Infectious Keratitis Research Articles

The antibiotic resistance profiles of Pseudomonas aeruginosa in the Asia Cornea Society Infectious Keratitis Study

PurposeTo describe the prevalence and antibiotic resistance profiles of Pseudomonasaeruginosa isolated from the Asia Cornea Society Infectious Keratitis Study (ACSIKS).MethodsAll bacterial isolates from ACSIKS underwent repeat microbiological identification in a central repository in Singapore. Minimum inhibitory concentration (MIC) determination was conducted for isolates of P. aeruginosa against thirteen antibiotics from 6 different classes, and categorized based on Clinical Laboratory Standard Institutes’ reference ranges. The percentage rates of resistance (non-susceptibility) to each antibiotic included isolates of both intermediate and complete resistance. Multi-drug resistance (MDR) was defined as non-susceptibility to at least one agent in three or more antimicrobial classes.ResultsOf the 1493 unique bacterial specimens obtained from ACSIKS, 319 isolates were of P. aeruginosa. The majority of isolates were from centers in India (n = 118, 37%), Singapore (n = 90, 28.2%), Hong Kong (n = 31, 9.7%) and Thailand (n = 30, 9.4%). The cumulative antibiotic resistance rate was the greatest for polymyxin B (100%), ciprofloxacin (17.6%) and moxifloxacin (16.9%), and lowest for cefepime (11.6%) and amikacin (13.5%). Isolates from India demonstrated the highest antibiotic resistance rates of all the centers, and included moxifloxacin (47.5%) and ciprofloxacin (39.8%). Forty-eight of the 59 MDR isolates also originated from India. Antibiotic resistance rates were significantly lower in the other ACSIKS centers, and were typically less than 10%.ConclusionsThe antibiotic resistance profiles of P. aeruginosa varied between different countries. While it was low for most countries, substantial antibiotic resistance and a significant number of multi-drug resistant isolates were noted in the centers from India.

Antibiotic-free ocular sterilization while suppressing immune response to protect corneal transparency in infectious keratitis treatment

Clinical guidelines for infectious keratitis treatment require that anti-inflammatory drugs can only be used after infection elimination, which causes irreversible inflammatory damage to the cornea. In this work, photodynamic metal organic frameworks (PCN-224) were used as drug carrier to load Pt NPs with catalase-like activity and anti-inflammatory drug (Dexamethasone, DXMS) for endogenous oxygen generation and reduced corneal damage, respectively. The photodynamic therapy (PDT) effect was greatly enhanced in bacteria elimination and bacterial biofilms removal through catalysis of overexpressed hydrogen peroxide (H2O2, ∼8.0 and 31.0 μM in bacterial solution and biofilms, respectively) into oxygen by Pt NPs. More importantly, the cationic liposome modified PCN-224@Pt@DXMS@Liposomes (PPDL NPs) greatly enhanced the adhesion to negatively charged ocular surface and penetration into corneal barrier and bacterial biofilms. Both in vitro cell viability test and in vivo eye irritation tests proved good biocompatibility of PPDL NPs under 660 nm laser irradiation. Furthermore, PDT of PPDL NPs in rapid bacteria killing was verified through infectious keratitis animal model. The superior bactericidal effect of antibacterial materials could largely replace the bactericidal effect of the immune system. It is worth mentioning that this simultaneous sterilization and anti-inflammation treatment mode is a new exploration against the clinical treatment guidelines.

Steroids and Cross-Linking for Ulcer Treatment Trial II: Baseline Characteristics.

The Steroids and Cross-linking for Ulcer Treatment Trial is an NIH-funded international, randomized, double-masked, sham and placebo-controlled clinical trial to determine the benefit of adjunctive corneal cross-linking with riboflavin and/or topical difluprednate in addition to topical antibiotic drops for treatment of smear-positive bacterial ulcers. The purpose of this study was to explore the baseline characteristics for infection of patients enrolled, and the ocular comorbidities of patients screened for inclusion. Of the 2005 patients with smear-positive bacterial ulcers screened, 280 patients were enrolled. Descriptive statistics were used to summarize and characterize the data. Eligible patients in India had baseline factors associated with agricultural work (N = 132; 47%) and manual labor (N = 54; 19%), whereas patients in the United States were associated with contact lens wear (N = 11; 69%) (P <0.001). Nearly, 10% of patients with unilateral infectious keratitis are at risk of bilateral blindness because of preexisting visual disability in their other eye and thus ineligible for inclusion. India had higher rates of exclusionary factors for blindness in the other eye such as cataract (N = 48; 27%) and glaucoma (N = 24; 13) compared with the United States (N = 0; 0%) (P <0.001). While corneal ulceration is an important cause of disability in technologically advanced countries, it occurs more frequently in low and middle-income countries, and the implications on these populations should be considered. These baseline factors can be evaluated to address such health care disparities.

A Comprehensive Review on Acanthamoeba Keratitis: An Overview of Epidemiology, Risk Factors, and Therapeutic Strategies.

Acanthamoeba keratitis (AK) is a rare but severe corneal infection caused by the free-living amoeba, Acanthamoeba, which is ubiquitously present in the environment. This condition predominantly affects contact lens wearers but can also occur in non-lens users, particularly those exposed to contaminated water or with compromised immune systems. AK is characterized by progressive corneal inflammation, epithelial defects, and ulceration, which can lead to significant visual impairment or blindness if not promptly diagnosed and treated. This review aims to provide a comprehensive overview of AK by synthesizing current knowledge on its epidemiology, risk factors, pathophysiology, clinical manifestations, diagnostic approaches, and therapeutic strategies. The review also highlights preventive measures and public health strategies to reduce the incidence of this debilitating condition. A detailed examination of existing literature was conducted, focusing on the global incidence of AK, demographic trends, and various risk factors such as contact lens use, environmental exposures, and immunity status. The review also delves into the pathophysiology of Acanthamoeba infection, the host immune response, and the challenges in distinguishing AK from other forms of infectious keratitis. Therapeutic strategies, including medical and surgical interventions, are analyzed, along with emerging treatments. The global incidence of AK has increased, particularly among contact lens users, due to poor hygiene practices and environmental exposures. Early diagnosis remains challenging, often leading to delayed treatment and poorer outcomes. Biguanides and diamidines are the mainstays of medical therapy, with surgical options considered in advanced cases. Emerging therapies, such as photodynamic therapy and antimicrobial peptides, show promise in enhancing treatment outcomes.AK poses a significant threat to ocular health due to its potential for severe visual impairment and the complexities associated with its diagnosis and treatment. Early recognition, appropriate management, and public health initiatives focused on prevention are crucial for improving patient outcomes. Ongoing research and a collaborative approach among healthcare providers are essential to advancing the understanding and management of AK.

Bacterial keratitis : Clinical aspects, pathogens and treatment

Bacterial infections are by far the most frequent cause of infectious keratitis in high-income countries. The clinical appearance can vary widely depending on the type and species of bacteria, ranging from small superficial infiltrates to necrotizing forms. The numerous classes of available antibiotics render the treatment scope diverse and complex, especially before the pathogen has been specified and the sensitivity to antibiotics has been tested. New therapeutic approaches to reduce bacterial virulence are in development. This CME article focuses on the clinical, diagnostic and therapeutic approaches to recognize and treat bacterial keratitis.

A surgical alternative of fusiform penetrating keratoplasty for the management of severe infectious keratitis.

To describe the surgical procedure of fusiform penetrating keratoplasty (FPK) using multiple trephines of different sizes for treating patients with severe infectious keratitis. Fourteen eyes underwent FPK, and 15 eyes received conventional penetrating keratoplasty (PK) were included in the study. The best-corrected visual acuity (BCVA), refractive outcomes, endothelial cell density, and postoperative complications were recorded. The FPK group was followed for an average of 15.3±2.1mo, whereas the PK group was followed for 16.1±1.9mo. The corneal ulcers were elliptical-shaped in all 14 eyes in the FPK group. The mean BCVA (logMAR, 0.26±0.13) showed no statistically significant differences from that in the PK group (logMAR, 0.21±0.12, P>0.05) at 1y after surgery. But the mean curvature, mean astigmatism, and mean spherical equivalent in the FPK group were lower than those in the PK group (P<0.05). Peripheral anterior synechia was observed in one patient in the FPK group, whereas 6 patients in the PK group. Suture loosening and neovascularization were observed in 4 and 5 eyes in the PK group, respectively. No graft immune rejection or elevation of intraocular pressure was observed in the two groups. For patients with elliptical-shaped corneas or corneal ulcers, FPK can avoid disrupting of corneal limbus, reduce the risk of postoperative complications, and can result in satisfactory visual quality.

Cyanoacrylate glue: An emerging alternative for sealing of corneal perforation

Maintaining corneal wound integrity is an important goal in corneal perforations resulting from either traumatic or non- traumatic etiology. Tissue adhesives (TA’s) are group of synthetic or naturally occurring compounds, which helps in wound reconstruction and have emerged as alternatives to conventional sutures. Our study aims to evaluate the efficacy N- butyl cyanoacrylate TA in corneal perforations following infectious keratitis by assessment of its morphological and functional outcome. A prospective observational study conducted over a period of 6 months on 42 eyes of 42 patients with perforated corneal ulcer, fulfilling the inclusion criteria, presenting to our outpatient department. A standard technique was used to apply TA to the site of perforation under topical anaesthesia in all patients and they were followed-up for a period of 6 weeks. Data analysis was done using SPSS software (Version 22) and P value calculated by Pearson Chi-square test (Fisher exact test). P- value &amp;#60; 0.05 was considered statistically significant. Morphological outcome in this study showed statistically significant relationship with causative organism and size of the perforations (p&amp;#60;0.05). The functional outcome showed statistically significant relationship with location of perforation, duration of symptoms and duration of stay of glue (p&amp;#60;0.05). TA’s works well when the corneal perforation is &amp;#60;1.5 mm in diameter. The morphological outcome of TA depends upon etiology, size of perforations and complications significantly. Functional outcome of tissue adhesive shows significant association with location of perforation, duration of symptoms and stay of glue.

Complications After Pediatric Penetrating Keratoplasty: An IRIS Registry Study.

To describe the frequency of postoperative complications in children undergoing penetrating keratoplasty (PK). This retrospective cohort study included pediatric patients (aged 0-18 years) in the Intelligent Research in Sight (IRIS) Registry who underwent primary PK between January 2013 and December 2020. Patients were identified using Current Procedure Terminology codes. Postoperative complications were identified using International Classification of Diseases Revision 9 and 10 codes and categorized as complications affecting the anterior segment (epithelial defect, infectious keratitis, neurotrophic keratitis, and glaucoma) or posterior segment (vitreous hemorrhage, retinal detachment, choroid detachment, choroidal hemorrhage, endophthalmitis, epiretinal membrane, and proliferative vitreoretinopathy). Of the 544 pediatric patients undergoing PK, 259 (47.6%) experienced postoperative complications. Anterior segment complications (n = 222, 40.8%) were more common than posterior segment complications (n = 96, 17.6%). The most common anterior complication was infectious keratitis (n = 163, 30.0%) with a median onset time of 275 days (IQR 50-560 days) after surgery. Vitreous hemorrhage (n = 52, 9.6%) and retinal detachment (n = 48, 8.8%) were the most common posterior segment complications. Infectious keratitis was the most common postoperative complication in children undergoing PK. More complications occurred in the anterior segment (70%) of the eye as compared with the posterior segment (30%). These findings demonstrate the challenges associated with pediatric PK and may help guide postoperative monitoring and management.

Dual Role of Cutibacterium acnes: Commensal Bacterium and Pathogen in Ocular Diseases.

Microbiota present around the ocular surface, encompassing the eyelid skin, the conjunctival sac, and the meibomian glands, play a significant role in various inflammatory conditions associated with the ocular surface. Cutibacterium acnes (C. acnes), formerly, Propionibacterium acnes, is one of the most predominant commensal bacteria and its relative abundance declines with aging. However, it can act as both an infectious and an immunogenic pathogen. As an infectious pathogen, C. acnes has been reported to cause late onset endophthalmitis post-cataract surgery and infectious keratitis. On the other hand, it can trigger immune responses resulting in conditions such as phlyctenules in the cornea, chalazion in the meibomian glands, and granuloma formation in ocular sarcoidosis. This review explores the role of C. acnes in ocular inflammation, specifically highlighting its implications for diagnosis and management.

Microbiological culture versus 16S/18S rRNA gene PCR-sanger sequencing for infectious keratitis: a three-arm, diagnostic cross-sectional study.

To compare the diagnostic performance of microbiological culture and 16S/18S rRNA gene polymerase chain reaction (PCR)-Sanger sequencing for infectious keratitis (IK) and to analyse the effect of clinical disease severity on test performance and inter-test concordance. This was a three-arm, diagnostic cross-sectional study. We included all eligible patients who presented with presumed bacterial/fungal keratitis to the Queen's Medical Centre, Nottingham, UK, between June 2021 and September 2022. All patients underwent simultaneous culture (either direct or indirect culture, or both) and 16S (pan-bacterial)/18S (pan-fungal) ribosomal RNA (rRNA) PCR-Sanger sequencing. The bacterial/fungal genus and species identified on culture were confirmed using matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry. Relevant clinical data were also collected to analyze for any potential clinico-microbiological correlation. Main outcome measures included the diagnostic yield, test accuracy (including sensitivity and specificity), and inter-test agreement [including percent agreement and Cohen's kappa (k)]. A total of 81 patients (86 episodes of IK) were included in this study. All organisms identified were of bacterial origin. Diagnostic yields were similar among direct culture (52.3%), indirect culture (50.8%), and PCR (43.1%; p = 0.13). The addition of PCR enabled a positive diagnostic yield in 3 (9.7%) direct culture-negative cases. Based on composite reference standard, direct culture had the highest sensitivity (87.5%; 95% CI, 72.4-95.3%), followed by indirect culture (85.4%; 95% CI, 71.6-93.5%) and PCR (73.5%; 95% CI, 59.0-84.6%), with 100% specificity noted in all tests. Pairwise comparisons showed substantial agreement among the three tests (percent agreement = 81.8-86.2%, Cohen's k = 0.67-0.72). Clinico-microbiological correlation demonstrated higher culture-PCR concordance in cases with greater infection severity. This study highlights a similar diagnostic performance of direct culture, indirect culture and 16S rRNA PCR for bacterial keratitis, with substantial inter-test concordance. PCR serves as a useful diagnostic adjuvant to culture, particularly in culture-negative cases or those with lesser disease severity (where culture-PCR concordance is lower).

Novel treatment of infectious keratitis in canine corneas using ultraviolet C (UV-C) light.

To investigate the therapeutic effect of 275 nm wavelength ultraviolet C (UV-C) light for treatment of bacterial keratitis in canine corneas using an affordable, broadly available modified handheld device. UV-C therapy (UVCT) was evaluated in two experiments: invitro using triplicates of three bacterial genera (Staphylococcus, Streptococcus, Pseudomonas spp., and a mix of all species) where the UVCT was performed at a distance of 10, 15, and 20 mm with 1 or 2 doses (4 h apart) for 5, 15, or 30 s; exvivo model where healthy canine corneal buttons were inoculated superficially and deep (330 μm) with the same bacterial isolates and treated at a 10 mm distance for 15 s with one dose of 22.5 mJ/cm2. Fluorescent marker (STYO9-PI) was used to label (green = live bacteria, red = dead bacteria), and confocal microscopy was used to image the bacteria. In vitro results showed all plates treated with UVCT had 100% bactericidal effect for all isolates with single dose of 15 s at 10 mm distance or two doses, 4 h apart at 15 mm and was ineffective with single dose at 15-20 mm. The exvivo results confirmed a significant decrease in bacterial load for all isolates on samples inoculated superficially but were inconclusive for intrastromal ones. UVCT confirmed the therapeutic potential for all tested isolates, for both invitro and exvivo experiments using a single exposure of 15 s. While safety studies are underway, clinical trials are warranted.

Fungal keratitis among inpatients with corneal ulcers in Thai Binh, Vietnam: A retrospective observational study

Background: Infectious keratitis can be caused by bacteria, fungi, and viruses. Fungi are a common pathogen, especially in developing countries like India, Nepal, and Bangladesh where the prevalence ranges from 20% to 60%. In Vietnam, fungal keratitis accounted for the highest number of keratitis cases in a study conducted at the central eye hospital over a 5-year period (57%). Therefore, it is necessary to collect specific background information connected to the types of fungal keratitis in corneal ulcer cases in this region. Aims and Objectives: The aim of this study was to investigate the prevalence of fungal keratitis and the epidemiological features in 216 cases of fungal keratitis out of a total of 240 cases of infectious keratitis. Materials and Methods: This retrospective study collected secondary data from medical records of 240 inpatients with infectious keratitis who were treated at the ophthalmology hospital in Thai Binh, Vietnam, from January 01st, 2021 to June 30th, 2022. Patients with a positive fungal-directed smear were analyzed in detail for the type of fungus isolated, sociodemographic data, predisposing risk factors, prior treatment modalities, and laboratory results for the distribution pattern of fungus species. Results: Among the 240 cases, 126 (52.5%) were diagnosed with fungal keratitis by direct microscopic examination. Culture results showed the highest rate of Fusarium spp. (43.3%). The age group of 41–60 years was most commonly involved (40.5%). Males were more affected by fungal keratitis than females, (53.2% compared to 46.8%), with farmers being the most common occupation correlated with fungal keratitis (55.6%). The rate of fungal keratitis patients due to agricultural injuries was the highest compared to other risks (47.6%) and most patients self-medicated before going to the hospital, with many not knowing or remembering what medications they had taken (52.4%). Conclusion: The study revealed a high rate of fungal keratitis among the total of infectious keratitis cases in Thai Binh, Vietnam. Fusarium spp. was the most commonly isolated fungi. The study also highlighted the impact of agricultural injuries on fungal keratitis, especially in regions like Thai Binh.

Utilization of multiplex polymerase chain reaction for simultaneous and rapid detection of viral infections from different ocular structures

The impact of viral keratitis (VK) on individuals and society is notable. Early diagnosis and treatment are crucial in managing viral keratitis effectively. Timely intervention with antiviral medications and supportive care can help mitigate the severity of the infection and improve visual outcomes. We examined the prevalence of varicella-zoster virus (VZV), herpes simplex virus type 1 (HSV-1), adenovirus (AdV) and herpes simplex virus type 2 (HSV-2) in patients suspected for ocular infections. Patients included in the study exhibited various clinical manifestations indicative of ocular pathology, such as infectious keratitis, corneal scar, endogenous endophthalmitis, panuveitis, endothelitis, stromal edema, and other relevant conditions. Four different types of tear fluid, corneal samples epithelium, aqueous humor and vitreous humor were taken. After genome extraction, multiplex real-time PCR was used for diagnosis of viruses. 48 (29.6%) out of the total of 162 (100%) eye specimen were positive. The dominant prevalence was VZV (12.3%) and HSV-1 (11.7%) followed by AdV (4.9%) and HSV-2 (0.6%). There were 4 (8.3%) coinfections within the samples (HSV-1 and VZV). Aqueous humor samples demonstrated superior virus detection ability and our only HSV-2 positive sample was from aqueous humor. The utilization of multiplex real-time PCR assays in differential diagnosis of VK holds promise for expeditious diagnoses while also preventing unwarranted antibiotic prescriptions. Moreover, the aqueous humor appears to be a more sensitive site for detecting viral keratitis.

The immunobiology of corneal HSV-1 infection and herpetic stromal keratitis.

SUMMARYHuman alphaherpesvirus 1 (HSV-1) is a highly successful neurotropic pathogen that primarily infects the epithelial cells lining the orofacial mucosa. After primary lytic replication in the oral, ocular, and nasal mucosal epithelial cells, HSV-1 establishes life-long latency in neurons within the trigeminal ganglion. Patients with compromised immune systems experience frequent reactivation of HSV-1 from latency, leading to virus entry in the sensory neurons, followed by anterograde transport and lytic replication at the innervated mucosal epithelial surface. Although recurrent infection of the corneal mucosal surface is rare, it can result in a chronic immuno-inflammatory condition called herpetic stromal keratitis (HSK). HSK leads to gradual vision loss and can cause permanent blindness in severe untreated cases. Currently, there is no cure or successful vaccine to prevent latent or recurrent HSV-1 infections, posing a significant clinical challenge to managing HSK and preventing vision loss. The conventional clinical management of HSK primarily relies on anti-virals to suppress HSV-1 replication, anti-inflammatory drugs (such as corticosteroids) to provide symptomatic relief from pain and inflammation, and surgical interventions in more severe cases to replace damaged cornea. However, each clinical treatment strategy has limitations, such as local and systemic drug toxicities and the emergence of anti-viral-resistant HSV-1 strains. In this review, we summarize the factors and immune cells involved in HSK pathogenesis and highlight alternate therapeutic strategies for successful clinical management of HSK. We also discuss the therapeutic potential of immunoregulatory cytokines and immunometabolism modulators as promising HSK therapies against emerging anti-viral-resistant HSV-1 strains.

Clinical and Etiology Presentations of Keratitis Caused by Mixed Infectious Agents (Bacteria and Fungi)

Introduction: Microbiological studies following the culture of corneal infiltrates are the gold standard for determining the etiology of infectious keratitis caused by bacteria or fungi; however, even if a culture of the corneal ulcer is obtained. Purpose: To investigate the predisposing factors and clinical and Etiology presentations of keratitis caused by mixed infectious agents (bacteria and fungi). Methods: This was a prospective study of cases with mixed bacterial and fungal keratitis, done between July to December 2022 in Department of Ophthalmology, Netraloy Eye Care Center, Thanthania, Bogura Sadar, Bogura, Bangladesh. Sixty (60) cases of mixed bacterial and fungal keratitis were identified. Samples (corneal swabs and scrapings) were collected aseptically from corneal ulcer patients. Isolation and identification of the microbial agents and antimicrobial susceptibility testing were done in the Microbiology and Pathology departments. Results: 38 cases (63.3%) were men, and the mean age was 54.2±9.3 years. The affected people were mostly (50; 83.3%) residing in the rural areas. 34 patients (56.7%) were involved in agricultural activities. The people of 41- 60 years of age were particularly prone to this disease (40; 66.7%). The most common predisposing factor for mixed keratitis was a history of ocular trauma (42; 70%) and 28 patients (46.7%) had a history of trauma with vegetative matter. The incidence of the disease was highest in the monsoon season, between June to September (32; 53.3%). The most common causative bacterial organisms was Staphylococcus aureus (26;43.3%) followed by Pseudomonas secies (10;16.7%) and among fungal organisms was Aspervgillus fumigates (22;36.7%) followed by Fusarium species (12;20%). Conclusion: The identification of the etiology and the predisposing factors of corneal ulcers in this region are important for the prevention and early treatment of the disease. Usually, patients with mixed bacterial and fungal keratitis have poor prognosis. Thus, when the infectious keratitis is running an atypical course or found unresponsive to the initial medical treatment, the possibility of a mixed infection by bacterial and fungal organisms should be considered.

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

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. 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. 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). 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.

Membrane Disruption-Enhanced Photodynamic Therapy against Gram-Negative Bacteria by a Peptide-Photosensitizer Conjugate.

Photodynamic therapy (PDT) emerges as a promising strategy for combating bacteria with minimal drug resistance. However, a significant hurdle lies in the ineffectiveness of most photosensitizers against Gram-negative bacteria, primarily attributable to their characteristic impermeable outer membrane (OM) barrier. To tackle this obstacle, we herein report an amphipathic peptide-photosensitizer conjugate (PPC) with intrinsic outer membrane disruption capability to enhance PDT efficiency against Gram-negative bacteria. PPC is constructed by conjugating a hydrophilic ultrashort cationic peptide to a hydrophobic photosensitizer. PPC could efficiently bind to the OM of Gram-negative bacteria through electrostatic adsorption, and subsequently disrupt the structural integrity of the OM. Mechanistic investigations revealed that PPC triggers membrane disruption by binding to both lipopolysaccharide (LPS) and phospholipid leaflet in the OM, enabling effective penetration of PPC into the Gram-negative bacteria interior. Upon light irradiation, PPC inside bacteria generates singlet oxygen not only to effectively decrease the survival of Gram-negative bacteria P. aeruginosa and E. coli to nearly zero in vitro, but also successfully cure the full-thickness skin infection and bacterial keratitis (BK) induced by P. aeruginosa in animal models. Thus, this study provides a broad-spectrum antibacterial phototherapeutic design strategy by the synergistic action of membrane disruption and PDT to combat Gram-negative bacteria.

Influence of Opacity Depth on Big Bubble Formation During Deep Anterior Lamellar Keratoplasty in Corneal Stromal Scars.

To identify the key preoperative predictors of big bubble (BB) formation during deep anterior lamellar keratoplasty in patients with corneal stromal scars (CSS). This retrospective cohort study included consecutive patients with CSS after infective keratitis who underwent BB-deep anterior lamellar keratoplasty between January 2021 and July 2023 at a tertiary referral center. Topographic and tomographic data were collected to compare the rates and types of BB formations. Anterior segment optical coherence tomography (AS-OCT) was employed to assess the maximum depth of opacity by dividing the stroma into 3 zones of equal thickness: anterior (stage A), mid (stage B), and posterior stroma (stage C). Multivariate logistic regression analysis was performed to identify the potential preoperative predictors of bubble formation. Pneumatic dissection was achieved in 13 of 33 eyes (39.4%), with 11 BB type 1 eyes (33.3%) and 2 BB type 2 eyes (6.1%). According to AS-OCT grading, bubble formation was more frequent with CSS involving more superficial stromal layers (P <0.032). In the eyes with stage C, bubble formation failed 12 out of 14 times (85.7%, P <0.026). Spearman correlation showed that bubble formation was inversely associated with the AS-OCT grading (rho = -0.443, P = 0.001). After logistic regression analysis, AS-OCT grading was found to be the sole factor that predicted bubble formation (coeff. -1.58, confidence interval 95% -3.03 to -0.12, P = 0.034). Depth of opacity in CSS was the key determinant for predicting the success of pneumatic dissection, as advanced AS-OCT stages are strongly associated with BB failure.

Clinical applications of in vivo confocal microscopy enhance the detection and management of ocular surface disease in dogs and cats.

In vivo confocal microscopy (IVCM) is a unique imaging technique that permits noninvasive evaluation of the ocular surface on the cellular level. High-resolution images of all layers of the cornea are obtained in real-time with IVCM, and the acquired images are often comparable to ex vivo histochemical analysis of corneal biopsy specimens. The basic morphological features of the healthy living cornea as viewed by IVCM are reported in many domestic animal species, and the number of published descriptions of ocular surface pathologies in companion animals is progressively expanding. There is great potential for IVCM to improve the detection, characterization, and management of diverse ocular surface diseases in companion animals. This review summarizes several established and emerging clinical applications of IVCM in companion animal ocular surface disease, including infectious keratitis, corneal foreign bodies, corneal dystrophies and degenerations, ocular surface masses, corneal endotheliitis, pigmentary keratitis, and evaluation of corneal nerves.

Infectious keratitis in pediatric population aged less than two years: a tertiary eye institute experience

BackgroundInfectious keratitis is a serious ocular condition, which can lead to corneal scarring, vision loss, and even blindness. Pediatric infectious keratitis accounts for about 13% of all cases, although there is a lack of comprehensive data regarding keratitis in less than two years of age population group. This study was aimed to determine predisposing factors, clinical characteristics, microbial profile, and management of infectious keratitis in a population of children aged less than two years.Materials and methodsA retrospective study was carried out in a tertiary eye institute over a period of 18 years from July 2005 to December 2022. Collected data was analyzed for demographics, predisposing factors, clinical features, and treatment methods.ResultsFifty-seven cases of keratitis were identified. Age of the patients ranged from 1 to 24 months (Median: 6, interquartile range: 2–10). Thirty cases were male (52.6%). Predisposing factors were identified in 39 cases (68.4%): consisting of prior ocular trauma (n = 15), previous intraocular surgery (n = 11), ocular surface disease (n = 10), nasolacrimal duct obstruction (n = 4), prematurity (n = 3), developmental delay (n = 2), TORCH infection (n = 1), and contact lens (n = 1). Corneal thinning was observed in 29 eyes (50.9%), which progressed to perforation in 13 eyes (22.8%). Three patients developed endophthalmitis (95% CI, 1.5–13.4%). Most eyes had negative smear (60.4%) and culture (59.6%) results. Pseudomonas aeruginosa was the most common microorganism (11 of 21). Candida albicans was isolated in one case. In vitro susceptibility results showed good coverage of the combined ceftazidime and vancomycin regimen (100%). Surgical procedures were carried out in 35 eyes (61.4%) and 15 eyes required tectonic procedures (26.3%).ConclusionDespite good coverage of medical treatment over cultured isolates, surgical tectonic intervention was required in nearly a quarter of cases to resolve the corneal infection. This finding indicates the necessity of prompt patient referring, corneal sampling and initiation of the treatment.