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He X, Zhou DR, Sun YW, Zhang Y, Zhang XG, Weng YB, Lin RQ. A PCR assay with high sensitivity and specificity for the detection of swine toxoplasmosis based on the GRA14 gene. Vet Parasitol 2021; 299:109566. [PMID: 34509125 DOI: 10.1016/j.vetpar.2021.109566] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Revised: 08/30/2021] [Accepted: 08/31/2021] [Indexed: 10/20/2022]
Abstract
Toxoplasma gondii, an intracellular apicomplexan protozoan parasite, can infect all warm-blooded animals. Infected swine are considered one of the most important sources of T. gondii infection in humans. Rapidly and effectively diagnosing T. gondii infection in swine is essential. PCR-based diagnostic tests have been fully developed, and very sensitive and specific PCR is crucial for the diagnosis of swine toxoplasmosis. In this study, we used the T. gondii dense granule protein 14 (GRA14) gene as a target to design specific primers and established a high-specificity and high-sensitivity PCR detection method for swine toxoplasmosis. Notably, this PCR method could detect T. gondii tachyzoite DNA in the acute infection phase. The GRA14 gene PCR assay detected a minimum of 2.35 tachyzoites of T. gondii and can be used for T. gondii detection in blood, tissue, semen, urine and waste feed specimens. A total of 5462 blood specimens collected from pigs in 5 provinces and autonomous regions in southern China during 2016-2017 were assessed by the newly established GRA14 gene PCR method. The overall T. gondii infection rate was 18.9 % (1033/5462). According to the statistical analysis of different regions in China, the positive rates of swine toxoplasmosis from 2016 to 2017 were highest in the Shaanxi, Fujian and Guangdong areas, at 31.7 % (44/139), 21.9 % (86/391) and 18.8 % (874/4645), respectively. Specimens collected in 2017 had a higher positive rate (19.1 %) than those collected in 2016 (16.1 %). In addition, specimens collected in autumn (39.4 %), spring (22.8 %) and winter (18.2 %) had higher positive rates than those collected in summer (3.8 %). These results indicate that the new PCR method based on the T. gondii GRA14 gene has utility for the diagnosis of swine toxoplasmosis and can facilitate the diagnosis of toxoplasmosis in clinical laboratories.
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Affiliation(s)
- Xi He
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, Guangdong Province, 510642, People's Republic of China; Key Laboratory of Zoonosis Prevention and Control of Guangdong Province, Guangzhou, Guangdong Province 510642, People's Republic of China.
| | - De-Rong Zhou
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, Guangdong Province, 510642, People's Republic of China; Key Laboratory of Zoonosis Prevention and Control of Guangdong Province, Guangzhou, Guangdong Province 510642, People's Republic of China.
| | - Yan-Wu Sun
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, Guangdong Province, 510642, People's Republic of China; Key Laboratory of Zoonosis Prevention and Control of Guangdong Province, Guangzhou, Guangdong Province 510642, People's Republic of China.
| | - Yuan Zhang
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, Guangdong Province, 510642, People's Republic of China.
| | - Xiao-Gang Zhang
- Foshan Standard Bio-Tech Co., Ltd., Foshan 528138, People's Republic of China.
| | - Ya-Biao Weng
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, Guangdong Province, 510642, People's Republic of China.
| | - Rui-Qing Lin
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, Guangdong Province, 510642, People's Republic of China; Key Laboratory of Zoonosis Prevention and Control of Guangdong Province, Guangzhou, Guangdong Province 510642, People's Republic of China.
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Robert MG, Brenier-Pinchart MP, Garnaud C, Fricker-Hidalgo H, Pelloux H. Molecular diagnosis of toxoplasmosis: recent advances and a look to the future. Expert Rev Anti Infect Ther 2021; 19:1529-1542. [PMID: 34112045 DOI: 10.1080/14787210.2021.1941867] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
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.
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Affiliation(s)
- Marie Gladys Robert
- Service de Parasitologie-Mycologie, CHU Grenoble Alpes, Grenoble, France.,Université Grenoble Alpes, Institut pour l'Avancée des Biosciences (IAB), Grenoble, France
| | - Marie-Pierre Brenier-Pinchart
- Service de Parasitologie-Mycologie, CHU Grenoble Alpes, Grenoble, France.,Université Grenoble Alpes, Institut pour l'Avancée des Biosciences (IAB), Grenoble, France.,Centre National de Référence Toxoplasmose - Pôle Biologie Moléculaire, France
| | - Cécile Garnaud
- Service de Parasitologie-Mycologie, CHU Grenoble Alpes, Grenoble, France.,Université Grenoble Alpes, CNRS, CHU Grenoble Alpes, Grenoble INP, TIMC-IMAG, Grenoble, France
| | | | - Hervé Pelloux
- Service de Parasitologie-Mycologie, CHU Grenoble Alpes, Grenoble, France.,Université Grenoble Alpes, Institut pour l'Avancée des Biosciences (IAB), Grenoble, France.,Centre National de Référence Toxoplasmose - Pôle Biologie Moléculaire, France
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Prenatal therapy with pyrimethamine + sulfadiazine vs spiramycin to reduce placental transmission of toxoplasmosis: a multicenter, randomized trial. Am J Obstet Gynecol 2018; 219:386.e1-386.e9. [PMID: 29870736 DOI: 10.1016/j.ajog.2018.05.031] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2018] [Revised: 05/15/2018] [Accepted: 05/24/2018] [Indexed: 12/20/2022]
Abstract
BACKGROUND The efficacy of prophylaxis to prevent prenatal toxoplasmosis transmission is controversial, without any previous randomized clinical trial. In France, spiramycin is usually prescribed for maternal seroconversions. A more potent pyrimethamine + sulfadiazine regimen is used to treat congenital toxoplasmosis and is offered in some countries as prophylaxis. OBJECTIVE We sought to compare the efficacy and tolerance of pyrimethamine + sulfadiazine vs spiramycin to reduce placental transmission. STUDY DESIGN This was a randomized, open-label trial in 36 French centers, comparing pyrimethamine (50 mg qd) + sulfadiazine (1 g tid) with folinic acid vs spiramycin (1 g tid) following toxoplasmosis seroconversion. RESULTS In all, 143 women were randomized from November 2010 through January 2014. An amniocentesis was later performed in 131 cases, with a positive Toxoplasma gondii polymerase chain reaction in 7/67 (10.4%) in the pyrimethamine + sulfadiazine group vs 13/64 (20.3%) in the spiramycin group. Cerebral ultrasound anomalies appeared in 0/73 fetuses in the pyrimethamine + sulfadiazine group, vs 6/70 in the spiramycin group (P = .01). Two of these pregnancies were terminated. Transmission rates, excluding 18 children with undefined status, were 12/65 in the pyrimethamine + sulfadiazine group (18.5%), vs 18/60 in the spiramycin group (30%, P = .147), equivalent to an odds ratio of 0.53 (95% confidence interval, 0.23-1.22) and which after adjustment tended to be stronger (P = .03 for interaction) when treatment started within 3 weeks of seroconversion (95% confidence interval, 0.00-1.63). Two women had severe rashes, both with pyrimethamine + sulfadiazine. CONCLUSION There was a trend toward lower transmission with pyrimethamine + sulfadiazine, but it did not reach statistical significance, possibly for lack of statistical power because enrollment was discontinued. There were also no fetal cerebral toxoplasmosis lesions in the pyrimethamine + sulfadiazine group. These promising results encourage further research on chemoprophylaxis to prevent congenital toxoplasmosis.
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Roux G, Varlet-Marie E, Bastien P, Sterkers Y. Evolution of Toxoplasma-PCR methods and practices: a French national survey and proposal for technical guidelines. Int J Parasitol 2018; 48:701-707. [DOI: 10.1016/j.ijpara.2018.03.011] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2017] [Revised: 02/27/2018] [Accepted: 03/05/2018] [Indexed: 11/15/2022]
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Abstract
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.
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Berredjem H, Aouras H, Benlaifa M, Becheker I, Djebar MR. Contribution of IgG avidity and PCR for the early diagnosis of toxoplasmosis in pregnant women from the North-Eastern region of Algeria. Afr Health Sci 2017; 17:647-656. [PMID: 29085392 PMCID: PMC5656190 DOI: 10.4314/ahs.v17i3.7] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022] Open
Abstract
Background Acute toxoplasmosis in pregnant women presents a high risk of Toxoplasma transmission to the fetus. Early diagnosis is difficult, especially when serological testing for IgG/IgM antibodies fail to differentiate between a recent and a past infection. In this case, we rely on IgG avidity or PCR assays. Objectives The aim of this study was to compare conventional ELISA and IgG avidity, with PCR using B1 and P30 primers for the early diagnosis of toxoplasmosis in pregnant women. Methods Sera were collected from 143 pregnant women and measured by ELISA for anti-Toxoplasma IgG, IgM, IgA and IgG avidity. DNA was extracted from 57 peripheral blood and 14 amniotic fluid samples for PCR amplification. Results A total of 57 out 143 women were seropositive: 30 (52.6%) were IgG+/IgM− and 27 (43.8%) were IgG+/IgM+; IgA antibodies were positive in 7 (12.2%) cases. IgG avidity was low in 9 women suggesting an acute infection; 3 women presented an intermediate avidity. PCR detected Toxoplasma DNA in 9 women presenting low avidity and was negative for the intermediate avidity cases. Conclusion PCR combined to avidity IgG performed better than ELISA IgG, IgM and/or IgA assays alone. PCR was useful in the case of intermediate avidity.
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Affiliation(s)
- Hajira Berredjem
- Department of Biochemistry, Faculty of Sciences, University of Badji Mokhtar, Annaba, Algeria
- Laboratory of Cellular Toxicology, Faculty of Sciences, University of Badji Mokhtar, Annaba, Algeria
| | - Hayette Aouras
- Service of Gynecology, EHS Abdallah Nouaouria Hospital, El Bouni-Annaba, Algeria
| | - Meriem Benlaifa
- Laboratory of Cellular Toxicology, Faculty of Sciences, University of Badji Mokhtar, Annaba, Algeria
| | - Imène Becheker
- Department of Biochemistry, Faculty of Sciences, University of Badji Mokhtar, Annaba, Algeria
| | - Mohamed Reda Djebar
- Laboratory of Cellular Toxicology, Faculty of Sciences, University of Badji Mokhtar, Annaba, Algeria
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Delhaes L, Filisetti D, Brenier-Pinchart MP, Pelloux H, Yéra H, Dalle F, Sterkers Y, Varlet-Marie E, Touafek F, Cassaing S, Bastien P. Freezing and storage at −20 °C provides adequate preservation of Toxoplasma gondii DNA for retrospective molecular analysis. Diagn Microbiol Infect Dis 2014; 80:197-9. [DOI: 10.1016/j.diagmicrobio.2014.08.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2014] [Revised: 07/06/2014] [Accepted: 08/21/2014] [Indexed: 12/01/2022]
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Characterization and multicentric validation of a common standard for Toxoplasma gondii detection using nucleic acid amplification assays. J Clin Microbiol 2014; 52:3952-9. [PMID: 25187637 DOI: 10.1128/jcm.01906-14] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
The molecular diagnosis of toxoplasmosis essentially relies upon laboratory-developed methods and suffers from lack of standardization, hence the large diversity of performances between laboratories. Moreover, quantifications of parasitic loads differ among centers, a fact which prevents the possible prediction of the severity of this disease as a function of parasitic loads. The objectives of this multicentric study performed in eight proficient laboratories of the Molecular Biology Pole of the French National Reference Center for Toxoplasmosis (NRC-T) were (i) to assess the suitability of a lyophilized preparation of Toxoplasma gondii as a common standard for use in this PCR-based molecular diagnosis and (ii) to make this standard available to the community. High-quality written procedures were used for the production and qualification of this standard. Three independent batches of this standard, containing concentrations ranging from 10(4) to 0.01 T. gondii genome equivalents per PCR, were first assessed: the linear dynamic range was ≥ 6 log, the intra-assay coefficients of variation (CV) from a sample containing 10 T. gondii organisms per PCR were 0.3% to 0.42%, and the interassay CV over a 2-week period was 0.76% to 1.47%. A further assessment in eight diagnostic centers showed that the standard is stable, robust, and reliable. These lyophilized standards can easily be produced at a larger scale when needed and can be made widely available at the national level. To our knowledge, this is the first quality control assessment of a common standard which is usable both for self-evaluation in laboratories and for accurate quantification of parasitic loads in T. gondii prenatal infections.
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Murat JB, Fricker Hidalgo H, Brenier-Pinchart MP, Pelloux H. Human toxoplasmosis: which biological diagnostic tests are best suited to which clinical situations? Expert Rev Anti Infect Ther 2014; 11:943-56. [DOI: 10.1586/14787210.2013.825441] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Comparative assessment of a commercial kit and two laboratory-developed PCR assays for molecular diagnosis of congenital toxoplasmosis. J Clin Microbiol 2012; 50:3977-82. [PMID: 23035184 DOI: 10.1128/jcm.01959-12] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Toxoplasmosis is a worldwide infection that may cause severe disease and is regarded as a serious health problem in France. Detection of the parasite by molecular methods is crucial for diagnosing the disease. The extreme diversity of methods and performances of Toxoplasma PCR assays makes the use of commercial PCR kits an attractive alternative, as they offer a chance for standardization. We compared the performances of three molecular methods for the detection of Toxoplasma gondii DNA in amniotic fluid: a commercial method using nested PCR and two laboratory-developed methods, one using conventional PCR and the other one real-time PCR. This evaluation was based upon a T. gondii DNA serial dilution assay, three amniotic fluid samples spiked with T. gondii at different concentrations, and a clinical cohort of 33 amniotic fluid samples. The T. gondii DNA serial dilution assay showed a much lower sensitivity for the commercial kit than for the laboratory-developed methods. Moreover, out of 12 proven congenital toxoplasmosis cases, 91.7% were detected by the laboratory-developed assays, whereas only 50% were detected by the commercial kit. A lack of sensitivity of the method, partly due to the presence of PCR inhibitors, was the main drawback of the commercial method. This study emphasizes that commercial PCR diagnostic kits do not systematically perform better than carefully optimized laboratory-developed methods. There is a need for thorough evaluation of such kits by proficient groups, as well as for performance standards that commercial kits can be tested against to improve confidence in those selected by health care providers.
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Mandelbrot L. Prévention de la transmission mère-enfant de la toxoplasmose : perspectives. ACTA ACUST UNITED AC 2012; 40:591-8. [DOI: 10.1016/j.gyobfe.2012.07.033] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2012] [Accepted: 07/05/2012] [Indexed: 10/27/2022]
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Rahumatullah A, Khoo BY, Noordin R. Triplex PCR using new primers for the detection of Toxoplasma gondii. Exp Parasitol 2012; 131:231-8. [PMID: 22561042 DOI: 10.1016/j.exppara.2012.04.009] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2012] [Revised: 03/31/2012] [Accepted: 04/11/2012] [Indexed: 11/19/2022]
Abstract
Molecular methods are used increasingly for the detection of Toxoplasma gondii infection. This study developed a rapid, sensitive, and specific conventional triplex PCR for the detection of the B1 gene and ITS1 region of T. gondii using newly designed primers and an internal control based on the Vibrio cholerae HemM gene. The annealing temperature and concentrations of the primers, MgCl(2), and dNTPs were optimized. Two sets of primers (set 1 and 2) were tested, which contained different segments of the T. gondii B1 gene, 529 repeat region and ITS1 region. A series of sensitivity tests were performed using parasite DNA, whole parasites, and spiked human body fluids. Specificity tests were performed using DNA from common protozoa and bacteria. The newly developed assay based on set 2 primers was found to be specific and sensitive. The test was capable of detecting as little as 10 pg T. gondii DNA, 10(4) tachyzoites in spiked body fluids, and T. gondii DNA in the organ tissues of experimentally infected mice. The assay developed in this study will be useful for the laboratory detection of T. gondii infection.
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Affiliation(s)
- Anizah Rahumatullah
- Institute for Research in Molecular Medicine, Universiti Sains Malaysia, Penang, Malaysia.
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Faucher B, Miermont F, Ranque S, Franck J, Piarroux R. Optimization of Toxoplasma gondii DNA extraction from amniotic fluid using NucliSENS easyMAG and comparison with QIAamp DNA minikit. Eur J Clin Microbiol Infect Dis 2011; 31:1035-9. [PMID: 21898160 DOI: 10.1007/s10096-011-1402-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2011] [Accepted: 08/18/2011] [Indexed: 11/29/2022]
Abstract
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.
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Affiliation(s)
- B Faucher
- Laboratoire de Parasitologie-Mycologie, Centre Hospitalo-Universitaire de la Timone, 264 rue St-Pierre, 13385, Marseille CEDEX 05, France.
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Sterkers Y, Varlet-Marie E, Marty P, Bastien P. Diversity and evolution of methods and practices for the molecular diagnosis of congenital toxoplasmosis in France: a 4-year survey. Clin Microbiol Infect 2010. [DOI: 10.1111/j.1469-0691.2010.03101.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Multicentric comparative analytical performance study for molecular detection of low amounts of Toxoplasma gondii from simulated specimens. J Clin Microbiol 2010; 48:3216-22. [PMID: 20610670 DOI: 10.1128/jcm.02500-09] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
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.
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Abstract
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.
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Multicenter comparative evaluation of five commercial methods for toxoplasma DNA extraction from amniotic fluid. J Clin Microbiol 2009; 47:3881-6. [PMID: 19846633 DOI: 10.1128/jcm.01164-09] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
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.
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Okay TS, Yamamoto L, Oliveira LC, Manuli ER, Andrade Junior HFD, Del Negro GMB. Significant performance variation among PCR systems in diagnosing congenital toxoplasmosis in São Paulo, Brazil: analysis of 467 amniotic fluid samples. Clinics (Sao Paulo) 2009; 64:171-6. [PMID: 19330240 PMCID: PMC2666456 DOI: 10.1590/s1807-59322009000300004] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/20/2008] [Accepted: 11/01/2008] [Indexed: 12/02/2022] Open
Abstract
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.
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Affiliation(s)
- Thelma Suely Okay
- Laboratory of Medical Investigation, Instituto da Criança, Faculdade de Medicina da Universidade de São Paulo - São Paulo/SP, Brazil.
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Quantitative real-time PCR is not more sensitive than "conventional" PCR. J Clin Microbiol 2008; 46:1897-900. [PMID: 18400914 DOI: 10.1128/jcm.02258-07] [Citation(s) in RCA: 113] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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Barbi M, MacKay WG, Binda S, van Loon AM. External quality assessment of cytomegalovirus DNA detection on dried blood spots. BMC Microbiol 2008; 8:2. [PMID: 18182096 PMCID: PMC2263050 DOI: 10.1186/1471-2180-8-2] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2007] [Accepted: 01/08/2008] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Testing for viral DNA in neonatal blood dried on paper (DBS) has proved a valid means of diagnosing congenital CMV infection with both clinical and epidemiological relevance. To assess the quality of the detection of CMV-DNA on DBS in laboratories performing this test a proficiency panel consisting of nine samples with two blood spots on each filter paper was produced and distributed. Six samples were derived from whole blood, negative for CMV DNA and antibody, and spiked with cell-grown CMV Towne in various concentrations (7.3 x 102 - 9.6 x 105 copies/ml), one was a CMV positive clinical specimen (3.9 x 106 copies/ml), and two samples were CMV-negative whole blood. RESULTS The 27 responding laboratories from 14 countries submitted 33 datasets obtained by means of conventional PCR (n = 5) or real-time PCR (n = 28) technologies. A correct positive result was reported in at least 91% of datasets in samples with a viral load of 8.8 x 104 copies/ml or higher. However only 59% and 12% identified the 9.4 x 103 and 7.3 x 102 copies/ml samples, respectively, correctly as positive. False positive results were reported by 9% of laboratories and in 11% of datasets. CONCLUSION These results indicate a clear need for improvement of methods as sensitivity and false-positivity still appear to be a major problem in a considerable number of laboratories.
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Affiliation(s)
- Maria Barbi
- Department of Public Health-Microbiology-Virology, University of Milan, Italy.
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Surveillance and monitoring of Toxoplasma in humans, food and animals - Scientific Opinion of the Panel on Biological Hazards. EFSA J 2007. [DOI: 10.2903/j.efsa.2007.583] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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Lago EG, Neto EC, Melamed J, Rucks AP, Presotto C, Coelho JC, Parise C, Vargas PR, Goldbeck AS, Fiori RM. Congenital toxoplasmosis: late pregnancy infections detected by neonatal screening and maternal serological testing at delivery. Paediatr Perinat Epidemiol 2007; 21:525-31. [PMID: 17937738 DOI: 10.1111/j.1365-3016.2007.00869.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The first aim of this study was to determine the prevalence of congenital toxoplasmosis in newborn infants treated by the public health system in Porto Alegre, a city in southern Brazil, using neonatal screening for Toxoplasma gondii-specific IgM. The second aim was to investigate whether the cases detected by this approach could have been identified by the prenatal screening for antibodies to T. gondii that was performed in the same population. A fluorometric assay was used to analyse T. gondii-specific IgM in filter paper specimens obtained from newborn infants for routine screening for metabolic diseases. When the specific IgM was positive, serum samples from the infant and the mother were requested for confirmatory serological testing, and the infant underwent clinical examination. Among 10 000 infants screened for T. gondii-specific IgM, seven filter paper samples were positive, and congenital toxoplasmosis was confirmed in six patients. The prevalence of IgM specific for T. gondii was 6/10 000 [95% CI 2/10 000, 13/10 000]. One infected infant had already been identified in the maternity ward before birth, three had been identified by maternal serology at delivery, and two infants with congenital toxoplasmosis were identified solely through neonatal screening. Although four mothers of the patients with congenital toxoplasmosis received prenatal care, and three mothers had one or two serological tests for T. gondii-specific antibodies (one at first trimester, one at first and second trimesters, and the other at second and third trimesters), they were not identified during pregnancy as infected. Neonatal screening identified cases of infection not detected by obtaining only one or two serum samples from pregnant women for T. gondii serology, mainly when infection was acquired and transmitted in late pregnancy. Maternal serology at delivery and neonatal screening were especially useful in the identification of infants with congenital toxoplasmosis when the mother did not receive regular prenatal serological testing or prenatal care.
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Affiliation(s)
- Eleonor G Lago
- Department of Pediatrics, Pontifícia Universidade Católica do Rio Grande do Sul, Porto Alegre, Brazil.
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Bastien P, Jumas-Bilak E, Varlet-Marie E, Marty P. Three years of multi-laboratory external quality control for the molecular detection of Toxoplasma gondii in amniotic fluid in France. Clin Microbiol Infect 2007; 13:430-3. [PMID: 17359328 DOI: 10.1111/j.1469-0691.2006.01642.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Between 2002 and 2004, panels of amniotic fluid containing varying concentrations of Toxoplasma gondii were sent to up to 23 laboratories in France for molecular (PCR-based) detection as part of a national quality assurance initiative in the molecular prenatal diagnosis of toxoplasmosis. Participants were free to enroll and no fees were required. The general level of sensitivity was high, and the rate of false-positive reactions was relatively low. Considerable diversity among PCR methods and primers was revealed. This external quality assurance scheme provided the opportunity to improve laboratory practice and performance, and to increase communication among laboratories involved in making this diagnosis.
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Affiliation(s)
- P Bastien
- Laboratoire de Parasitologie-Mycologie, Centre Hospitalier Universitaire (CHU), Université Montpellier I, Montpellier, France.
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