A case of congenital toxoplasmosis whose mother demonstrated serum low IgG avidity and positive tests for multiplex‐nested PCR in the amniotic fluid

Abstract

We encountered a woman whose infant developed congenital toxoplasmosis. Serum Toxoplasma gondii antibody titers (320x) at 12 weeks of gestation increased to 5120x at 25 weeks. Toxoplasma immunoglobulin M was 2.8 index, and immunoglobulin G avidity index was 23%. Cyclic administration of acetylspiramycin was maintained from 22 weeks until delivery. Multiplex-nested polymerase chain reaction of maternal blood and amniotic fluid at 28 weeks both tested positive for Toxoplasma DNA. A male neonate weighing 2916 g was born at 38 weeks via cesarean section. No abnormalities were detected by physical and funduscopic examinations, whereas a head computed tomography of the neonate revealed three independent intracranial calcifications. The infant underwent therapy with pyrimethamine and sulfadiazine for one year. Serum titers of Toxoplasma gondii antibodies were all less than cut-off values between 5 and 12 months after birth, but all increased up to positive levels 18 months after birth.

Prospective Study of Congenital Toxoplasmosis Screening with Use of IgG Avidity and Multiplex Nested PCR Methods

“…Of the nine women whose amniotic fluids had positive PCR tests, three were diagnosed as having congenital toxoplasmosis (cases 1, 2, and 3 in Table 1). Case 1 was previously reported (16). Briefly, serum T. gondii antibody titers (320ϫ) at 12 GW increased to 5,120ϫ at 25 GW.…”

“…As a nested PCR method, the primer pairs in the second multiplex PCR were designed so that each of the PCR products should be 5 bp smaller than that of the first multiplex PCR. These primer sequences are shown elsewhere (16). Figure 2 shows the products of the first/second PCRs as follows: BSR4, 170/ 165 bp; cdk, 283/278 bp; B1, 425/420 bp; and SAG5E, 527/522 bp.…”

Importance of Nonenteric Protozoan Infections in Immunocompromised People

“…In these patients, PCR applied to peripheral blood specimens could eliminate the requirement for invasive CNS biopsy techniques (429). A number of PCR assays have also been optimized for use on amniotic fluid for the diagnosis of congenital toxoplasmosis (188,404,409). As mentioned above in the section on pregnancy, primary Toxoplasma infections acquired prior to the commencement of a pregnancy pose little threat to the fetus.…”

IgG Avidity ELISA Test for Diagnosis of Acute Toxoplasmosis in Humans

“…Some assays have been used to measure Toxoplasma specific IgM antibodies as indicators of the acute phase infection [7,13-15]. Toxoplasma IgM antibodies can be detected for 1 year or longer in some cases, so in asymptomatic individuals with stable titers of Toxoplasma IgG antibodies, positive IgM results are not easy to interpret [8].…”