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

Molecular detection of Toxoplasma gondii in placentas of women who received therapy during gestation in a toxoplasmosis outbreak

Toxoplasmosis is a disease caused by T. gondii, a protozoa which affects humans and animals and is widely distributed worldwide. In humans, there is great concern due to the serious consequences that can occur in the infection of pregnant women and the newborn. The early diagnosis of gestational toxoplasmosis is important for treatment to be carried out in order to prevent vertical transmission or reduce damage. The diagnosis can be made through the detection of antibodies in pregnant women or neonates and PCR of amniotic fluid. Previous studies have also reported PCR of the placenta as a good diagnostic test. Our study evaluated the detection of T. gondii DNA in placenta samples from parturients seen at the University Hospital of Santa Maria, Southern Brazil and treated during the pregnancy. We performed PCR in forty samples and five were positive, representing 12.5%. When correlating the treatment time and the detection of DNA in the placentas, no significant result was found. The prevalence of positive samples was lower than in other studies in the literature. The data reaffirm the importance of carrying out the analysis of the placenta.

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.

Detection of toxoplasmosis in aborted women in Alexandria, Egypt using ELISA and PCR

Toxoplasmosis is a worldwide infection that can be acquired through the ingestion of tissue cysts in poorly cooked meat, and/or oblivious intake of sporulated oocysts in cat faeces, and transplacental. The infection in pregnant women is mainly asymptomatic. It produces abortion or congenital infection. The present study aimed to test the utility of polymerase chain reaction (PCR) on placental tissues in comparison to enzyme-linked immunosorbent assay (ELISA) to detect infections with Toxoplasma gondii in aborted women presented to Al-Shatby Maternity Hospital, Alexandria University, Egypt. Specific Toxoplasma gondii IgG and IgM were detected in serum by ELISA. Placental tissues from each participant were subjected to DNA extraction and PCR amplification. It was found that overall seroprevalence was 73%, DNA was detected in placenta tissues by using PCR analysis in 46% of cases. {× 2 (p) 18.124(< 0.001)}. Toxoplasma IgG/IgM by ELISA was positive in 23% of the cases, 20% showed amplified DNA by PCR. Positive IgG without IgM was seen in 27% cases, only 2% of them were positive by PCR. Moreover, positive PCR among positive ELISA IgM aborted women was 21 of the 23 cases. Positive PCR was obtained in three seronegative women. Our results showed that PCR sensitivity was 58.90 specificity 88.89, positive predictive value was 93.48%, and negative predictive value 44.44%. Although ELISA assay is still the gold standard of diagnosis of Toxoplasmosis, other diagnostic modalities are highly required particularly in those ELISA seronegative cases. PCR can be used as a sensitive and precise modality.

First isolation and molecular characterization of Toxoplasma gondii strains from human congenital toxoplasmosis cases in Monastir, Tunisia

Toxoplasma gondii is a protozoon parasite that can cause severe clinical problems such as congenital toxoplasmosis. The distribution of T. gondii genotypes varies from one geographic area to another. So far, little is known about the parasite genotypes in Tunisia, North Africa. The present study aimed isolating and genotyping T. gondii from the amniotic fluid (AF) and placenta of pregnant women in Monastir, Tunisia. Amniotic fluid and/or placenta from 80 women who acquired toxoplasma infection during pregnancy were tested by PCR and/or mouse bioassay. Genotyping of T. gondii isolates from these samples was performed with 15 microsatellite markers. Four viable T. gondii strains were isolated from either the AF or placenta of four women. Specifically, strains TUN001-MON1 and TUN002-MON2 were isolated from both the AF and placenta, TUN003-AHA from only the placenta, and TUN004-NEL from only the AF. The four viable strains were not virulent for mice. Genotyping revealed that the four strains were type II strains. This is the first report on isolation and genotyping of T. gondii from AF human samples in Tunisia. Further studies focused on T. gondii genotyping on a larger number of human cases and on animals in Tunisia are needed to improve the knowledge and epidemiology of toxoplasmosis.

Detection of Toxoplasma gondii B1 gene in placenta does not prove congenital toxoplasmosis

BACKGROUND

Congenital toxoplasmosis is an important disease that occurs when pregnant women become infected with Toxoplasma gondii during pregnancy. The aim of this study was to investigate the presence of T. gondii B1 gene in placental tissues of IgM seronegative women.

MATERIALS AND METHODS

In this research, chronic toxoplasmosis was identified through examination of blood samples in a group of pregnant women by anti-Toxoplasma IgG and IgM ELISA and nested-PCR techniques. IgG avidity test was used to estimate the onset of infection in some pregnant women with chronic infection. After delivery, some umbilical cord and neonatal blood were tested by anti-Toxoplasma IgM ELISA, and also the B1 gene of T. gondii was investigated in their placental tissue by nested-PCR. Some factors such as blood sampling time and some clinical symptoms experienced during pregnancy were recorded.

RESULTS

One hundred and sixty seven out of 653 (25.6%) pregnant women were positive for anti-Toxoplasma IgG. Of them, 165 (98.8%) were negative for anti-T. gondii IgM. Six out of 10 (60%) placental tissues from IgG seropositive, IgM seronegative women were positive for T. gondii B1 gene, while anti-Toxoplasma IgM was negative in the umbilical cord and neonatal blood samples. The results of IgG avidity test showed low avidity in one and high avidity in two women's samples. The B1 gene was not found in the blood samples of any of the six mothers. The most symptoms experienced during pregnancy were headache and nausea.

CONCLUSION

The detection of B1 gene in placental tissues of the healthy newborn infants reiterates that presence of T. gondii in the placenta does not always result in congenital toxoplasmosis.

New approach to differentiate primary from latent Toxoplasma gondii abortion through immunoglobulin and DNA interpretation

BACKGROUND

Toxoplasma gondii is an acute or latent zoonotic abortifacient human protozoan. Women may be aborted due to recent or latent infection during pregnancy or order to flare up of the dormant bradyzoites to acute tachyzoites (latent opportunistic relapse).

AIMS

1) to validate the interpretation of IgM and IgG immunoglobulins seromonotoring with DNA comparative results in differentiating recent from latent T. gondii abortion.

METHOD

Blood with the corresponding placental or uterine wash samples were collected from 73 aborted Egyptian women from Cairo and Giza labour wards. Patients aborted in any of the phases (Ph-1, Ph-2, Ph-3 and Ph-4 were corresponding to abortion at the 1st, 2nd and 3rd trimesters plus females who gave birth with congenital anomalies), respectively. All aborted patients were assayed serologically by Enzyme Linked Immunosorbent Assay (ELISA) for IgM and IgG titers and the compatible DNA from placenta and uterine wash tissues by conventional Polymerase Chain Reaction (PCR) specific for T. gondii.

RESULTS

Sero-positive aborted women were 50.7% by ELISA versus 37% by PCR. Not all T. gondii sero-positive aborted women were having T. gondii DNA or harboring compatible placental T. gondii cysts. This denotes that immunoglobulins alone are insufficient criteria for confirming toxoplasma abortion.

CONCLUSION

Immunoglobulins with DNA comparative results can possibly differentiate recent from latent T. gondii abortion at higher precision. We recommend the need for routine monitoring of T. gondii i.e. (pre-, during and post-delivery).

Evaluation of Toxoplasma gondii B1 gene in Placental Tissues of Pregnant Women with Acute Toxoplasmosis

Background:

One of the consequences of toxoplasmosis is the risk of passing it from mother to fetus and the onset of congenital toxoplasmosis during pregnancy. The purpose of this study was to evaluate the B1 gene of Toxoplasma gondii in the placental tissues of pregnant women with acute toxoplasmosis.

Materials and Methods:

The study was a cross-sectional study. Serum samples of pregnant women who attended to Fatemieh Hospital of Hamadan University of Medical Sciences were tested for immunoglobulin G (IgG) antibodies against T. gondii by enzyme-linked immunosorbent assay. Then, polymerase chain reaction was used to identify the specific B1 gene of T. gondii in IgG seropositive women. The placental tissues of the pregnant women with positive serum B1 gene examined for this gene. Anti-Toxoplasma immunoglobulin M (IgM) was performed on the umbilical cord and neonate blood.

Results:

Anti-Toxoplasma IgG was detected in 167 out of 653 (25.6%) pregnant women. T. gondii B1 gene was identified in 36 out of 167 (21.6%) of IgG seropositive women. After delivery, the B1 gene was evaluated in 15 out of 36 (41.7%) patients’ placental tissues, 13 of which were positive for this gene (86.7%). Anti-Toxoplasma IgM was detected neither in any umbilical cord nor in neonatal blood samples. All newborns, with the exception of one case, were born with normal birth weight and in term birth.

Conclusion:

The B1 gene was detected in 86.7% of the placental tissue of women who were involved in acute toxoplasmosis during pregnancy.

Detection of Toxoplasma gondii DNA in horse meat from supermarkets in France and performance evaluation of two serological tests

In France, some cases of severe toxoplasmosis have been linked to the consumption of horse meat that had been imported from the American continent where atypical strains of Toxoplasma gondii are more common than in Europe. Many seroprevalence studies are presented in the literature but risk assessment of T. gondii infection after horse meat consumption is not possible in the absence of validated serological tests and the unknown correlation between detection of antibodies against T. gondii and presence of tissue cysts. We performed magnetic-capture polymerase chain reaction (MC-PCR) to detect T. gondii DNA in 231 horse meat samples purchased in supermarkets in France and evaluated the performance and level of agreement of the modified agglutination test (MAT) and enzyme-linked immunosorbent assay (ELISA) in the meat juices. The serological tests lacked sensitivity, specificity, and agreement between them, and there was no correlation with the presence of T. gondii DNA in horse meat, raising concerns about the reliability of T. gondii seroprevalence data in horses from the literature. T. gondii DNA was detected in 43% of horse meat samples but the absence of strain isolation in mice following inoculation of more than 100 horse meat samples suggests a low distribution of cysts in skeletal muscles and a low risk of T. gondii infection associated with horse meat consumption. However, to avoid any risk of toxoplasmosis, thorough cooking of horse meat is recommended.

Novel interpretation of molecular diagnosis of congenital toxoplasmosis according to gestational age at the time of maternal infection

From a prospective cohort of 344 women who seroconverted for toxoplasmosis during pregnancy, 344 amniotic fluid, 264 placenta, and 216 cord blood samples were tested for diagnosis of congenital toxoplasmosis using the same PCR assay. The sensitivity and negative predictive value of the PCR assay using amniotic fluid were 86.3% and 97.2%, respectively, and both specificity and positive predictive value were 100%. Using placenta and cord blood, sensitivities were 79.5% and 21.2%, and specificities were 92% and 100%, respectively. In addition, the calculation of pretest and posttest probabilities and the use of logistic regression allowed us to obtain curves that give a dynamic interpretation of the risk of congenital toxoplasmosis according to gestational age at maternal infection, as represented by the three sample types (amniotic fluid, placenta, and cord blood). Two examples are cited here: for a maternal infection at 25 weeks of amenorrhea, a negative result of prenatal diagnosis allowed estimation of the probability of congenital toxoplasmosis at 5% instead of an a priori (pretest) risk estimate of 33%. For an infection at 10 weeks of amenorrhea associated with a pretest congenital toxoplasmosis risk of 7%, a positive PCR result using placenta at birth yields a risk increase to 43%, while a negative result damps down the risk to 0.02%. Thus, with a molecular diagnosis performing at a high level, and in spite of the persistence of false negatives, posttest risk curves using both negative and positive results prove highly informative, allowing a better assessment of the actual risk of congenital toxoplasmosis and finally an improved decision guide to treatment.

Congenital parasitic infections: a review

This review defines the concepts of maternal-fetal (congenital) and vertical transmissions (mother-to-child) of pathogens and specifies the human parasites susceptible to be congenitally transferred. It highlights the epidemiological features of this transmission mode for the three main congenital parasitic infections due to Toxoplasma gondii, Trypanosoma cruzi and Plasmodium sp. Information on the possible maternal-fetal routes of transmission, the placental responses to infection and timing of parasite transmission are synthesized and compared. The factors susceptible to be involved in parasite transmission and development of congenital parasitic diseases, such as the parasite genotypes, the maternal co-infections and parasitic load, the immunological features of pregnant women and the capacity of some fetuses/neonates to overcome their immunological immaturity to mount an immune response against the transmitted parasites are also discussed and compared. Analysis of clinical data indicates that parasitic congenital infections are often asymptomatic, whereas symptomatic newborns generally display non-specific symptoms. The long-term consequences of congenital infections are also mentioned, such as the imprinting of neonatal immune system and the possible trans-generational transmission. The detection of infection in pregnant women is mainly based on standard serological or parasitological investigations. Amniocentesis and cordocentesis can be used for the detection of some fetal infections. The neonatal infection can be assessed using parasitological, molecular or immunological methods; the place of PCR in such neonatal diagnosis is discussed. When such laboratory diagnosis is not possible at birth or in the first weeks of life, standard serological investigations can also be performed 8-10 months after birth, to avoid detection of maternal transmitted antibodies. The specific aspects of treatment of T. gondii, T. cruzi and Plasmodium congenital infections are mentioned. The possibilities of primary and secondary prophylaxes, as well as the available WHO corresponding recommendations are also presented.

The placenta: a main role in congenital toxoplasmosis?

Systemic infections, such as toxoplasmosis, acquired during pregnancy can lead to placental infection and have profound effects on the mother-to-child relationship and the success of pregnancy. Placental permeability to Toxoplasma gondii is a main parameter that determines parasite transmission to the foetus, and the use of antibiotics to decrease placental parasite load and prevent congenital toxoplasmosis has been suggested for decades. Although parasitological examination of the placenta at birth is commonly used to diagnose neonatal congenital toxoplasmosis, this approach can be controversial. Here we argue in favour of placental examination for both diagnostic and epidemiological purposes.