Genotyping of Toxoplasma gondii in domestic animals from Campeche, México, reveals virulent genotypes and a recombinant ROP5 allele.

Toxoplasma gondii has at least 318 genotypes distributed worldwide, and tropical regions usually have greater genetic diversity. Campeche is a state located in the southeastern region of México and has favourable climate conditions for the replication and dissemination of this protozoan, similar to those in South American countries where broad genetic diversity has been described. Thus, in this study, 4 T. gondii isolates were obtained from tissues of stray dogs and free-range chickens in Campeche, México, and were genotyped by Mn-PCR-RFLP with 10 typing markers (SAG1, altSAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1 and Apico) and 5 virulence markers (CS3, ROP16, ROP17, ROP18 and ROP5) to provide new information about the distribution and virulence prediction of T. gondii genotypes. Two isolates of T. gondii genotype #116 and 2 of genotype #38 were obtained from stray dogs and chickens, respectively. The parasite load found in these species was between <50 and more than 35 000 tachyzoites per mg of tissue. Virulence marker genotyping revealed a recombinant 1&3 ROP5 RFLP pattern in 2 ToxoDB #116 isolates with no prediction of virulence in a murine model, while in the 2 ToxoDB #38 isolates, the ROP18/ROP5 combination predicted high virulence. Considering all the typed markers, there is a predominance of type I and III alleles, as constantly reported for the isolates characterized in various regions of México. It is crucial to determine their phenotype to corroborate the genetic virulence profile of the T. gondii isolates obtained in this study.

A Toxoplasma gondii Oxopurine Transporter Binds Nucleobases and Nucleosides Using Different Binding Modes.

Toxoplasma gondii is unable to synthesize purines de novo, instead salvages them from its environment, inside the host cell, for which they need high affinity carriers. Here, we report the expression of a T. gondii Equilibrative Nucleoside Transporter, Tg244440, in a Trypanosoma brucei strain from which nucleobase transporters have been deleted. Tg244440 transported hypoxanthine and guanine with similar affinity (Km ~1 µM), while inosine and guanosine displayed Ki values of 4.05 and 3.30 µM, respectively. Low affinity was observed for adenosine, adenine, and pyrimidines, classifying Tg244440 as a high affinity oxopurine transporter. Purine analogues were used to probe the substrate-transporter binding interactions, culminating in quantitative models showing different binding modes for oxopurine bases, oxopurine nucleosides, and adenosine. Hypoxanthine and guanine interacted through protonated N1 and N9, and through unprotonated N3 and N7 of the purine ring, whereas inosine and guanosine mostly employed the ribose hydroxy groups for binding, in addition to N1H of the nucleobase. Conversely, the ribose moiety of adenosine barely made any contribution to binding. Tg244440 is the first gene identified to encode a high affinity oxopurine transporter in T. gondii and, to the best of our knowledge, the first purine transporter to employ different binding modes for nucleosides and nucleobases.

The ROP16III-dependent early immune response determines the subacute CNS immune response and type III Toxoplasma gondii survival.

Toxoplasma gondii is an intracellular parasite that persistently infects the CNS and that has genetically distinct strains which provoke different acute immune responses. How differences in the acute immune response affect the CNS immune response is unknown. To address this question, we used two persistent Toxoplasma strains (type II and type III) and examined the CNS immune response at 21 days post infection (dpi). Contrary to acute infection studies, type III-infected mice had higher numbers of total CNS T cells and macrophages/microglia but fewer alternatively activated macrophages (M2s) and regulatory T cells (Tregs) than type II-infected mice. By profiling splenocytes at 5, 10, and 21 dpi, we determined that at 5 dpi type III-infected mice had more M2s while type II-infected mice had more pro-inflammatory macrophages and that these responses flipped over time. To test how these early differences influence the CNS immune response, we engineered the type III strain to lack ROP16 (IIIΔrop16), the polymorphic effector protein that drives the early type III-associated M2 response. IIIΔrop16-infected mice showed a type II-like neuroinflammatory response with fewer infiltrating T cells and macrophages/microglia and more M2s and an unexpectedly low CNS parasite burden. At 5 dpi, IIIΔrop16-infected mice showed a mixed inflammatory response with more pro-inflammatory macrophages, M2s, T effector cells, and Tregs, and decreased rates of infection of peritoneal exudative cells (PECs). These data suggested that type III parasites need the early ROP16-associated M2 response to avoid clearance, possibly by the Immunity-Related GTPases (IRGs), which are IFN-γ- dependent proteins essential for murine defenses against Toxoplasma. To test this possibility, we infected IRG-deficient mice and found that IIIΔrop16 parasites now maintained parental levels of PECs infection. Collectively, these studies suggest that, for the type III strain, rop16III plays a key role in parasite persistence and influences the subacute CNS immune response.

Early immune responses and parasite tissue distribution in mice experimentally infected with oocysts of either archetypal or non-archetypal genotypes of Toxoplasma gondii.

In most of the world Toxoplasma gondii is comprised of archetypal types (types I, II and III); however, South America displays several non-archetypal strains. This study used an experimental mouse model to characterize the immune response and parasite kinetics following infection with different parasite genotypes. An oral inoculation of 50 oocysts per mouse from T. gondii M4 type II (archetypal, avirulent), BrI or BrIII (non-archetypal, virulent and intermediate virulent, respectively) for groups (G)2, G3 and G4, respectively was used. The levels of mRNA expression of cytokines, immune compounds, cell surface markers and receptor adapters [interferon gamma (IFNγ), interleukin (IL)-12, CD8, CD4, CD25, CXCR3 and MyD88] were quantified by SYBR green reverse transcription-quantitative polymerase chain reaction. Lesions were characterized by histology and detection by immunohistochemistry established distribution of parasites. Infection in G2 mice was mild and characterized by an early MyD88-dependent pathway. In G3, there were high levels of expression of pro-inflammatory cytokines IFNγ and IL-12 in the mice showing severe clinical symptoms at 8­11 days post infection (dpi), combined with the upregulation of CD25, abundant tachyzoites and tissue lesions in livers, lungs and intestines. Significant longer expression of IFNγ and IL-12 genes, with other Th1-balanced immune responses, such as increased levels of CXCR3 and MyD88 in G4, resulted in survival of mice and chronic toxoplasmosis, with the occurrence of tissue cysts in brain and lungs, at 14 and 21 dpi. Different immune responses and kinetics of gene expression appear to be elicited by the different strains and non-archetypal parasites demonstrated higher virulence.

Global Lysine Crotonylation and 2-Hydroxyisobutyrylation in Phenotypically Different Toxoplasma gondii Parasites.

Toxoplasma gondii is a unicellular protozoan parasite of the phylum Apicomplexa. The parasite repeatedly goes through a cycle of invasion, division and induction of host cell rupture, which is an obligatory process for proliferation inside warm-blooded animals. It is known that the biology of the parasite is controlled by a variety of mechanisms ranging from genomic to epigenetic to transcriptional regulation. In this study, we investigated the global protein posttranslational lysine crotonylation and 2-hydroxyisobutyrylation of two T. gondii strains, RH and ME49, which represent distinct phenotypes for proliferation and pathogenicity in the host. Proteins with differential expression and modification patterns associated with parasite phenotypes were identified. Many proteins in T. gondii were crotonylated and 2-hydroxyisobutyrylated, and they were localized in diverse subcellular compartments involved in a wide variety of cellular functions such as motility, host invasion, metabolism and epigenetic gene regulation. These findings suggest that lysine crotonylation and 2-hydroxyisobutyrylation are ubiquitous throughout the T. gondii proteome, regulating critical functions of the modified proteins. These data provide a basis for identifying important proteins associated with parasite development and pathogenicity.

Detection of Toxoplasma gondii oocysts on organic and conventionally grown produce.

Toxoplasma gondii infection can result in toxoplasmosis and potential psychological effects. Research commonly focuses on infection through contact with cat fecal matter or consumption of contaminated meat. However, T. gondii oocysts can persist in the environment for years and may be present in soils and on soil-grown produce. Rates of oocyst DNA recovery from produce were high, with 18% of vegetable samples testing positive for T. gondii via PCR test and melt curve analysis. Radishes had significantly higher oocyst counts than arugula, collard greens, kale, lettuce, and spinach. There were no significant differences in oocyst detection rates between samples taken from organic farmer's markets and conventional grocery stores. This study demonstrates that these oocysts can transfer to produce grown both conventionally and using organic techniques.

Herd-level contamination of Neospora caninum, Toxoplasma gondii and Brucella in milk of Iranian dairy farms.

The bulk milk examination is a reliable screening tool for monitoring the quality of milk in the farms. The infection to Neospora caninum, Toxoplasma gondii and Brucella sp. Was evaluated in bulk milk samples of dairy farms in Hamedan province, West part of Iran. All the dairy farms (n = 149) were examined for N. caninum, T. gondii and Brucella infections using milk ring test (MRT), microbiology, serology (Enzyme-linked Immunosorbent Assay), and molecular techniques. Based on molecular methods, Brucella-infection was negative in all farms; while, 55 %, 5.4 % and 2.7 % of samples were positive for N. caninum, T. gondii and mix infection, respectively. The highest Neospora-infection was detected in the farms with history of abortion in fall and winter. There was significant association between Neospora-infection and the presence of dogs and rodents in the farms, herd size, and age of the animals. Also, a significant association was seen between Toxoplasma-infection and the presence of cats and rodents in the farms, as well as age of the animals. Average total bacterial count (TBC) was calculated 1.14 × 106±1.1 × 106. The highest TBC was in the farms from Central locations of studied area (5.7 × 106±2.24 × 106), farms with more than 120 animals (7.9 × 106±2.8 × 106), and farms with ≥50-months age (1.74 × 106±6.3 × 105) in spring and summer (6.9 × 106±3.7 × 106). The number of somatic cells was estimated between 1 × 104 and 2 × 106 (Average = 4.2 × 105±3.39 × 105). The current study was a comprehensive evaluation of Neospora, Toxoplasma and Brucella infections in milk samples of Iranian dairy farms for the first time. Neospora-infection is responsible for economic losses in the region. Health education and milk pasteurization are so helpful for inhibiting the milk borne diseases. To reduce the risk factors, predict and design the appropriate schemes like redundant of heterogeneous animals are recommended.

Toxoplasma gondii isolated from a Brazilian patient with rare pulmonary toxoplasmosis has a novel genotype and is closely related to Amazonian isolates.

Pulmonary toxoplasmosis is rare in immunocompetent patients. Herein, a Toxoplasma gondii strain isolated in Brazil from an immunocompetent patient who had severe pulmonary involvement was biologically and molecularly characterized for the first time. The TgHumIMTBr1 isolate was bioassayed in mice showing a virulent phenotype. Restriction fragment length polymorphism (RFLP) genotyping using 11 markers [SAG1, SAG2 (5´3´SAG2 and alt. SAG2), SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1, Apico and CS3] revealed a new non-archetypal genotype assigned as #312. Genotyping using ROP18/ROP5 markers exhibited the virulent combination of alleles 4 and 1. Microsatellite analysis using 15 markers (TUB2, W35, TgM-A, B18, B17, M33, IV.1, X1.1, N60, N82, AA, N61, N83, M48 and M102) revealed an atypical genotype with three unique alleles and a rare combination of alleles 246 (W35) and 203 (TgM-A) that is typical of the Amazon region. Non-archetypal genotypes with unique alleles may function in the occurrence of severe toxoplasmosis in immunocompetent patients in Brazil. Attempts to isolate or molecularly detect T. gondii for further genotyping studies would contribute to the understanding of causes related to the severity of toxoplasmosis in immunocompetent patients.

Is Real-Time PCR Targeting Rep 529 Suitable for Diagnosis of Toxoplasmosis in Patients Infected with Non-Type II Strains in North America?

Toxoplasma gondii DNA detection is essential to antenatally diagnose a congenital infection and reactivation of a past infection in an immunocompromised patient. Initially, PCR methods targeted the 35-fold repetitive B1 gene, and more recently, coding sequence Rep 529 has been preferred, as it was reported to be repeated 200- to 300-fold and yielded far better sensitivity than amplification of the B1 sequence. To date, few data are available in regard to the efficacy of Rep 529 for non-type II genotypes. In this study, we compared the results of B1 quantitative PCR (qPCR) with those of two different Rep 529 qPCRs performed on 111 samples in two different laboratories (Rep 529-1 and Rep 529-2). The performances of the 3 qPCRs were also compared according to the genotypes of the isolates for 13 type II and 21 non-type II samples. The performance of the Rep 529 target was superior to that of the B1 target regardless of the genotype (threshold cycle [CT ] values for the Rep 529-1 and Rep 529-2 qPCRs were lower than those for the B1 qPCR [P < 0.001 and P < 0.01, respectively]). The same results were observed when a comparison was made according to the genotype of the strain (type II and non-type II genotypes). To our knowledge, these results provide the first relative quantitative data revealing that the efficiency of Rep 529 qPCR does not depend on the genotype of T. gondii isolates and that, in fact, it is superior to B1 qPCR.

Application of Toxoplasma gondii GRA15 peptides in diagnosis and serotyping.

Previous studies showed that three clonal strain types (I, II, and III) of Toxoplasma gondii can be distinguished using serotyping based on a series of polymorphic proteins. However, to establish a systematic serotyping method with higher resolution even being equal to that of genotyping, more specific peptide markers are needed. The objective of the present study was to determine the possibility of the polymorphic dense granule protein 15 (GRA15) for diagnosis and serotyping of T. gondii infection. Three different T. gondii GT1 strain GRA15 gene fragments encoding a 584-residue peptide, a 199-residue peptide and a 84-residue peptide were amplified, expressed and purified, respectively. Anti-T. gondii GT1 strain antibodies, anti-T. gondii RH strain antibodies and anti-T. gondii PRU strain antibodies were used for immunoblotting analysis of the three peptides. Western blotting analysis showed that the 584-residue peptide of GT1 strain GRA15 was a potential candidate for serological diagnosis of T. gondii infection. RH strain from GT1 strain could be distinguished by serotyping based on the GRA15199 or GRA1584, and T. gondii GT1 strain could be distinguished from PRU strain by using serotyping based on the GRA1584. These findings reveal, for the first time, a novel potential role of GRA15-derived peptides in diagnosis and serological differentiation of T. gondii infection.

Spinal cord toxoplasmosis in a young immunocompetent patient.

We report a case of spinal cord toxoplasmosis occurring as a primary infection in a 31-year-old immunocompetent man. Exhaustive immunologic and genetic investigations did not identify any immunodeficiency. The causative agent was a typical type 2 strain. In cases of spinal cord lesions, toxoplasmosis should be considered, even in an immunocompetent patient.

A review of toxoplasmosis in humans and animals in Turkey.

Infections by the protozoan parasite Toxoplasma gondii are widely prevalent in humans and animals in Turkey but little is known of the burden of their clinical toxoplasmosis. Many early papers on toxoplasmosis in Turkey were published in Turkish and often not available widely. Here, we review prevalence, clinical spectrum, epidemiology and diagnosis of T. gondii in humans and animals in Turkey. This knowledge should be useful to biologists, public health workers, veterinarians and physicians. Although one-third of the human population in Turkey is seropositive, the rate of congenital toxoplasmosis is unknown and no information is available in children 12 years old or younger. One large outbreak of acute toxoplasmosis has been reported in 14-18-year old school children in Turkey. An alarming rate (36%) of T. gondii tissue cysts were reported in tissues of sheep and water buffalo meats destined for human consumption; these reports require verification. Genetically, T. gondii strains from domestic cats and wild birds in Turkey were generally classical type II and III, like those prevalent in Europe. A separate genotype, Type 1 Africa, was isolated from two congenitally infected children and a domestic cat in Turkey.

Toxoplasma gondii: Cytokine responses in mice reinfected with atypical strains.

This study aimed to elucidate the cellular immune response against Toxoplasma gondii in chronically infected mice reinfected with different strains of the parasite to elucidate the immunological basis for chronicity or virulence and to uncover the involvement of genes that encode virulence proteins and modulate the immune response. BALB/c mice were infected by oral gavage with non-virulent D8 strain and challenged 45 days post-infection with virulent EGS or CH3 strains. Cytokine measurement was performed 2 days post-challenge in cell extracts of the small intestine and 2, 7, and 14 days post-challenge in serum. Virulence gene allele type of these strains was analyzed. Challenged mice survived by avoiding exacerbated inflammation and inhibiting the overproduction of cytokines. Local and systemic cytokine response in challenged mice was similar to chronic controls and quite distinct in mice acutely infected with the EGS or CH3 strains. Allelic combinations of the virulence genes ROP5/ROP18 was predictive of virulence in mice when tested in these T. gondii strains. Other allelic combinations of rhoptries and dense granules genes showed discrepancies.

Atypical Toxoplasma gondii genotype from a sheep and a pig on Fernando de Noronha Island, Brazil, showed different mouse virulence profiles.

Toxoplasma gondii is a zoonotic parasite which can infect almost all warm-blooded animals. Toxoplasma gondii isolates from Brazil have greater genetic diversity with a predominance of virulent and atypical genotypes, compared with the Northern Hemisphere. Considering that previous studies have demonstrated a high seroprevalence of T. gondii antibodies in animals from Fernando de Noronha Island, the aim of this study was to isolate, genetically characterize, and determine mouse virulence of isolates of T. gondii from livestock from this Brazilian island. Two T. gondii isolates were obtained by mouse bioassay from brain from one sheep and one pig. Genotyping was performed by PCR-RFLP using 10 genetic markers (SAG1, SAG2, SAG3, BTUB, GRA6, c22- 8, c29-2, PK1, L358, and Apico) and an atypical genotype of T. gondii (ToxoDB #146) was identified for both isolates. Genotyping of four ROP loci indicated different alleles for ROP16 and mouse virulence analysis revealed different profiles (intermediate and low virulence). This is the first report of this genotype being described in a pig and a sheep.

Molecular Detection and Genotyping of Toxoplasma gondii and Neospora caninum in Slaughtered Goats in Central China.

Toxoplasma gondii and Neospora caninum infections can cause reproductive failure in animals, including goats, and toxoplasmosis is one of the most important foodborne diseases. However, information on the molecular prevalence and genetic characterization of T. gondii and N. caninum in the tissues of goats in China is limited. In this study, brain samples of 422 slaughtered goats were collected from slaughterhouses in Henan and Anhui provinces, Central China, and examined for the presence of T. gondii and N. caninum by nested polymerase chain reaction (PCR) based on B1 and NC5 genes, respectively. The prevalence of T. gondii and N. caninum DNA was 5.2% and 2.8%, respectively. No significant differences were found between the prevalences of two parasite infections and animal age, sex, and region (p > 0.05). Two of 22 T. gondii-positive samples were completely genotyped at 11 genetic markers (SAG1, [3' + 5'] SAG2, alternative SAG2 [alt. SAG2], SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1, and Apico) using PCR-restriction fragment length polymorphism, and were identified as genotype ToxoDB no. 225, which has not been previously reported in goats in any country worldwide. For N. caninum, two different sequences at the ITS1 region, three genotypes at the MS5 microsatellite locus, and one genotype at the MS8 locus were identified. This study showed that T. gondii and N. caninum are moderately prevalent in goats in Central China; however, it should be emphasized that T. gondii prevalence in goats poses a potential health threat for consumers in the investigated areas. To the best of our knowledge, this is the first report on the genetic characterization of N. caninum isolates from goats in China. Our results have important implications for a better understanding of the genetic diversity of these parasites in China.

Detection and genetic characterization of Toxoplasma gondii in market-sold mussels (Mytilus edulis) in certain provinces of China.

Mussels, randomly collected from fish markets in China, were analyzed by a semi-nested PCR to detect B1 gene of Toxoplasma gondii. Out of the 2215 samples, fifty-five (2.48%) were detected T. gondii-positive. The prevalence in Shandong province, Liaoning province and Zhejiang province were 2.51%, 2.26% and 2.69%, respectively. T. gondii oocysts were more frequently detected in digestive glands (1.04%) and haemolymph (1.49%) when compared with gills (0.23%). Of the 55 positive DNA, only two samples showed complete genotype at 11 locus and were authenticated as ToxoDB Genotype #9. To our knowledge, the present study is the first to confirm the presence of T. gondii in market-sold mussels in China. The findings point to the risk of humans acquiring T. gondii infection by consuming mussels bought in the aquatic product market.

Systematic review and meta-analysis of variation in Toxoplasma gondii cyst burden in the murine model.

Toxoplasma gondii is an obligate intracellular protozoan parasite that infects approximately 30% of the population of the United States, with worldwide distribution. The chronic (latent) infection, mediated by the bradyzoite parasite life stage, has attracted attention due to possible links to host behavioral alteration and psychomotor effects. Mice are a common model organism for studying the chronic stage, as they are natural hosts of infection. Notably, published studies demonstrate vast ranges of measured cyst burden within the murine brain tissue. The inconsistency of measured cyst burden within and between experiments makes interpretation of statistical significance difficult, potentially confounding studies of experimental anti-parasitic approaches. This review analyzes variation in measured cyst burden in a wide array of experimental mouse infections across published literature. Factors such as parasite infection strain, mouse strain, mode of infection, and infectious dose were all examined. The lowest variation in measured cyst burden occurred with the commonly available Balb/c and CBA mice undergoing infection by the ME49 strain of T. gondii. A summary of cyst variation and average cyst counts in T. gondii mouse models is presented, which may be useful for designing future experiments.

Inter- and intra-genotype differences in induced cystogenesis of recombinant strains of Toxoplasma gondii isolated from chicken and pigs.

The ability to differentiate from the proliferative (tachyzoite) to the latent (bradyzoite) stage of isolates of Toxoplasma gondii recombinant genotypes (I/II/III and I/III) and reference strains from a clonal line (RH and ME49) was investigated in this study. Two isolates from chicken (#114 and #277; ToxoDB) and 3 from pigs (#114; ToxoDB) were the subjects for evaluation. The isolates were grown in cell culture under 2 different conditions: culture medium at pH 7.0 (neutral, without stress induction) or pH 8.0 (alkaline, stress inducing). After 4 days, the cultures were fixed and the events resulting from infection and induction were labeled. T. gondii cysts were labeled using Dolichos biflorus-FITC lectin (DBL-cysts) and free tachyzoites or vacuolar were labeled using an anti-T. gondii polyclonal antibody followed by an Alexa 594-conjugated secondary antibody (DBL-negative structures compatible with parasite structures - lysis plaques or vacuole). Differences in DBL-cysts formation in vitro in response to exogenous stress were observed between recombinant genotype isolates and the typical genotypes. The differences in conversion rates and the patterns of lysis plate production between genotype I/III isolates (#114) indicate that care should be taken when extrapolating the in vitro phenotypic characteristics of parasites from the same genotype.

Exploring protein myristoylation in Toxoplasma gondii.

Toxoplasma gondii is an important human and veterinary pathogen and the causative agent of toxoplasmosis, a potentially severe disease especially in immunocompromised or congenitally infected humans. Current therapeutic compounds are not well-tolerated, present increasing resistance, limited efficacy and require long periods of treatment. On this context, searching for new therapeutic targets is crucial to drug discovery. In this sense, recent works suggest that N-myristoyltransferase (NMT), the enzyme responsible for protein myristoylation that is essential in some parasites, could be the target of new anti-parasitic compounds. However, up to date there is no information on NMT and the extent of this modification in T. gondii. In this work, we decided to explore T. gondii genome in search of elements related with the N-myristoylation process. By a bioinformatics approach it was possible to identify a putative T. gondii NMT (TgNMT). This enzyme that is homologous to other parasitic NMTs, presents activity in vitro, is expressed in both intra- and extracellular parasites and interacts with predicted TgNMT substrates. Additionally, NMT activity seems to be important for the lytic cycle of Toxoplasma gondii. In parallel, an in silico myristoylome predicts 157 proteins to be affected by this modification. Myristoylated proteins would be affecting several metabolic functions with some of them being critical for the life cycle of this parasite. Together, these data indicate that TgNMT could be an interesting target of intervention for the treatment of toxoplasmosis.

Efficacy of sulfadiazine and pyrimetamine for treatment of experimental toxoplasmosis with strains obtained from human cases of congenital disease in Brazil.

Toxoplasmosis in South America presents great health impacts and is a topic of research interest not only because of the severity of native cases but also due to the predominant atypical genotypes of the parasite circulating in this continent. Typically, symptomatic toxoplasmosis is treated with a combination of sulfadiazine (SDZ) and pyrimethamine (PYR). However, some clinical cases present treatment failures due to an inability of the drugs to control the infection or their significant adverse effects, which can lead to treatment interruption. Although resistance/susceptibility to the aforementioned drugs has been well described for clonal strains of Toxoplasma gondii spread to the Northern Hemisphere, less is known about the South American atypical strains. In this study, the effectiveness of SDZ and PYR for the treatment of mice during acute infection with different atypical T. gondii strains was evaluated. Swiss mice were infected with seven T. gondii strains obtained from newborn patients with congenital toxoplasmosis in Brazil. The infected mice were treated with 10-640 mg/kg per day of SDZ, 3-200 mg/kg per day of PYR, or a combination of both drugs with a lower dosage. The mice were evaluated for parameters including mortality, anti-T. gondii IgG production by ELISA and the presence of brain cysts. In addition, the presence of polymorphisms in the dhps gene was verified by gene sequencing. A descriptive analysis was used to assess the association between susceptibility to SDZ and/or PYR and the genotype. The TgCTBr4 and TgCTBr17 strains (genotype 108) presented lower susceptibility to SDZ or PYR treatment. The TgCTBr1 and TgCTBr25 strains (genotype 206) presented similar susceptibility to PYR but not SDZ treatment. The TgCTBr9 strain (genotype 11) was the only strain with high susceptibility to treatment with both drugs. The TgCTBr13 strain (genotype 208) was not susceptible to treatment with the lower PYR or SDZ doses. The TgCTBR23 strain (genotype 41) was more susceptible to PYR than to SDZ treatment. However, the association of low SDZ and PYR doses showed good efficacy for the treatment of experimental toxoplasmosis with T. gondii atypical strains obtained from newborns in Brazil. A new mutation in the T. gondii dhps gene (I347M) was identified that might be associated with the SDZ low sensitivity profile observed for the TgCTBr4 and TgCTBr17 isolates.