Diagnosis of herpes simplex virus-1 keratitis using Giemsa stain, immunofluorescence assay, and polymerase chain reaction assay on corneal scrapings

Viral Keratitis, Surgical Intervention in Viral Keratitis, Challenges in Diagnosis and Treatment of Viral Keratitis, HSV, HZV

Viral keratitis is a significant cause of ocular morbidity and visual impairment worldwide. In recent years, there has been a growing understanding of the pathogenesis, clinical manifestations, and diagnostic modalities for viral keratitis. The most common viral pathogens associated with this condition are adenovirus, herpes simplex (HSV), and varicella-zoster virus (VZV). However, emerging viruses such as cytomegalovirus (CMV), Epstein-Barr virus (EBV), and Vaccinia virus can also cause keratitis. Non-surgical interventions are the mainstay of treatment for viral keratitis. Antiviral agents such as Acyclovir, Ganciclovir, and trifluridine have effectively reduced viral replication and improved clinical outcomes. Additionally, adjunctive measures such as lubrication, corticosteroids, and immunomodulatory agents have alleviated symptoms by reducing inflammation and facilitating tissue repair. Despite these conservative approaches, some cases of viral keratitis may progress to severe forms, leading to corneal scarring, thinning, or perforation. In such instances, surgical intervention becomes necessary to restore corneal integrity and visual function. This review article aims to provide an overview of the current perspectives and surgical interventions in managing viral keratitis. The choice of surgical technique depends on the extent and severity of corneal involvement. As highlighted in this article, on-going research and advancements in surgical interventions hold promise for further improving outcomes in patients with viral keratitis.

Virus-Induced Cell Fusion and Syncytia Formation

Most enveloped viruses encode viral fusion proteins to penetrate host cell by membrane fusion. Interestingly, many enveloped viruses can also use viral fusion proteins to induce cell-cell fusion, both in vitro and in vivo, leading to the formation of syncytia or multinucleated giant cells (MGCs). In addition, some non-enveloped viruses encode specialized viral proteins that induce cell-cell fusion to facilitate viral spread. Overall, viruses that can induce cell-cell fusion are nearly ubiquitous in mammals. Virus cell-to-cell spread by inducing cell-cell fusion may overcome entry and post-entry blocks in target cells and allow evasion of neutralizing antibodies. However, molecular mechanisms of virus-induced cell-cell fusion remain largely unknown. Here, I summarize the current understanding of virus-induced cell fusion and syncytia formation.

Highly sensitive and naked-eye detection of herpes simplex virus type 1 using LAMP- CRISPR/Cas12 diagnostic technology and gold nanoparticles

Herpes simplex virus type 1 (HSV-1) Keratitis (HSK) is a highly prevalent eye disease worldwide, characterized by lifelong recurrent episodes and a major risk of leading to blindness. Detecting HSV-1 promptly and accurately can initiate a timely and appropriate therapeutic regimen, minimizing tissue damage and preventing vision impairment. Currently, PCR is the most reliable method for identifying HSV-1, but its utilization for point-of-care (POC) HSV-1 detection is limited due to the need for sophisticated equipment, particularly in areas with limited resources. Here, we propose a new method for on-site HSV detection by using LAMP-Cas12 diagnostic technology and gold nanoparticles. This technique possesses comparable sensitivity to qPCR, and its detection results could be easily read and interpreted without the need for complex equipment. In detecting HSV in clinical tear specimens, this strategy achieved a 93.9 % consistency in positive detection and a 100 % consistency in negative detection compared to qPCR. Our strategy innovates the technique of current HSV-1 detections and is expected to play a crucial role in POC diagnosis of HSK in the future.

Microbiological Profile in Patients Having Keratitis in a Tertiary Care Hospital in India

Background Corneal ulcer or keratitis is defined as a loss of corneal epithelium with underlying stromal infiltration and suppuration associated with signs of inflammation. Corneal blindness is a significant public health problem worldwide; infectious keratitis is one of the predominant preventable causes of blindness. Several studies have evaluated microbial infectious keratitis's etiology, management, and outcome. However, there are regional variations in corneal ulcers' prevalence, risk factors, and outcome. The objective of this study was to isolate and identify the bacterial, fungal, viral, and protozoal etiological organisms causing infectious corneal ulcers along with their prevalence and antimicrobial sensitivity pattern. Methods A prospective observational study was done in the Department of Microbiology and RIO, Medical College & Hospital, Kolkata, for a period of 1 year (February 2019 to January 2020) after obtaining clearance from the Institutional Ethics Committee. Informed consent, demographic data, history of disease onset, duration of symptoms, associated co-morbidities, etc., were taken from the patients fulfilling the inclusion criteria. Corneal scraping samples were collected sterilely to detect bacterial, fungal, parasitic, and viral isolates and identified by standard laboratory procedures. Results A total of 80 patients were included in the study. The risk factors included foreign body in 24 (30%), blunt trauma in 10 (12.5%), steroid use in 8 (10%), contact lens user 4 (5%), and spontaneous in 34 (42.5%). Among these 80 patients, 18 showed growth of bacteria, including Staphylococcus aureus, Streptococcus pneumoniae, Streptococcus pyogenes, and Pseudomonas aeruginosa; four had growth of fungi, including Aspergillus spp. and Fusarium spp, and two were positive for Herpes simplex virus by IFA. Conclusion Early diagnosis and prompt keratitis treatment are critical for preventing visual loss. The identification of the various causative agents of keratitis is essential for the proper management of the cases.

Herpes Simplex Virus Anterior Uveitis in a Child Presenting as a Hypopyon in a White Eye

PURPOSE

To report a rare ocular presentation of unilateral anterior uveitis with hypopyon in a 5-year-old child, suspected as masquerade.

METHODS

Retrospective report.

RESULTS

A 5-year-old boy presented with hypopyon-uveitis. Detailed systemic work-up was negative for masquerade and uveitis entities. He was started on oral and topical steroids but had reactivation on taper. Real-time polymerase chain reaction (PCR) test of aqueous fluid was positive for herpes simplex virus (HSV)-1 DNA. The inflammation resolved completely on oral acyclovir and topical corticosteroids. He subsequently underwent pars plana lensectomy, primary posterior capsulotomy and vitrectomy for complicated cataract. Post-operatively, vision improved to 20/400 with aphakic correction. Maintenance oral acyclovir was stopped after 3 months with no reactivation and amblyopia therapy was continued.

CONCLUSION

This is a rare presentation of hypopyon uveitis due to HSV-1 in a child. The role of real-time PCR in establishing the diagnosis is crucial in such cases of diagnostic dilemma.

Quantitative analysis of herpes simplex virus-1 transcript in suspected viral keratitis corneal buttons and its clinical significance

Purpose:

The evaluation of Herpes Simplex virus-1 (HSV-1) transcript by different investigative methods (qPCR, PCR and IHC) in corneal buttons from suspected viral keratitis patients and the comparison of results with histopathological findings and clinical diagnosis.

Methods:

Sixty corneal buttons, 30 suspected viral keratitis, and 30 controls (keratoconus and bullous keratopathy) obtained after primary penetrating keratoplasty, were included in the study. All the corneal buttons were subjected to reverse transcriptase quantitative PCR (qPCR) for the detection of latency-associated transcript (LAT) gene, conventional PCR for polymerase (pol) gene, and immunohistochemistry (IHC) for HSV-1 antigen respectively. After obtaining baseline preoperative clinical data, all the patients were followed up for three years. The results obtained were correlated with clinicopathological features and follow-up data.

Results:

Of the 30 suspected viral keratitis patients there were 6 females and 24 males with mean age 46.5 ± 24.62 years (3-80 yrs). There was a marked male preponderance (80%). HSV-1 LAT transcript was detected in 23% (7/30) corneal buttons by qPCR, HSV-1 DNA in 6.7% (2/30) and HSV-1 antigen in 30% (9/30) cases by conventional PCR and IHC respectively. A statistically significant association was found between qPCR and DNA PCR (P = 0.04). All the 30 control corneas were negative for HSV-1 LAT gene, DNA and antigen.

Conclusion:

Detection of HSV-1 LAT transcript by qPCR may be superior to HSV-1 DNA PCR (conventional) and IHC, which has low sensitivity. However, the utility of HSV-1 LAT mRNA analysis as a diagnostic modality by qPCR needs to be validated on a larger patient cohort.

Quantitative real-time polymerase chain reaction analysis in herpes simplex virus keratitis with and without epithelial involvement

PURPOSE

To evaluate the quantitative real-time polymerase chain reaction (qRT-PCR) analysis in herpes simplex virus (HSV) keratitis with and without epithelial involvement.

METHODS

This cross-sectional study was performed on 70 patients with different HSV types and an active ocular lesion in Farabi Eye Hospital, Tehran, Iran. From these 70 patients, 171 samples were collected, including seventy tear samples and 33 scraping samples from involved eyes; and 68 samples from uninvolved fellow eyes. Samples were frozen at - 70 °C until DNA extraction was performed. Quantity of HSV was measured using qRT-PCR in all three samples.

RESULTS

The mean age of HSV patients was 52.19 ± 20.42 years (range, 4-85 years). Forty-one (58.6%) HSV patients had epithelial involvement, and 29 (41.4%) patients did not have epithelial involvement. In PCR-positive cases, the mean number of viruses in affected eyes' tears (8,831,234 ± 4,051,979) was significantly higher than uninvolved eyes' tears (182,603 ± 69,141) (P = 0.02). The mean of PCR in HSV patients with and without epithelial involvement was 10,320,269 ± 5,329,800 and 1,469,419 ± 1,070,396, respectively (P = 0.04). The qRT-PCR of involved tears in both groups (with and without epithelial involvement) was significantly higher than unaffected eyes' tears (P < 0.0001 and P = 0.01, respectively). In cases with and without epithelial involvement, the cutoff points of viral load in involved eyes' tears were 281,000 and 126,000 copies, respectively.

CONCLUSION

The results indicated that qRT-PCR is an excellent method for the detection of herpes simplex keratitis.

Virus-Mediated Cell-Cell Fusion

Cell-cell fusion between eukaryotic cells is a general process involved in many physiological and pathological conditions, including infections by bacteria, parasites, and viruses. As obligate intracellular pathogens, viruses use intracellular machineries and pathways for efficient replication in their host target cells. Interestingly, certain viruses, and, more especially, enveloped viruses belonging to different viral families and including human pathogens, can mediate cell-cell fusion between infected cells and neighboring non-infected cells. Depending of the cellular environment and tissue organization, this virus-mediated cell-cell fusion leads to the merge of membrane and cytoplasm contents and formation of multinucleated cells, also called syncytia, that can express high amount of viral antigens in tissues and organs of infected hosts. This ability of some viruses to trigger cell-cell fusion between infected cells as virus-donor cells and surrounding non-infected target cells is mainly related to virus-encoded fusion proteins, known as viral fusogens displaying high fusogenic properties, and expressed at the cell surface of the virus-donor cells. Virus-induced cell-cell fusion is then mediated by interactions of these viral fusion proteins with surface molecules or receptors involved in virus entry and expressed on neighboring non-infected cells. Thus, the goal of this review is to give an overview of the different animal virus families, with a more special focus on human pathogens, that can trigger cell-cell fusion.

Concomitant herpes simplex keratitis and autoimmune-associated ulcerative keratitis in rheumatoid arthritis patients

Purpose

To describe four cases of concomitant herpes simplex keratitis (HSK) and autoimmune-associated ulcerative keratitis (UK) in patients with rheumatoid arthritis (RA).

Observations

All patients developed HSK and UK while undergoing treatment for RA. The average age of onset for RA, UK and HSK was 49.3, 69.5 and 70.5 years, respectively. UK preceded HSK in three cases and followed HSK in one case. Two patients had bilateral UK and two had unilateral UK. HSK was unilateral in all cases. All the cases had been treated with immunosuppressive agents including steroid, methotrexate, calcineurin inhibitors, etanercept and tocilizumab at the onset of HSK. Every patient was treated for HSK with topical acyclovir ointment combined with oral valacyclovir. The final visual outcome was extremely poor despite intensive therapy.

Conclusions and Importance

These cases raise the possibility that RA patients have an increased risk of HSK, and that HSK may tend to be severe in these patients because of their immunocompromised condition. Furthermore, the complication of HSK and UK in RA patients is difficult to treat because of the atypical clinical manifestation. Thus, the emergence of corneal ulcer, especially in patients with a long clinical history of RA, calls for careful follow-up.

Atypical herpes simplex keratitis: frequency, clinical presentations and treatment results

AIMS

To determine herpes simplex virus (HSV) DNA positivity in corneal scraping samples obtained from patients with microbial keratitis whose findings were not specific for HSV keratitis and to evaluate these particular cases with respect to clinical features and antiviral treatment results.

METHODS

Records of patients with microbial keratitis treated in a tertiary eye care hospital within the 3-year period were evaluated retrospectively. Real-time polymerase chain reaction (PCR) was used to identify HSV DNA. Smear slides were evaluated by light microscopy. Patients with typical presentations and histories of HSV keratitis were excluded.

RESULTS

Two hundred and seventy-six eyes of 276 patients were included in the study. HSV-1 DNA was detected in 25 eyes (9%). In these 25 eyes, the initial diagnosis was fungal or bacterial keratitis. The mean symptom duration was 20 ± 14 days (2-60 days). The risk factors were ocular surgery (20%), blepharitis (16%), trauma (8%) and contact lens wear (4%); however, the majority of patients did not have any specific cause for keratitis (52%). Clinical features were variable and not typical for any particular etiology. Culture and microscopic examinations revealed bacteria and/or fungi in 6 patients in addition to herpes infection. Antiviral treatment was successful in 72% of patients.

CONCLUSION

Herpetic corneal infections can present without typical dendritic or geographic ulcers and may be masked by other infections. Real-time PCR is a useful method for rapid and definitive diagnosis. HSV infection should be considered for microbial keratitis without specific risk factors, with negative culture results and poor response to antimicrobial agents.

Coexistence of herpes simplex virus infection in microsporidial stromal keratitis associated with granulomatous inflammation

Background:

Microsporidial stromal keratitis poses several diagnostic challenges. Patients may present with corneal ulceration, marked stromal thinning, or even as a quite corneal scar. The presentation of microsporidial stromal keratitis commonly mimics viral keratitis. Microbiology scrapings are usually helpful; however, scraping and culture-negative cases pose a significant diagnostic dilemma. Histopathological examination is diagnostic but shows varying degree of inflammation, predominantly composed of polymorphonuclear leukocytes. Granulomatous inflammation, in microsporidial stromal keratitis, is never well described, and the authors in this article aim to describe the presence of granulomatous inflammation in microsporidial stromal keratitis, in patients with associated herpes simplex virus (HSV) keratitis.

Methods:

This was a retrospective and observational study conducted at a tertiary eye care center.

Results:

Of 263 patients who underwent therapeutic penetrating keratoplasty for infectious keratitis, during 2011–2013, seven patients were diagnosed as microsporidial stromal keratitis. Microsporidial spores could be demonstrated on microbiological scrapings in 5/7 (71%) of cases, but identified on histopathological examination and also confirmed on polymerase chain reaction (PCR) for microsporidium in 100% of cases. There was evidence of diffuse stromal necrosis with markedly severe degree of polymorphonuclear leukocytic infiltrates, with granulomatous inflammation in 42% of cases. Interestingly, these were positive for HSV-1 DNA on PCR. Review of medical records revealed much severe clinical presentations in patients with granulomatous inflammation, in comparison to cases without granulomatous inflammation.

Conclusions:

The authors hereby recommend that severe clinical presentation in patients with microsporidial stromal keratitis, markedly dense polymorphonuclear leukocytic infiltrates or the presence of granulomatous inflammation on the histopathological examination, should be investigated further for the presence of HSV-1 DNA for better patient management and good visual outcome.

Cell-fusion events induced by α-herpesviruses

ABSTRACT 

Enveloped viruses encode proteins that can induce cell fusion to allow spread of infection without exposure to immune surveillance. In this review, we discuss cell fusion events caused by neurotropic α-herpesviruses. Syncytia (large, multinucleated cells) are clinically indicative of α herpesvirus infections, and peripheral neuropathies are clinical hallmarks. We examine the viral and cellular factors required for cell fusion, as well as mutations which confer a more aggressive ‘hypersyncytial’ phenotype. Finally, we consider the causes of fusion events in infected neurons, and the implications for neuronal dysfunction and pathophysiology.

Antiviral treatment and other therapeutic interventions for herpes simplex virus epithelial keratitis

BACKGROUND

Eye disease due to herpes simplex virus (HSV) commonly presents as epithelial keratitis which, though usually self-limiting, may persist or progress without treatment.

OBJECTIVES

To compare the relative effectiveness of antiviral agents, interferon, and corneal debridement in the treatment of HSV epithelial keratitis.

SEARCH METHODS

We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (2014, Issue 12), PubMed (January 1946 to 31 December 2014), EMBASE (January 1980 to 31 December 2014), Latin American and Caribbean Health Sciences Literature Database (LILACS) (January 1982 to 31 December 2014), System for Information on Grey Literature in Europe (OpenGrey) (January 1995 to 31 December 2014), BIOSIS (January 1926 to 5 May 2014), Scopus (January 1966 to 31 December 2014), Japan Science and Technology Institute (J-Global) (January 1975 to 31 December 2014), China National Knowledge Infrastructure (CNKI) (January 1979 to 31 December 2014), British Library's Electronic Table of Contents (Zetoc) (January 1993 to 7 May 2014). We looked for trials listed on the the metaRegister of Controlled Trials (www.controlled-trials.com), ClinicalTrials.gov (www.clinicaltrials.gov), the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en), Chinese Clinical Trial Registry, the U.S. Food and Drug Administration (FDA) (www.fda.gov/), National Institute for Health and Clinical Excellence (NICE) (www.

EVIDENCE

nhs.uk) and the European Medicines Agency (EMA) (www.ema.europa.eu/ema/) as of 31 December 2014. There were no language or date restrictions in the search for trials. We also culled literature digests and conference proceedings as of 15 April 2014. There were no language or date restrictions in the search for trials.

SELECTION CRITERIA

Randomised and quasi-randomised trials of HSV dendritic or geographic epithelial keratitis were included that reported the proportion of eyes healed at one week, two weeks, or both after enrolment.

DATA COLLECTION AND ANALYSIS

We tabulated data on study characteristics, risk of bias, and outcomes and used direct comparisons to estimate a risk ratio (RR) and, when feasible, a hazard ratio (HR) with a 95% confidence interval (CI). Heterogeneity was assessed by an inconsistency index. A multiple treatment comparison meta-analysis consolidated direct and indirect comparisons of relative healing at 14 days.

MAIN RESULTS

One hundred thirty-seven studies involving 8333 eyes met the inclusion criteria. Placebo-controlled studies were heterogeneous in comparison with idoxuridine (RR 1.74; 95% CI 1.03 to 2.91) and few in number for vidarabine (RR 1.81; 95% CI 1.09 to 3.01), interferon (RR 1.32; 95% CI 1.06 to 1.64), and debridement. Vidarabine (RR 1.13; 95% CI 1.02 to 1.25), trifluridine (RR 1.30; 95% CI 1.18 to 1.43), acyclovir (RR 1.23; 95% CI 1.14 to 1.34), and brivudine (RR 1.34; 95% CI 1.18 to 1.51) were more effective than idoxuridine. Trifluridine (RR 1.17; 95% CI 1.03 to 1.32) and acyclovir (RR 1.11; 95% CI 1.03 to 1.19) were more effective than vidarabine. No significant differences in healing emerged among trifluridine, acyclovir, brivudine, and foscarnet although few studies compared brivudine or foscarnet with other antivirals. Any potential advantage of ganciclovir compared to acyclovir was mitigated by study heterogeneity and possible publication bias. Only one study evaluated the joint use of two topical antivirals. In a limited number of studies, oral acyclovir (RR 0.92; 95% CI 0.79 to 1.07) or the combination of oral acyclovir with a topical antiviral (RR 1.36; 95% CI 0.68 to 2.74) appeared as effective as a single topical antiviral agent. Compared to topical antiviral monotherapy, the combination of an antiviral with either interferon or debridement had inconsistent effects on expediting healing and improving outcome.

AUTHORS' CONCLUSIONS

Placebo-controlled studies of HSV epithelial keratitis are limited to superseded interventions. Trifluridine and acyclovir are more effective than idoxuridine or vidarabine and similar in therapeutic effectiveness. Brivudine and foscarnet do not substantially differ in effectiveness from trifluridine or acyclovir. Ganciclovir is at least as effective as acyclovir. The addition of interferon to a nucleoside antiviral agent and the combination of debridement with antiviral treatment need to be further assessed to substantiate any possible advantage in healing.

Ocular herpes: the pathophysiology, management and treatment of herpetic eye diseases

Herpesviruses are a prominent cause of human viral disease, second only to the cold and influenza viruses. Most herpesvirus infections are mild or asymptomatic. However, when the virus invades the eye, a number of pathologies can develop and its associated sequelae have become a considerable source of ocular morbidity. The most common culprits of herpetic eye disease are the herpes simplex virus (HSV), varicella zoster virus (VZV), and cytomegalovirus (CMV). While primary infection can produce ocular disease, the most destructive manifestations tend to arise from recurrent infection. These recurrent infections can wreck devastating effects and lead to irreversible vision loss accompanied by a decreased quality of life, increased healthcare usage, and significant cost burden. Unfortunately, no method currently exists to eradicate herpesviruses from the body after infection. Treatment and management of herpes-related eye conditions continue to revolve around antiviral drugs, although corticosteroids, interferons, and other newer therapies may also be appropriate depending on the disease presentation. Ultimately, the advent of effective vaccines will be crucial to preventing herpesvirus diseases altogether and cutting the incidence of ocular complications.

Herpes Simplex Keratitis in Rheumatoid Arthritis Patients

PURPOSE

To describe a series of 5 patients with herpes simplex virus keratitis (HSK) and rheumatoid arthritis (RA) under immunosuppressive treatment.

METHODS

Retrospective study. Detailed data were obtained regarding symptoms and signs at the initial evaluation, treatment, microbiological diagnostic tests, evolution, and outcomes.

RESULTS

Five patients with HSK and RA were identified. Bilateral involvement occurred in 2 patients (40%). Epithelial keratitis was diagnosed in 5 eyes. Three eyes showed severe melting with eye perforation. Gram-positive bacterial co-infections were common in the group with stromal keratitis. We did not find differences in the evolution of the disease based on anti-rheumatoid treatment.

CONCLUSIONS

The characteristics of HSK in patients with RA differed from HSK in immunocompetent patients. The stromal keratitis cases were very aggressive and difficult to manage, with perforation and gram-positive bacterial co-infection as frequently associated conditions. Prophylactic therapy at standard doses was unsuccessful to avoid recurrences.

Role of molecular diagnostics in ocular microbiology

Although microbial culture remains the gold standard for diagnosis of many ocular infections, the technique is limited by low yield, inability to detect certain organisms, and potentially long delays to results. DNA-based molecular diagnostic techniques use detection of specific nucleic acid sequences as evidence for presence of suspected pathogens. The polymerase chain reaction (PCR) is a powerful molecular biology technique that allows for detection of fewer than 10 copies of pathogen genome. Recent technical advances in PCR have permitted quantitation of pathogen load using quantitative PCR (qPCR), and have permitted multiplexing of primer sets. Use of pan-bacterial and pan-fungal primers for ribosomal DNA sequences has allowed diagnosis of bacterial and fungal infections using molecular techniques. In this review, we highlight recent advances in the application of PCR to the diagnosis of anterior segment and posterior segment ocular infectious diseases.

Could polymerase chain reaction tests on conjunctival swabs be useful to diagnose herpetic keratitis?

INTRODUCTION

Diagnosis of HSV-1 keratitis (HK) is frequently based on clinical findings. Invasive specimens (corneal scrapings, biopsies) are required for microbiological diagnosis.

METHODS

Corneal scrapings and conjunctival swabs were collected on patients with/without clinical suspicion of HK from 2007 to 2012.

RESULTS

The sensitivity, specificity, positive and negative predictive values for conjunctival swabs by PCR was 77.8, 92.1, 84.4 and 88.3, respectively.

DISCUSSION

Conjunctival swabs by PCR may help in the diagnosis of HK, despite the limited sensitivity.

Comparative analysis of polymerase chain reaction assay for herpes simplex virus 1 detection in tear

Purpose

To comparatively analyze the methodological efficacy of the polymerase chain reaction (PCR) assay for herpes simplex virus 1 (HSV) detection in tears.

Methods

This retrospective study reviewed the medical records of 115 patients who were clinically diagnosed with herpes keratitis, and their tear samples were collected for HSV detection. PCR positive rates were analyzed for their dependence on the PCR primers used (conventional PCR primer vs. nested PCR primer), the tear collecting method used (micropipetting vs. collection with schirmer strip), the disease manifestation and the patient's previous medication history.

Results

HSV DNA was detected in 23 out of 115 (20%) tear samples. The PCR positive rate in tear samples did not differ depending on the PCR primer or tear collection method used. Typical epithelial lesions showed a higher positive rate (31.4%) than atypical epithelial lesions (10.9%). The previous history of the antiviral agent seemed to affect the PCR positive rate.

Conclusions

Although the PCR positive rate was not dependent on the tear collection method or primers, HSV detection in tears using PCR was shown to be a supplementary diagnostic test in typical and atypical herpes epithelitis.

Pharmacological treatment for infectious corneal ulcers

INTRODUCTION

Cornea ulceration and infectious keratitis are leading causes of corneal morbidity and blindness. Infectious causes are among the most frequent and most severe. Management strategies for bacterial corneal ulcers have changed significantly over the last decades, however with a more limited progress in the treatment and management of nonbacterial, infectious ulcers.

AREAS COVERED

This paper provides an overview of the current principles, strategies and treatment choices for infectious corneal ulcers in adults.

EXPERT OPINION

Topical application with a broad-spectrum antimicrobial remains the preferred method for the pharmacological management of infectious corneal ulcers. Increasing reports of clinical failures and in vitro resistance to antibiotics to treat the most common infectious (bacterial) corneal ulcers are increasing concerns. New approaches for improvement in the pharmacological management of corneal ulcers should focus on strategies for a more rational and evidence-based use of current antimicrobials and development of products to modulate the host immune response and to neutralize microbial toxins and other immune modulators.

Difficulties imaging herpes simplex keratitis with fluorescein isothiocynate-labeled anti-HSV-1 antibodies in an ex vivo model

AIM

The aim of this study was to attempt to visualize herpes simplex keratitis in an ex vivo model using currently available ophthalmological equipment and anti-herpes simplex virus 1 (HSV-1) fluorescein isothiocynate-labeled antibody.

METHODS

Sixteen donor human corneas were included in this study. Eight corneas were infected with HSV-1, whereas 8 remained uninfected. Abrasions were made on 2 infected and 2 uninfected corneas to assess a possible nonspecific absorption of antibodies in the sites of corneal epithelial defects. Corneas were examined before and after antibody application using a slit lamp, the fluorescein enhancing filter settings of fundus camera, and Confoscan 3. All corneas were further imaged using multiphoton laser confocal microscopy.

RESULTS

Before anti-HSV-1 antibody application, no fluorescence was detected in donor corneas with the blue light of the slit lamp and fundus camera at fluorescein enhancing filter settings. Examination with the fundus camera after antibody application detected increased background fluorescence in all the corneas with more highlighted areas of epithelial defects in abraded infected and uninfected corneas. Confoscan 3 did not show a significant difference between the appearances of HSV-1-infected and control corneas with and without application of the antibody. However, specific staining was confirmed by multiphoton laser confocal microscopy in all infected corneas.

CONCLUSION

Further refinement of currently available ophthalmological tools is required to aid in vivo visualization of herpes simplex keratitis using fluorescein isothiocynate-labeled antibodies.

Herpetic keratitis after descemet stripping automated endothelial keratoplasty for failed graft

OBJECTIVES

To report a case of herpetic epithelial keratitis after Descemet stripping automated endothelial keratoplasty (DSAEK) for a failed graft.

METHODS

A 31-year-old female patient underwent DSAEK for failed graft in left eye. She previously had undergone penetrating keratoplasty for keratoconus in that eye.

RESULTS

One week after DSAEK, the patient presented with pain in left eye. The cornea showed two epithelial defects with dendritic edges that involved the penetrating keratoplasty graft host junction and showed positive fluorescein staining. Diagnosis of herpes simplex virus keratitis was made and the patient was started on oral acyclovir and topical trifluiridine. The epithelial lesions showed complete resolution in 3 days.

CONCLUSIONS

Herpes simplex virus epithelial keratitis can occur after DSAEK for failed grafts even in the absence of previous history of herpes simplex virus infection and should be considered in the differential diagnosis of postoperative epithelial defects.

Applications of the polymerase chain reaction in clinical ophthalmology

Molecular biology has become a valuable component in many areas of medicine, including ophthalmology. Polymerase chain reaction (PCR) is the most widely used tool. It has proven to be a powerful technique in diagnosis and quantification of microorganisms and antibiotic resistance screening. For a growing number of ophthalmic conditions PCR testing can be conducted. It is therefore important that clinicians be knowledgeable about the indications, strengths, and limitations of the technique. The purpose of this review is to explore the current role of PCR in the diagnosis and management of eye disease.

Prospective comparison of microbial culture and polymerase chain reaction in the diagnosis of corneal ulcer

PURPOSE

To compare polymerase chain reaction (PCR) to microbial culture for the detection and identification of bacterial and fungal pathogens in microbial keratitis.

DESIGN

Prospective cohort study.

METHODS

A total of 108 consecutive corneal ulcers were cultured and analyzed by PCR using pan-bacterial and pan-fungal primers. PCR products were cloned, sequenced, and compared to culture results using standard bioinformatics tools.

RESULTS

Of the 108 samples, 56 were culture-positive, 25 for bacteria and 31 for fungi; 52 were culture-negative. After eliminating false-positive PCR products, 94 of 108 were positive by PCR, 37 for bacteria and 57 for fungi. Nineteen of 25 bacterial culture-positive samples were positive by PCR, and 29 of 31 samples culture-positive for fungi were positive by PCR. The majority of sequenced PCR products matched the positive culture results. Of the 52 culture-negative samples, 46 (88%) yielded pathogen deoxyribonucleic acid (DNA) PCR products, 18 bacterial and 28 fungal. These represented a variety of species, including at least three novel previously uncultured microbes.

CONCLUSIONS

PCR detects microbial DNA in the majority of bacterial and fungal corneal ulcers, and identifies potentially pathogenic organisms in a high proportion of culture-negative cases. Yield and concordance with culture are higher for fungal than bacterial ulcers. Practical use of the technique is limited by artefactual amplification of nonpathogenic organisms. PCR may be used as an adjunct to culture to identify potential pathogens in microbial keratitis.

Rapid detection of oculopathogenic adenovirus in conjunctivitis

Ocular adenovirus (Ad) infections occur throughout the world in both sporadic and epidemic forms. Accurate laboratory diagnosis of Ad in conjunctival samples is always valuable. The present study was carried out to explore the presence of Ad as a causative agent in clinically suspected viral conjunctivitis and to compare the performance of conventional virus isolation on cell cultures, direct detection of Ad antigens in conjunctival cells by a direct fluorescence assay, Ad DNA detection by polymerase chain reaction (PCR), and specific IgM measurement by ELISA. Samples included scrapes from conjunctiva. Scrapes were subjected to study by direct immunofluorescence stain, culture on the Hep-2 cell line, and PCR for Ad detection. Blood samples were also taken and subjected to study for specific anti-Ad IgM determination. The culture for Ad was positive in 77.8%, direct antigen detection by fluorescent stain was positive in 72.2%, PCR was positive in 83.3%, and serology was positive in 88.9% of patients. Both determination of antibody IgM and PCR correctly identified a larger group of patients compared to cell culture. The most sensitive and specific method for diagnosis of Ad compared to culture was PCR (100%), followed by IgM detection (92.9%) then direct antigen detection by fluorescent stain (85.8%). From this study, we conclude that Ad is a common pathogen in sporadic cases of conjunctivitis. Screening of adenoviral conjunctivitis is possible by using specific IgM due to its high sensitivity. A confirmatory test can be done by PCR for diagnosis of Ad, as it is a rapid, specific, and accurate method.

Role of 3-O-sulfated heparan sulfate in virus-induced polykaryocyte formation

One way herpes simplex virus type-1 (HSV-1) spreads in vivo is by polykaryocytes formation. Here we demonstrate that polykaryocyte production during HSV-1 spread in cultured human corneal fibroblasts (CF) required heparan sulfate (HS) and more specifically 3-O sulfated HS (3-OS HS). The polykaryocyte formation heavily depended on the expression of HS on target (CF) cells but not on glycoprotein expressing effector cells. Furthermore, we provide the first visual evidence of 3-OS HS and HSV-1 gD colocalization during the membrane fusion process. Taken together our results provide novel insight into the significance of HS in polykaryocyte formation.

Effects of topical anaesthetics and fluorescein on the real-time PCR used for the diagnosis of Herpesviruses and Acanthamoeba keratitis

BACKGROUND

The early microbiological diagnosis of corneal infections may prevent the condition from worsening.

AIM

To study the potential interferences of oxybuprocain and fluorescein solutions used by ophthalmologists on the performances of the real-time polymerase chain reaction (PCR) carried out as routine test for diagnosis of keratitis.

METHODS

Quantified suspensions of Herpes simplex virus (HSV1), Varicella zoster virus (VZV), Cytomegalovirus (CMV) and Acanthamoeba with and without oxybuprocain or fluorescein added before DNA extraction were tested by real-time PCR.

RESULTS

The capacities of the real-time PCR to detect HSV, VZV, CMV and Acanthamoeba were reduced by oxybuprocain and fluorescein. Both products diluted to 1/16 reduced the PCR detection capacities for more than 2 logs (DNA copies/sample).

CONCLUSIONS

The simultaneous introduction of fluorescein or topical anaesthetics into the tubes containing the specimens to be tested by PCR may lead to false negative results. Because corneal specimens for microbiological diagnosis of keratitis are obtained after topical administration of anaesthetics and corneal staining with fluorescein, ophthalmologists should be aware to rinse the eye surface intensively with appropriate eye solutions to minimise the risks of misdiagnosis.

Evaluation of herpes simplex detection in corneal scrapings by three molecular methods

Herpes simplex virus (HSV)-1 keratitis (HSK) is a sight-threatening ocular infection with worldwide occurrence. A prompt laboratory diagnosis is often very useful. The purpose of this study was to evaluate molecular methods as rapid diagnostic tools compared with cell culture of HSK. Corneal scrapings from patients with clinically suspected HSK were tested by direct immunofluorescence assay (IFA) for HSV-1 antigen and by polymerase chain reaction (PCR) for HSV-1 DNA, and an attempt for viral isolation was performed on Vero cell line culture. Positive samples by cell culture were 20.8%, whereas PCR was positive in 29.2%, and IFA was positive in 33.3%. IFA had better sensitivity (80%) and negative predictive value (81.8%) than PCR (70% and 76.9%, respectively); however, PCR had better specificity (71.4%) and positive predictive value (63.6%). This indicates that a combination of cell culture, IFA and PCR constitutes the best set of tools for diagnosis of clinically suspected cases of HSK. Documented infection can be further assessed by cell-culture technique or PCR depending laboratory availability.