Toxoplasmosis congénita: Diagnóstico serológico, RPC, aislamiento y caracterización molecular de Toxoplasma gondii

Abstract

Congenital toxoplasmosis diagnosis in the newborn is a very important issue due to the need for early treatment to prevent future sequels. Aim To compare available methods at the institution for the diagnosis of congenital toxoplasmosis. Material and Methods In this study we have evaluated the different diagnostic tests used in 67 congenital exposed newborns, including serological tests, PCR, parasite isolation and molecular characterization. Results The ISAGA IgM and IgA tests showed sensitivity (Se) of 87 and 91%, respectively, and specificity (Sp) of 100%. When ISAGA IgM and IgA were performed simultaneously, the Se increased to 98% and the Sp was 100%. The presence of IgE contributed to the diagnosis when it was detected in the child's serum but not in maternal blood. In four congenital infected children the parasite was isolated and genotyped: one was genotype II and the other three were "atypical" genotypes. No parasite was isolated in children without congenital toxoplasmosis. Discussion Overall, serological tests showed a good diagnostic performance although in one case they were all negative and isolation was the only tool to identify the infection. We conclude that it is essential to use all diagnostic tests in every single exposed child, including if possible, molecular characterization due to its epidemiological implication.

The Important Role of Laboratories in the Diagnosis and Prevention of Toxoplasma Infection

“…Reference Laboratories: must enlarge the sample with other specific tests such as those named above. At the time of delivery, isolation of Toxoplasma gondii parasite in placenta and umbilical blood cord can be done and, furthermore, studied the type of strain to which it belongs to know the degree of impact to the newborn [12][13][14][15][16][17]. Once SC is confirmed, the doctor in charge must be notified as soon as possible, so these women can be medicated to avoid parasites infect placenta and make sure the newborn does not have any immediate or late clinical consequences [1-5, 7, 8].…”

“…Reference Laboratories must do not only IgG and IgM, but also the most sensitive ones have the best brands. Besides that, must do ISAGA´s Tests ISAGA M, ISAGA A, and ISAGA E, Western blot, PCR [8,23], and if possible Sabin Feldman or Cellular Culture and sequence [12][13][14][15][16][17][19][20][21][22][23].…”

Abordaje de diagnóstico y terapéutico de la toxoplasmosis congénita

“…Si se necesita un conocimiento más preciso del momento de la infección, entonces una persona con IgG positiva debe realizarse una prueba de IgM mediante un procedimiento con reacciones inespecíficas mínimas, como EIA de captura de IgM (16). Una prueba de IgM negativa esencialmente excluye una infección reciente, pero una prueba de IgM positiva es difícil de interpretar porque los anticuerpos IgM específicos de Toxoplasma pueden detectarse mediante EIA hasta 18 meses después de la infección aguda adquirida (19).…”

“…Este último está más estandarizado y tiene sus propios controles y estándares de sistema. En una mujer embarazada cuya muestra se toma en el segundo trimestre en lugar de idealmente en el primer trimestre, y se encuentra IgG positiva, pero IgM negativa, es más recomendable realizar una prueba de avidez de IgG (19). Las pruebas de IgG de alta avidez indican que adquirió la infección hace más de 4 meses.…”

Toxoplasmosis congénita en gemelos

“…En estudios que comparaban el compromiso en embarazos monocigóticos y dicigóticos, se detectó que, en los primeros, ambos gemelos presentaban manifestaciones clínicas mientras que, en los segundos, uno de los RN podía ser completamente asintomático [4][5][6][10][11][12] . En una serie de Argentina, 79% de los RN con toxoplasmosis congénita presentaron coriorretinitis, calcificaciones cerebrales y compromiso macular con frecuencia variable 10 . En nuestro caso, ambas gemelas tuvieron igual compromiso (oftalmológico y cerebral) lo cual coincide con lo descrito en embarazos monocigóticos monocoriales.…”