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.

Biophilic Positive Carbon Dot Exerts Antifungal Activity and Augments Corneal Permeation for Fungal Keratitis

Fungal keratitis (FK) is an infectious eye disease that poses a significant risk of blindness. However, the effectiveness of conventional antifungal drugs is limited due to the intrinsic ocular barrier that impedes drug absorption. There is an urgent need to develop new therapeutic strategies to effectively combat FK. Herein, we synthesized an ultrasmall positively charged carbon dot using a simple stage-melting method. The carbon dot can penetrate the corneal barrier by opening the tight junctions, allowing them to reach the lesion site and effectively kill the fungi. The results both in vitro and in vivo demonstrated that it exhibited good biocompatibility and antifungal activity, significantly improving the therapeutic effect in a mouse model of FK. Therefore, this biophilic ultrasmall size and positive carbon dot, characterized by its ability to penetrate the corneal barrier and its antifungal properties, may offer valuable insights into the design of effective ocular nanomedicines.

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

Purpose

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

Methods

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

Results

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

Conclusions

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

Ocular infections associated with atypical mycobacteria: A review

Atypical mycobacteria or non-tuberculous mycobacteria (NTM) are a group of acid-fast bacteria that are pathogenic to different parts of the eye. The organisms can cause a spectrum of ocular infections including keratitis, scleritis, uveitis, endophthalmitis and orbital cellulitis. Trauma, whether surgical or nonsurgical, has the highest correlation with development of this infection. Common surgeries after which these infections have been reported include laser in situ keratomileusis (LASIK) and scleral buckle surgery. The organism is noted to form biofilms with sequestration of the microbe at different inaccessible locations leading to high virulence. Collection of infective ocular material (corneal scraping/necrotic scleral tissue/abscess material/vitreous aspirate, etc.) and laboratory identification of the organism through microbiologic testing are vital for confirming presence of the infection and initiating treatment. In cluster infections, tracing the source of infection in the hospital setting via testing of different in-house samples is equally important to prevent further occurrences. Although the incidence of these infections is low, their presence can cause prolonged disease that may often be resistant to medical therapy alone. In this review, we describe the various types of NTM-ocular infections, their clinical presentation, laboratory diagnosis, management, and outcomes.

Microbial keratitis in lattice corneal dystrophy: microsporidia as a new cause

A patient in his sixth decade presented to us with redness, pain and a deterioration of vision in his left eye. He had previously been diagnosed with lattice corneal dystrophy (LCD). He was diagnosed with microbial keratitis, and mixed infection was confirmed on culture (bacteria and fungus) with a protracted healing period before resolution of keratitis. He presented 2 years later with similar issues in the same eye and was noted to have a second episode of microbial keratitis, with microsporidia spores noted on gram, potassium hydroxide and calcofluor white stains. He was diagnosed with microsporidial stromal keratitis and underwent therapeutic penetrating keratoplasty. Unfortunately, he suffered a recurrence of microsporidial keratitis following surgery with eventual transplant failure. Microsporidia as an infection in LCD has, to our knowledge, not been previously reported. We aim to discuss microsporidial infection and recurrent microbial keratitis in the setting of LCD.

Quantifying Clinicians' Diagnostic Uncertainty When Making Initial Treatment Decisions for Microbial Keratitis

PURPOSE

There is a need to understand physicians' diagnostic uncertainty in the initial management of microbial keratitis (MK). This study aimed to understand corneal specialists' diagnostic uncertainty by establishing risk thresholds for treatment of MK that could be used to inform a decision curve analysis for prediction modeling.

METHODS

A cross-sectional survey of corneal specialists with at least 2 years clinical experience was conducted. Clinicians provided the percentage risk at which they would always or never treat MK types (bacterial, fungal, herpetic, and amoebic) based on initial ulcer sizes and locations (<2 mm 2 central, <2 mm 2 peripheral, and >8 mm 2 central).

RESULTS

Seventy-two of 99 ophthalmologists participated who were 50% female with an average of 14.7 (SD = 10.1) years of experience, 60% in academic practices, and 38% outside the United States. Clinicians reported they would "never" and "always" treat a <2 mm 2 central MK infection if the median risk was 0% and 20% for bacterial (interquartile range, IQR = 0-5 and 5-50), 4.5% and 27.5% for herpetic (IQR = 0-10 and 10-50), 5% and 50% for fungal (IQR = 0-10 and 20-75), and 5% and 50.5% for amoebic (IQR = 0-20 and 32-80), respectively. Mixed-effects models showed lower thresholds to treat larger and central infections ( P < 0.001, respectively), and thresholds to always treat differed between MK types for the United States ( P < 0.001) but not international clinicians.

CONCLUSIONS

Risk thresholds to treat differed by practice locations and MK types, location, and size. Researchers can use these thresholds to understand when a clinician is uncertain and to create decision support tools to guide clinicians' treatment decisions.

Evaluation of a commercial NGS service for detection of bacterial and fungal pathogens in infectious ulcerative keratitis

OBJECTIVES

To compare results from a commercial next-generation sequencing (NGS) service to corneal cytology and culture for identification of causative organisms in veterinary patients presenting for infectious ulcerative keratitis (IUK).

PROCEDURE

Swabs for corneal aerobic and fungal cultures and DNA swabs for NGS were submitted for canine and equine normal controls (n = 11 and n = 4, respectively) and IUK patients (n = 22 and n = 8, respectively) for which microbrush cytology specimens confirmed the presence of infectious organisms. The sensitivity of the NGS results was compared with bacterial and fungal culture results. Concordance between the NGS and culture results was determined.

RESULTS

The NGS results were positive for bacterial and fungal organisms in 5 and 1 normal and 18 and 1 IUK cases, respectively. Bacterial and fungal cultures were positive for 7 and 2 normal and 20 and 5 IUK cases, respectively. Sensitivity of NGS was 82.14% (95% confidence interval (CI), 63.11% to 93.94%) and specificity was 76.47% (95% CI, 50.10% to 93.19%). Concordance (complete and partial) between identified bacterial and fungal organisms was found in 79% and 100% of cases, respectively. NGS identified organisms in 3 culture-negative IUK samples.

CONCLUSION

A commercial NGS service may be useful in the identification of causative agents in IUK cases with a sensitivity greater than the sensitivity previously reported for aerobic culture. Further testing is needed to determine the clinical significance of additional organisms isolated by NGS from infected cases, as well as organisms isolated from normal corneas.

A 5-Year Review of Coinfections in Acanthamoeba keratitis From South India

PURPOSE

To ascertain the frequency of coinfections in Acanthamoeba keratitis, the nature of copathogens involved, and to analyze the implications in the context of current research on amoebic interactions.

METHODS

A retrospective case review from a Tertiary Care Eye Hospital in South India. Smear and culture data for coinfections in Acanthamoeba corneal ulcers were collected from records over a 5-year period. The significance and relevance of our findings in the light of current research on Acanthamoeba interactions were analyzed.

RESULTS

Eighty-five cases of culture-positive Acanthamoeba keratitis were identified over a 5-year period (43 of them being coinfections). Fusarium was most commonly identified species, followed by Aspergillus and the dematiaceous fungi. Pseudomonas spp was the commonest bacterial isolate.

CONCLUSION

Coinfections with Acanthamoeba are common at our centre, and account for 50% of Acanthamoeba keratitis. The diverse nature of the organisms involved in coinfections suggest that such amoebic interactions with other organisms are probably more widespread than recognized. To the best of our knowledge, this is the first documentation from a long-term study of pathogen diversity in Acanthamoeba coinfections. It is possible that Acanthamoeba itself may be virulence enhanced and secondary to the co-organism, breaching the ocular surface defenses in an already compromised cornea. However, observations from the existing literature on Acanthamoeba interactions with bacteria and certain fungi are based mainly on nonocular or nonclinical isolates. It would be illuminating if such studies are performed on Acanthamoeba and coinfectors from corneal ulcers-to ascertain whether interactions are endosymbiotic or virulence enhanced through amoebic passage.

Immunity to pathogenic fungi in the eye

Fusarium, Aspergillus and Candida are important fungal pathogens that cause visual impairment and blindness in the USA and worldwide. This review will summarize the epidemiology and clinical features of corneal infections and discuss the immune and inflammatory responses that play an important role in clinical disease. In addition, we describe fungal virulence factors that are required for survival in infected corneas, and the activities of neutrophils in fungal killing, tissue damage and cytokine production.

Utility of investigation for suspected microbial keratitis: a diagnostic accuracy study

PURPOSE

The true disease status of a population with suspected microbial keratitis (MK) cannot be verified. There is not an accurate (gold) reference standard to confirm infection and inter-test comparisons of sensitivity and specificity therefore lead to bias with questionable estimates of test utility. We present an alternative method to report results.

METHODS

We used a decision to treat as the definition for MK. We retrospectively compared the results of corneal culture and polymerase chain reaction (PCR) as these are objective tests available for the three principal groups of pathogens. We then estimated the potential contribution of positive results, either alone or in combination, to support the working diagnosis.

RESULTS

We included 2021 (77.4%) eyes with suspected bacterial keratitis, 365 (14.0%) with suspected acanthamoeba keratitis, and 226 (8.6%) with suspected fungal keratitis, all treated between July 2013 and December 2019. In these groups, there were 51.6% positive culture and 6.5% positive PCR results for bacteria, 19.0% and 40.5% for acanthamoeba, and 28.3% and 15.0% for fungi. Between groups the differences in the proportions of positive results from culture and PCR was statistically significant (P < 0.001). The added benefit of PCR to the result of culture in identifying a potential pathogen was 1.4% for bacteria (P = 0.6292), 24.4% for acanthamoeba (P = 0.0001), and 5.8% for fungi (P = 0.3853).

CONCLUSIONS

For suspected MK a comparison of the test positivity rate is an easily comprehensible outcome measure of test utility.

Effect of Increasing Povidone-Iodine Exposure on Corneal Epithelium and Impact on Donor Rim Cultures

PURPOSE

The purpose of this study was to assess the effect of a second povidone-iodine (PVP-I) application at the time of donor tissue recovery on overall tissue quality and to analyze the rate of positive fungal and bacterial rim cultures before and after implementing increased PVP-I exposure.

METHODS

The left cornea was recovered after a single application of PVP-I, while the right cornea was recovered after double PVP-I application in research-consented donors. The epithelial cell death rate was estimated using viability assay in corneal whole mounts under 10× objective (n = 5). Clinical characteristics of epithelium, stroma, and endothelium; positive rim culture rate; and incidences of infectious postoperative adverse reactions were compared for a period of 14 months before and after implementation of increased PVP-I protocol.

RESULTS

The average epithelial cell death rate was unaltered between single and double PVP-I exposure groups. We observed a modest 10% increase in the number of tissues with mild edema after implementation of increased PVP-I exposure. Nonetheless, the percentage of tissues with moderate or severe edema was unaltered. The average positive rim culture rate decreased from 1.17% to 0.88% (P = 0.075) after implementation of the double PVP-I soak procedure. There has been only one report of infectious postoperative adverse reactions since this procedure change. By contrast, there were 5 reports for a period of 14 months before implementation of this protocol.

CONCLUSIONS

These results indicate that new donor preparation methods with an additional 5 minutes of PVP-I exposure do not affect tissue quality, reduce positive rim cultures, and lead to lower incidence of postoperative infection.

Gram stain and addition of amphotericin B to improve the microbial safety of human donor corneas

To determine the effectiveness of two methods to improve the microbial safety of human corneas preserved in organ culture. We compared the number of positive preservation solutions of corneas in organ culture in which the initial short-term hypothermic corneal maintenance solution was supplemented with amphotericin B 2.5 µg/mL and the historical data of microbial test results (2015-2019). In addition, we appraised the efficacy of Gram stain to detect bacterial or fungal contamination in the organ culture solutions of corneas from at-risk donors compared to the culture tests of corneas from not-at-risk donors. Statistical analysis was performed using STATA and statistical significance set at p < 0.05. The number of positive culture tests after preservation was 15 (0.5%) in 2020 compared to a mean of 37 (1.2%) in the period 2015-2019 (p < 0.01), with 10 (1.0%) positive samples in the cohort of 998 corneas from at-risk donors and 5 (0.2%) in the 2046 corneas from not-at-risk donors (p < 0.01). All corneas from at-risk donors tested positive at Gram stain and the results were available 1-3 days before those of the conventional culture tests. Amphotericin B supplementation in the short-term maintenance solution markedly reduced the number of positive microbial tests after organ culture and the early detection of contaminants, including slow-growing microorganisms, by Gram stain before the standard culture results. This meant fewer corneas being discarded and a greater likelihood of preventing post-graft infections.

Innate Immune System Activation, Inflammation and Corneal Wound Healing

Corneal wounds resulting from injury, surgeries, or other intrusions not only cause pain, but also can predispose an individual to infection. While some inflammation may be beneficial to protect against microbial infection of wounds, the inflammatory process, if excessive, may delay corneal wound healing. An examination of the literature on the effect of inflammation on corneal wound healing suggests that manipulations that result in reductions in severe or chronic inflammation lead to better outcomes in terms of corneal clarity, thickness, and healing. However, some acute inflammation is necessary to allow efficient bacterial and fungal clearance and prevent corneal infection. This inflammation can be triggered by microbial components that activate the innate immune system through toll-like receptor (TLR) pathways. In particular, TLR2 and TLR4 activation leads to pro-inflammatory nuclear factor kappa-light-chain-enhancer of activated B cells (NFκB) activation. Similarly, endogenous molecules released from disrupted cells, known as damage-associated molecular patterns (DAMPs), can also activate TLR2, TLR4 and NFκB, with the resultant inflammation worsening the outcome of corneal wound healing. In sterile keratitis without infection, inflammation can occur though TLRs to impact corneal wound healing and reduce corneal transparency. This review demonstrates the need for acute inflammation to prevent pathogenic infiltration, while supporting the idea that a reduction in chronic and/or excessive inflammation will allow for improved wound healing.

Clinical characteristics of external bacterial ocular and periocular infections and their antimicrobial treatment patterns among a Ghanaian ophthalmic population

Empirical antimicrobial therapy is linked to a surge in antimicrobial resistant infections. However, an insight on the bacteria etiology of ocular infections is essential in the appropriation of choice of antimicrobial among clinicians, yet there remains a dearth of data from Ghana. We investigated the bacteria etiology of external ocular and periocular infections and antimicrobial treatment patterns among a Ghanaian ophthalmic population. A multicenter study design with purposive sampling approach was employed. Patients demographics and clinical data were collated using a pretested structure questionnaire. Cornea specimens and conjunctival swabs were obtained for bacterial isolation following standard protocols. About 95% (98/103) of ocular samples were positive for bacteria culture. The proportion of Gram-negative bacteria was 58.2%, and the predominant bacteria species were Pseudomonas aeruginosa 38.8% and Staphylococcus aureus 27.6%. Conjunctivitis 40.0% and keratitis 75.0% were mostly caused by Pseudomonas aeruginosa. The routinely administered antimicrobial therapy were polymyxin B 41.2%, neomycin 35.1% and ciprofloxacin 31.6%. Participants demographic and clinical characteristics were unrelated with positive bacteria culture (p > 0.05). Our results showed a markedly high burden of ocular bacterial infections and variations in etiology. Bacterial infection-control and antimicrobial agent management programs should be urgently institutionalized to prevent the emergence of resistant infections.

Subpalpebral Antibiotic Lavage as Safe, Emergent, and Cost-Effective Management of Acute Infectious Keratitis Related to Contact Lens Overwear: Case Report and Literature Review

PURPOSE

The aim of this study is to describe the technique of subpalpebral antibiotic lavage (SAL), which is a highly therapeutic, efficient, and cost-effective method for managing severe bacterial keratitis.

METHODS

This case report describes a 26-year-old woman with severe bacterial keratitis in the right eye due to contact lens overwear, with progressive corneal thinning, a hypopyon, impending perforation, and marked visual loss to perception of light despite treatment with intensive topical antibiotics. This was managed with SAL that involves the insertion of a cannula transcutaneously into the upper conjunctival fornix to provide continuous antibiotic irrigation of the ocular surface.

RESULTS

By 11 weeks after presentation, the cornea and anterior chamber appeared clinically quiescent, and visual acuity improved to 20/40 corrected in the right eye.

CONCLUSIONS

Bacterial keratitis is a potentially blinding condition for which contact lens wear is an important risk factor. Most cases are successfully managed with topical medications; however, in cases of treatment failure, a second-line approach such as SAL can be sight-saving. SAL uses readily available equipment for the delivery of high concentrations of antibiotics to the ocular surface, thus increasing therapeutic efficacy and reducing nursing staff workload. Despite its advantages, the literature reveals apparent underutilization of this technique.

Diagnostic Utility of CDC DPDx for an Atypical Presentation of Infectious Crystalline Keratopathy-Like Infiltrate Secondary to Microsporidia

PURPOSE

To report a case of atypical infectious crystalline keratopathy-like stromal infection secondary to microsporidia wherein diagnosis of the causative organism was aided by use of the Center for Disease Control (CDC) DPDx program.

METHODS

We report the case of a 73-year-old woman who presented with atypical infectious crystalline keratopathy-like corneal infection without previous surgical history.

RESULTS

The patient had previously been treated for recalcitrant corneal infection with topical antibiotics and steroids at an outside provider before referral. Further treatment with topical fortified antibiotics failed to improve the infection. Corneal biopsy was performed and sent to the CDC DPDx for diagnostic confirmation for presumptive microsporidia. The patient underwent therapeutic penetrating keratoplasty without recurrence of ocular infection.

CONCLUSIONS

Utilization of the DPDx resource may help guide appropriate and timely diagnosis and management strategies in atypical presentations of infectious keratitis.

Impact of Sample Collection Order on the Diagnostic Performance of Metagenomic Deep Sequencing for Infectious Keratitis

PURPOSE

The purpose of this article was to evaluate the impact of sample collection order on the diagnostic yield of metagenomic deep sequencing (MDS) for determining the causative pathogen in infectious keratitis.

METHODS

We performed a cross-sectional diagnostic test evaluation among subjects with infectious keratitis at Aravind Eye Hospital in Madurai, India. All subjects underwent corneal scrapings of the affected eye to obtain potassium hydroxide smear, Gram stain, bacterial culture, and fungal culture, in this order. The order of MDS specimen collection relative to smear and culture samples was randomized and served as the primary predictor. Outcomes included the normalized copy number of pathogenic RNA detected by MDS, the proportion of MDS samples that were diagnostic, and the agreement of MDS results with cultures.

RESULTS

MDS samples from 46 subjects with corneal ulcers were evaluated. MDS was positive in 33 subjects (76%) and had 74% overall agreement with culture results. There was no association between order of MDS sample collection and normalized copy number of genetic material detected (P = 0.62) or the likelihood of MDS positivity (P = 0.46). However, the likelihood of agreement between MDS and cultures decreased when MDS corneal swabs were collected after other diagnostic corneal scrapings (P = 0.05).

CONCLUSIONS

The overall yield of MDS for detecting the cause of infectious keratitis was not affected by sample collection order. However, diagnostic agreement between MDS and cultures decreased when MDS samples were collected after other specimens. Additional investigation is warranted to determine whether this represents increased sensitivity of MDS compared with cultures or higher susceptibility to contaminants.

Commensals Serve as Natural Barriers to Mammalian Cells during Acanthamoeba castellanii Invasion

Acanthamoeba castellanii is a free-living, pathogenic ameba found in the soil and water. It invades the body through ulcerated skin, the nasal passages, and eyes and can cause blinding keratitis and granulomatous encephalitis. However, the mechanisms underlying the opportunistic pathogenesis of A. castellanii remain unclear. In this study, we observed that commensal bacteria significantly reduced the cytotoxicity of the ameba on mammalian cells. This effect occurred in the presence of both Gram-positive and Gram-negative commensals. Additionally, commensals mitigated the disruption of cell junctions. Ex vivo experiments on mouse eyeballs further showed that the commensals protected the corneal epithelial layer. Together, these findings indicate that A. castellanii is pathogenic to individuals with a dysbiosis of the microbiota at infection sites, further highlighting the role of commensals as a natural barrier during parasite invasion. IMPORTANCE Acanthamoeba castellanii, an opportunistic protozoan widely present in the environment, can cause Acanthamoeba keratitis and encephalitis in humans. However, only a few reports describe how the ameba acts as an opportunistic pathogen. Our study showed that the normal microbiota interfered with the cytotoxicity of Acanthamoeba, persevered during Acanthamoeba invasion, and reduced corneal epithelium peeling in the mouse eyeball model. This suggests that commensals may act as a natural barrier against Acanthamoeba invasion. In future, individuals who suffer from Acanthamoeba keratitis should be examined for microbiota absence or dysbiosis to reduce the incidence of Acanthamoeba infection in clinical settings.

Adjunctive Thymosin Beta-4 Treatment Influences PMN Effector Cell Function during Pseudomonas aeruginosa-Induced Corneal Infection

Previous work examining the therapeutic efficacy of adjunct thymosin beta 4 (Tβ4) to ciprofloxacin for ocular infectious disease has revealed markedly reduced inflammation (inflammatory mediators and innate immune cells) with increased activation of wound healing pathways. Understanding the therapeutic mechanisms of action have further revealed a synergistic effect with ciprofloxacin to enhance bacterial killing along with a regulatory influence over macrophage effector cell function. As a natural extension of the aforementioned work, the current study uses an experimental model of P. aeruginosa-induced keratitis to examine the influence of Tβ4 regarding polymorphonuclear leukocyte (PMN/neutrophil) cellular function, contributing to improved disease response. Flow cytometry was utilized to phenotypically profile infiltrating PMNs after infection. The generation of reactive oxygen species (ROS), neutrophil extracellular traps (NETs), and PMN apoptosis were investigated to assess the functional activities of PMNs in response to Tβ4 therapy. In vitro work using peritoneal-derived PMNs was similarly carried out to verify and extend our in vivo findings. The results indicate that the numbers of infiltrated PMNs into infected corneas were significantly reduced with adjunctive Tβ4 treatment. This was paired with the downregulated expression of proinflammatory markers on these cells, as well. Data generated from PMN functional studies suggested that the corneas of adjunctive Tβ4 treated B6 mice exhibit a well-regulated production of ROS, NETs, and limited PMN apoptosis. In addition to confirming the in vivo results, the in vitro findings also demonstrated that neutrophil elastase (NE) was unnecessary for NETosis. Collectively, these data provide additional evidence that adjunctive Tβ4 + ciprofloxacin treatment is a promising option for bacterial keratitis that addresses both the infectious pathogen and cellular-mediated immune response, as revealed by the current study.

Application of Trypan Blue Stain in the Microbiological Diagnosis of Infectious Keratitis-A Case Series

PURPOSE

The purpose of this study was to report 3 cases of microbial keratitis, wherein trypan blue staining was used to aid the microbiological diagnosis of fungal keratitis and Pythium keratitis in a rural setup.

METHODS

Three consecutive patients who presented with a diagnosis of infectious keratitis underwent corneal scraping, and the smears were assessed using trypan blue stain and potassium hydroxide (KOH) mount.

RESULTS

Of the 3 cases, the first 2 cases showed septate fungal filaments in trypan blue-stained preparation and KOH mount. Case 3 showed the presence of broad aseptate filaments with ribbon-like folds on both KOH mount and trypan blue stain, consistent with the diagnosis of Pythium keratitis. The first 2 cases improved with topical and systemic antifungals. Case 1 healed with scarring at 7 weeks with improvement in best-corrected visual acuity (BCVA) to 20/60. Case 2 healed within 2 weeks, and BCVA improved to 20/40. Case 3 received topical linezolid (0.2%), azithromycin eye ointment, and oral azithromycin. At 5 weeks the infection decreased but thinning was noted, which necessitated tissue adhesive and bandage contact lens application. Scarring was noted at 10 weeks, and BCVA improved to 20/40.

CONCLUSIONS

In this case series, trypan blue staining showed promising results in the easy identification of aseptate and septate fungal elements. This is the first case series showing the utility of this stain in the management of microbial keratitis.

Genipin in an Ex Vivo Corneal Model of Bacterial and Fungal Keratitis

Purpose

To determine whether genipin (a natural crosslinker) could reduce the colonization and proliferation of bacteria and fungi in an ex vivo model of corneal infection.

Methods

This study, using an ex vivo model of bacterial and fungal keratitis, investigated the antimicrobial efficacy of genipin crosslinking. Excised corneoscleral buttons were wounded by scalpel incision and subsequently infected with Staphylococcus aureus, Pseudomonas aeruginosa, or Candida albicans. After inoculation, corneas were treated with genipin for 24 hours at 37°C. Histologic examinations were carried out, and the number of viable colony-forming units (CFU)/cornea was determined.

Results

Genipin exerts bactericidal action against S. aureus and P. aeruginosa, as well as fungicidal action against C. albicans and significantly reduced the CFU compared to contralateral eyes that received saline treatment (P < 0.05).

Conclusions

These data identify genipin as a novel ocular antimicrobial agent that has the potential to be incorporated into the therapeutic armamentarium against microbial keratitis.

Translational Relevance

This study provided evidence for the antimicrobial and antifungal properties of genipin as an alternative crosslinker that could be used in the management of infectious keratitis.

Foundational concepts in the biology of bacterial keratitis

Bacterial infections of the cornea, or bacterial keratitis (BK), are notorious for causing rapidly fulminant disease and permanent vision loss, even among treated patients. In the last sixty years, dramatic upward trajectories in the frequency of BK have been observed internationally, driven in large part by the commercialization of hydrogel contact lenses in the late 1960s. Despite this worsening burden of disease, current evidence-based therapies for BK - including broad-spectrum topical antibiotics and, if indicated, topical corticosteroids - fail to salvage vision in a substantial proportion of affected patients. Amid growing concerns of rapidly diminishing antibiotic utility, there has been renewed interest in urgently needed novel treatments that may improve clinical outcomes on an individual and public health level. Bridging the translational gap in the care of BK requires the identification of new therapeutic targets and rational treatment design, but neither of these aims can be achieved without understanding the complex biological processes that determine how bacterial corneal infections arise, progress, and resolve. In this chapter, we synthesize the current wealth of human and animal experimental data that now inform our understanding of basic BK pathophysiology, in context with modern concepts in ocular immunology and microbiology. By identifying the key molecular determinants of clinical disease, we explore how novel treatments can be developed and translated into routine patient care.

Oxygen Self-Supplying Nanotherapeutic for Mitigation of Tissue Hypoxia and Enhanced Photodynamic Therapy of Bacterial Keratitis

Hypoxia, a common characteristic of bacterial infections, is known to be closely associated with the emergence of multidrug-resistant bacteria, which hastens the need to develop advanced microbicides and antibacterial techniques. Photodynamic therapy is a promising strategy to reduce bacterial antibiotic resistance and employs photosensitizers, excitation light sources, and sufficient oxygen to generate toxic reactive oxygen species (ROS). The inherent limitation of PDT is that the generation of ROS is restricted by the hypoxic microenvironment in infection sites. Here, an oxygen self-supplying nanotherapeutic is developed to enhance antibacterial activity against multidrug-resistant bacteria on the basis of fluorinated boron dipyrromethene (BODIPY)-based glycomimetics. The nanotherapeutic not only could capture the bacteria efficiently but also was able to act as an oxygen carrier to relieve the hypoxic microenvironment of bacterial infections, thus achieving enhanced PDT efficacy. In a Pseudomonas aeruginosa infection of a rat cornea, typical administration of the nanotherapeutic decreased the infiltrate and showed a faster healing capacity in comparison with BODIPY-based glycomimetics. Self-supplying oxygen nanotherapeutics that relieve the hypoxic microenvironment and interfere with bacterial colonization have been shown to be a promising candidate for the management of drug-resistant microbial keratitis.

12-year analysis of incidence, microbiological profiles and in vitro antimicrobial susceptibility of infectious keratitis: the Nottingham Infectious Keratitis Study

BACKGROUND/AIMS

To examine the incidence, causative microorganisms and in vitro antimicrobial susceptibility and resistance profiles of infectious keratitis (IK) in Nottingham, UK.

METHODS

A retrospective study of all patients who were diagnosed with IK and underwent corneal scraping between July 2007 and October 2019 (a 12-year period) at a UK tertiary referral centre. Relevant data, including demographic factors, microbiological profiles and in vitro antibiotic susceptibility of IK, were analysed.

RESULTS

The estimated incidence of IK was 34.7 per 100 000 people/year. Of the 1333 corneal scrapes, 502 (37.7%) were culture-positive and 572 causative microorganisms were identified. Sixty (4.5%) cases were of polymicrobial origin (caused by ≥2 different microorganisms). Gram-positive bacteria (308, 53.8%) were most commonly isolated, followed by Gram-negative bacteria (223, 39.0%), acanthamoeba (24, 4.2%) and fungi (17, 3.0%). Pseudomonas aeruginosa (135, 23.6%) was the single most common organism isolated. There was a significant increase in Moraxella spp (p<0.001) and significant decrease in Klebsiella spp (p=0.004) over time. The in vitro susceptibilities of Gram-positive and Gram-negative bacteria to cephalosporin, fluoroquinolone and aminoglycoside were 100.0% and 81.3%, 91.9% and 98.1%, and 95.2% and 98.3%, respectively. An increase in resistance against penicillin was observed in Gram-positive (from 3.5% to 12.7%; p=0.005) and Gram-negative bacteria (from 52.6% to 65.4%; p=0.22).

CONCLUSION

IK represents a relatively common and persistent burden in the UK and the reported incidence is likely underestimated. Current broad-spectrum antimicrobial treatment provides a good coverage for IK, although challenged by some level of antimicrobial resistance and polymicrobial infection.

Corneal Infection Models: Tools to Investigate the Role of Biofilms in Bacterial Keratitis

Bacterial keratitis is a corneal infection which may cause visual impairment or even loss of the infected eye. It remains a major cause of blindness in the developing world. Staphylococcus aureus and Pseudomonas aeruginosa are common causative agents and these bacterial species are known to colonise the corneal surface as biofilm populations. Biofilms are complex bacterial communities encased in an extracellular polymeric matrix and are notoriously difficult to eradicate once established. Biofilm bacteria exhibit different phenotypic characteristics from their planktonic counterparts, including an increased resistance to antibiotics and the host immune response. Therefore, understanding the role of biofilms will be essential in the development of new ophthalmic antimicrobials. A brief overview of biofilm-specific resistance mechanisms is provided, but this is a highly multifactorial and rapidly expanding field that warrants further research. Progression in this field is dependent on the development of suitable biofilm models that acknowledge the complexity of the ocular environment. Abiotic models of biofilm formation (where biofilms are studied on non-living surfaces) currently dominate the literature, but co-culture infection models are beginning to emerge. In vitro, ex vivo and in vivo corneal infection models have now been reported which use a variety of different experimental techniques and animal models. In this review, we will discuss existing corneal infection models and their application in the study of biofilms and host-pathogen interactions at the corneal surface.

Exploratory Use of Fluorescent SmartProbes for the Rapid Detection of Microbial Isolates Causing Corneal Ulcer

PURPOSE

To explore the use of optical SmartProbes for the rapid evaluation of corneal scrapes from patients with suspected microbial keratitis, as a clinical alternative to Gram stain.

DESIGN

Experimental study with evaluation of a diagnostic technology.

METHODS

Corneal scrapes were collected from 267 patients presenting with microbial keratitis at a referral cornea clinic in South India. Corneal scrapes were flooded with SmartProbes (BAC One or BAC Two) and evaluated by fluorescence microscopy (without the need for sample washing or further processing). The SmartProbe-labeled samples were scored as bacteria/fungi/none (BAC One) or gram-negative bacteria/none (BAC Two) and compared to Gram stain results.

RESULTS

Compared to Gram stain, BAC One demonstrated sensitivity and specificity of 80.0% and 87.5%, respectively, positive and negative predictive values (PPV, NPV) of 93.8% and 65.1%, and an accuracy of 82.2. BAC Two demonstrated sensitivity and specificity of 93.3% and 84.8%, respectively, an NPV of 99.2%, and an accuracy of 85.6%. When the corresponding culture results were compared to the Gram stain result, the sensitivity and specificity were 73.4% and 70.7%, the PPV and NPVs were 86.5% and 51.0%, and overall accuracy was 72.6.

CONCLUSIONS

Fluorescent SmartProbes offer a comparative method to Gram stain for delineating gram-positive or gram-negative bacteria or fungi within corneal scrapes. We demonstrate equivalent or higher sensitivity, specificity, PPV and NPVs, and accuracy than culture to Gram stain. Our approach has scope for point-of-care clinical application to aid in the diagnosis of microbial keratitis.

A new ophthalmic formulation containing antiseptics and dexpanthenol: In vitro antimicrobial activity and effects on corneal and conjunctival epithelial cells

Antibiotic resistance is increasing even in ocular pathogens, therefore the interest towards antiseptics in Ophthalmology is growing. The aim of this study was to analyze the in vitro antimicrobial efficacy and the in vitro effects of an ophthalmic formulation containing hexamidine diisethionate 0.05%, polyhexamethylene biguanide (PHMB) 0.0001% disodium edetate (EDTA) 0.01%, dexpanthenol 5% and polyvinyl alcohol 1.25% (Keratosept, Bruschettini, Genova, Italy) on cultured human corneal and conjunctival cells. The in vitro antimicrobial activity was tested on Staphylococcus aureus, Methicillin-Resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa, Streptococcus pneumoniae, Streptococcus pyogenes and Streptococcus mitis. For each microbial strain 10 μL of a 0.5 MacFarland standardized bacterial inoculum were incubated at 25 °C with 100 μL of ophthalmic solution for up to 6 h. After different periods of time, samples were inoculated on blood agar with 5% sheep blood. Moreover, a 0.5 MacFarland bacterial inoculum was seeded in triplicate on Mueller-Hinton Agar or on Mueller-Hinton Fastidious Agar; then a cellulose disc soaked with 50 μL of ophthalmic solution was applied on the surface of agar and plates were incubated for 18 h at 37 °C, in order to evaluate the inhibition of bacterial growth around the disc. Human corneal and conjunctival epithelial cells in vitro were incubated for 5, 10 and 15 min with Keratosept or its components. The cytotoxicity was assessed through the release of cytoplasmic enzyme lactate dehydrogenase (LDH) into the medium immediately after exposure to the drugs; the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was performed to evaluate the metabolic cell activity. Our results show that Keratosept ophthalmic solution gave an average logarithmic (log) reduction of bacterial load of 2.14 ± 0.35 within 6 h of exposure (p-value < 0.05 versus control saline solution). On agar plates, all microbial strains, excluding P. Aeruginosa, showed an inhibition zone of growth around the Keratosept-soaked discs. Keratosept and its components after 5 and 10 min did not show any cytotoxic effect on cultured corneal and conjunctival cells, and only after 15 min a significant reduction of cell viability and an increase of cytotoxicity compared to control (vehicle) was seen; dexpanthenol 5% and polyvinyl alcohol accelerated the wounding of corneal cells in vitro. In conclusion, Keratosept showed good antimicrobial activity on the tested strains; the ophthalmic solution and its components were safe and non-toxic for the corneal and conjunctival epithelial cells for 5 and 10 min at the concentrations analyzed, and dexpanthenol 5% and polyvinyl alcohol promoted the wounding of corneal cells.

Exophiala lecanii-corni keratitis presenting as a serpiginous pigmented superficial lesion: a case report

RATIONALE

Patients with bullous keratopathy (BK) treated by Descemet stripping automated endothelial keratoplasty (DSAEK) have a compromised cornea, due to the administration of topical steroid, postsurgical use of contact lenses, and impaired barrier function of the corneal epithelium by BK. We report a case of Exophiala lecanii-corni (E lecanii-corni) keratitis presenting as a serpiginous pigmented superficial lesion after DSAEK.

PATIENT CONCERNS

An 81-year-old woman who had undergone cataract surgeries, suffered from decreased vision in the left eye. She was diagnosed BK and she underwent DSAEK. Two months after DSAEK, a pigmented superficial lesion developed on the left cornea. The lesion migrated and recurred repeatedly and she was referred to our department. Best corrected vision was 20/220.

DIAGNOSES

Light microscopy of a corneal scraping revealed branching fungal hyphae. Fungal culture showed growth of a black colony, identified as E lecanii-corni by ribosomal DNA sequencing.

INTERVENTIONS

We started topical treatment with 1% voriconazole and 1.5% levofloxacin. Antifungal susceptibility testing showed that the minimum inhibitory concentration of voriconazole was 0.06 μg/mL.

OUTCOMES

The lesion scarred after treatment for 3 months, and left best corrected vision improved to 20/40.

LESSONS

Genus Exophiala is known as 1 of the "black molds" and a cause of chromomycosis. This is the first description of E lecanii-corni keratitis, and pigmented corneal epithelial lesions may be characteristic of this fungal genus.

Topical Steroids as Adjunctive Therapy for Bacterial Keratitis: Evidence From a Retrospective Case Series of 313 Cases

PURPOSE

The aim of this study was to report topical steroid usage in bacterial keratitis and analyze the effects of steroids on patients' outcomes to the main causative organisms.

DESIGN

A retrospective case-series.

METHODS

This study included all patients with corneal scrape positive bacterial keratitis from January 2012 to December 2016 at the Sydney Eye Hospital, Sydney, Australia. Cases were identified from pathology results and hospital coding, and data collected from medical records.

RESULTS

A total of 313 eyes from 308 patients with a mean age of 51 years [interquartile range (IQR) 36-72] were included. Of these patients, 192 (61%) were treated with topical steroids. High-dose steroids were prescribed in 22 (11%) cases, regular-dose in 88 (46%), and low-dose in 82 (43%). The median time until the implementation of steroid use was 4 days (IQR 3-7). Patients prescribed with topical steroids had significantly longer healing times than the "no steroid" group (11 vs 6.5, P < 0.001). Patients with Pseudomonas aeruginosa keratitis and topical steroid use had worse clinical outcomes, with a higher proportion having longer healing times (P = 0.04) and corneal scarring (P = 0.02).

CONCLUSIONS

Adjuvant topical steroid therapy did not affect visual acuity, patient outcomes or the rate of adverse effects but may delay epithelial healing in bacterial keratitis in these patients. Topical steroids may have a differential effect depending on the specific causative organisms; however, a clinical trial is needed to assess this.

Monocaprin eye drop formulation to combat antibiotic resistant gonococcal blindness

Neisseria gonorrhoeae bacteria are acknowledged as an urgent threat to human health because this species has developed resistances to all of the antibiotics used clinically to treat its infections. N. gonorrhoeae causes the sexually transmitted disease gonorrhoea, but also causes blindness when the bacteria infect the eyes. Infants are particularly susceptible, acquiring the infection from their mothers at birth. We have shown that the monoglyceride monocaprin rapidly kills N. gonorrhoeae and other bacterial species and is non-irritating in ocular assays. Here we show that the physical and chemical properties of monocaprin make it ideal for use in a thickened eye drop formulation to combat eye infections. Monocaprin-containing formulations were assessed using analytical techniques and for antimicrobial activity in vitro and in ex vivo infections. Monocaprin-containing formulations retained activity after three years and are non-irritating, unlike preparations of povidone iodine in our assays. A recommended formulation for further development and investigation is 0.25% monocaprin in 1% HPMC with 1% polysorbate 20.

Mycotic keratitis due to Cylindrocarpon lichenicola: Successful salvage of the eye

We hereby report a successfully salvaged eye due to mycotic keratitis by Cylindrocarpon lichenicola in a 60-year-old female from Kasaragod (Kerala). The patient came with a history of pain, photophobia and decreased vision of the right eye. The microbiological investigations of the corneal scraping revealed C. lichenicola. C. lichenicola is a soil saprophyte. Since the ulcer worsened paracentesis followed by therapeutic keratoplasty and adjunct therapy with natamycin drops, voriconazole drops and oral ketoconazole was given. We stress that evidence-based timely medical and surgical intervention helped in the restoration of the vision in an infected eye.

Resistance of the murine cornea to bacterial colonization during experimental dry eye

The healthy cornea is remarkably resistant to infection, quickly clearing deliberately inoculated bacteria such as Pseudomonas aeruginosa and Staphylococcus aureus. Contrasting with the adjacent conjunctiva and other body surfaces, it also lacks a resident viable bacterial microbiome. Corneal resistance to microbes depends on intrinsic defenses involving tear fluid and the corneal epithelium. Dry eye, an ocular surface disease associated with discomfort and inflammation, can alter tear fluid composition and volume, and impact epithelial integrity. We previously showed that experimentally-induced dry eye (EDE) in mice does not increase corneal susceptibility to P. aeruginosa infection. Here, we explored if EDE alters corneal resistance to bacterial colonization. EDE was established in mice using scopolamine injections and dehumidified air-flow, and verified by phenol-red thread testing after 5 and 10 days. As expected, EDE corneas showed increased fluorescein staining versus controls consistent with compromised epithelial barrier function. Confocal imaging using mT/mG knock-in mice with red-fluorescent membranes revealed no other obvious morphological differences between EDE corneas and controls for epithelium, stroma, and endothelium. EDE corneas were imaged ex vivo and compared to controls after alkyne-functionalized D-alanine labeling of metabolically-active colonizing bacteria, or by FISH using a universal 16S rRNA gene probe. Both methods revealed very few viable bacteria on EDE corneas after 5 or 10 days (median of 0, upper quartile of ≤ 1 bacteria per field of view for each group [9–12 eyes per group]) similar to control corneas. Furthermore, there was no obvious difference in abundance of conjunctival bacteria, which included previously reported filamentous forms. Thus, despite reduced tear flow and apparent compromise to corneal barrier function (fluorescein staining), EDE murine corneas continue to resist bacterial colonization and maintain the absence of a resident viable bacterial microbiome.

Fungal Keratitis, or Misled by a Small Insect?

The pine processionary caterpillar is an insect that has multiple small, thin hairs around its body as a defense mechanism. These hairs have a hazardous effect on ocular structures and cause a broad range of reactions from conjunctivitis to endophthalmitis, referred to as ophthalmia nodosa. The diagnosis of the disease is based on the patient's history and the detection of the hairs on ocular structures. In this report, we present a patient with ophthalmia nodosa misdiagnosed as fungal keratitis, and the actual diagnosis was made by in vivo confocal microscopy. We also would like to increase awareness among ophthalmologists about the disease which has a growing distribution area due to climate change.

The Regulating Role of SB216763 in Pseudomonas aeruginosa Keratitis

BACKGROUND

Glycogen synthase kinase 3 beta (GSK3b) is a multifunctional molecule, which plays a critical role in the regulation of various signaling pathways including cell proliferation, growth and development, and inflammation. However, whether GSK3b is involved in the pathological process of Pseudomonas aeruginosa keratitis remains unknown.

METHODS

First, western blots were performed to measure the phosphorylated level of GSK3β at Ser9 (inactive form) in an animal model of Pseudomonas aeruginosa keratitis. Second, the keratitis model received the GSK3β inhibitor SB216763, and the inflammation of cornea was evaluated by clinical scores and slit photos. The expressions of inflammatory cytokines were assessed by real-time PCR, and the corneal bacterial burden was determined by plate count.

RESULTS

The phosphorylated level of GSK3β at Ser9 in the cornea markedly decreased after Pseudomonas aeruginosa infection. The inhibition of GSK3β by SB216763 significantly ameliorated the progress of corneal disease and alleviated corneal opacity. SB216763 suppressed the expression of inflammatory cytokines IL-6 and IL-1b, but exhibited no effects on TNF-a and IL-10 expression. SB216763 dramatically decreased cornea bacterial burden at 5 days after infection with Pseudomonas aeruginosa.

CONCLUSIONS

The activity of GSK3b was enhanced in Pseudomonas aeruginosa keratitis. The inhibition of GSK3β by SB216763 promoted host resistance against Pseudomonas aeruginosa keratitis, via down regulating inflammatory cytokines and bacterial burden.

Safety of retrocorneal plaque aspiration for managing fungal keratitis

PURPOSE

To evaluate the safety of retrocorneal plaque aspiration in patients with fungal keratitis.

STUDY DESIGN

Retrospective study.

METHODS

A retrospective case series of fungal keratitis seen at Kyoto Prefectural University of Medicine between November 2013 and September 2018. Patients with retrocorneal plaque who underwent retrocorneal plaque aspiration for the diagnosis and treatment of fungal keratitis were included. The retrocorneal plaques were either aspirated using a tuberculin syringe with a 27-gauge blunt needle or were directly pulled out using a forceps. The anterior chamber was carefully washed out using bimanual irrigation and aspiration (I/A). Diagnosis accuracy and treatment safety were evaluated.

RESULTS

Five eyes of five patients aged 68.4 ± 13.0 years old (range: 45-81 years) were included. Three of the five patients (60%) were positive for fungus obtained from corneal scrapings. Retrocorneal plaque aspiration improved the diagnosis accuracy to five out of five patients (100%), including two cases positive to Fungiflora Y^® staining. Three of the five patients (60%) had good response rapidly after retrocorneal plaque aspiration, and two patients received therapeutic keratoplasty. All cases were finally stabilized without severe complications.

CONCLUSION

Retrocorneal plaque aspiration may be useful for the precise diagnosis of fungal keratitis.

Label-Free Quantitative Proteomics Distinguishes General and Site-Specific Host Responses to Pseudomonas aeruginosa Infection at the Ocular Surface

Mass spectrometry-based proteomics enables the unbiased and sensitive profiling of cellular proteomes and extracellular environments. Recent technological and bioinformatic advances permit identifying dual biological systems in a single experiment, supporting investigation of infection from both the host and pathogen perspectives. At the ocular surface, Pseudomonas aeruginosa is commonly associated with biofilm formation and inflammation of the ocular tissues, causing damage to the eye. The interaction between P. aeruginosa and the immune system at the site of infection describes limitations in clearance of infection and enhanced pathogenesis. Here, the extracellular environment (eye wash) of murine ocular surfaces infected with a clinical isolate of P. aeruginosa is profiled and neutrophil marker proteins are detected, indicating neutrophil recruitment to the site of infection. The first potential diagnostic markers of P. aeruginosa-associated keratitis are also identified. In addition, the deepest murine corneal proteome to date is defined and proteins, categories, and networks critical to the host response are detected. Moreover, the first identification of bacterial proteins attached to the ocular surface is reported. The findings are validated through in silico comparisons and enzymatic profiling. Overall, the work provides comprehensive profiling of the host-pathogen interface and uncovers differences between general and site-specific host responses to infection.

Sphingomonas paucimobilis keratitis post cataract surgery: First case report from India

Sphingomonas paucimobilis is a rare, aerobic Gram-negative soil bacillus rarely associated with intraocular infections. With only 3 cases of ophthalmic manifestations reported so far, we are presenting the fi rst case of S. Paucimobilis, causing keratitisafter cataract surgery, from India. The organism, which was resistant to initial medical treatment, eventually responded to a patch graft and the patient improved to a final visual acuity of 20/40.

Usability of donor corneas harvested from the deceased having septicaemia or malignancy

CONTEXT

There is a wide gap between supply and demand in relation to healthy corneal grafts. Specific contraindications like infection and malignancy lead to non-usage of many grafts, despite the fact that deeming graft unhealthyness for these two contraindications is debatable.

AIMS

This study was conceptualized to assess if corneas donated from the deceased with septicaemia or malignancy can be deemed fit for implantation.

SETTINGS AND DESIGN

Retrospective histopathological and microbiological analysis of cadaveric donor corneas.

METHODS

A total of 76 donor corneas from 38 patients rejected for corneal transplantation in view of patient having septicaemia or malignancy were analysed for pathological and microbiological workup, to look for dissemination of disease within corneal tissue. Pathology workup included gross and microscopic histopathological evaluation of tissue. Microbiology workup included Grams stain and KOH with calcofluor mount, culture in blood agar, chocolate agar, Sabourauds dextrose agar and Mc Conkeys broth.

RESULTS

A total of 46 donor corneas of 23 septicaemia patients when evaluated showed presence of culture positive infection in 18 patients (78.2%). Histopathological examination done for 30 donor corneas from 15 cancer patients did not reveal presence of tumour cells in the specimen. Corneas of two of cancer patients having septicaemia revealed growth on cultures.

CONCLUSIONS

Corneal tissues harvested from septicaemia donors showed significantly higher incidence of corneal contamination, confirming their unsuitability for usage. However, there was no incidence of tumour transmission in corneal tissues of the patients with malignancies, suggesting that they can be considered for ophthalmic purpose.

Ocular Glands Become Infected Secondarily to Infectious Keratitis and Play a Role in Corneal Resistance to Infection

Ocular glands play a critical role in eye health through the secretion of factors directly onto the ocular surface. The cornea is a normally transparent tissue necessary for visual acuity located in the anterior segment of the eye. Corneal damage can occur during microbial infection of the cornea, resulting in potentially permanent visual deficits. The involvement of ocular glands during corneal infection has been only briefly described. We hypothesized that ocular glands contribute to resistance as an arm of the eye-associated lymphoid tissue and may also be susceptible to infection secondary to microbial keratitis. Utilizing a mouse model of herpes simplex virus 1 (HSV-1) keratitis, we found that infection of corneas resulted in subsequent infection of ocular glands, including harderian glands (HGs) and extraorbital glands. Similarly, infection of corneas with Pseudomonas aeruginosa resulted in secondary infection of ocular glands. A robust immune response, characterized by increased numbers of immune cells and inflammatory mediators, occurred within ocular glands following HSV-1 keratitis. Removal of HGs altered corneal resistance to HSV-1, as measured by increased viral load, decreased corneal edema, and decreased inflammatory cell infiltration. These novel findings suggest that ocular glands are involved in microbial keratitis through their susceptibility to secondary infection and contribution to corneal resistance.IMPORTANCE Microbial keratitis accounts for up to 700,000 clinical visits annually in the United States. The involvement of ocular glands during microbial keratitis is not readily appreciated, and treatment options do not address the consequences of ocular gland dysfunction. The present study shows that ocular glands are susceptible to direct infection by common ocular pathogens, including HSV-1 and Pseudomonas aeruginosa, subsequent to microbial keratitis. Additionally, ocular glands contribute soluble factors that play a role in corneal resistance to HSV-1 and alter viral load, corneal edema, and immune cell infiltration. Further studies are needed to elucidate the mechanisms by which this occurs.

Visual Impairment in Fungal Versus Bacterial Corneal Ulcers 4 Years After Successful Antimicrobial Treatment

PURPOSE

To compare longitudinal outcomes of visual acuity after fungal corneal ulcers with those of bacterial ulcers.

DESIGN

Prospective cohort study.

METHODS

This study was conducted in a tertiary eye hospital in South India. The population consisted of 100 of 152 individuals whose fungal or bacterial keratitis had been diagnosed 4 years prior and had been enrolled in 1 of 2 concurrent randomized trials. Causative organisms of infectious keratitis were either bacterial or fungal. Presenting visual acuity consisted of best spectacle corrected visual acuity (BSCVA) and hard contact lens-corrected visual acuity (CLVA).

RESULTS

Fifty study participants with prior fungal keratitis and 50 with prior bacterial keratitis were enrolled. Four years after treatment for keratitis, participants' presenting vision in the better eye was worse than 20/60 for 12 individuals (24.0%) in the fungal group and 10 individuals (20.0%) in the bacterial group. Median BSCVA in the affected eye at the 4-year visit in the fungal group was similar to that in the bacterial group (Snellen equivalent, 20/32 for each), although vision worse than 20/400 was more common in the fungal ulcer group after spectacle correction (odds ratio [OR] 4.19; 95% confidence interval [CI], 1.11-15.8) and contact lens correction (OR, 5.74; 95% CI, 1.37-24.1).

CONCLUSIONS

In this South Indian population with a previous episode of fungal or bacterial keratitis, correctable bilateral visual impairment was common. Although long-term visual outcomes were, on average, similar between fungal and bacterial ulcers, fungal ulcers were more likely to produce severe visual impairment.

Contact Lenses Delivering Nitric Oxide under Daylight for Reduction of Bacterial Contamination

Ocular infection due to microbial contamination is one of the main risks associated with the wearing of contact lens, which demands novel straightforward strategies to find reliable solutions. This contribution reports the preparation, characterization and biological evaluation of soft contact lenses (CL) releasing nitric oxide (NO), as an unconventional antibacterial agent, under daylight exposure. A tailored NO photodonor (NOPD) was embedded into commercial CL leading to doped CL with an excellent optical transparency (transmittance = 100%) at λ ≥ 450 nm. The NOPD results homogeneously distributed in the CL matrix where it fully preserves the photobehavior exhibited in solution. In particular, NO release from the CL and its diffusion in the supernatant physiological solution is observed upon visible light illumination. The presence of a blue fluorescent reporting functionality into the molecular skeleton of the NOPD, which activates concomitantly to the NO photorelease, allows the easy monitoring of the NO delivery in real-time and confirms that the doped CL work under daylight exposure. The NO photoreleasing CL are well-tolerated in both dark and light conditions by corneal cells while being able to induce good growth inhibition of Staphylococcus aureus under visible light irradiation. These results may pave the way to further engineering of the CL with NOPD as innovative ocular devices activatable by sunlight.

Evaluation of corneal cross-linking as adjuvant therapy for the management of fungal keratitis

PURPOSE

To evaluate the efficacy of corneal cross-linking (CXL) as adjuvant therapy for the treatment of fungal ulcerative keratitis.

METHODS

Forty-one patients with fungal ulcerative keratitis were recruited and assigned into two randomized controlled groups. These groups were treated with CXL combined with antifungal medications (CXL-M) or antifungal medications alone (M). The ulcers were assessed by slit-lamp biomicroscopy, slit-lamp images, in vivo confocal microscopy (IVCM), and anterior segment optical coherence tomography (AS-OCT). The patients were followed up before surgery/first visit (FV), 1 day after surgery, 1 and 2 weeks, and 1, 2, 3, 4, 5, and 6 months after surgery/FV.

RESULTS

In the cured patients, the area of corneal ulcers, the duration of ulcer healing, the time to non-observed fungal hyphae by IVCM, the number of antifungal medications, the frequency of administered medications, and the maximum ulcer depth decreased significantly after CXL (all P < 0.05) compared with the M group. There were no significant differences in either corneal thickness or epithelial thickness of ulcers after healing between 5 and 6 months after surgery in the CXL-M group, while these were increased significantly at 6 months compared with 5 months after FV in the M group (both P < 0.05).

CONCLUSIONS

In our study, CXL accelerated healing of the fungal ulcers, shortened the treatment duration, and minimized the need for medications and surgery. It appears that CXL is an effective procedure and adjuvant therapy for managing fungal keratitis.

Celastrol ameliorates Aspergillus fumigatus keratitis via inhibiting LOX-1

PURPOSE

To investigate the effect of Celastrol (CLT) on Aspergillus fumigatus (A. fumigatus) keratitis.

METHODS

Primary peritoneal macrophages of C57BL/6 mice were pretreated with CLT before A. fumigatus hyphae stimulation. C57BL/6 mice were infected with A. fumigatus. Mice corneas were treated with CLT from 1 day post infection. Clinical score, PCR, ELISA and Western blot were used to test expression of anti-inflammatory mediators, proinflammatory mediators and Lectin-like oxidized low-density lipoprotein receptor 1(LOX-1). The protein levels of p38MAPK after pretreated with CLT in macrophages of C57BL/6 mice challenged with A. fumigatus were tested by Western blot.

RESULTS

C57BL/6 mice treated with CLT from 1 day post infection showed decreased disease, IL-1β, TNF-α, IL-10, TGF-β, MIP-2 and LOX-1 levels. CLT treatment markedly inhibiting mRNA and proteins levels of anti-inflammatory mediators, proinflammatory mediators and LOX-1 in macrophages of C57BL/6 mice compared with control group. CLT pretreatment before A. fumigatus stimulation obviously inhibiting protein levels of p38MAPK versus DMSO pretreated group in macrophages of C57BL/6 mice challenged with A. fumigatus.

CONCLUSION

These data provide evidences that CLT ameliorates A. fumigatus keratitis of C57BL/6 mice via inhibiting LOX-1. CLT pretreatment before A. fumigatus stimulation decreased levels of inflammation in macrophages of C57BL/6 mice, which may be regulated by p-p38MAPK.

Direct microscopy in suppurative keratitis: a report from tertiary level hospital in Nepal

INTRODUCTION

Infective keratitis is an ocular emergency that requires prompt diagnosis for appropriate management. This study was done todetermine the sensitivity, specificity and predictive values of Gram stain and potassium hydroxide (KOH) wet mount in the diagnosis of suppurative keratitis.

MATERIALS AND METHODS

A prospective hospital based study of all patients with clinically diagnosed suppurative keratitis presenting between January 2011 and June 2012 was carried out. Corneal scrapes were taken and subjected to direct microscopy and culture.

RESULTS

Corneal scrapings were obtained from 108 eyes with suppurative keratitis. Direct microscopy was positive in 39.2% of cases and organisms were grown in 50.9 % of the cases. Bacteria were responsible in 76.4% and fungi in 23.6%. Of the bacterial isolates, 66.7% was Staphylococcus aureus and of the fungal isolates, 30.7% was Aspergillus species. Sensitivity in vitro showed that Cefazolin, Chloramphenicol and Ofloxacin were most effective against bacteria. Sensitivity of Gram stain in detecting bacteria was 50% (95% CI, 34.43 to 65.56) and specificity was 77.3% (95% CI, 65.0 to86.3) and sensitivity of KOH wet mount in detecting fungi was 53.8% (95% CI, 26.12 to79.6) and specificity was 98.9% (95% CI, 93.44 to 99.9). Positivity of direct smear (65.1%) was found to be higher among eyes with larger ulcers (>2mm) than eyes with smaller ulcers ( less than 2mm).

CONCLUSION

Direct microscopy is of great diagnostic value in the management of suppurative keratitis and it is recommended in all ophthalmic clinics without exception for establishing timely, appropriate and effective treatment.

Incidence and Outcomes of Positive Donor Rim Cultures and Infections in the Cornea Preservation Time Study

PURPOSE

To assess donor rim culture results and outcomes of ocular infections in the Cornea Preservation Time Study (CPTS).

METHODS

Donor corneal rim cultures were optional. Donor characteristics were assessed for association with positive cultures using the Fisher exact test and Poisson regression analyses. Incidence rates of ocular infections were estimated, and 95% confidence intervals were calculated.

RESULTS

Cultures were performed in 784 (58.9%) of the 1330 cases. For the 0 to 7-day versus 8 to 14-day preservation time groups, respectively, positive fungal growth occurred in 10 of 397 (2.5%) versus 5 of 387 (1.3%) corneas (P = 0.30), whereas positive bacterial cultures occurred in 6 of 397 (1.5%) versus 4 of 387 (1.0%) corneas (P = 0.75). Surgeon-prepared tissue remained a significant risk for positive fungal cultures [relative risk (RR) of surgeon- versus eye-bank-prepared, 2.85; 95% CI (1.02-7.98)], whereas younger donors [RR per year of age, 0.96; 95% CI (0.93-1.00)] and accidental death donors [RR of accident versus disease, 3.71; 95% CI (1.36-10.13)] were at a greater risk for positive bacterial cultures. Fungal infection (Candida glabrata) developed in 1 (6.7%) of 15 recipients with a positive fungal culture, and no recipient infections occurred with positive bacterial culture. With one additional fungal keratitis (Candida albicans) and one bacterial endophthalmitis (E. coli) with no rim culture performed, a total of 2 of 1330 eyes (0.15%) developed fungal and 1/1330 eyes (0.08%) developed bacterial postkeratoplasty infections.

CONCLUSIONS

A longer preservation time was not associated with a higher rate of positive donor rim cultures. The overall rate of infection across the entire cohort was low.

Factors influencing the contamination rates of the conjunctival swabs and organ culture media of human donor eyes

This study assessed the influence of donor, environmental, and logistical factors on the contamination rates of the conjunctival swabs and organ culture media of human donor eyes.In total, 1008 conjunctival swabs and 418 organ culture media samples from 504 consecutive human donor eyes were analyzed. Cross-tabulation, chi-squared tests, and Fisher's exact tests were used to assess the influence of the different factors on the contamination rates of the conjunctival swabs and organ culture media.The overall contamination rates were 28.4% for the conjunctival swabs and 1.0% for the organ culture media. A prolonged time between death and the conjunctival swab collection was associated with an increased conjunctival swab contamination rate [odds ratio (OR) = 1.9, 95% confidence interval (CI) = 1.2-3.0, P = .007]. The highest conjunctival swab contamination rate was found in the corneas procured in external institutions (outside the university hospital) (44.1%, OR = 3.6, 95%CI = 1.5-8.4, P = .003). Hospitalization times of 2 to 7 days prior to death were associated with an increased conjunctival swab contamination risk (OR = 2.6, 95%CI = 1.1-5.8, P = .021). However, the sex, age, cause of donor death, differentiation between septic and aseptic donors, differentiation between heart-beating brain-dead multiorgan donors and cadaveric donors, a warmer mean monthly temperature, and death to corneoscleral disc excision time did not significantly increase the conjunctival swab contamination risk. In addition, none of these factors affected the organ culture media contamination risk. Moreover, a positive conjunctival swab did not significantly increase the media contamination risk (P = .08). Surprisingly, the microorganisms causing media contamination were present at 50% of the amount detected on the conjunctival surface of the respective donor eye.A prolonged time between death and the conjunctival swab collection, a hospitalization time of 2 to 7 days prior to death, and corneal collection outside the university hospital seemed to be the main factors responsible for an increased conjunctival swab contamination risk. In addition, our investigation illustrated that a positive conjunctival swab is not a strong indicator for organ culture media contamination. Critical discussion is necessary regarding the validity of conjunctival swabs as prognostic parameters for organ culture media contamination.

Therapeutic Penetrating Keratoplasty Button Cultures in The Mycotic Ulcer Treatment Trial II: A Randomized Trial Comparing Oral Voriconazole Versus Placebo

OBJECTIVE

To compare oral voriconazole vs placebo in addition to topical antifungals in the treatment of filamentous fungal keratitis.

DESIGN

Non-prespecified, secondary case-control analysis from a multicenter, double-masked, randomized placebo-controlled clinical trial.

METHODS

Study Participants: Patients with smear-positive filamentous fungal ulcers and visual acuity of 20/400 or worse who eventuated to therapeutic penetrating keratoplasty (TPK).

INTERVENTION

Study participants were randomized to oral voriconazole vs oral placebo; all received topical antifungal drops.

MAIN OUTCOME MEASURES

TPK button culture positivity.

RESULTS

A total of 95 of 194 (49.5%) study participants enrolled at Madurai, Coimbatore, or Pondicherry, India eventuated to TPK in an average of 20.9 days (standard deviation 15.2 days, range 2-71 days). TPK button cultures were available for 67 of 95 (71%) of the TPKs performed and were positive for filamentous fungus in 45 of 67 (67%) cases. For each 1-day increase in the time to TPK there was 0.94-fold decreased odds of fungal culture positivity (95% confidence interval [CI] 0.90-0.98, P = .005). Those randomized to oral voriconazole had 1.26-fold increased odds of TPK button culture positivity after controlling for time to TPK and baseline organism, but this was not statistically significant (95% CI 0.32-4.87; P = .74). Those who underwent TPK for lack of response to medical therapy were 10.64-fold more likely to be culture positive than if the indication for surgery was perforation and this was statistically significant (95% CI 2.16-51.70; P = .003).

CONCLUSIONS

There appears to be no benefit to adding oral voriconazole to topical antifungal agents in the treatment of severe filamentous fungal ulcers. Infection rather than inflammation appears to be the reason for the worsening clinical picture in many of these patients.