Value of PCR for detection of Toxoplasma gondii in aqueous humor and blood samples from immunocompetent patients with ocular toxoplasmosis

Coinfection Suspicion is Imperative in Immunosuppressed Patients with Suspected Infectious Uveitis and Inadequate Treatment Response: A Case Report

BACKGROUND

To report a case of coinfection of Toxoplasma gondii (Tg) and Epstein Barr Virus (EBV) in a diabetic patient with rheumatoid arthritis and immunosuppressive biological therapy.

CASE PRESENTATION

A 70-year-old female with a history of rheumatoid arthritis on therapy with corticosteroids, methotrexate, and abatacept presented bilateral granulomatous panuveitis associated with retinal necrosis and macular involvement. A diagnostic vitrectomy detected Tg and EBV. Treatment with clindamycin, trimethoprim-sulfamethoxazole, and acyclovir was established, achieving improvement.

CONCLUSIONS

Patients undergoing immunosuppressive therapy are at risk of developing opportunistic infections, often presenting with severe and atypical clinical manifestations. In such cases, multiplex polymerase chain reaction is an invaluable diagnostic tool that helps identify the specific pathogens involved. This enables healthcare professionals to make informed treatment decisions and provide targeted therapy for each identified pathogen.

The impact of aqueous humor polymerase chain reaction and serological test results for establishing infectious uveitis diagnosis: An Indonesian experience

Objective

To assess the clinical value of aqueous humor real-time polymerase chain reaction (RT-PCR) and serological antibody tests among uveitis patients in Indonesian cohort.

Methods

In this prospective cohort study, single-plex RT-PCR analysis of aqueous samples from 86 new uveitis patients was performed to detect Mycobacterium tuberculosis, Toxoplasmosis gondii, cytomegalovirus, herpes simplex virus, varicella-zoster virus, Epstein-Barr virus, and rubella virus. Specific serological antibodies for suspected pathogens were also obtained. Comparison of PCR and serological antibodies with the initial and final diagnosis were presented.

Results

The diagnostic positivity of aqueous RT-PCR in our cohort was 20% (17/86). The rate of infection as final etiological classification was higher after RT-PCR was performed (45 patients, 52%) compared to initial diagnosis based on clinical presentation alone (38 patients, 44%). In particular, the RT-PCR positivity among patients with infection as the final etiological classification was 33.33% (15/45). A significant difference in the IgG but not IgM toxoplasma value among those with ocular toxoplasmosis as the final diagnosis compared to the other etiologies were observed (3953 (IQR 2707–19562) IU/mL vs 428 (IQR 82–1807) IU/mL; p < 0.0001).

Conclusion

RT-PCR analysis of aqueous fluid from uveitis patients helped confirm a third of infectious uveitis cases in Indonesia. In ocular toxoplasmosis, high IgG but not IgM antibody value might help differentiate those with other etiology.

Toxoplasmosis chorioretinitis mimicking cytomegalovirus retinitis in an immunocompromised pediatric patient following bone marrow transplantation

Objective

To review a case of toxoplasmosis chorioretinitis mimicking cytomegalovirus retinitis in an immunocompromised patient following bone marrow transplantation.

Methods

Retrospective chart review of a 14-year-old female who had a history of leukemia and allogeneic bone marrow transplants prior to her ocular symptoms.

Results

Anterior chamber fluid analysis was positive for Toxoplasma gondii. The patient responded well when cytomegalovirus retinitis treatment was switched to intravitreal clindamycin with systemic sulfadiazine and prednisone.

Conclusions

This case demonstrates the challenges of diagnosing and treating retinal infections in immunocompromised patients as they may present with atypical findings that mimic other pathologies and may have contraindications against standard treatment.

Utility of blood as the clinical specimen for the diagnosis of ocular toxoplasmosis using uracil DNA glycosylase-supplemented loop-mediated isothermal amplification and real-time polymerase chain reaction assays based on REP-529 sequence and B1 gene

BACKGROUND

Ocular infection with Toxoplasma gondii is a major preventable cause of blindness, especially in young people. The aim of the present study was to assess detection rate of T. gondii DNA in blood samples of clinically diagnosed of ocular toxoplasmosis using uracil DNA glycosylase-supplemented loop-mediated isothermal amplification (UDG-LAMP) and real-time quantitative PCR (qPCR) based on REP-529 and B1.

METHODS

One hundred and seventeen patients with clinically diagnosed ocular toxoplasmosis (OT) were participated in the study as well as 200 control patients. Peripheral blood samples were assessed using UDG-LAMP and qPCR techniques targeting REP-529 and B1.

RESULTS

Detection limits of qPCR using REP-529 and B1 were estimated as 0.1 and 1 fg of T. gondii genomic DNA, respectively. The limits of detection for UDG-LAMP using REP-529 and B1 were 1 and 100 fg, respectively. In this study, 18 and 16 patients were positive in qPCR using REP-529 and B1, respectively. Based on the results of UDG-LAMP, 15 and 14 patients were positive using REP-529 and B1, respectively. Results of the study on patients with active ocular lesion showed that sensitivity of REP-529 and BI targets included 64 and 63%, respectively using qPCR. Sensitivity of 62 and 61%, were concluded from UDG-LAMP using REP-529 and B1 in the blood cases of active ocular lesion. qPCR was more sensitive than UDG-LAMP for the detection of Toxoplasma gondii DNA in peripheral blood samples of patients with clinically diagnosed toxoplasmic chorioretinitis. Furthermore, the REP-529 included a better detection rate for the diagnosis of ocular toxoplasmosis in blood samples, compared to that the B1 gene did. Moreover, the qPCR and UDG-LAMP specificity assessments have demonstrated no amplifications of DNAs extracted from other microorganisms based on REP-529 and B1.

CONCLUSIONS

Data from the current study suggest that qPCR and UDG-LAMP based on the REP-529 are promising diagnostic methods for the diagnosis of ocular toxoplasmosis in blood samples of patients with active chorioretinal lesions.

Comparison of real-time PCR and nested PCR for toxoplasmosis diagnosis in toxoplasmic retinochoroiditis patients

Backgrounds

PCR is a proper technique that significantly improves toxoplasmosis diagnosis. However, a more sensitive technique is required. This study compared real-time PCR with nested PCR using B1, SAG-4, and MAG-1 bradyzoite genes to diagnose toxoplasmosis in toxoplasmic retinochoroiditis patients.

Methods

Blood samples were collected from 10 patients with active toxoplasmic chorioretinal lesions and 10 healthy individuals. Blood samples including peripheral blood mononuclear cells (PBMCs), serum and whole blood samples were used for DNA extraction. Serum was also used to detect anti-toxoplasma IgG and IgM antibodies. Nested PCR and real-time PCR were performed using B1, SAG-4, and MAG-1 target genes.

Results

Five (50%) out of the 10 patients were tested positive for toxoplasmosis with nested PCR using the PBMC samples. All the five patients tested positive with nested PCR were also tested positive for toxoplasmosis with real-time PCR using the PBMC samples. The real-time PCR results demonstrated that 9(90%) out of the 10 patients were positive based on B1 and the remaining one (10%) was positive only based on MAG-1. In general, of the patients, five (50%) were positive using SAG-4 and three (30%) were positive in term of MAG-1 using PBMCs with real-time PCR.

Conclusion

It appears that PBMC samples have the best performance as the PCR extraction method and are a good source for toxoplasmosis diagnosis. The use of B22 and B23 target genes due to their high sensitivity and specificity along with bradyzoite genes are recommended for toxoplasmosis diagnosis using PBMC samples with real-time PCR.

Acute Posterior Ocular Toxoplasmosis: An Optical Coherence Tomography Angiography and Dye Angiography Study

PURPOSE

To compare Indocyanine Green (ICGA) and fundus fluorescein angiography (FFA) with Optical Coherence Tomography Angiography (OCTA) findings in toxoplasmic chorioretinitis (TCR).

METHODS

Patients affected by active TCR were included. FFA, ICGA, and OCTA images were analyzed and lesions were compared between different modalities. Satellite dark dots (SDD) were compared between modalities.

RESULTS

Fifteen patients were enrolled. The mean lesion area was similar between fundus photography (FP), FFA, and OCTA-Retina. The mean lesion area was similar between ICGA and OCTA-Choroid slab. ICGA and OCTA-Choroid showed a larger extension of the lesion compared to FP, FFA, and OCTA-Retina (p = .01, 0.0001, and 0.0002 for ICG angiography and p = .03, 0.008, and 0.0002 for OCTA-Choroid, respectively). On OCTA B-scans, the retinal flow defects were smaller than the underlying choroidal non-perfusion. The number of SDD was similar between ICGA and OCTA.

CONCLUSIONS

OCTA is a reliable method to assess retinal and choroidal involvement in TCR. OCTA confirmed a wider involvement of the choroid than the retina.

ACUTE MYOCARDITIS WITH CARDIOGENIC SHOCK AND MULTIPLE ORGAN FAILURE, FOLLOWED BY BILATERAL PANUVEITIS MASQUERADING AS ENDOGENOUS ENDOPHTHALMITIS, DUE TO TOXOPLASMA GONDII IN AN IMMUNOCOMPETENT PATIENT

PURPOSE

To report a case of systemic and ocular toxoplasmosis in an immunocompetent patient, who developed myocarditis with resulting cardiogenic shock and multiple organ failure, followed by bilateral panuveitis masquerading as endogenous endophthalmitis.

METHODS

Single case report with images.

RESULTS

A 59-year-old man with a history of monoclonal gammopathy of undetermined significance and associated scleromyxedema but otherwise immunocompetent was admitted to the intensive care unit for cardiogenic shock and multiple organ failure due to presumed viral myocarditis. After hospital discharge, ophthalmic examination revealed what seemed to be endogenous fungal endophthalmitis in both eyes. The ocular inflammation failed to improve on local and systemic antifungal therapies. After repeated testing and vitrectomy, the causative organism responsible for his intraocular inflammation remained elusive. The patient was then found to have significantly elevated serum titers of anti-Toxoplasma gondii IgG and IgM, followed by an appearance of a focal retinochoroidal lesion more typical of ocular toxoplasmosis. Systemic anti-Toxoplasma therapy led to resolution of intraocular inflammation, and the patient had since fully recovered from the myocarditis and its multiple comorbidities. Of note, myocardial biopsy and polymerase chain reaction testing of aqueous and vitreous fluids were all negative for Toxoplasma.

CONCLUSION

Even in an immunocompetent patient, Toxoplasma can result in myocarditis with significant morbidities and even death, and its ocular manifestation may be quite different from the classic focal retinochoroiditis. In addition, polymerase chain reaction analysis of ocular fluids can be unreliable in an immunocompetent host, and thus treatment decision should be guided by clinical history and examination findings.

Molecular diagnosis of toxoplasmosis: recent advances and a look to the future

INTRODUCTION

Toxoplasmosis is a globally distributed parasitic infection that can be particularly severe when opportunistic or congenital. Its diagnosis requires accurate and rapid techniques that rely mainly on serology and molecular methods.

AREAS COVERED

The aim of this review was to discuss the positioning of the molecular diagnosis of toxoplasmosis according to the different clinical situations possibly resulting from infection with T. gondii, and to detail recent developments in this technique. The English and French literature were searched with the following keywords: 'Toxoplasmosis', "Molecular diagnosis" and 'PCR'.

EXPERT OPINION

Molecular techniques have revolutionized the diagnosis of toxoplasmosis, and practices have considerably evolved over the past decades. However, there is still a high degree of inter-laboratory heterogeneity which impairs comparisons between results and studies. Efforts to standardize practices are underway.

The Diagnostic Conundrum of Retinitis and a Pigmented Scar

We report a finding of a pigmented chorioretinal scar with acute retinal necrosis (ARN) caused by herpes simplex virus 2 (HSV-2) infection rather than toxoplasma, creating an initial diagnostic dilemma. A 53-year-old functionally monocular male presented with painless floaters and blurry vision in his seeing eye over a period of 4 days. An exam demonstrated anterior chamber (AC) reaction, vitritis, multifocal patches of whitening, and an occlusive retinal vasculitis. A superior pigmented chorioretinal scar with overlying contracted vitreous was noted in the periphery with no adjacent retinal whitening. The patient was treated for both ARN and toxoplasma chorioretinitis until PCR study of the vitreous and AC returned positive for HSV-2 and negative for toxoplasmosis. Management consisted of a dual therapy regimen of both oral and intravitreal antiviral agents as well as oral corticosteroids. The patient's clinical course was complicated by rhegmatogenous retinal detachment within 2 weeks after symptom onset, requiring pars plana vitrectomy with silicone oil and intraoperative intraocular incubation with foscarnet. We review emerging evidence for pigmented chorioretinal scars in ARN specifically caused by HSV-2, as well as diagnostic and treatment dilemmas in the management of ARN and ARN detachments.

Detection of Toxoplasma gondii bradyzoite genes in the peripheral blood mononuclear cells among patients with toxoplasmic chorioretinitis

BACKGROUND

Toxoplasmic chorioretinitis may occur as a result of acquired toxoplasmosis or reactivated congenital toxoplasmosis. In this study, Toxoplasma gondii bradyzoite genes along with the B1 gene were evaluated to detect T. gondii DNA in serum and peripheral blood mononuclear cells (PBMCs) of patients with toxoplasmic chorioretinitis.

METHODS

Blood samples were collected from 10 patients (7 cases of active chorioretinal lesions and 3 cases of old chorioretinal scars). The genomic DNA was extracted from the patients' serum and PBMCs and a polymerase chain reaction (PCR) assay was performed using bradyzoite genes along with B1. The subjects were also evaluated in terms of the T. gondii antibodies.

RESULTS

The PCR results were positive in four of seven patients (57.1%) with active ocular toxoplasmosis lesions. In three patients (42.8%), the PCR results were positive for MAG-1 and SAG-4 and in one patient (14.3%) the PCR results were only positive for the B1 gene. The PCR results were positive only in the PBMCs, whereas they were negative in the serum samples. Two patients with positive PCR results showed high Toxoplasma immunoglobulin G (IgG) antibody titres. However, none of the patients showed positive Toxoplasma IgM antibodies.

CONCLUSIONS

The PBMCs are suitable for evaluating toxoplasmic chorioretinitis. The present results showed that PCR with bradyzoite genes is useful in the diagnosis of toxoplasmic chorioretinitis in PBMCs.

Rational laboratory testing in uveitis: A Bayesian analysis

Uveitis encompasses a heterogeneous group of clinical entities with the common feature of intraocular inflammation. In addition to patient history and examination, a focused set of laboratory investigations is frequently necessary to establish a specific diagnosis. There is limited consensus among uveitis specialists regarding appropriate laboratory evaluation for many distinct patient presentations. The appropriateness of a laboratory test for a given case of uveitis will depend on patient-specific as well as epidemiologic factors. Bayesian analysis is a widely used framework for the interpretation of laboratory testing, but is seldom adhered to in clinical practice. Bayes theorem states that the predictive value of a particular laboratory test depends on the sensitivity and specificity of that test, as well as the prevalence of disease in the population being tested. In this review we will summarize the performance of commonly-utilized laboratory tests for uveitis, as well as the prevalence of uveitic diagnoses in different geographic practice settings. We will propose a logical framework for effective laboratory testing in uveitic disease through rigorous application of Bayesian analysis. Finally, we will demonstrate that while many highly sensitive laboratory tests offer an effective means to rule out associated systemic disease, limited test specificity and low pretest probability often preclude the diagnosis of systemic disease association with any high degree of certainty, even in the face of positive testing.

The Next Generation of Ocular Pathogen Detection

ABSTRACT

Metagenomic next-generation sequencing is a powerful method for pathogen detection that combines advanced genome sequencing technology with cutting-edge bioinformatics to analyze microbial populations. Metagenomic next-generation sequencing has the potential to identify uncommon, unculturable, and even previously unidentified pathogens from a clinical isolate. Of particular interest to ophthalmology, this robust data extraction can occur from very small volume clinical samples. Here we discuss the opportunities and limitations of this technique and their current and future application to ophthalmic diagnostics.

Study of toxoplasmosis and toxocariasis in patients suffering from ophthalmic disorders using serological and molecular methods

Introduction

Toxoplasma gondii is an intracellular protozoan parasite that can cause ocular toxoplasmosis with most complications such as retinal detachment. Toxocara parasite, round worm, found in dogs and cats appears as larva migrans in humans can cause serious ocular complications such as debilitating vision loss.In Khuzestan province, southwest of Iran, T. gondii infection has been reported to be significant but toxocariasis was rare. However, the frequency of ocular toxoplasmosis and toxocariasis has not been studied in this area. The aim of this study was to evaluate the ocular toxoplasmosis and ocular toxocariasis using serological and molecular methods.

Method

In this case control study, 310 patients were identified by ophthalmologist as ocular toxoplasmosis and then 5 cc of venous blood samples were taken from each of them. Serum samples and buffy coat were prepared and ELISA was used to detect IgG and IgM anti-Toxoplasma antibodies and the molecular PCR was used to detect Toxoplasma DNA parasite in buffy coats. ELISA test was used to detect of IgG anti-Toxocara antibodies.

Results

Totally, for ocular toxoplasmosis, 130 (41.93%) of 310 patients were positive by ELISA, of them 121 (39%) IgG positive and nine (2.9%) IgM positive were diagnosed. Of 121 cases with IgG⁺, 119 (98.35%) were diagnosed with high IgG avidity indicating chronic phase of the infection. For ocular toxocariasis evaluation, antibodies against Toxocara were not detected in any of the samples. By PCR molecular method, 11 out of 310 patients (3.54%) had T. gondii DNA in the blood. In control, in total, 21 cases were detected positive by serology method, which showed a significant difference with the results of the case group(P < 0.05).By PCR method, only three cases showed positive which also indicated significant difference with result of case group (3 vs 9) (P < 0.05). In the control group, also no anti-toxocara antibodies were found.

Conclusion

It can be concluded that T. gondii in Khuzestan province as the etiologic agent of ocular toxoplasmosis and physicians should consider diagnostic methods for identifying the infection when they visit the patients.

Serological and molecular approaches in clinical diagnosis of ocular toxoplasmosis in Iran

Background:Toxoplasma gondii (T. gondii) is the most common parasite that can lead to a disease called toxoplasmosis. In this study, serological and molecular complementary tests have been conducted to detect or diagnose this parasite.

Methods: A total of 71 patients with clinical symptoms of ocular toxoplasmosis and 20 patients with other ocular infections were evaluated. Serum and buffy coat samples were collected and tested using enzyme-linked immunosorbent assay (ELISA) and nested polymerase chain reaction (nPCR) assessments. Superficial T. gondii B1 gene was evaluated in PCR. The ocular toxoplasmosis patients were followed-up 2 weeks after the first sampling and 4 weeks following the first laboratory testing. The main outcome measures were the efficiency of the diagnostic procedure and positive and negative predictive values (PPV and NPV).

Results: Overall, of the samples, 69% were PCR+, IgG+, and IgM-, and 4.2% showed PCR+, IgG+, and IgM+. In the first follow-up, after 2 weeks, from the 41 referred patients, 29 (70%) showed PCR+, IgG+, and IgM-, which confirmed the results of the first sampling. In the second follow-up, 9 (47%) patients were PCR+, IgG+, and IgM-. A correlation was observed between the first referral and the follow-ups. Also, from 71 patients, diagnosed clinically as ocular toxoplasmosis, the disease was confirmed in 73.2% and 26.8% of those suffering from other ocular infections. Of the 20 control group samples, 55% showed PCR-, IgG+, and IgM-. The sensitivity, specificity, negative and positive predictive values, and negative and positive likelihoods were analyzed for IgG and IgM antibodies and for PCR using ELISA method.

Conclusion: As the ophthalmologic signs of T. gondii may be mimicked by other infections, clinical methods may be complemented by laboratory approaches for a definite diagnosis. This would assist clinicians to achieve timely diagnosis and successful therapy and to control the infection.

Evaluation of RE and B1 Genes as Targets for Detection of Toxoplasma gondii by Nested PCR in Blood Samples of Patients with Ocular Toxoplasmosis

INTRODUCTION

To evaluate B1 and RE genes as targets to detect Toxoplasma gondii, nested PCR is used in blood samples of patients with ocular toxoplasmosis.

MATERIALS AND METHODS

Following the measurement of IgG and IgM antibodies using indirect ELISA, IgG avidity and assessment of blood samples by nested PCR, the agreement between various test results was studied.

RESULTS

From 117 patients, 77 (65.81%) were found to be positive for IgG anti-Toxoplasma antibody, 12 cases were positive for both IgG and IgM, and 1 patient was positive for IgM only. The detection limit for the RE-nested PCR assay was one T. gondii tachyzoite, whereas the limit for B1-nested PCR was five tachyzoites. Nested PCR results showed higher agreement with IgM test results than IgG test results.

CONCLUSION

The results of this study showed that nested PCR of peripheral blood is a useful and non-invasive method for detection of T. gondii in patients with OT, especially in case of recently acquired infections, and RE targeted assay is more sensitive than B1 targeted assay for this purpose.

A Guide to Utilization of the Microbiology Laboratory for Diagnosis of Infectious Diseases: 2018 Update by the Infectious Diseases Society of America and the American Society for Microbiology

The critical nature of the microbiology laboratory in infectious disease diagnosis calls for a close, positive working relationship between the physician/advanced practice provider and the microbiologists who provide enormous value to the healthcare team. This document, developed by experts in laboratory and adult and pediatric clinical medicine, provides information on which tests are valuable and in which contexts, and on tests that add little or no value for diagnostic decisions. This document presents a system-based approach rather than specimen-based approach, and includes bloodstream and cardiovascular system infections, central nervous system infections, ocular infections, soft tissue infections of the head and neck, upper and lower respiratory infections, infections of the gastrointestinal tract, intra-abdominal infections, bone and joint infections, urinary tract infections, genital infections, and other skin and soft tissue infections; or into etiologic agent groups, including arthropod-borne infections, viral syndromes, and blood and tissue parasite infections. Each section contains introductory concepts, a summary of key points, and detailed tables that list suspected agents; the most reliable tests to order; the samples (and volumes) to collect in order of preference; specimen transport devices, procedures, times, and temperatures; and detailed notes on specific issues regarding the test methods, such as when tests are likely to require a specialized laboratory or have prolonged turnaround times. In addition, the pediatric needs of specimen management are also emphasized. There is intentional redundancy among the tables and sections, as many agents and assay choices overlap. The document is intended to serve as a guidance for physicians in choosing tests that will aid them to quickly and accurately diagnose infectious diseases in their patients.

Isothermal PCR for Feasible Molecular Diagnosis of Primary Toxoplasmosis in Women Recently Experienced Spontaneous Abortion

AIM:

The current study aimed to assess the practicability of a simple loop-mediated isothermal amplification (LAMP) about real-time quantitative PCR to diagnose primary toxoplasmosis among high-risk pregnant women.

METHODS:

Cloned Toxoplasma samples were used to calculate the analytical sensitivity while specificity was assessed using pooled DNA samples extracted from other parasitic stages.

RESULTS:

Both techniques showed 100% sensitivity and specificity and then applied to detect recent Toxoplasma infection in peripheral blood of 77 IgG negative women out of a total 139 women lately experienced spontaneous abortion. The 2 techniques obtained positive results in 8 samples confirming primary toxoplasmosis.

CONCLUSION:

Generally, LAMP assay is a simple, cost-effective molecular technique can be completed in less than half an hour to diagnose primary Toxoplasma infection. The technique can be applied in a minimally equipped laboratory by ordinary workers to screen the vulnerable groups. Further analysis using larger samples with the quantitative approach is recommended to confirm the sensitivity of this emergent molecular technique.

Molecular diagnosis of toxoplasmosis in immunocompromised patients

PURPOSE OF REVIEW

Toxoplasmosis in immunocompromised patients is associated with a high mortality rate. Molecular techniques are important tools to diagnose acute disease in immunocompromised patients, but there are various methods with variable efficiency. Some of them have been validated for the diagnosis of congenital toxoplasmosis, but the impact of their use has not been evaluated in immunocompromised patients.

RECENT FINDINGS

Toxoplasmosis is of increasing importance in non-HIV immunocompromised patients. In addition, the picture of disease shows greater severity in South America, both in immunocompetent study participants and in congenitally infected infants. These epidemiological differences could influence the sensitivity of diagnostic methods. This review analyzes recent data on molecular diagnosis and compares them with older ones, in light of progress gained in molecular techniques and of recent epidemiological findings. Most recent studies were conducted in South America and used PCR targeting the B1 gene. PCR on blood could allow diagnosing a significant proportion of patients with ocular toxoplasmosis in Brazil.

SUMMARY

Quantitative PCR methods with specific probes should be used to improve sensitivity and warrant specificity. Performance of quantitative PCR targeting the repeated 529 bp sequence for the diagnosis of toxoplasmosis in immunocompromised patients needs evaluation in field studies in South America and in western countries.

Specific IgM, IgG and IgG1 directed against Toxoplasma gondii detected by flow cytometry and their potential as serologic tools to support clinical indirect fundoscopic presumed diagnosis of ocular disease

In the present study we evaluated the anti-Toxoplasma gondii immunoglobulin profiles of a group of 118 individuals living in an endemic area. The aim of the study was to select biomarkers to support the ophthalmological diagnosis of retinal/retinochoroidal scars presumably caused by T. gondii infection. Overall anti-T. gondii reactivity of the IgM, IgG, IgA, IgE and IgG subclasses was investigated by flow cytometry-based anti-fixed tachyzoite antibodies (FC-AFTA) in four groups of subjects, referred to as: i) TOXO(L)--seropositive patients with retinal/retinochoroidal scars presumably caused by T. gondii infection; these patients were further subdivided according to morphological aspects of their ocular scar lesions as A, B or C; ii) TOXO(NL)--seropositive patients without ocular scar lesions; iii) NEG(L)--T. gondii seronegative patients presenting retinal lesions; and iv) NEG(NL)--T. gondii seronegative without retinal lesions (negative controls). Our data demonstrated that anti-T. gondii IgG profiles were able to discriminate the mean reactivity of TOXO(L) from all other clinical groups. Analysis of anti-T. gondii immunoglobulin profiles revealed that IgM and IgG were good biomarkers capable of discriminating between individual reactivity in patients with retinal/retinochoroidal scars presumably caused by T. gondii infection [TOXO(L)] from those caused by other clinical conditions. Furthermore, anti-T. gondii IgG1 reactivity was able to discriminate TOXO(L) from all other clinical groups. In conclusion, the pre-selected IgM, IgG and IgG1 anti-T. gondii antibody subclasses were able to segregate both TOXO(L) and the other subgroups, including the scar lesion group types (A, B, C), from other clinical conditions. These results suggest the applicability of this technique in the clinical laboratory to detect putative biomarker for diagnosis of ocular lesions in T. gondii-infected patients. Studies in other areas implementing the methods described in the present study would be of value and enable evaluation of a system for classification of presumed ocular toxoplasmosis scar lesions. This classification would make comparative studies on ocular toxoplasmosis conducted in different regions around the world possible.

PCR-based detection of Toxoplasma gondii DNA in blood and ocular samples for diagnosis of ocular toxoplasmosis

PCR detection of Toxoplasma gondii in blood has been suggested as a possibly efficient method for the diagnosis of ocular toxoplasmosis (OT) and furthermore for genotyping the strain involved in the disease. To assess this hypothesis, we performed PCR with 121 peripheral blood samples from 104 patients showing clinical and/or biological evidence of ocular toxoplasmosis and from 284 (258 patients) controls. We tested 2 different extraction protocols, using either 200 μl (small volume) or 2 ml (large volume) of whole blood. Sensitivity was poor, i.e., 4.1% and 25% for the small- and large-volume extractions, respectively. In comparison, PCR with ocular samples yielded 35.9% sensitivity, while immunoblotting and calculation of the Goldmann-Witmer coefficient yielded 47.6% and 72.3% sensitivities, respectively. Performing these three methods together provided 89.4% sensitivity. Whatever the origin of the sample (ocular or blood), PCR provided higher sensitivity for immunocompromised patients than for their immunocompetent counterparts. Consequently, PCR detection of Toxoplasma gondii in blood samples cannot currently be considered a sufficient tool for the diagnosis of OT, and ocular sampling remains necessary for the biological diagnosis of OT.

A guide to utilization of the microbiology laboratory for diagnosis of infectious diseases: 2013 recommendations by the Infectious Diseases Society of America (IDSA) and the American Society for Microbiology (ASM)(a)

The critical role of the microbiology laboratory in infectious disease diagnosis calls for a close, positive working relationship between the physician and the microbiologists who provide enormous value to the health care team. This document, developed by both laboratory and clinical experts, provides information on which tests are valuable and in which contexts, and on tests that add little or no value for diagnostic decisions. Sections are divided into anatomic systems, including Bloodstream Infections and Infections of the Cardiovascular System, Central Nervous System Infections, Ocular Infections, Soft Tissue Infections of the Head and Neck, Upper Respiratory Infections, Lower Respiratory Tract infections, Infections of the Gastrointestinal Tract, Intraabdominal Infections, Bone and Joint Infections, Urinary Tract Infections, Genital Infections, and Skin and Soft Tissue Infections; or into etiologic agent groups, including Tickborne Infections, Viral Syndromes, and Blood and Tissue Parasite Infections. Each section contains introductory concepts, a summary of key points, and detailed tables that list suspected agents; the most reliable tests to order; the samples (and volumes) to collect in order of preference; specimen transport devices, procedures, times, and temperatures; and detailed notes on specific issues regarding the test methods, such as when tests are likely to require a specialized laboratory or have prolonged turnaround times. There is redundancy among the tables and sections, as many agents and assay choices overlap. The document is intended to serve as a reference to guide physicians in choosing tests that will aid them to diagnose infectious diseases in their patients.

Toxoplasma serotype is associated with development of ocular toxoplasmosis

BACKGROUND

Worldwide, ocular toxoplasmosis (OT) is the principal cause of posterior uveitis, a severe, life-altering disease. A Toxoplasma gondii enzyme-linked immunoassay that detects strain-specific antibodies present in serum was used to correlate serotype with disease.

METHODS

Toxoplasma serotypes in consecutive serum samples from German uveitis patients with OT were compared with non-OT seropositive patients with noninfectious autoimmune posterior uveitis. OT patients were tested for association of parasite serotype with age, gender, location, clinical onset, size, visual acuity, or number of lesions (mean follow-up, 3.8 years) to determine association with recurrences.

RESULTS

A novel, nonreactive (NR) serotype was detected more frequently in serum samples of OT patients (50/114, 44%) than in non-OT patients (4/56, 7%) (odds ratio, 10.0; 95% confidence interval 3.4-40.8; P < .0001). Non-OT patients were predominantly infected with Type II strains (39/56; 70%), consistent with expected frequencies in Central Europe. Among OT patients, those with NR serotypes experienced more frequent recurrences (P = .037). Polymerase chain reaction detected parasite DNA in 8/60 OT aqueous humor specimens but failed to identify Type II strain alleles.

CONCLUSIONS

Toxoplasma NR and Type II serotypes predominate in German OT patients. The NR serotype is associated with OT recurrences, underscoring the value of screening for management of disease.

Ocular Toxoplasmosis: Controversies in Primary and Secondary Prevention

Ocular toxoplasmosis is the most common cause of posterior uveitis in the United States and worldwide. It commonly follows a relapsing course with the potential for multiple adverse visual sequelae and, rarely, blindness. Both immune-competent and immune-suppressed populations can develop severe relapsing disease. There is considerable debate regarding the initial treatment of ocular toxoplasmosis in both groups, with multiple antiparasitic agents commonly used with little evidence to support any particular regimen. The precise role of corticosteroids in treatment also has yet to be rigorously defined. Secondary prevention is commonly implemented in the immune suppressed population, but there is a lack of level one evidence to support its role in immune-competent patients, though it warrants future investigation.

Diagnostic approach to ocular toxoplasmosis

Toxoplasmic retinochoroiditis is deemed a local event, which may fail to evoke a detectable systemic immune response. A correct diagnosis of the disease is a necessary basis for estimating its clinical burden. This is not so difficult in a typical clinical picture. In atypical cases, further diagnostic efforts are to be installed. Although the aqueous humor may be analyzed for specific antibodies or the presence of parasitic DNA, the DNA burden therein is low, and in rare instances a confirmation would necessitate vitreous sampling. A laboratory confirmation of the diagnosis is frustrated by individual differences in the time elapsing between clinical symptoms and activation of specific antibody production, which may result in false negatives. In congenital ocular toxoplasmosis, a delay in the onset of specific local antibody production could reflect immune tolerance. Herein, the authors attempt to provide a simple and practicable algorithm for a clinically tailored diagnostic approach in atypical instances.

Specific, sensitive, and rapid diagnosis of active toxoplasmosis by a loop-mediated isothermal amplification method using blood samples from patients

Loop-mediated isothermal amplification (LAMP), a rapid nucleic acid amplification method, was developed for the clinical diagnosis of toxoplasmosis. Three LAMP assays based on the SAG1, SAG2, and B1 genes of Toxoplasma gondii were developed. The sensitivities and specificities of the LAMP assays were evaluated by comparison with the results of conventional nested PCR. The LAMP assays were highly sensitive and had a detection limit of 0.1 tachyzoite, and no cross-reactivity with the DNA of other parasites was observed. Blood was collected from 105 individuals to test the LAMP assays: 40 patients with active toxoplasmosis, 40 negative controls, and 25 patients with other parasitic infections. The SAG2-based LAMP (SAG2-LAMP) had a greater sensitivity (87.5%) than the SAG1-LAMP (80%), B1-LAMP (80%), and nested PCR (62.5%). All the LAMP assays and nested PCR were 100% specific. This is the first report of a study which applied the LAMP method to diagnose toxoplasmosis from human blood samples. Due to its simplicity, sensitivity, and specificity, LAMP is suggested as an appropriate method for routine diagnosis of active toxoplasmosis in humans.

The importance of toxoplasma gondii infection in diseases presenting with headaches. Headaches and aseptic meningitis may be manifestations of the Jarisch-Herxheimer reaction

Worldwide, approximately 2 billion people are chronically infected with T. gondii with largely unknown consequences. This review presents clinical symptoms, differential diagnosis, triggering factors, treatment, and pathomechanisms responsible for idiopathic intracranial hypertension, pseudotumor cerebri, and aseptic meningitis. Literature cited in this work illustrates that immune state and other biologic mediator imbalances due to various endogenous and exogenous triggering factors may markedly affect latent central nervous system T. gondii infection/inflammation intensity, and cause reactivation of cerebral toxoplasmosis (CT). Irregularities in pro- and anti-inflammatory processes may markedly disturb the host and/or T. gondii defense mechanisms important for immune control of the parasite thereby manifesting as a wide range of neurologic symptoms and signs observed in some patients with migraine, epilepsy, celiac disease, Henoch-Schönlein purpura, and other brain disorders. This is consistent with reactivation of CT in mice after treatment with dexamethasone associated with depression of type T(H)1 immune response, and development of CT after administration of etanercept or other bioproducts. It seems that various types of headaches, epilepsy, aseptic meningitis, systemic adverse reactions to drugs or other substances represent the Jarisch-Herxheimer reaction due to apoptosis of T. gondii tachyzoites. Also development of some brain tumors, such as ependymoma and glioma may be associated with a chronic course of CT. Thus, all these patients should be tested for T. gondii infection.

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.

Polymerase chain reaction in intraocular inflammation

Polymerase chain reaction (PCR) is a technique involving enzymatic amplification of nucleic acid sequences in repeated cycles of denaturation, oligonucleotide annealing and DNA polymerase extension. It is a powerful molecular biologic tool that allows the rapid production of analytic quantities of DNA from small amounts of starting material. PCR can be performed on nearly any ocular specimen or biopsy. For diagnosis of uveitis, the obtained sample is usually an anterior chamber paracentesis or vitreous tap. PCR potentially is more sensitive than culture for detection of many organisms. By utilizing a secondary detection system in concert with the initial PCR reaction, perfect specificity can be assured. The initial application of PCR diagnostics to ophthalmic disease was in the detection of viral uveitis. PCR has also been implicated in studies of noninfectious uveitis. The most common application is HLA typing. A universal bacterial PCR can be very helpful for the diagnosis of bacterial endophthalmitis at an early stage of the disease.

Association of ocular toxoplasmosis with type I Toxoplasma gondii strains: direct genotyping from peripheral blood samples

Toxoplasma gondii strains were genotyped directly from blood samples of patients with ocular toxoplasmosis. Analysis of nontranscribed spacer 2 revealed that all detected strains belonged to type I, suggesting an association of ocular toxoplasmosis with this type. The method shows the usefulness of blood samples for genotyping in ocular toxoplasmosis.

Diagnostic value of specific local antibody production and nucleic acid amplification technique-nested polymerase chain reaction (nPCR) in clinically suspected ocular toxoplasmosis

OBJECTIVE

The study was to evaluate the diagnostic efficacy of nested polymerase chain reaction (nPCR) using primers targeting B1 gene of Toxoplasma gondii (T. gondii) with Witmer Desmonts coefficient (WDC) technique in intraocular fluids of clinically suspected toxoplasma retino choroiditis (TRC) patients.

MATERIALS AND METHODS

Two hundred and seventy eight specimens from 189 patients (25 TRC patients and 164 controls) consisting of 189 serum samples and 89 intraocular fluids were included in the study. The clinical specimens were categorized into TRC patients (typical TRC lesion-group I & atypical TRC lesion-group II) and controls (voluntary blood donors-group III, patients undergoing uncomplicated cataract surgery-group IV, ocular inflammation of non-toxoplasma origin-group V). Detection of anti T. gondii IgG and IgM antibodies in serum samples and intraocular fluids were performed and WDC was calculated by the standard method. The standardized nPCR was applied on the 89 intraocular fluids.

RESULTS

Clinical diagnosis of TRC based on fundus examination was considered to be the "gold standard." Anti T. gondii IgG/IgM antibodies were detected in serum by ELISA in 95.6% of 25 clinically suspected TRC patients (gp I and II), 28% of gp III, 40.4% of gp IV, and in 58.3% of gpV. Witmer Desmont's coefficient was positive in 72.7% (16/22) and nPCR in 59.1% (13/22) of TRC patients (gp I and II). Both WDC and nPCR were negative in all the controls. The difference in sensitivity of WDC and nPCR was not statistically significant (p=0.5247).

CONCLUSIONS

Though both WDC and nPCR were reliable diagnostic techniques for ocular toxoplasmosis, nPCR is more acceptable because of the amount of specimen(s) required, rapidity, cost effectiveness, and direct evidence of T. gondii DNA in the intraocular fluids.

Recent trends in molecular diagnostics for Toxoplasma gondii infections

Toxoplasmosis is an important parasitic infection of man and animals. It is well-known that the progression and severity of disease depend on the immunological status of the host, but recent studies suggest that the genetics of the parasite can also play a role. Diagnosis based on clinical appearance and serology is not always easy. However, molecular methods do not depend on an immune response, and allow direct detection of the parasite in biological samples. Thus they can be used to establish a diagnosis when serological tests are not definitive. Multicopy sequences specific for Toxoplasma gondii, e.g., the B1 gene or the 529-bp sequence, are especially useful in molecular tests. Real-time PCR is very sensitive and is a promising technique that is capable of providing a quantitative result. Molecular methods are also used for genotypic characterisation of T. gondii isolates. Analysis of polymorphic sequences determines the precise strain. The choice of sequence is critical when undertaking studies on the correlation between clinical signs and symptoms of disease and the T. gondii genotype. Further studies involving direct genotyping of T. gondii from clinical samples are needed.

Determinants of immunodiagnostic success in human ocular toxoplasmosis

Ocular toxoplasmosis is a local manifestation of systemic infection in which Toxoplasma spreads into the eye, affecting mainly the posterior segment of the eye. Reactivation of the initial retinal condition presumably results from the rupture of quiescent parasitic cysts lying adjacent to pre-existing scars and may secondarily involve the choroid (leading to retinochoroiditis). Although the molecular mechanisms underlying host-parasite interaction are largely unknown, toxoplasmic retinochoroiditis usually remains a local event, and does not necessarily evoke a detectable systemic immune response. Local immunotolerance mechanisms may likewise confound attempts to confirm the clinical diagnosis by serology. Aqueous humour may be analysed for the presence of parasite DNA or of specific antibodies, but the DNA burden therein is low, and a more definite confirmation would require risky puncturing of the vitreous. Laboratory confirmation of the diagnosis is also frustrated by marked individual differences in the time elapsing between the onset of clinical symptoms and the activation of specific antibody production, resulting in a high proportion of false negative results. Whether a delay in the onset of local specific antibody production reflects immunotolerance in cases of congenital - but not obviously in those of acquired - infection remains an open question, but it could account for a relatively low confirmation rate in laboratory tests for local antibody production. Against this background, current diagnostic strategies need to be re-evaluated with a view to future improvements.

Evaluation of a Real-time PCR-based assay using the lightcycler system for detection of Toxoplasma gondii bradyzoite genes in blood specimens from patients with toxoplasmic retinochoroiditis

PCR based methods have advantages over traditional methods for the diagnosis of toxoplasmosis, especially when serology fails and clinical symptoms are not evident. However, current PCR-based assays are often labour-intensive and not readily quantifiable and have the potential for contamination due to a requirement for postamplification sample handling. Real-time PCR can address these limitations. We have developed and evaluated a highly sensitive Real-time PCR (Light-cycler, LC-PCR) to detect and quantify Toxoplasma gondii B1 and bradyzoite specific genes (SAG-4, MAG-1) in serum and peripheral blood mononuclear cells (PBMC) specimens, from five immunocompetent subjects with clinically suspected toxoplasmic retinochoroiditis (TRC) or without a suspected T. gondii infection. A standard curve for quantitation of parasitic load was generated using SYBR Green I fluorescent detection. The results were compared with those obtained with a nested PCR (n-PCR). In TRC patients, both PCR methods confirmed ophtalmoscopy and fluorangiographic findings. Among the TRC patients, the use of LC-PCR was more sensitive than n-PCR for detection and quantification of either B1 gene (P<0.001) or SAG-4/MAG-1 gene (P<0.05). LC-PCR has been shown particularly useful to accurately determine the parasite DNA load in follow-up specimens in whom the performance of either B1 or SAG-4 and MAG-1 in detecting T. gondii loads, varied with respect to specific antitoxoplasmic treatment.

Necrotising retinopathies simulating acute retinal necrosis syndrome

AIM

To determine an aetiological diagnosis in patients presenting with necrotising retinopathies that simulate acute retinal necrosis (ARN).

METHODS

Retrospective non-comparative case series. The charts of 16 patients presenting with a clinical impression of ARN at Pitie-Salpetriere Hospital, Paris, France, between 1994 and 1999, who required initial antiviral therapy were reviewed. All of the patients had extensive laboratory tests. Anterior chamber paracentesis was performed on 14 patients and evaluated by polymerase chain reaction (PCR) and/or the Witmer-Goldmann coefficient to determine the cause of retinitis. Three of the 14 cases also had diagnostic vitrectomy. Responses to specific treatment, initiated based on laboratory results, and the final outcome were evaluated.

RESULTS

Seven of the 16 patients were female and nine were male. The retinitis was bilateral in five patients and unilateral in 11 patients. The average age of the patients at presentation was 53.6 years. 13 patients were immune deficient for various reasons. Upon initial presentation, the patients' visual acuities were less than 20/200 in 68% of the affected eyes. The final diagnoses, based on laboratory data and therapeutic response were toxoplasmic retinochoroiditis (62.5%), syphilitic retinitis (12.5%), aspergillus endophthalmitis (12.5%), Behcet's disease (6.2%), and intraocular lymphoma (6.2%). Visual acuity was stabilised or improved in 12 patients (75%). Two patients with aspergillosis died despite antifungal therapy.

CONCLUSIONS

Toxoplasmic retinochoroiditis is the major cause of retinal necrosis that simulates ARN, and PCR analysis of the aqueous humour is helpful in establishing the diagnosis. Such atypical toxoplasma retinochoroiditis may be associated with poor visual outcome.

The role of choroidal and retinal biopsies in the diagnosis and management of atypical presentations of uveitis

PURPOSE

Choroidal and retinal biopsies are often the investigation of last resort in evaluating patients with uveitis, because of the possible morbidity of the procedure. The most common indication is atypical uveitis, in which a diagnosis of malignancy or infection may be suspected. Here, we describe our experience at the Casey Eye Institute.

METHODS

This was a retrospective case series from January 2000 through October 2004. Cases labeled as "retinal or choroidal biopsy" were drawn from the pathology database at the Casey Eye Institute, and the pathology and clinic charts were reviewed. In all cases, the retinal and choroidal biopsies were obtained via an internal approach with a three-port pars plana vitrectomy.

RESULTS

Eight cases of atypical uveitis were found for which choroidal biopsies were performed. Five patients had had previous vitrectomies, in which examination of the vitreal sample had been inconclusive. Five patients had a definitive diagnosis after the biopsy and a good response to tailored therapy. In one case, diagnosis was made after biopsy, but clinical improvement was minimal despite appropriate treatment. One case had an inconclusive biopsy that enabled the exclusion of malignancy and infection with good response to immune suppression. In another case, choroidal biopsy was inconclusive and the eventual diagnosis was made only after enucleation.

CONCLUSION

Retinal and choroidal biopsies can be extremely useful in the diagnosis and further management of atypical, aggressive presentations of uveitis. In this small series, risk of complications was low. However, in patients with an inconclusive biopsy, an additional biopsy or enucleation should be considered in cases that progress or behave atypically on treatment based on the initial biopsy findings.

Aqueous humor and serum immunoblotting for immunoglobulin types G, A, M, and E in cases of human ocular toxoplasmosis

The purpose of this study was to compare the local and systemic Toxoplasma-specific humoral immune responses in individuals with ocular toxoplasmosis (OT). To this end, paired aqueous humor and serum samples from 46 individuals with active OT and from 30 individuals without inflammatory eye disease (controls) were analyzed by immunoblotting for anti-Toxoplasma immunoglobulin G (IgG), IgA, IgM, and IgE directed against 20- to 120-kDa antigens. The presence in the aqueous humor of a unique band, or of at least three bands that were at least three times more intense in aqueous humor than in serum, was taken as evidence of local antibody production. IgG bands were detected in 98% of the aqueous humor samples, while IgA bands were detected in 76%, IgM bands were detected in 8%, and IgE bands were not detected in any. Evidence of local production of specific antibodies was found in 32 cases (70%) (IgG in 23 [50%]; IgA in 16 [35%]). In 10 instances (22%), routine laboratory tests were not indicative of OT. In 14 cases (30%), no local antibody production was detected by immunoblotting; 3 of these cases yielded evidence of local antibody production according to the Goldmann-Witmer coefficient. Local antibody production was revealed for 7 of the 30 controls (23%). Hence, the sensitivity of immunoblotting for IgG and IgA is 70%, and the specificity is 77%. We conclude that immunoblotting for local specific IgG and IgA supports the clinical diagnosis of OT in 70% of cases. In 22% of these, the diagnosis is not confirmed by other laboratory tests. Hence, immunoblotting increases the sensitivity of routine laboratory tests and should be considered for samples that register negative by such tests.

Use of fluorescence resonance energy transfer hybridization probes to evaluate quantitative real-time PCR for diagnosis of ocular toxoplasmosis

Toxoplasma gondii infection is an important cause of chorioretinitis in Europe and the United States. Ophthalmological examination and a good clinical response to adequate therapy mainly support ocular toxoplasmosis diagnosis. However, clinical diagnostic may be difficult in some atypical cases. In these cases, laboratory confirmation, based on detection of local specific antibodies and parasite DNA by conventional PCR, is therefore important to confirm the disease etiology. More recently, real-time PCR has been developed to improve prenatal congenital toxoplasmosis diagnosis. We therefore examined the diagnostic value of quantitative real-time PCR for the detection of T. gondii in aqueous humor samples, associated with quantification of human beta-globin to control sample quantitative quality, by using a double fluorescence resonance energy transfer hybridization probes system with a double fluorescence reading. Of the 23 the clinically toxoplasmosis suspect patients, 22 showed serological evidence of exposure to Toxoplasma; one had a serological profile indicative of active infection. The analysis of paired aqueous humor and serum samples revealed an intraocular antibody production in 9 of 23 cases (39.1%). The quantitative real-time PCR revealed positive and high parasite numbers and high Toxoplasma/human genome ratios in three cases. Furthermore, PCR was the only positive confirmatory test in two cases (11.1%). None of the patients included in the control group (n = 7) had evidence of either local specific antibody production or T. gondii DNA detection, suggesting a good relative assay specificity. On the whole, quantitative real-time PCR appears to be useful for diagnosing atypical ocular toxoplasmosis presentations.