Diagnosis of congenital toxoplasmosis: comparison of targets for detection of Toxoplasma gondii by PCR

Identification and multilocus genotyping of Toxoplasma gondii isolates from congenital infection in north of Iran

Congenital toxoplasmosis can cause severe consequences in the fetus, such as spontaneous abortion which is affected by parasite strain. Also, recent studies revealed the high genetic diversity of Toxoplasma gondii. This study aims to investigate the serological status of T. gondii in pregnant women, multilocus genotyping in aborted fetuses' tissue, and archived formalin-fixed paraffin-embedded placenta. This study was performed on 100 pregnant women with spontaneous abortion and their aborted fetuses, and 250 of the archived placentae in Iran. The blood and tissue were examined for seroprevalence and genotype determination of T. gondii using ELISA and multilocus nested-PCR-RFLP, respectively. Anti-T. gondii IgG and IgM were detected in 68 samples (68%) and 1 (1%) out of 100 serums. Toxoplasma DNA was identified in 1 (1%) aborted fetuses' tissue and 32 (12.8%) placenta samples. Overall, ten positive DNA samples were successfully genotyped, and five genotypes were recognized (ToxoDB#1, #2, #10, #27, and #48). The obtained results indicated congenital toxoplasmosis is a severe risk in this region. As type I is highly pathogen and can lead to severe complications, the prevention of the infection should be considered in seronegative pregnant women.

Parasitological Contamination of Vegetables Sold in Tunisian Retail Markets with Helminth Eggs and Protozoan Cysts

ABSTRACT

Foodborne diseases continue to represent an important threat to public health in many parts of the world and are particularly widespread in developing countries. They are essentially acquired through an oro-fecal route via the consumption of uncooked fruits and vegetables. This study evaluated the parasitological contamination of vegetables for sale to humans in Tunisian retail markets. A total of 240 samples of fresh vegetables were examined for helminth eggs and protozoan cysts and oocysts (collectively, (oo)cysts) contamination. The parasitic elements (helminth eggs and protozoan (oo)cysts) were concentrated by sucrose flotation and identified by microscopic examination. The molecular identification of Echinococcus granulosus eggs was carried out using PCR. Helminth eggs and protozoan (oo)cysts eggs were found in 12.5% of the unwashed vegetables, and the most common parasites observed in vegetables were coccidian oocysts (4.1%), Toxocara spp. (2.5%), hookworm (2.1%), and Taenia spp. (1.25%) eggs, followed by Pseudolimax butschlii (1.6%) and Entamoeba coli (1.6%) protozoan cysts. Furthermore, parasite contamination differed significantly from one city to another. Taeniid eggs were identified by PCR as E. granulosus sensu stricto (s.s.) (genotype G1). To our knowledge, this study highlights for the first time in Tunisia that fresh vegetables for sale in markets are contaminated with helminths and protozoan cysts, which are potentially pathogenic for humans. The control of these pathogens is in part a question of sanitary education, especially for retail vendors, and in part of improvement in hygiene measures throughout the food production chain, from the field to the consumer.

HIGHLIGHTS

Loop mediated isothermal amplification (LAMP) of Toxoplasma DNA from dried blood spots

INTRODUCTION

The cosmopolitan protozoan Toxoplasma gondii is a major parasite of warm-blooded animals including man. Early and accurate diagnosis is a must for proper treatment that prevents life threatening sequels. Loop-mediated isothermal amplification (LAMP) is a novel technique that can amplify DNA with high sensitivity and specificity under isothermal conditions.

AIM OF THE STUDY

To validate a LAMP-specific protocol for detection of Toxoplasma DNA using dried blood spots (DBS) from mice experimentally infected with the cystogenic Toxoplasma ME-49 strain.

METHODS

In this study, the target DNA fragment was the Toxoplasma 529-bp repeat element that exists in 200-300 copies per T. gondii genome. The sensitivity of both LAMP and conventional PCR techniques was estimated in DBS samples from experimental mice at 1-week and 8-weeks post-infection.

RESULTS

Out of 20 blood samples gathered on Whatman filter paper from mice at 1-week post-infection, 18 and 16 were positive by LAMP and conventional PCR, respectively. Neither techniques detected parasite DNA in blood at 8th week of infection.

CONCLUSION

Dried blood spots are easy source of material for molecular studies. LAMP assay proved higher sensitivity than the conventional PCR in detecting parasitemia in early infection with the cystogenic Toxoplasma strain.

Comparison of an in house and a commercial real-time polymerase chain reaction targeting Toxoplasma gondii RE gene using various samples collected from patients in Turkey

Background

Toxoplasma gondii is an opportunistic protozoan parasite that can infect all warm-blooded animals including humans and cause serious clinical manifestations. Toxoplasmosis can be diagnosed using histological, serological, and molecular methods. In this study, we aimed to detect T. gondii RE gene in various human samples by in house and commercial real time polymerase chain reactions.

Methods

A total of 38 suspected cases of toxoplasmosis [peripheral blood (n:12), amnion fluid (n:11), tissue (n:9), cerebrospinal fluid (n:5), and intraocular fluid (n:1)] were included to the study. An in house and a commercial RT-PCR were applied to investigate the T. gondii RE gene in these samples.

Results

The compatibility rate of the two tests was 94.7% (37/38). When the commercial RT-PCR kit was taken as reference, the sensitivity and specificity of in house RT-PCR test was 87.5 and 100%. When the in house RT-PCR test was taken as reference, the commercial RT-PCR kit has 100% sensitivity and 96.8% specificity. Incompatibility was detected in only in a buffy coat sample with high protein content.

Conclusions

Both the commercial and in house RT-PCR tests can be used to investigate T. gondii RE gene in various clinical specimens with their high sensitivity and specificity. In house RT-PCR assay can be favorable due to cost savings compared to using the commercial test.

Cytokine Profile in Sweet's Syndrome under the Treatment of Pulmonary Toxoplasmosis Complicated with Myelodysplastic Syndrome

We herein describe a case of Sweet's syndrome (SS) in a patient being treated for pulmonary toxoplasmosis complicated with myelodysplastic syndrome (MDS). The patient's SS developed after the pulmonary toxoplasmosis improved following treatment. We searched his cytokine profiles comprehensively using a bead-based immunoassay. The results showed no elevation of interleukin (IL)-2, interferon (IFN)-γ or IL-17A, and IL-6 was only observed to have increased at the onset of SS, suggesting that the pulmonary toxoplasmosis had been well controlled and that chronic inflammation may have been the cause of SS. Pulmonary toxoplasmosis is an extremely rare occurrence. The cytokine profile can help to clarify the pathological condition of SS and MDS complicated with severely invasive infectious diseases.

Comparison of Placenta PCR and Maternal Serology of Aborted Women for Detection of Toxoplasma gondii in Ardabil, Iran

Primary maternal infection with toxoplasmosis during pregnancy is frequently associated with transplacental transmission of the parasite to the fetus. This study was conducted to test the utility of PCR assay to detect recent infections with Toxoplasma in aborted women at various gestational ages who referred to Obstetrics and Gynecology Department of Alavi Hospital in Ardabil during 2014 and 2016. Two hundred women with a history of single or repeated abortion were investigated in this study. Blood samples were tested for specific anti-Toxoplasma IgM and IgG antibodies by ELISA. According to the results, 53.5% of the women under study were positive for anti-Toxoplasma antibodies: 4.0% of them had IgM, 43.0% had IgG, and 6.5% had both IgM and IgG. Subsequently, Nested-PCR analysis was used to detect T. gondii DNA in the placenta of subjects. In 10.5% of the women, the results were positive for 529 bp element of T. gondii. Among them, 5 (23.8%) cases were IgM positive, 1 (4.8%) case was IgG positive, and 11 (52.4%) were both IgM and IgG positive. In 4 (19.0%) patients, none of the antibodies were found to be positive. In total, 16 patients had positive results in both ELISA and PCR methods, and 174 cases had negative results for new infection. The findings of this study revealed that T. gondii might be one of the significant factors leading to abortion, and that the analysis of placenta can be important in order to achieve increased detection sensitivity.

Molecular diagnosis of Toxoplasma gondii infection in Libya

Background

Toxoplasma gondii infections are prevalent in humans and animals throughout Libya. Current diagnosis is based on detection of Toxoplasma-specific IgM and IgG. In this study, we established and optimized a diagnostic PCR assay for molecular diagnosis of T. gondii in Libya.

Methods

From January to December, 2010, 177 blood and serum samples were collected from suspected patients. This includes: 140 women who have had spontaneous abortions, 26 HIV-positive patients, nine patients with leukemia and lymphoma, and two infants with ocular infection. Samples were screened for anti-Toxoplasma IgG and IgM antibodies before DNA extraction. The surface antigen gene 2 (SAG2) was targeted in a semi-nested PCR to amplify a 999 bp and a 614 bp fragment in the first and the second run respectively.

Results

A total of 54/140 (38.5 %) women who have had spontaneous abortions, 23/26 (88 %) HIV patients, 6/9 (66.6 %) of the leukaemia and lymphoma patients, and one child with ocular infection were seropositive for anti-Toxoplasma IgG and/or IgM. Genomic DNA was extracted from 38 selected seropositive samples. The PCR was sensitive enough to detect DNA concentration of 12 ng/μL. PCR analysis was performed for 38 selected seropositive patients (16 women who have had spontaneous abortions, 15 positive HIV patients, six leukaemia patients and one child with ocular infection). Our designed primers were successfully amplified in 22/38 (57.9 %) samples; 5/12 (35.7 %) from serum and 17/26 (65.8 %) from whole blood samples. All PCR positive samples were IgG-positive except two samples which were IgM and IgG & IgM-positive serum samples respectively. The semi-nested PCR confirmed five more samples. These included two leukaemia and two HIV-positive whole blood samples and one serum sample from an aborted woman.

Conclusion

The ability of PCR to diagnose active toxoplasmosis is needed in immunocompromised patients and congenital toxoplasmosis cases, especially when serological techniques fail. For the first time in Libya, we established and optimized semi-nested PCR of SAG2 gene. The developed PCR method was able to detect as little as 12 ng/μL of T. gondii DNA and was useful to diagnose the diseases in women who have had spontaneous abortions, HIV-positive patients, patients with leukemia and lymphoma, and infants with ocular infection.

Detection of Toxoplasma gondii in Diabetic Patients Using the Nested PCR Assay via RE and B1 Genes

BACKGROUND

Toxoplasma gondii is an obligate intracellular protozoan parasite that exists worldwide. Various techniques have been developed for T. gondii detection.

OBJECTIVES

The aim of this study was the detection of T. gondii in diabetic patients with RE and B1 genes and the comparison of these two genes for diagnosis using the nested-PCR assay method.

PATIENTS AND METHODS

DNA samples from 205 diabetic patients who had been referred to the diabetes center of Ali Asghar hospital in Zahedan, Iran, were collected and analyzed using the nested-PCR assay method. Toxoplasma antibody data gathered using the enzyme-linked immunosorbent assay (ELISA) method from a previous study was used to group patients. The data were analyzed using SPSS 18. The chi-square test was used for comparison.

RESULTS

Of the diabetic patients selected, the following results were obtained: 53 (IgG+, IgM+); 20 (IgG-, IgM+); 72 (IgG+, IgM-); and 60 (IgG-, IgM-). The nested-PCR detected the following: in the acute group, 21/53 (39.63%), 30/53 (56.60%) (IgM+, IgG+); in the chronic group, 40/72 (55.56%), 51/72 (70.83%), (IgG+, IgM-); in the false positive group, 18/20 (90%), 17/20 (85%) (IgM+, IgG-); and sero-negative samples of 38/60 (63.33%) and 60/ 41 (77.35%) for RE and B1 genes, respectively. The prevalence of toxoplasmosis showed positive in patients with diabetes in the B1 gene 139 (67.8%) and RE gene 117 (57.1%).

CONCLUSIONS

Our study demonstrated that the B1 gene, more so than the RE gene, showed positive samples and can be used to detect toxoplasmosis, although the B1 gene, in comparison to the RE gene, did not show any superiority of molecular diagnosing capability. Results also showed that toxoplasma molecular detection methods can be used instead of routine serological detection methods in a clinical laboratory testing.

Toxoplasma gondii: history and diagnostic test development

Toxoplasma gondiiis a protozoa that causes toxoplasmosis in people and other animals. It is considered one of the most common parasitic infections in the world due to its impressive range of hosts, widespread environmental contamination and the diverse means by which animals can be infected. Despite its ubiquity and numerous ongoing research efforts into both its basic biology and clinical management, many aspects of diagnosis and management of this disease are poorly understood. The range of diagnostic options that is available for veterinary diagnostic investigators are notably more limited than those available to medical diagnosticians, making accurate interpretation of each test result critical. The current review joins other reviews on the parasite with a particular emphasis on the history and continued development of diagnostic tests that are useful for veterinary diagnostic investigations. An understanding of the strengths and shortcomings of current diagnostic techniques will assist veterinary and public health officials in formulating effective treatment and control strategies in diverse animal populations.

Contribution of neonatal amniotic fluid testing to diagnosis of congenital toxoplasmosis

We evaluated the molecular diagnosis of congenital toxoplasmosis (CT) on neonatal amniotic fluid samples from 488 mother-child pairs. Maternal infection during pregnancy was diagnosed and dated or could not be ruled out. Forty-six cases of CT were defined according to the European Research Network on CT classification system and case definitions. Neonatal amniotic fluid testing had an overall sensitivity of 54% (95% confidence interval [95% CI], 39 to 69%) and a specificity of 100% (95% CI, 99 to 100%). Its sensitivity was 33% (95% CI, 13 to 59%) when antenatal diagnosis was positive and 68% (95% CI, 48 to 84%) when antenatal diagnosis was negative or lacking. This difference in sensitivity may have been due to treatment of antenatally diagnosed cases. Relative to postnatal serology, neonatal amniotic fluid testing allowed an earlier diagnosis to be made in 26% of the cases (95% CI, 9 to 51%).

A 10-year retrospective comparison of two target sequences, REP-529 and B1, for Toxoplasma gondii detection by quantitative PCR

This study aimed to evaluate the repeated sequence REP-529 compared to that of the B1 gene in the molecular diagnosis of toxoplasmosis by quantitative PCR (qPCR) in routine diagnosis. Over a 10-year period (2003 to 2013), all patients prospectively diagnosed with a positive REP-529 qPCR result for toxoplasmosis were included. All DNA samples (76 samples from 56 patients) were simultaneously tested using the two qPCR methods (REP-529 and B1). The mean cycle threshold (CT) obtained with the B1 qPCR was significantly higher (+4.71 cycles) than that obtained with REP-529 qPCR (P<0.0001). Thirty-one out of 69 extracts (45.6%) positive with REP-529 qPCR were not amplified with the B1 qPCR (relative sensitivity of 54.4% compared to that with REP-529), yielding false-negative results with 15/28 placenta, 5 cord blood, 2 amniotic fluid, 4 cerebrospinal fluid, 1 aqueous humor, 2 lymph node puncture, and 1 abortion product sample. This defect in sensitivity would have left 20/56 patients undiagnosed, distributed as follows: 12/40 congenital toxoplasmosis, 4/5 cerebral toxoplasmosis, 2/8 patients with retinochoroiditis, and 2 patients with chronic lymphadenopathy. This poor performance of B1 qPCR might be related to low parasite loads, since the mean Toxoplasma quantification in extracts with B1 false-negative results was 0.4 parasite/reaction. These results clearly show the superiority of the REP-529 sequence in the diagnosis of toxoplasmosis by PCR and suggest that this target should be adopted as part of the standardization of the PCR assay.

The utility of cerebrospinal fluid for the molecular diagnosis of toxoplasmic encephalitis

The aim of this study was to assess the efficacy of nested polymerase chain reaction (PCR) and the loop-mediated isothermal amplification (LAMP) assay, which were developed to detect and identify toxoplasma parasites in human cerebrospinal fluid (CSF). Nested PCR was performed using primers generated by Dr. L.D. Sibley to target the 18S rDNA instead of the conventionally used primers which target the B1 gene. We also designed Toxoplasma gondii-specific LAMP primers targeting both genes. In vitro detection sensitivity was evaluated using 10-fold serially diluted genomic DNA purified from RH tachyzoites, and clinical sensitivity and specificity were evaluated using clinical CSF samples from 16 patients with toxoplasmic encephalitis (TE) and from 12 patients with other diseases. The 18S rDNA nested PCR showed the highest detection sensitivity limit with a minimum of 1.0 × 10(-8) ng/μL. However, sensitivity and specificity of nested PCR with clinical specimens were 50% and 100%, respectively. The sensitivity of molecular diagnosis of TE is not sufficient; therefore, patients clinically suspected of having TE should be treated promptly. Our molecular diagnostic tool would restrictively facilitate a definitive diagnosis of TE at an early stage in approximately 50% of patients.

Detection and Identification of Toxoplasma gondii Type One Infection in Sheep Aborted Fetuses in Qazvin Province of Iran

BACKGROUND

The aim of this study was to apply the nested-PCR and bioassay methods in detection and genotyping of Toxoplasma gondii infection in provided sheep aborted fetus samples from Qazvin Province of Iran.

METHODS

Eighteen sheep aborted fetal samples were studied by nested-PCR-RFLP, histopathological observation and microbiological assay. Bioassay in mice was carried out by inoculating the brain samples intraperitoneally.

RESULTS

The results demonstrated the frequency of 66% infected sheep aborted fetal samples with T. gondii type one. Although we could not isolate any parasite from inoculated mice even after three passages, but it was confirmed histopathologically formation of cyst like bodies in prepared mice brain sections.

CONCLUSION

The results of the performed nested-PCR and formation of brain cyst in inoculated mice exhibited that T. gondii type one infection might be considered as one of the major causative agents for abortion in ewes.

Optimization of Toxoplasma gondii DNA extraction from amniotic fluid using NucliSENS easyMAG and comparison with QIAamp DNA minikit

Antenatal diagnosis of congenital toxoplasmosis relies on PCR in amniotic fluid. Because parasitic load is often low, DNA extraction must be optimized. Manual methods remain widespread although automated methods appear more effective. This study aimed at optimizing an automated method and at comparing it with a widespread manual method: QIAamp DNA minikit. To optimize NucliSens easyMAG, we evaluated the addition of proteinase K pre-treatment and the increase of the amount of silica particles used for the extraction. The optimized method was then compared to QIAamp DNA minikit on samples containing less than 25 tachyzoites/ml. NucliSens easyMAG DNA yield was improved after proteinase K pre-treatment (p < 0.01), but not with a higher silica particle input. The optimized method yielded more positive PCRs than the manual method, especially for samples containing 5 tachyzoites/ml or less (71% vs 26%, p < 10(-4)). The DNA amount in samples found positive by PCR was higher after optimized automated extraction than after manual extraction (p < 10(-4)). Proteinase K pre-treatment should be added to extract DNA from amniotic fluid using NucliSens easyMAG. Using this optimized automated method rather than manual methods would improve the sensitivity of Toxoplasma PCR and simplify the daily workflow.

Polymerase chain reaction in the diagnosis of congenital toxoplasmosis: more than two decades of development and evaluation

Toxoplasmosis, a protozoan disease caused by the coccidian parasite Toxoplasma gondii, is one of the most prevalent parasitic diseases of humans. Although most infections are subclinical and asymptomatic, it has a great importance with respect to immunocompromized hosts and congenitally infected newborns. The diagnosis of T. gondii infection has gained in great interest over the past decades with a wide variety of techniques being investigated from animal inoculation to advanced molecular techniques. This paper reviews and highlights the development and evaluation of polymerase chain reaction in the diagnosis of congenital toxoplasmosis in human population to present the redundant research on it in a chronologically simple approach.

Multicentric comparative analytical performance study for molecular detection of low amounts of Toxoplasma gondii from simulated specimens

Although screening for maternal toxoplasmic seroconversion during pregnancy is based on immunodiagnostic assays, the diagnosis of clinically relevant toxoplasmosis greatly relies upon molecular methods. A problem is that this molecular diagnosis is subject to variation of performances, mainly due to a large diversity of PCR methods and primers and the lack of standardization. The present multicentric prospective study, involving eight laboratories proficient in the molecular prenatal diagnosis of toxoplasmosis, was a first step toward the harmonization of this diagnosis among university hospitals in France. Its aim was to compare the analytical performances of different PCR protocols used for Toxoplasma detection. Each center extracted the same concentrated Toxoplasma gondii suspension and tested serial dilutions of the DNA using its own assays. Differences in analytical sensitivities were observed between assays, particularly at low parasite concentrations (<or=2 T. gondii genomes per reaction tube), with "performance scores" differing by a 20-fold factor among laboratories. Our data stress the fact that differences do exist in the performances of molecular assays in spite of expertise in the matter; we propose that laboratories work toward a detection threshold defined for a best sensitivity of this diagnosis. Moreover, on the one hand, intralaboratory comparisons confirmed previous studies showing that rep529 is a more adequate DNA target for this diagnosis than the widely used B1 gene. But, on the other hand, interlaboratory comparisons showed differences that appear independent of the target, primers, or technology and that hence rely essentially on proficiency and care in the optimization of PCR conditions.

Placental testing for Toxoplasma gondii is not useful to diagnose congenital toxoplasmosis

We examined 785 placentas, including 51 from documented cases of congenital toxoplasmosis. Toxoplasma was detected in 16 placentas, including 1 in which congenital toxoplasmosis was ruled out. Placental screening had poor sensitivity (25%) but good specificity (99%), positive predictive value (93%), and negative predictive value (95%).

Accuracy of real-time polymerase chain reaction for Toxoplasma gondii in amniotic fluid

OBJECTIVE

To provide clinicians with information about the accuracy of real-time polymerase chain reaction (PCR) analysis of amniotic fluid for the prenatal diagnosis of congenital Toxoplasma infection.

METHODS

This was a prospective cohort study of women with Toxoplasma infection identified by prenatal screening in three centers routinely carrying out real-time PCR for the detection of Toxoplasma gondii in amniotic fluid. The data available were gestational age at maternal infection, types and dates of maternal treatment, results of amniocentesis and neonatal work-up and definitive infectious status of the child. We estimated sensitivity, specificity and positive and negative predictive values both overall and per trimester of pregnancy at the time of maternal infection.

RESULTS

Polymerase chain reaction analysis was carried out on amniotic fluid for 261 of the 377 patients included (69%). It was accurate with the exception of four negative results in children who were infected. Overall sensitivity and negative predictive value were 92.2% (95% confidence interval [CI] 81-98%) and 98.1% (95% CI 95-99.5%), respectively. There was no significant association with the trimester of pregnancy during which maternal infection occurred. Specificity and positive predictive values of 100% were obtained for all trimesters.

CONCLUSION

Real-time PCR analysis significantly improves the detection of T. gondii on amniotic fluid. It provides an accurate tool to predict fetal infection and to decide on appropriate treatment and surveillance. However, postnatal follow-up remains necessary in the first year of life to fully exclude infection in children for whom PCR results were negative.

LEVEL OF EVIDENCE

III.

In utero and at birth diagnosis of congenital toxoplasmosis: use of likelihood ratios for clinical management

BACKGROUND

The results of the ante- and neonatal diagnostic tests for congenital toxoplasmosis influence the decision to treat the newborn immediately after birth. Here, we estimate the positive and negative likelihood ratios (LRs) and the probabilities of congenital infection according to PCR and IgM-IgA tests results.

METHODS

The study concerned 767 children born between 1996 and 2002 and followed-up for 1-year at Croix-Rousse hospital, Lyon, France. The LRs and the post-test probabilities were estimated conditionally on gestational age at maternal infection using a logistic regression approach.

RESULTS

For the PCR and the IgM-IgA tests, the positive LRs were high. In children with one positive test when only one test was done, the probability of infection reached 90% when the maternal infection occurred at 18-weeks gestation or later. This probability was close to 100% when the 2 tests were positive, whatever the gestational age. The negative LRs of the 2 tests moved closer to 0 at later gestational ages. However, when the tests were negative, the probability of infection remained greater or equal to 10%, except in early maternal infection. When the 2 tests were discordant, the probability of infection was about 50% in early maternal infection.

CONCLUSION

Providing reliable probabilities of congenital infection, the PCR and IgM-IgA tests guide clinical management and counseling of parents.

Serological prevalence of Toxoplasma gondii antibodies in pregnant women from Southern Brazil

During 15 months (01 April 2003-31 July 2004), 20,389 women showing positive pregnancy tests were included in a serological evaluation of toxoplasmosis prevalence using automated immunoenzymatic assays. The women's serum samples were tested for the presence of IgG and/or IgM antibodies. Overall, 53.03% of the women were positive for IgG and 3.26% were positive for IgM; the analysis used a chi-square adherence test and a significance level of 0.05 (chi(2)=14,720.35; p=0.00). To discriminate between recent and past infection, IgG avidity tests (n=166) were carried out, of which 28.3% (n=47) presented low avidity. The seroconversion index observed in this study was 0.44%. The seroprevalence results obtained were similar to other serology data found in other regions of Brazil. These data demonstrate the importance of continuous regional and national seroepidemiological inquiries to define public health strategies that can revert and reduce serological prevalence, as described in other countries where toxoplasmosis monitoring is mandatory.

Comparative study between serological and molecular methods for diagnosis of toxoplasmosis in women and small ruminants in Egypt

Routine serological diagnosis of toxoplasmosis provides high sensitivity, but specificity varies depending on the test used; false-positive results (IgM) have been reported. Blood samples were collected from 88 women (59 pregnant and 29 nonpregnant) and 86 contact animals (62 sheep and 24 goats) at El Fayoum Governorate during the period from October 2005 to December 2006. All collected samples were tested for Toxoplasma gondii infection by serological tests (ELISA IgM & IgG and Sabin-Feldman dye test) and polymerase chain reaction (PCR). Results revealed specific IgG in 45.8% and 41.4%, IgM in 30.5% and 24.2%, and positive Sabin-Feldman dye test in 23.7% and 17.2% in pregnant and nonpregnant women, respectively. Positive PCR products were detected in 32.2% and 27.6% in pregnant and nonpregnant women, respectively. Regarding animals, positive ELISA IgG and PCR were detected in 98.4% and 67.7% of sheep and 41.7% and 25.0% of goats, respectively. It was concluded that serological tests can detect higher rate of toxoplasmosis than PCR, so ELISA combined with the PCR technique is a recommended tool for accurate diagnosis of toxoplasmosis.

Clinical relevance of placenta examination for the diagnosis of congenital toxoplasmosis

BACKGROUND

Neonates with congenital toxoplasmosis, even asymptomatic at birth, should be treated early to reduce long-term sequelae. Postnatal diagnosis of congenital toxoplasmosis is essential because prenatal diagnosis fails to detect approximately 15% of cases or cannot be performed when maternal infection is acquired in late pregnancy. Detection of parasites in the placenta is one diagnostic approach to the early neonatal diagnosis of congenital toxoplasmosis.

METHODS

The parasitic analyses of 102 placentas from cases of toxoplasmosis acquired during gestation were reviewed, with complete biologic follow-up of neonates. The value of quantitative PCR and mouse inoculation was assessed, and results are discussed in light of prenatal treatment and postnatal outcome.

RESULTS

Congenital toxoplasmosis was diagnosed in 28 of the 102 cases. A prenatal diagnosis was obtained in only 16 cases. Specific IgM was detected in 57% of the babies at birth. A positive placental examination by PCR and mouse inoculation was the only evidence of infection in 3 neonates (11%) who were asymptomatic at birth. The sensitivities of PCR and mouse inoculation were 71% and 67%, respectively, and the specificities were 97% and 100%. Parasites were detected more often when maternal infection was acquired during the third trimester of pregnancy (P < 0.01), regardless the type of treatment. The sensitivity of IgM detection appeared to be related to maternal treatment since IgM was positive in 43% and 75% when mothers were treated or not, respectively (P < 0.01). Though 5/7 symptomatic infants had a positive placenta examination, there was no correlation between a positive placenta and the presence of clinical signs during the first year of life. The positive and negative predictive values of placental examination were 91% and 90%, respectively.

CONCLUSION

Placental examination is an efficient tool for the early diagnosis of congenital toxoplasmosis.

Multicenter comparative evaluation of five commercial methods for toxoplasma DNA extraction from amniotic fluid

Over the past few years, a number of new nucleic acid extraction methods and extraction platforms using chemistry combined with magnetic or silica particles have been developed, in combination with instruments to facilitate the extraction procedure. The objective of the present study was to investigate the suitability of these automated methods for the isolation of Toxoplasma gondii DNA from amniotic fluid (AF). Therefore, three automated procedures were compared to two commercialized manual extraction methods. The MagNA Pure Compact (Roche), BioRobot EZ1 (Qiagen), and easyMAG (bioMérieux) automated procedures were compared to two manual DNA extraction kits, the QIAamp DNA minikit (Qiagen) and the High Pure PCR template preparation kit (Roche). Evaluation was carried out with two specific Toxoplasma PCRs (targeting the 529-bp repeat element), inhibitor search PCRs, and human beta-globin PCRs. The samples each consisted of 4 ml of AF with or without a calibrated Toxoplasma gondii RH strain suspension (0, 1, 2.5, 5, and 25 tachyzoites/ml). All PCR assays were laboratory-developed real-time PCR assays, using either TaqMan or fluorescent resonance energy transfer probes. A total of 1,178 PCRs were performed, including 978 Toxoplasma PCRs. The automated and manual methods were similar in sensitivity for DNA extraction from T. gondii at the highest concentration (25 Toxoplasma gondii cells/ml). However, our results showed that the DNA extraction procedures led to variable efficacy in isolating low concentrations of tachyzoites in AF samples (<5 Toxoplasma gondii cells/ml), a difference that might have repercussions since low parasite concentrations in AF exist and can lead to congenital toxoplasmosis.

Detection of Toxoplasma gondii oocysts in water sample concentrates by real-time PCR

PCR techniques in combination with conventional parasite concentration procedures have potential for the sensitive and specific detection of Toxoplasma gondii oocysts in water. Three real-time PCR assays based on the B1 gene and a 529-bp repetitive element were analyzed for the detection of T. gondii tachyzoites and oocysts. Lower sensitivity and specificity were obtained with the B1 gene-based PCR than with the 529-bp repeat-based PCR. New procedures for the real-time PCR detection of T. gondii oocysts in concentrates of surface water were developed and tested in conjunction with a method for the direct extraction of inhibitor-free DNA from water. This technique detected as few as one oocyst seeded to 0.5 ml of packed pellets from water samples concentrated by Envirocheck filters. Thus, this real-time PCR may provide a detection method alternative to the traditional mouse assay and microscopy.

Significant performance variation among PCR systems in diagnosing congenital toxoplasmosis in São Paulo, Brazil: analysis of 467 amniotic fluid samples

INTRODUCTION

Performance variation among PCR systems in detecting Toxoplasma gondii has been extensively reported and associated with target genes, primer composition, amplification parameters, treatment during pregnancy, host genetic susceptibility and genotypes of different parasites according to geographical characteristics.

PATIENTS

A total of 467 amniotic fluid samples from T. gondii IgM- and IgG-positive Brazilian pregnant women being treated for 1 to 6 weeks at the time of amniocentesis (gestational ages of 14 to 25 weeks).

METHODS

One nested-B1-PCR and three one-round amplification systems targeted to rDNA, AF146527 and the B1 gene were employed.

RESULTS

Of the 467 samples, 189 (40.47%) were positive for one-round amplifications: 120 (63.49%) for the B1 gene, 24 (12.69%) for AF146527, 45 (23.80%) for both AF146527 and the B1 gene, and none for rDNA. Fifty previously negative one-round PCR samples were chosen by computer-assisted randomization analysis and re-tested (nested-B1-PCR), during which nine additional cases were detected (9/50 or 18%).

DISCUSSION

The B1 gene PCR was far more sensitive than the AF146527 PCR, and the rDNA PCR was the least effective even though the rDNA had the most repetitive sequence. Considering that the four amplification systems were equally affected by treatment, that the amplification conditions were optimized for the target genes and that most of the primers have already been reported, it is plausible that the striking differences found among PCR performances could be associated with genetic diversity in patients and/or with different Toxoplasma gondii genotypes occurring in Brazil.

CONCLUSION

The use of PCR for the diagnosis of fetal Toxoplasma infections in Brazil should be targeted to the B1 gene when only one gene can be amplified, preferably by nested amplification with primers B22/B23.

A prospective study of diagnosis of Toxoplasma gondii infection after bone marrow transplantation

Active infection with Toxoplasma gondii in immunocompromised transplant recipients can lead to toxoplasmosis, which may have a rapid disease course and in some cases be fatal. It is of paramount importance to diagnose toxoplasmosis at an early stage, and to initiate specific treatment to improve the outcome. Polymerase chain reaction (PCR) is today the primary diagnostic tool to diagnose toxoplasmosis in immunocompromised patients. Timely diagnosis may, however, be difficult if toxoplasmosis is at first asymptomatic. To investigate the magnitude of toxoplasmosis after bone marrow transplantation (BMT), we conducted a screening study by PCR where 21 autologous and 12 allogeneic BMT recipients were included. Peripheral blood samples were taken one week prior to BMT; thereafter, blood samples were drawn weekly for the first 6 months, and monthly up to one year after BMT. The samples were analyzed by conventional PCR and real-time PCR. T. gondii DNA was detected in peripheral blood from one patient 5 days post allogeneic BMT. There were no clinical signs of toxoplasmosis. Medical records were reviewed and showed a previously undiagnosed eye infection in another allogeneic BMT recipient. These two patients were seropositive for T. gondii. We concluded that monitoring for T. gondii DNA in peripheral blood samples using PCR might be a valuable method for identifying toxoplasma-seropositive stem cell transplant recipients.

Detection of Toxoplasma gondii in amniotic fluid using quantitative real-time PCR method

Bevezetés: A Toxoplasma gondii (T. gondii) által okozott fertőzés általában tünetmentes, vagy csak enyhe panaszokat okoz. A terhesekre azonban veszélyt jelent a parazita. A T. gondiiv al fertőzött anyáról a kórokozó transplacentalisan a magzatot is megfertőzheti és congenitalis toxoplasmosist okozhat, amely súlyos magzati elváltozásokat idézhet elő. A korai diagnózis a kezelés sikerét növeli. A congenitalis toxoplasmosis kimutatható szerológiai és molekuláris biológiai módszerekkel. Cél: A T. gondii kimutatása a kvantitatív valós idejű PCR-módszerrel magzatvízből. Módszerek: A magzatvízből a DNS-t szilika adszorbciós módszerrel izoláltuk. A T. gondii kimutatása 74 mintából történt meg kvantitatív valós idejű PCR-módszerrel. Eredmények: A szerzők 74 magzatvízmintából hat esetben mutatták ki a parazita jelenlétét. Konklúzió: A kvantitatív valós idejű PCR-módszer megnöveli a kimutatás gyorsaságát és érzékenységét, valamint lehetőséget nyújt a kórokozó mennyiségi meghatározására is. Ez új utat nyithat a prognózis megállapítására, valamint a kezelés eredményességének a monitorizálására.

[Real-time PCR in the diagnosis of toxoplasmosis: the way to standardisation?]

Severity of toxoplasmosis is highly correlated to the immune status of the infected individual. Foetus and immunocompromised patient are mostly at risk to develop life threatening forms. In this situation, serological diagnosis gives poor information. DNA detection using polymerase-chain-reaction technology (PCR) has significantly improved the management of this disease. Even so, the growing number of conventional PCR assays has finally led to variable performance results. Real-Time PCR (RT-PCR) in toxoplasmosis has been developed since 2000. This new technology can improve standardisation. Moreover, quantification of parasitic load in samples becomes possible. This review describes the main RT-PCR procedures actually under use and the studies comparing different target genes. The effective benefit of quantification is also discussed. Reducing number of procedures and more systematic external quality control should be considered, in order to improve reliability in PCR results, which has undoubtedly become a major tool in toxoplasmosis diagnosis.

Real-time PCR targeting a 529-bp repeat element for diagnosis of toxoplasmosis

Sensitive and rapid detection of infection with Toxoplasma gondii in transplanted immunocompromised patients is crucial for a good prognosis. Two DNA fragments are used currently for detecting T. gondii infection by PCR, i.e., the B1 gene and a 529-bp repeat element that exists in 200-300 copies/genome. This study investigated whether targeting the 529-bp repeat element gives better sensitivity and accuracy than can be obtained when targeting the B1 gene (35 copies) when concentrations of T. gondii DNA are low. The results demonstrated that detection of the 529-bp repeat element increased diagnostic sensitivity and accuracy. Addition of an internal amplification control did not affect the PCR performance and was useful in order to monitor PCR inhibition by non-specific DNA in the LightCycler instrument. The real-time PCR was used successfully in a clinical context to monitor parasitaemia in the blood of a transplant recipient suffering from toxoplasmosis.

Detection of Toxoplasma gondii from amniotic fluid, a comparison of four different molecular biological methods

BACKGROUND

The infection caused by the parasite Toxoplasma gondii (T. gondii) is often asymptomatic or has mild symptoms. The infection can cause serious problems in pregnant women who acquire the infection during gestation and their fetuses are congenitally infected.

METHODS

We tested 64 amniotic fluid samples for the presence of T. gondii by using fluorescent PCR and DNA fragment analysis. Later we compared four different molecular biological methods for the detection of the presence of T. gondii on same frozen DNA samples. These methods are the conventional PCR, fluorescent PCR with DNA fragment analysis, quantitative real-time PCR with SYBRGreen I and with fluorescence energy transfer hybridization probe detection. We determined the detection limit of these methods.

RESULTS

The conventional PCR and quantitative real-time PCR with SYBRGreen I detection have the detection limit of 1000 parasites, followed by fluorescent PCR with the detection limit of 10-100 parasites. The real-time PCR using fluorescence energy transfer hybridization probes can detect one parasite. This is the most sensitive and the fastest method. We detected 5 T. gondii positive samples with all methods from the studied 64 amniotic fluids.

CONCLUSIONS

All studied molecular biological methods are suitable for the detection of congenital toxoplasmosis. The quantitative real-time PCR based methods are more sensitive, simple and easy to perform these are opening the avenue to find out the effect of the number of parasites on fetal abnormalities.

DNA extraction and PCR assays for detection of Toxoplasma gondii

For detection of Toxoplasma gondii we compared the sensitivity of two different DNA extraction methods and three different PCR assays. Sensitivities of DNA extraction by QIAamp DNA mini Kit or MagNa pure followed by PCR, nested PCR and oligochromatography or Light Cycler PCR using either SYBR green chemistry or TaqMan probe were compared. No significant difference between extraction methods was found using pure T. gondii tachyzoites. Spiked blood samples, 10(4) to 10 parasites per sample, generated no difference in sensitivity between the two DNA extraction methods when analysed by nested PCR detected by oligochromatography or analysed by Light Cycler PCR TaqMan. In spiked blood samples Light Cycler PCR SYBR green was unable to detect the parasite and a reduction in sensitivity was observed with the TaqMan assay. Conventional PCR was more sensitive when DNA was extracted from the spiked samples using the QIAamp DNA mini Kit. Conventional and nested PCR were found to be more sensitive than Light Cycler PCR TaqMan using the QIAamp DNA mini Kit. It was not possible to use Light Cycler PCR SYBR green in blood samples. Conventional PCR was more sensitive for detection of T. gondii in spiked blood samples using QIAamp DNA mini Kit DNA extraction, suggesting that the choice of DNA extraction method may affect PCR assays differently.

Toxoplasmosis

Toxoplasma gondii is a protozoan parasite that infects up to a third of the world's population. Infection is mainly acquired by ingestion of food or water that is contaminated with oocysts shed by cats or by eating undercooked or raw meat containing tissue cysts. Primary infection is usually subclinical but in some patients cervical lymphadenopathy or ocular disease can be present. Infection acquired during pregnancy may cause severe damage to the fetus. In immunocompromised patients, reactivation of latent disease can cause life-threatening encephalitis. Diagnosis of toxoplasmosis can be established by direct detection of the parasite or by serological techniques. The most commonly used therapeutic regimen, and probably the most effective, is the combination of pyrimethamine with sulfadiazine and folinic acid. This Seminar provides an overview and update on management of patients with acute infection, pregnant women who acquire infection during gestation, fetuses or infants who are congenitally infected, those with ocular disease, and immunocompromised individuals. Controversy about the effectiveness of primary and secondary prevention in pregnant women is discussed. Important topics of current and future research are presented.