Leishmania species DNA detection by PCR

Detection and identification of Leishmania species DNA.

Leishmaniasis is a fatal or disfiguring disease caused by a protozoan parasite transmitted by hematophagous sand flies. Globally, 350 million people are estimated to be at risk, resulting in ~1 million cases per year. There are two major forms of the disease: visceral leishmaniasis (VL), which is always treated, otherwise case fatality is ~80%; and cutaneous leishmaniasis (CL), for which the decision to treat is more complicated. The disease is an important diagnostic consideration in travelers from Latin America, the Middle East, North or East Africa, and has been reported in the Southern United States (1). Populations at risk include immunosuppressed persons, immigrants, military and foreign service personnel, and staff or volunteers from non-governmental organizations (1).

Given the toxicity of anti-leishmanial drugs, a confirmed laboratory diagnosis is required prior to starting therapy (2). The decision to treat CL depends upon clinical factors - patient immune status; number, size, duration, and anatomic location of lesions – and the species of parasite (2). While many cutaneous cases of “Old World” Leishmania spp (OWL) will be treated, small, isolated lesions of L. tropica may resolve spontaneously. Among “New World” Leishmania spp (NWL), the Viannia subgenus members have a propensity for mucocutaneous involvement (MCL) and dissemination and thus require treatment to prevent profound disfigurement.

Our Leishmania PCR assay offers highly sensitivity molecular identification of Leishmania spp that infect humans, with a limit of detection of a single organism per reaction. When Leishmania parasites are detected by the assay, sequencing identifies the causative organism to the species or species-complex. This test can be ordered as a stand-alone assay and is performed reflexively if broad-range fungal PCR detects Leishmania sp as an incidental finding.

Acceptable specimens are listed below. Please see Molecular Microbiology Specimen Submission for complete specimen collection and handling instructions.

Shipping/Handling

• Fresh frozen tissue/fluid specimens should be collected into a DNA free container labeled with at least two identifiers and be submitted and maintained on dry ice.
• Formalin Fixed Paraffin-embedded tissues (FFPE, PET) can be sent ambient or with ice packs during warmer summer months to prevent melting.

Acceptable Specimens

• Fresh frozen tissue
• Fresh frozen fluid: any body fluid is acceptable if it is not listed under Unacceptable Specimens.
  • Common examples include: cerebrospinal fluid, pleural fluid, pericardial fluid, urine, bronchial lavage, joint fluid, bone marrow, vitreous fluid, etc.
• Formalin Fixed Paraffin-embedded tissues (FFPE, PET): blocks, scrolls, and unstained slides
• Sputum: acceptable - except for Bacterial PCR reflex NGS [BCTDNA]/Bacterial DNA Detection by PCR (without reflex to NGS) [NRBDNA], Fungal PCR reflex NGS [FUNDNA]/Fungal DNA Detection by PCR (without reflex to NGS) [NRFDNA], and Nontuberculous Mycobacteria DNA Detection [NTMDNA]* assays
• eSwabs**, UTM (universal transport media), body fluid/bone marrow in EDTA (not including blood)
• Sodium polyanethol sulfonate (SPS, Wampole Isolator Tubes) acceptable with disclaimer

*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

• Blood, serum, plasma, stool/rectal swabs
• No citrated or heparinized solutions
• Tissues floating in formalin
• Swab/fluid collected in tube containing agar

Optimal Quantity:

• Fresh Tissue: 0.3-1.0 cm^3
• Fluid: 0.2-1 mL
• Formalin Fixed Paraffin-embedded Tissue (FFPE/PET): blocks are preferred and will be sent back to client upon completion of testing
• Scrolls/unstained slides: cross-sectional area >1cm^2 send 10 sections of 10µm thickness, if <1cm^2 send 20 sections if available

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.

Conditionally Acceptable Specimens

• Buffy coat with stain positive whole blood: acceptable for Leishmania PCR only