Comparison of Clinical Features and Treatment Outcomes of Pseudomonas aeruginosa Keratitis in Contact Lens and Non-Contact Lens Wearers

Restoration of corneal epithelial barrier function: A possible target for corneal neovascularization

Corneal neovascularization (CoNV) is the second leading common cause of vision impairment worldwide and is a blinding pathological alteration brought on by ocular trauma, infection, and other factors. There are some limitations in the treatment of CoNV, hence it's critical to look into novel therapeutic targets. The corneal epithelial barrier, which is the initial barrier of the ocular surface, is an important structure that shields the eye from changes in the internal environment or invasion by the external environment. This study sought to collate evidence on the regulation of corneal epithelial barrier injury on the activation of vascular endothelial cells (VECs), basement membrane (BM) degradation, differentiation, migration, and proliferation of VECs, vascular maturation and stability, and other key processes in CoNV, so as to provide a novel concept for CoNV therapy targeting corneal epithelial barrier repair.

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

Purpose

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

Methods

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

Results

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

Conclusions

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

Monitoring the Progression of Clinically Suspected Microbial Keratitis Using Convolutional Neural Networks

Purpose

For this study, we aimed to determine whether a convolutional neural network (CNN)-based method (based on a feature extractor and an identifier) can be applied to monitor the progression of keratitis while managing suspected microbial keratitis (MK).

Methods

This multicenter longitudinal cohort study included patients with suspected MK undergoing serial external eye photography at the 5 branches of Chang Gung Memorial Hospital from August 20, 2000, to August 19, 2020. Data were primarily analyzed from January 1 to March 25, 2022. The CNN-based model was evaluated via F1 score and accuracy. The area under the receiver operating characteristic curve (AUROC) was used to measure the precision-recall trade-off.

Results

The model was trained using 1456 image pairs from 468 patients. In comparing models via only training the identifier, statistically significant higher accuracy (P  < 0.05) in models via training both the identifier and feature extractor (full training) was verified, with 408 image pairs from 117 patients. The full training EfficientNet b3-based model showed 90.2% (getting better) and 82.1% (becoming worse) F1 scores, 87.3% accuracy, and 94.2% AUROC for 505 getting better and 272 becoming worse test image pairs from 452 patients.

Conclusions

A CNN-based approach via deep learning applied in suspected MK can monitor the progress/regress during treatment by comparing external eye image pairs.

Translational Relevance

The study bridges the gap between the investigation of the state-of-the-art CNN-based deep learning algorithm applied in ocular image analysis and the clinical care of suspected patients with MK.

Diagnostic Potential of Anterior Segment Optical Coherence Tomography Scans for Pseudomonas Keratitis

Purpose

The purpose of this study was to investigate the diagnostic value of anterior segment optical coherence tomography (AS-OCT) scans for Pseudomonas keratitis.

Methods

Patients with treatment-naïve keratitis underwent AS-OCT imaging. The following parameters were evaluated: corneal thickness (CT), infiltrate thickness (IT), infiltrate diameter (ID), tissue loss/gain, entropy, and distance of the lesion from the corneal pupillary center. Three different OCT devices were used for the analysis. The relationship between the detected pathogen and the OCT patterns was analyzed.

Results

Nineteen eyes of 19 patients were included in the analysis: seven cases in the Pseudomonas group and 12 cases in the Gram-positive group. The mean (SD) values for the Pseudomonas and Gram-positive groups, respectively, were as follows: CT, 834 µm (165 µm) and 760 µm (120 µm); IT, 290 µm (152 µm) and 287 µm (84 µm); ID, 2067 µm (1470 µm) and 1307 µm (745 µm); distance to center, 3.0 mm (1.2 mm) and 3.0 mm (1.6 mm); epithelial defect, 1193 µm (586 µm) and 484 µm (615 µm); tissue gain, +31% (19%) and +10% (12%); and entropy level, 4.0 (0.8) and 3.9 (1.1).

Conclusions

This study introduces novel insights by identifying specific OCT parameters that distinguish Pseudomonas keratitis, including a 30% tissue gain. These findings align with earlier research that underscores the potential of OCT in differentiating various pathogens causing keratitis.

Translational Relevance

The findings of this study could be used to develop new diagnostic strategies for Pseudomonas keratitis. The OCT findings could be used to develop new biomarkers for the infection.

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

Introduction

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

Methods

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

Results

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

Discussion

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

Clinical comparative analysis of bacterial keratitis according to contact lens use: a retrospective study in a tertiary referral center of South Korea

PURPOSE

To compare the clinical aspects and treatment outcomes of contact lens-related bacterial keratitis (CLBK) and non-CLBK patients.

METHODS

Altogether 217 patients of bacterial keratitis (CLBK; 62, non-CLBK; 155) hospitalized between January 2012 and December 2020 were retrospectively analyzed for epidemiology, microbiological profiles, predisposing factors, clinical characteristics, and treatment outcomes. Poor treatment outcomes (PTO) were defined as a final BCVA < 0.3 (Snellen), a decreased visual acuity after treatment, complications, or surgical intervention. Relative importance of the initial clinical features leading to PTO was assessed using the random forest model and two-proportion Z-test.

RESULTS

The most common predisposing factors were sleeping with wearing CL (51.6%) in the CLBK group and trauma (55.5%) in the non-CLBK group. There were significant differences between the two groups in mean age (35.1:55.1 years, p < 0.001), female sex (56.5:34.8%, p = 0.003), symptom duration (6.2:6.9 days, p = 0.019), gram-negative organisms (83.3:48.3%, p = 0.008), epithelial healing time (8.5:14.1 days, p = 0.004), final BCVA (0.15:0.46 logMAR, p = 0.015), and PTO (9.7:21.9%, p = 0.035). For the entire group, the initial BCVA < 0.1 (27.9%), symptom duration ≥ 5 days (19.4%), age ≥ 60 years (16.4%), and hypopyon (14.0%) were important initial clinical features leading to PTO in the random forest model. In CLBK group, the type of CL or CL-related history was not significantly related to PTO.

CONCLUSION

CLBK patients had a higher proportion of females, younger age, gram-negative bacteria, and better treatment outcomes than those of non-CLBK patients. There were no significant risk factors leading to PTO in either the type of CL or CL-related history.

Prenylcysteine oxidase 1 like protein is required for neutrophil bactericidal activities

The bactericidal function of neutrophils is dependent on a myriad of intrinsic and extrinsic stimuli. Using systems immunology approaches we identify microbiome- and infection-induced changes in neutrophils. We focus on investigating the Prenylcysteine oxidase 1 like (Pcyox1l) protein function. Murine and human Pcyox1l proteins share ninety four percent aminoacid homology revealing significant evolutionary conservation and implicating Pcyox1l in mediating important biological functions. Here we show that the loss of Pcyox1l protein results in significant reductions in the mevalonate pathway impacting autophagy and cellular viability under homeostatic conditions. Concurrently, Pcyox1l CRISPRed-out neutrophils exhibit deficient bactericidal properties. Pcyox1l knock-out mice demonstrate significant susceptibility to infection with the gram-negative pathogen Psuedomonas aeruginosa exemplified through increased neutrophil infiltrates, hemorrhaging, and reduced bactericidal functionality. Cumulatively, we ascribe a function to Pcyox1l protein in modulation of the prenylation pathway and suggest connections beween metabolic responses and neutrophil functionality.

The Antibacterial Efficacy of High-Fluence PACK Cross-Linking Can Be Accelerated

Purpose

To determine whether high-fluence photoactivated chromophore for keratitis cross-linking (PACK-CXL) can be accelerated.

Methods

Solutions of Staphylococcus aureus and Pseudomonas aeruginosa with 0.1% riboflavin were prepared and exposed to 365 nm ultraviolet (UV)-A irradiation of intensities and fluences from 9 to 30 mW/cm2 and from 5.4 to 15.0 J/cm2, respectively, representing nine different accelerated PACK-CXL protocols. Irradiated solutions and unirradiated controls were diluted, plated, and inoculated on agar plates so that the bacterial killing ratios (BKR) could be calculated. Additionally, strains of Achromobacter xylosoxidans, Staphylococcus epidermidis, and Stenotrophomonas maltophilia were exposed to a single accelerated PACK-CXL protocol (intensity: 30 mW/cm2, total fluence: 15.0 J/cm2).

Results

With total fluences of 5.4, 10.0, and 15.0 J/cm2, the range of mean BKR for S. aureus was 45.78% to 50.91%, 84.13% to 88.16%, and 97.50% to 99.90%, respectively; the mean BKR for P. aeruginosa was 69.09% to 70.86%, 75.37% to 77.93%, and 82.27% to 91.44%, respectively. The mean BKR was 41.97% for A. xylosoxidans, 65.38% for S. epidermidis, and 78.04% for S. maltophilia for the accelerated PACK-CXL protocol (30 mW/cm2, 15 J/cm2).

Conclusions

The BKR of high-fluence PACK-CXL protocols can be accelerated while maintaining a high, but species-dependent, BKR. The Bunsen to Roscoe law is respected in fluences up to 10 J/cm2 in S. aureus and P. aeruginosa, whereas fluences above 10 J/cm2 show strain dependence.

Translational Relevance

The high-fluence PACK-CXL protocols can be accelerated in clinical practice while maintaining high levels of BKR.

Pseudomonas aeruginosa: Infections, Animal Modeling, and Therapeutics

Pseudomonas aeruginosa is an important Gram-negative opportunistic pathogen which causes many severe acute and chronic infections with high morbidity, and mortality rates as high as 40%. What makes P. aeruginosa a particularly challenging pathogen is its high intrinsic and acquired resistance to many of the available antibiotics. In this review, we review the important acute and chronic infections caused by this pathogen. We next discuss various animal models which have been developed to evaluate P. aeruginosa pathogenesis and assess therapeutics against this pathogen. Next, we review current treatments (antibiotics and vaccines) and provide an overview of their efficacies and their limitations. Finally, we highlight exciting literature on novel antibiotic-free strategies to control P. aeruginosa infections.

Differential Proteomic and Genomic Comparison of Resistance Mechanism of Pseudomonas aeruginosa to Cefoperazone Sodium/Sulbactam Sodium

The aim of this study was to determine the resistance mechanism of Pseudomonas aeruginosa to cefoperazone sodium/sulbactam sodium. We retrospectively analyzed the drug resistance of P.a isolated at the First Affiliated Hospital of Guangxi Medical University. Drug-resistant P.a strains were constructed, then wild-type (WT) and drug-resistant (DR) strains were compared using protein and gene microarrays to determine differences between DR and WT strains. The resistance rates of P. aeruginosa during 2013, 2014 and 2015 were 21.2%, 21.4%, and 24.6% respectively. Among 242 protein peaks of WT and DR bacteriophage proteins, 41 were differentially expressed between the two groups. The expression of 26 and 15 proteins were respectively upregulated and downregulated in the DR compared with the WT group. Gene microarray results revealed 679 mutant loci in the DR group, of which 42 with the top 50 Q values were found in the NCBI database. The rate of P.a resistance to cefoperazone sodium/sulbactam sodium remained high between 2013 and 2015. The numbers of different proteins and genetic variations in the DR strains suggested that the resistance mechanism of P.a to cefoperazone sodium/sulbactam sodium involves multiple genes and proteins that might be key to controlling P.a resistance to cefoperazone sodium/sulbactam sodium.

Bacterial microbiota of the contact lens surface and associated care behaviours

Introduction

Contact lens (CL) wear has been reported to cause changes to the microbiome of the ocular surface. More insight into the alteration of this microenvironment can help to understand the pathogenesis of CL-related eye infections. Knowledge of the relationship between the CL wearer's behaviours and pathogens would help health care providers focus on each step of proper CL care. This study aims to determine the behaviours that might be associated with the community of bacteria on CL.

Methods

A cross-sectional design was performed using anonymous questionnaires to obtain demographic data and assess hygiene practices among volunteering wearers. The CLs used were collected to evaluate the prevalence of pathogenic bacteria associated with ocular infections by PCR and microbiota analysis.

Results

The bacterial microbiota study revealed a total of 19 genera and 26 isolated strains from 20 eligible CLs. Enterobacter, Staphylococcus, and Achromobacter were the main genus in this subject population. Staphylococcus pasteuri and Achromobacter agilis were the most common pathogens at 65% and 35%, respectively. Enterobacter mori, a nonpathogenic organism, was found to be the most predominant strain, accounting for 27.51% of the total bacterial constituents. The risk behaviour of CL wear that was significantly associated with A. agilis contamination was cleaning the CL case with tap water (P value = 0.04).

Conclusions

This is the first study focusing on the association between the culture selected microbial community on the CL surface and compehensive behavioural characteristics. Environmental contamination was the main source of microbes found on CL surfaces. An emphasis in patient education should be placed on careful handling during the CL care routine and managing the hygiene of the surroundings.

Epidemiology, Microbiology, and Genetics of Contact Lens-Related and Non-Contact Lens-Related Infectious Keratitis

ABSTRACT

Infectious keratitis is a rare but severe condition associated with a range of ocular and systemic predisposing conditions, including ocular trauma, prior surgery, surface disease, and contact lens (CL) wear. This review explores the epidemiology of infectious keratitis, specifically the differences in disease incidence and risk factors, causative organism profile and virulence characteristics and host microbiome, genetics, gene expression, proteomics, and metabolomic characteristics in CL-related and non-CL-related diseases. Differences exist in the epidemiology, demographics, causative organisms, and their virulence characteristics in CL-related and non-CL-related diseases, and there is less evidence to support differences between these groups of individuals in the ocular surface microbiome, genetics, and pathways of disease. Genetic variations, however, in the host immune profile are implicated in both the onset and severity of infectious keratitis in CL and non-CL wearers. As technologies in metabolomics, proteomics, and genomics improved to be better able to process small-volume samples from the ocular surface, there will be improved understanding of the interplay between the CL, ocular surface, host immune profile, and the microbial environment. This may result in a more personalized approach in the management of disease to reduce disease severity.

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

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