokines, to ameliorate keratitis was assessed in the present study.

METHODS

The effect of NaB on the viability of primary human corneal fibroblasts was assayed with a CCK-8 kit. Cell migration was assessed by an in vitro scratch assay. Cell phenotypes were assessed by Western blotting and immunofluorescence staining. An antibody array was used to measure the production of proinflammatory cytokines and chemokines.

RESULTS

At 0-1 mM, NaB had no significant effect on cell viability, promoted the expression of the keratocyte marker keratocan and inhibited the fibroblast marker vimentin. Inhibition of cell migration was observed in the wound healing assay. By targeting the Janus kinase/signal transducer and activator of transcription (JAK/STAT) signalling pathway, NaB decreased the levels of inflammation-related cytokines and chemokines whose expression was induced by LPS.

CONCLUSIONS

NaB maintained the keratocyte phenotype, inhibited cell migration, and relieved LPS-induced inflammatory responses through the JAK/STAT signalling pathway.

Audit of antibiotic utilization patterns and practice for common eye infections at the ambulatory clinic of a teaching hospital in Ghana: Findings and implications

BACKGROUND

Antimicrobial resistance (AMR) is a serious public health issue which is exacerbated by increased inappropriate use of antibiotics for common eye infections. This cross sectional survey was to assess the appropriate use of antibiotics for eye infections in an ambulatory clinic in Ghana and possible determinants.

METHOD

The medical records of all patients who sought eye care between January 2022 to December 2022 and were prescribed antibiotics were extracted from the hospital's electronic database. Descriptive, bivariate and multivariate analyses were then conducted.

RESULTS

A total of 1925 patient medical records were extracted, whose median age was 40 years (IQR 26-69), and were mostly females (58.91%, n = 1134/1925). The eye condition commonly treated with antibiotics was bacteria conjunctivitis (33.51%, n = 645/1925). The most prescribed antibiotic was gentamycin (22.96%, n = 442/1925) followed by ciprofloxacin (16.78%, n = 321/1925). These were mostly topical dosage forms (82.13%, n = 1581/1925). Systemic antibiotics prescribed were mostly from the WHO 'Access' class (83.33%, n = 280/338). The appropriate choice of antibiotic prescribed was 42.44% (n = 817/1925) and this was positivity associated with age (p<0.001), number of antibiotics prescribed (p <0.001), the prescription of topical dosage forms (p <0.001), and WHO 'Access' antibiotic class (p <0.034).

CONCLUSION

The level of appropriateness of antibiotic prescriptions for eye infections was sub-optimal. Antimicrobial stewardship programs, including prescriber education on guidelines and prescription audit to address associated factors, must now be instigated in this hospital to improve future antibiotic use and prevent the rise of AMR.

Photothermal Iron-Based Riboflavin Microneedles for the Treatment of Bacterial Keratitis via Ion Therapy and Immunomodulation

Bacterial biofilm formation protects bacteria from antibiotics and the immune system, excessive inflammation further complicates treatment. Here, iron-based metal-organic framework (MIL-101)-loaded riboflavin nanoparticles are designed for the therapeutic challenge of biofilm infection and hyperinflammation in bacterial keratitis. Specifically, MIL-101 produces a thermal effect under exogenous near-infrared light irradiation, which synergizes with ferroptosis-like bacterial death induced by iron ions to exert an effective biofilm infection eradication effect. On the other hand, the disintegration of MIL-101 sustains the release of riboflavin, which inhibits the pro-inflammatory response of macrophage over-activation by modulating their phenotypic switch. In addition, to solve the problems of short residence time, poor permeability, and low bioavailability of corneal medication, the MR@MN microneedle patch is further prepared by loading nanoparticles into SilMA hydrogel, which ultimately achieves painless, transepithelial, and highly efficient drug delivery. In vivo and ex vivo experiments demonstrate the effectiveness of this approach in eliminating bacterial infection and promoting corneal healing. Therefore, the MRMN patch, acting as an ocular drug delivery system with the ability of rapid corneal healing, promises a cost-effective solution for the treatment of bacterial keratitis, which may also lead to a new approach for treating bacterial keratitis in clinics.

PAX6-WNK2 Axis Governs Corneal Epithelial Homeostasis

Purpose

Limbal stem/progenitor cells (LSCs) continuously proliferate and differentiate to replenish the corneal epithelium and play a vital role in corneal function and normal vision. A previous study revealed that paired box 6 (PAX6) is a master transcription factor involved in determining the fate of corneal epithelial cells (CECs). However, the molecular events downstream of PAX6 remain largely unknown. In this study, we aimed to clarify the regulation network of PAX6 in driving CEC differentiation.

Methods

An air-liquid culture system was used to differentiate LSCs into mature CECs. Specific targeting PAX6 short-hairpin RNAs were used to knock down PAX6 in LSC. RNA sequencing (RNA-seq) was used to analyze shPAX6-transfected CECs and CEC differentiation-associated genes to identify the potential downstream targets of PAX6. RNA-seq analysis, quantitative real-time PCR, and immunofluorescence staining were performed to clarify the function of WNK lysine deficient protein kinase 2 (WNK2), a downstream target of PAX6, and its relationship with corneal diseases.

Results

WNK2 expression increased during CEC differentiation and decreased upon PAX6 depletion. The distribution of WNK2 was specifically limited to the central corneal epithelium and suprabasal layer of the limbus. Knockdown of WNK2 impaired the expression of CEC-specific markers (KRT12, ALDH3A1, and CLU), disrupted the corneal differentiation process, and activated the terms of keratinization, inflammation, and cell proliferation, consistent with PAX6-depleted CEC and published microbial keratitis. Thus, aberrant expression of WNK2 was linked to corneal ulcers.

Conclusions

As a downstream target of PAX6, WNK2 plays an essential role in corneal epithelial cell differentiation and maintenance of corneal homeostasis.

Drug-impregnated contact lenses via supercritical carbon dioxide: A viable solution for the treatment of bacterial and fungal keratitis

Keratitis is a corneal infection caused by various bacteria and fungi. Eye drop treatment of keratitis involves significant challenges due to difficulties in administration, inefficiencies in therapeutic dosage, and frequency of drug applications. All these are troublesome and result in unsuccessful treatment, high cost, time loss, development of drug resistance by microorganisms, and a massive burden on human health and the healthcare system. Most of the antibacterial and antifungal medications are non-water-soluble and/or include toxic drug formulations. Here, the aim was to develop drug-loaded contact lenses with therapeutic dosage formulations and extended drug release capability as an alternative to eye drops, by employing supercritical carbon dioxide (ScCO2) as a drug impregnation solvent to overcome inefficient ophthalmic drug use. ScCO2, known as a green solvent, has very low viscosity which provides high mass transfer power and could enhance drug penetration into contact lenses much better with respect to drug loading using other solvents. Here, moxifloxacin (MOX) antibiotic and amphotericin B (AMB) antifungal medicines were separately loaded into commercially available silicone hydrogel contact lenses through 1) drug adsorption from the aqueous solutions and 2) impregnation techniques via ScCO2 and their efficacies were compared. Drug impregnation parameters, i.e., 8-25 MPa pressure, 310-320 K temperature, 2-16-hour impregnation times, and the presence of ethanol as polar co-solvent were investigated for the optimization of the ScCO2 drug impregnation process. The highest drug loading and long-term release kinetic from the contact lenses were obtained at 25 MPa and 313 K with 2.5 h impregnation time by using 1 % ethanol (by volume). Furthermore, antibacterial/antifungal activities of the MOX- and AMB-impregnated contact lenses were effective against in vitro Pseudomonas aeruginosa (ATCC 10145) bacteria and Fusarium solani (ATCC 36031) fungus for up to one week. Consequently, the ScCO2 method can be effectively used to impregnate commercial contact lenses with drugs, and these can then be safely used for the treatment of keratitis. This offers a sustainable delivery system at effective dosage formulations with complete bacterial/fungal inhibition and termination, making it viable for real animal/human applications.

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.

Nanozybiotics: Advancing Antimicrobial Strategies Through Biomimetic Mechanisms

Infectious diseases caused by bacterial, viral, and fungal pathogens present significant global health challenges. The rapid emergence of antimicrobial resistance exacerbates this issue, leading to a scenario where effective antibiotics are increasingly scarce. Traditional antibiotic development strategies are proving inadequate against the swift evolution of microbial resistance. Therefore, there is an urgent need to develop novel antimicrobial strategies with mechanisms distinct from those of existing antibiotics. Nanozybiotics, which are nanozyme-based antimicrobials, mimic the catalytic action of lysosomal enzymes in innate immune cells to kill infectious pathogens. This review reinforces the concept of nanozymes and provides a comprehensive summary of recent research advancements on potential antimicrobial candidates. Initially, nanozybiotics are categorized based on their activities, mimicking either oxidoreductase-like or hydrolase-like functions, thereby highlighting their superior mechanisms in combating antimicrobial resistance. The review then discusses the progress of nanozybiotics in treating bacterial, viral, and fungal infections, confirming their potential as novel antimicrobial candidates. The translational potential of nanozybiotic-based products, including hydrogels, nanorobots, sprays, bandages, masks, and protective clothing, is also considered. Finally, the current challenges and future prospects of nanozybiotic-related products are explored, emphasizing the design and antimicrobial capabilities of nanozybiotics for future applications.

Antibiotic-loaded lactoferrin nanoparticles as a platform for enhanced infection therapy through targeted elimination of intracellular bacteria

Intracellular bacteria can multiply inside host cells and manipulate their biology, and the efficacy of traditional antibiotic drug therapy for intracellular bacteria is limited by inadequate drug accumulation. Fighting against these stealthy bacteria has been a long-standing challenge. Here, a system of stimuli-responsive lactoferrin (Lf) nanoparticles is prepared using protein self-assembly technology to deliver broad-spectrum antibiotic rifampicin (Rif) (Rif@Lf NPs) for enhanced infection therapy through targeted elimination of intracellular bacteria. Compared to Rif@BSA NPs, the Rif@Lf NPs can specifically target macrophages infected by bacteria, thus increasing the accumulation of Rif within macrophages. Subsequently, Rif@Lf NPs with positive surface charge further displayed targeted adherence to the bacteria within macrophages and released Rif rapidly in a redox-responsive manner. Combined with the antibacterial activities of Lf and Rif, the Rif@Lf NPs showed broad-spectrum antibiotic abilities to intracellular bacteria and biofilms. As a result, the Rif@Lf NPs with high safety exhibited excellent therapeutic efficacy in the disease models of subcutaneous infection, sepsis, and bacterial keratitis. Taken together, the antibiotic-loaded Lf nanoparticles present a promising platform to combat pathogen infections through targeted elimination of intracellular bacteria.

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.

Deep learning for multi-type infectious keratitis diagnosis: A nationwide, cross-sectional, multicenter study

The main cause of corneal blindness worldwide is keratitis, especially the infectious form caused by bacteria, fungi, viruses, and Acanthamoeba. The key to effective management of infectious keratitis hinges on prompt and precise diagnosis. Nevertheless, the current gold standard, such as cultures of corneal scrapings, remains time-consuming and frequently yields false-negative results. Here, using 23,055 slit-lamp images collected from 12 clinical centers nationwide, this study constructed a clinically feasible deep learning system, DeepIK, that could emulate the diagnostic process of a human expert to identify and differentiate bacterial, fungal, viral, amebic, and noninfectious keratitis. DeepIK exhibited remarkable performance in internal, external, and prospective datasets (all areas under the receiver operating characteristic curves > 0.96) and outperformed three other state-of-the-art algorithms (DenseNet121, InceptionResNetV2, and Swin-Transformer). Our study indicates that DeepIK possesses the capability to assist ophthalmologists in accurately and swiftly identifying various infectious keratitis types from slit-lamp images, thereby facilitating timely and targeted treatment.

Progressive ulcerative keratitis in dogs in the United Kingdom: Microbial isolates, antimicrobial sensitivity, and resistance patterns

OBJECTIVES

The objective of the study was to identify bacterial pathogens and their antimicrobial sensitivity profile associated with cases of canine progressive ulcerative keratitis.

MATERIALS AND METHODS

Analysis of microbial culture and sensitivity results from dogs with progressive ulcerative keratitis presenting to a UK referral practice between December 2018 and August 2020.

RESULTS

Positive bacterial cultures were obtained from 80/148 (54%) of the canine ulcers sampled with 99 bacterial isolates cultured. Streptococcus canis (n = 29), Pseudomonas aeruginosa (n = 19), and Staphylococcus pseudintermedius (n = 16) were the most common isolates. Pseudomonas aeruginosa was more likely to be isolated whether the ulcer was clinically malacic at the time of sampling (OR = 10.1, p < .001). Ulcers treated prior to culture with fusidic acid were 7.6 times more likely to be positive than those treated with any other antimicrobial(s). Bacterial isolates demonstrated resistance against neomycin (85%), fusidic acid (78%), and tetracycline (68%). Conversely, isolates were most likely to be sensitive to gentamicin (88%), ofloxacin (77%), ciprofloxacin (73%), and chloramphenicol (64%). Antimicrobial combinations of chloramphenicol or gentamicin with a fluoroquinolone (ofloxacin or ciprofloxacin) or chloramphenicol combined with gentamicin were the most effective on in vitro analysis (over 90% susceptibility of all isolates).

CONCLUSION

The most common bacterial species associated with canine progressive ulcerative keratitis in a UK referral population were S. canis, P. aeruginosa, and S. pseudintermedius. Combination antimicrobial therapy is recommended pending culture and sensitivity results given the varied antimicrobial susceptibility profiles and significant bacterial in vitro resistance to antimicrobial monotherapy.

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.

Increased tolerance to commonly used antibiotics in a Pseudomonas aeruginosa ex vivo porcine keratitis model

Introduction. Bacterial keratitis, particularly caused by Pseudomonas aeruginosa, is challenging to treat because of multi-drug tolerance, often associated with the formation of biofilms. Antibiotics in development are typically evaluated against planktonic bacteria in a culture medium, which may not accurately represent the complexity of infections in vivo.Hypothesis/Gap Statement. Developing a reliable, economic ex vivo keratitis model that replicates some complexity of tissue infections could facilitate a deeper understanding of antibiotic efficacy, thus aiding in the optimization of treatment strategies for bacterial keratitis.Methodology. Here we investigated the efficacy of three commonly used antibiotics (gentamicin, ciprofloxacin and meropenem) against Pseudomonas aeruginosa cytotoxic strain PA14 and invasive strain PA01 using an ex vivo porcine keratitis model.Results. Both strains of P. aeruginosa were susceptible to the MIC of the three tested antibiotics. However, significantly higher concentrations were necessary to inhibit bacterial growth in the minimum biofilm eradication concentration (MBEC) assay, with both strains tolerating concentrations greater than 512 mg l-1 of meropenem. When MIC and higher concentrations than MBEC (1024 mg l-1) of antibiotics were applied, ciprofloxacin exhibited the highest potency against both P. aeruginosa strains, followed by meropenem, while gentamicin showed the least potency. Despite this, none of the antibiotic concentrations used effectively cleared the infection, even after 18 h of continuous exposure.Conclusions. Further exploration of antibiotic concentrations and aligning dosing with clinical studies to validate the model is needed. Nonetheless, our ex vivo porcine keratitis model could be a valuable tool for assessing antibiotic efficacy.

Antimicrobials and antiseptics: Lowering effect on ocular surface bacterial flora - A systematic review

Topical antimicrobials and antiseptics are used perioperatively to reduce the ocular surface bacteria flora (OSBF) that are involved in the development of post-operative infectious complications. However, their effectiveness is still a controversial topic. This systematic review, performed according to the PRISMA guidelines and registered in PROSPERO, aims to provide an overview of the efficacy of the agents currently used in peri-cataract surgery and -intravitreal injections (IVI) in lowering the OSBF. Although effective in lowering OSBF, perioperative topical antimicrobials are associated with the risk of resistance development, with no obvious additional benefit compared with topical antisepsis. Conversely, the effectiveness of topical antiseptics before cataract surgery and IVI is strongly supported. Based on the available evidence, perioperative antimicrobials are not recommended, whereas the perioperative use of antiseptics is strongly recommended as prophylactic treatment for lowering the infection due to OSBF. Post-operative antimicrobials may be considered in eyes at higher risk for infection.

Microbial keratitis in Southern Malawi: a microbiological pilot study

OBJECTIVE

Microbial keratitis (MK) is a significant cause of blindness in sub-Saharan Africa. We investigated the feasibility of using a novel corneal impression membrane (CIM) for obtaining and processing samples by culture, PCR and whole-genome sequencing (WGS) in patients presenting with suspected MK in Malawi.

METHODS AND ANALYSIS

Samples were collected from patients presenting with suspected MK using a 12 mm diameter polytetrafluoroethylene CIM disc. Samples were processed using culture and PCR for Acanthamoeba, herpes simplex virus type 1 (HSV-1) and the bacterial 16S rRNA gene. Minimum inhibitory concentrations of isolates to eight antimicrobials were measured using susceptibility strips. WGS was used to characterise Staphylococcus aureus isolates.

RESULTS

71 eyes of 71 patients were included. The overall CIM isolation rate was 81.7% (58 positive samples from 71 participants). 69 (81.2%) of isolates were Gram-positive cocci. Coagulase-negative Staphylococcus 31.8% and Streptococcus species 14.1% were the most isolated bacteria. Seven (9.9%) participants were positive for HSV-1. Fungi and Acanthamoeba were not detected. Moxifloxacin and chloramphenicol offered the best coverage for both Gram-positive and Gram-negative isolates when susceptibility was determined using known antimicrobial first quartile concentrations and European Committee on Antimicrobial Susceptibility Testing breakpoints, respectively. WGS identified known virulence genes associated with S. aureus keratitis.

CONCLUSIONS

In a resource-poor setting, a CIM can be used to safely sample the cornea in patients presenting with suspected MK, enabling identification of causative microorganisms by culture and PCR. Although the microbiological spectrum found was limited to the dry season, these preliminary results could be used to guide empirical treatment.

Antimicrobial resistance in ocular infection: A review

Antimicrobial resistance (AMR) is a global public health threat with significant impact on treatment outcomes. The World Health Organization's Global Action Plan on AMR recommended strengthening the evidence base through surveillance programs and research. Comprehensive, timely data on AMR for organisms isolated from ocular infections are needed to guide treatment decisions and inform researchers and microbiologists of emerging trends. This article aims to provide an update on the development of AMR in ocular organisms, AMR in bacterial ocular infections and on AMR stewardship programs globally. The most common ocular pathogens are Pseudomonas aeruginosa, Staphylococcus spp., Streptococcus pneumoniae, and Haemophilus influenzae in ocular infections. A variety of studies and a few surveillance programs worldwide have reported on AMR in these infections over time. Fluoroquinolone resistance has increased particularly in Asia and North America. For conjunctivitis, the ARMOR cumulative study in the USA reported a slight decrease in resistance to ciprofloxacin. For keratitis, resistance to methicillin has remained stable for S. aureus and CoNS, while resistance to ciprofloxacin has decreased for MRSA globally. Methicillin-resistance and multidrug resistance are also emerging, requiring ongoing monitoring. Antimicrobial stewardship (AMS) programmes have a critical role in reducing the threat of AMR and improving treatment outcomes. To be successful AMS must be informed by up-to-date AMR surveillance data. As a profession it is timely for ophthalmology to act to prevent AMR leading to greater visual loss through supporting surveillance programmes and establishing AMS.

Applications of photodynamic therapy in keratitis

Keratitis is corneal inflammatory disease which may be caused by several reason such as an injury, allergy, as well as a microbial infection. Besides these, overexposure to ultraviolet light and unhygienic practice of contact lenses are also associated with keratitis. Based on the cause of keratitis, different lines of treatments are recommended. Photodynamic therapy is a promising approach that utilizes light activated compounds to instigate either killing or healing mechanism to treat various diseases including both communicable and non-communicable diseases. This review focuses on clinically-important patent applications and the recent literature for the use of photodynamic therapy against keratitis.

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.

Developments in Emerging Topical Drug Delivery Systems for Ocular Disorders

According to the current information, using nano gels in the eyes have therapeutic benefits. Industry growth in the pharmaceutical and healthcare sectors has been filled by nanotechnology. Traditional ocular preparations have a short retention duration and restricted drug bioavailability because of the eye's architectural and physiological barriers, a big issue for physicians, patients, and chemists. In contrast, nano gels can encapsulate drugs within threedimensional cross-linked polymeric networks. Because of their distinctive structural designs and preparation methods, they can deliver loaded medications in a controlled and sustained manner, enhancing patient compliance and therapeutic efficacy. Due to their excellent drugloading capacity and biocompatibility, nano-gels outperform other nano-carriers. This study focuses on using nano gels to treat eye diseases and provides a brief overview of their creation and response to stimuli. Our understanding of topical drug administration will be advanced using nano gel developments to treat common ocular diseases such as glaucoma, cataracts, dry eye syndrome, bacterial keratitis, and linked medication-loaded contact lenses and natural active ingredients.

In situ forming hydrogel loaded with predatory bacteria treats drug-resistant corneal infection

The development of potent bactericidal antibiotic alternatives is important to address the current antibiotic crisis. A representative example is the topical delivery of predatory Bdellovibrio bacteriovorus bacteria to treat ocular bacterial infection. However, the direct topical use of B. bacteriovorus suspensions has the problem of easy loss and inactivation. Here, a B. bacteriovorus in situ forming hydrogel (BIG) was constructed for the ocular delivery of B. bacteriovorus. BIGs, as a fluid in their primitive state, were temperature- and cation- dually sensitive, which was rapidly transformed into immobile gels in the ocular environment. BIGs not only kept the activity of B. bacteriovorus but also retained on the ocular surface for a long time. The biosafety of BIGs was good without HCEC cell toxicity and hemolysis. More importantly, BIGs highly inhibited the growth of drug-resistant Pseudomonas aeruginosa whether in vitro or in the infected rat eyes. The ocular infection was completely controlled by BIGs with no corneal ulcers and inflammations. This living bacteria gel is a promising medication for the local treatment of drug-resistant bacteria-induced ocular infection.

Rapid Point-of-Care Identification of Aspergillus Species in Microbial Keratitis

Importance

Microbial keratitis (MK) is a common cause of unilateral visual impairment, blindness, and eye loss in low-income and middle-income countries. There is an urgent need to develop and implement rapid and simple point-of-care diagnostics for MK to increase the likelihood of good outcomes.

Objective

To evaluate the diagnostic performance of the Aspergillus-specific lateral-flow device (AspLFD) to identify Aspergillus species causing MK in corneal scrape and corneal swab samples of patients presenting with microbial keratitis.

Design, Setting, and Participants

This diagnostic study was conducted between May 2022 and January 2023 at the corneal clinic of Aravind Eye Hospital in Madurai, Tamil Nadu, India. All study participants were recruited during their first presentation to the clinic. Patients aged 15 years or older met the eligibility criteria if they were attending their first appointment, had a corneal ulcer that was suggestive of a bacterial or fungal infection, and were about to undergo diagnostic scrape and culture.

Main Outcomes and Measures

Sensitivity and specificity of the AspLFD with corneal samples collected from patients with MK. During routine diagnostic scraping, a minimally invasive corneal swab and an additional corneal scrape were collected and transferred to aliquots of sample buffer and analyzed by lateral-flow device (LFD) if the patient met the inclusion criteria. Photographs of devices were taken with a smartphone and analyzed using a ratiometric approach, which was developed for this study. The AspLFD results were compared with culture reports.

Results

The 198 participants who met the inclusion criteria had a mean (range) age of 51 (15-85) years and included 126 males (63.6%). Overall, 35 of 198 participants with corneal scrape (17.7%) and 17 of 40 participants with swab samples (42.5%) had positive culture results for Aspergillus species. Ratiometric analysis results for the scrape samples found that the AspLFD achieved high sensitivity (0.89; 95% CI, 0.74-0.95), high negative predictive value (0.97; 95% CI, 0.94-0.99), low negative likelihood ratio (0.12; 95% CI, 0.05-0.30), and an accuracy of 0.94 (95% CI, 0.90-0.97). Ratiometric analysis results for the swab samples showed that the AspLFD had high sensitivity (0.94; 95% CI, 0.73-1.00), high negative predictive value (0.95; 95% CI, 0.76-1.00), low negative likelihood ratio (0.07; 95% CI, 0.01-0.48), and an accuracy of 0.88 (95% CI, 0.73-0.96).

Conclusions and Relevance

Results of this diagnostic study suggest that AspLFD along with the ratiometric analysis of LFDs developed for this study has high diagnostic accuracy in identifying Aspergillus species from corneal scrapes and swabs. This technology is an important step toward the provision of point-of-care diagnostics for MK and could inform the clinical management strategy.

Tuning Ligands Ratio Allows for Controlling Gold Nanocluster Conformation and Activating a Nonantimicrobial Thiol Fragrance for Effective Treatment of MRSA-Induced Keratitis

Bacterial keratitis is a serious ocular disease that affects millions of people worldwide each year, among which ≈25% are caused by Staphylococcus aureus. With the spread of bacterial resistance, refractory keratitis caused by methicillin-resistant S. aureus (MRSA) affects ≈120 000-190 000 people annually and is a significant cause of infectious blindness. Atomically precise gold nanoclusters (GNCs) recently emerged as promising antibacterial agents; although how the GNC structure and capping ligands control the antibacterial properties remains largely unexplored. In this study, by adjusting the ratio of a "bulky" thiol fragrance to a linear zwitterionic ligand, the GNC conformation is transformed from Au25 (SR)18 to Au23 (SR)16 species, simultaneously converting both inactive thiol ligands into potent antibacterial nanomaterials. Surprisingly, mixed-ligand capped Au23 (SR)16 GNCs exhibit superior antibacterial potency compared to their monoligand counterparts. The optimal GNC is highly potent against MRSA, showing >1024-fold lower minimum inhibitory concentration than the corresponding free ligands. Moreover, it displays excellent potency in treating MRSA-induced keratitis in mice with greatly accelerated corneal recovery (by approximately ninefold). Thus, this study establishes a feasible method to synthesize antibacterial GNCs by adjusting the ligand ratio to control GNC conformation and active non-antibacterial ligands, thereby greatly increasing the repertoires for combating multidrug-resistant bacterial infections.

A Biomimetic Peptide-drug Supramolecular Hydrogel as Eyedrops Enables Controlled Release of Ophthalmic Drugs

The rapid clearance of instilled drugs from the ocular surface due to tear flushing and excretion results in low drug bioavailability, necessitating the development of new drug delivery routes. Here, we generated an antibiotic hydrogel eye drop that can extend the pre-corneal retention of a drug after topical instillation to address the risk of side effects (e.g., irritation and inhibition of enzymes), resulting from frequent and high-dosage administrations of antibiotics used to obtain the desired therapeutic drug concentration. The covalent conjugation of small peptides to antibiotics (e.g., chloramphenicol) first endows the self-assembly ability of peptide-drug conjugate to generate supramolecular hydrogels. Moreover, the further addition of calcium ions, which are also widely present in endogenous tears, tunes the elasticity of supramolecular hydrogels, making them ideal for ocular drug delivery. The in vitro assay revealed that the supramolecular hydrogels exhibited potent inhibitory activities against both gram-negative (e.g., Escherichia coli) and gram-positive (e.g., Staphylococcus aureus) bacteria, whereas they were innocuous toward human corneal epithelial cells. Moreover, the in vivo experiment showed that the supramolecular hydrogels remarkably increased pre-corneal retention without ocular irritation, thereby showing appreciable therapeutic efficacy for treating bacterial keratitis. This work, as a biomimetic design of antibiotic eye drops in the ocular microenvironment, addresses the current issues of ocular drug delivery in the clinic and further provides approaches to improve the bioavailability of drugs, which may eventually open new directions to resolve the difficulty of ocular drug delivery. STATEMENT OF SIGNIFICANCE: Herein, we present a biomimetic design for antibiotic hydrogel eye drops mediated by calcium ions (Ca²⁺) in the ocular microenvironment, which can extend the pre-corneal retention of antibiotics after topical instillation. The mediation of Ca²⁺ which is widely present in endogenous tears, tunes the elasticity of hydrogels, making them ideal for ocular drug delivery. Since increasing the ocular retention of antibiotic eye drops enhances its action and reduces its adverse effects, this work may lead to an approach of peptide-drug-based supramolecular hydrogel for ocular drug delivery in clinics to combat ocular bacterial infections.

Cutibacterium (Formerly Propionibacterium ) acnes Keratitis: A Review

ABSTRACT

Infectious keratitis is a devastating cause of vision loss worldwide. Cutibacterium acnes ( C. acnes ), a commensal bacterium of the skin and ocular surface, is an underrecognized but important cause of bacterial keratitis. This review presents the most comprehensive and up-to-date information for clinicians regarding the risk factors, incidence, diagnosis, management, and prognosis of C. acnes keratitis (CAK). Risk factors are similar to those of general bacterial keratitis and include contact lens use, past ocular surgery, and trauma. The incidence of CAK may be approximately 10%, ranging from 5% to 25% in growth-positive cultures. Accurate diagnosis requires anaerobic blood agar and a long incubation period (≥7 days). Typical clinical presentation includes small (<2 mm) ulcerations with deep stromal infiltrate causing an anterior chamber cell reaction. Small, peripheral lesions are usually resolved, and patients recover a high visual acuity. Severe infections causing VA of 20/200 or worse are common and often do not significantly improve even after treatment. Vancomycin is considered the most potent antibiotic against CAK, although other antibiotics such as moxifloxacin and ceftazidime are more commonly used as first-line treatment.

Advances in Nanogels for Topical Drug Delivery in Ocular Diseases

Nanotechnology has accelerated the development of the pharmaceutical and medical technology fields, and nanogels for ocular applications have proven to be a promising therapeutic strategy. Traditional ocular preparations are restricted by the anatomical and physiological barriers of the eye, resulting in a short retention time and low drug bioavailability, which is a significant challenge for physicians, patients, and pharmacists. Nanogels, however, have the ability to encapsulate drugs within three-dimensional crosslinked polymeric networks and, through specific structural designs and distinct methods of preparation, achieve the controlled and sustained delivery of loaded drugs, increasing patient compliance and therapeutic efficiency. In addition, nanogels have higher drug-loading capacity and biocompatibility than other nanocarriers. In this review, the main focus is on the applications of nanogels for ocular diseases, whose preparations and stimuli-responsive behaviors are briefly described. The current comprehension of topical drug delivery will be improved by focusing on the advances of nanogels in typical ocular diseases, including glaucoma, cataracts, dry eye syndrome, and bacterial keratitis, as well as related drug-loaded contact lenses and natural active substances.

Efficient antibacterial AIEgens induced ROS for selective photodynamic treatment of bacterial keratitis

Bacterial keratitis (BK) is an acute infection of the cornea, accompanied by uneven epithelium boundaries with stromal ulceration, potentially resulting in vision loss. Topical antibiotic is the regular treatment for BK. However, the incidence rate of multidrug-resistant bacteria limits the application of traditional antibiotics. Therefore, a cationic aggregation-induced emission luminogens (AIEgens) named TTVP is utilized for the treatment of BK. TTVP showed no obvious cytotoxicity in maintaining the normal cell morphology and viability under a limited concentration, and revealed the ability to selectively combine with bacteria in normal ocular environment. After light irradiation, TTVP produced reactive oxygen species (ROS), thus exerting efficient antibacterial ability in vitro. What's more, in rat models of Staphylococcus aureus (S. aureus) infection, the therapeutic intervention of TTVP lessens the degree of corneal opacity and inflammatory infiltration, limiting the spread of inflammation. Besides, TTVP manifested superior antibacterial efficacy than levofloxacin in acute BK, endowing its better vision salvage ability than conventional method. This research demonstrates the efficacy and advantages of TTVP as a photodynamic drug in the treatment of BK and represents its promise in clinical application of ocular infections.

Artificial intelligence-assisted diagnosis of ocular surface diseases

With the rapid development of computer technology, the application of artificial intelligence (AI) in ophthalmology research has gained prominence in modern medicine. Artificial intelligence-related research in ophthalmology previously focused on the screening and diagnosis of fundus diseases, particularly diabetic retinopathy, age-related macular degeneration, and glaucoma. Since fundus images are relatively fixed, their standards are easy to unify. Artificial intelligence research related to ocular surface diseases has also increased. The main issue with research on ocular surface diseases is that the images involved are complex, with many modalities. Therefore, this review aims to summarize current artificial intelligence research and technologies used to diagnose ocular surface diseases such as pterygium, keratoconus, infectious keratitis, and dry eye to identify mature artificial intelligence models that are suitable for research of ocular surface diseases and potential algorithms that may be used in the future.

Membrane-Active Nonivamide Derivatives as Effective Broad-Spectrum Antimicrobials: Rational Design, Synthesis, and Biological Evaluation

Antibiotic resistance is emerging as a "global public health concern". To address the growing epidemic of multidrug-resistant pathogens, the development of novel antimicrobials is urgently needed. In this study, by biomimicking cationic antibacterial peptides, we designed and synthesized a series of new membrane-active nonivamide and capsaicin derivatives as peptidomimetic antimicrobials. Through modulating charge/hydrophobicity balance and rationalizing structure-activity relationships of these peptidomimetics, compound 51 was identified as the lead compound. Compound 51 exhibited potent antibacterial activity against both Gram-positive bacteria (MICs = 0.39-0.78 μg/mL) and Gram-negative bacteria (MICs = 1.56-6.25 μg/mL), with low hemolytic activity and low cytotoxicity. Compound 51 displayed a faster bactericidal action through a membrane-disruptive mechanism and avoided bacterial resistance development. Furthermore, compound 51 significantly reduced the microbial burden in a murine model of keratitis infected by Staphylococcus aureus or Pseudomonas aeruginosa. Hence, this design strategy can provide a promising and effective solution to overcome antibiotic resistance.

Recent Applications of Contact Lenses for Bacterial Corneal Keratitis Therapeutics: A Review

Corneal keratitis is a common but severe infectious disease; without immediate and efficient treatment, it can lead to vision loss within a few days. With the development of antibiotic resistance, novel approaches have been developed to combat corneal keratitis. Contact lenses were initially developed to correct vision. Although silicon hydrogel-based contact lenses protect the cornea from hypoxic stress from overnight wear, wearing contact lenses was reported as an essential cause of corneal keratitis. With the development of technology, contact lenses are integrated with advanced functions, and functionalized contact lenses are used for killing bacteria and preventing infectious corneal keratitis. In this review, we aim to examine the current applications of contact lenses for anti-corneal keratitis.