Detection of Toxoplasma gondii DNA
The protozoan Toxoplasma gondii is estimated to be carried by one third of the world's population with infection typically occurring by eating infected meat, contact with a cat that has itself recently been infected, or by transmission from mother to fetus. During acute toxoplasmosis, symptoms are often influenza-like: swollen lymph nodes, or muscle aches and pains that last for a month or more. Rarely, a patient with a fully functioning immune system may develop eye damage from toxoplasmosis.
Toxoplasmosis can be difficult to distinguish from that of primary central nervous system lymphoma, and as a result, the diagnosis is made by a trial of therapy (pyrimethamine, sulfadiazine + leucovorin), or a brain biopsy if the drugs produce no effect. Serologic testing for both IgG and IgM can determine if and when individual is/was infected. Additionally, PCR has been successfully used to diagnose congenital, ocular, cerebral and disseminated toxoplasmosis. PCR performed on amniotic fluid has revolutionized the diagnosis of fetal T. gondii infection by enabling an early diagnosis to be made, thereby avoiding the use of more invasive procedures on the fetus. PCR has allowed detection of T. gondii DNA in brain tissue, CSF, vitreous and aqueous fluid, BAL, urine and amniotic fluid.
Among PCR assays, the B1 gene is consistently determined to be a useful target. B1 is a tandem-arrayed 35-fold-repetitive gene which has been used for both detection and typing of Toxoplasma strains in clinical samples. The UWMC Molecular Diagnosis laboratory utilizes a 2-step, hemi-nested PCR approach to amplify a region of the B1 gene. Identification of Toxoplasma gondii depends on Real-Time PCR melting curve and evaluation of the sequenced product.
Code | Name |
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TOXRS | Toxoplasma PCR: Detection, B1 |
TOXID | Toxoplasma PCR: Identification, B1 |
TOXSI | Toxoplasma PCR: Specimen Description |
TOXSPI | Toxoplasma PCR: External Identifier |
TOXSR | Toxoplasma PCR: Special Requests |
TOXSC | Toxoplasma PCR: Specimen Comments |
TOXNAE | Toxoplasma PCR: Specimen DNA Extraction |
TOXREV | Toxoplasma PCR: Pathologist Review |
TOXME | Toxoplasma PCR: Method Note |
DNA extraction, nucleic acid purification, polymerase chain reaction (PCR), sequencing
Acceptable specimens are listed below. Please see Molecular Microbiology Specimen Submission for complete specimen collection and handling instructions.
Shipping/Handling
Acceptable Specimens
*Mycobacterium avium complex DNA Detection [MAVDNA] can be ordered on sputum
**Fungal PCR reflex NGS [FUNDNA] and Fungal DNA Detection by PCR (without reflex to NGS) [NRFDNA] may have interference due to some lots of eSwabs which have been found to contain Saccharomyces cerevisiae DNA, resulting in false positive detection. Clinical correlation and/or retesting with a different collection method is advised. The detection of S. cerevisiae from eSwab specimens can interfere with our ability to rule out other fungal DNA.
Unacceptable Specimens
Optimal Quantity:
Please note: We do not need a separate specimen aliquot for each test ordered. Only a single specimen aliquot or block of optimal quantity is necessary for performing multiple tests. If multiple aliquots or blocks of optimal quantity are sent, up to 2 will be pooled.
Fresh tissue is the optimal specimen of choice, as it reduces the chance of introducing exogenous DNA templates or microorganisms during embedding/fixation. Formalin fixation dramatically reduces the sensitivity of the assays due to reduced template yield and quality.
Please see Molecular Microbiology Specimen Submission for complete specimen collection and handling instructions.
UWMC/HMC: Store and send fresh tissue/fluid specimens refrigerated, if specimen storage and transport will exceed 8 hours, freeze at -20°C. Freeze all fresh tissue/fluid specimens at -20°C upon arrival in UW Molecular Microbiology.
UW-MT |
Microbiology, Molecular Diagnostics
206-520-4600 ---------------------------------------- Shipping Address Attn: Molecular Microbiology Performing Lab Address Clinical Microbiology Lab, NW177 |
Contact Information Please e-mail us with any questions or comments you may have. Your inquiry will be answered as soon as possible. email: molmicdx@uw.edu The Molecular Microbiology lab is open from Monday-Friday, 7am-4pm PDT. Billing inquiries and requests for faxed reports can be made to our Client Services Department at (206) 520-4600 or (800) 713-5198. For results or other inquiries, we can be reached by phone at the following numbers:
For assistance during weekends, holidays and after hours, please contact Lab Medicine Resident at (206) 598-6190 |
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