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- Title
Using Detergent to Enhance Detection Sensitivity of African Trypanosomes in Human CSF and Blood by Loop-Mediated Isothermal Amplification (LAMP).
- Authors
Grab, Dennis J.; Nikolskaia, Olga V.; Inoue, Noboru; Thekisoe, Oriel M. M.; Morrison, Liam J.; Gibson, Wendy; Dumler, J. Stephen
- Abstract
Background: The loop-mediated isothermal amplification (LAMP) assay, with its advantages of simplicity, rapidity and cost effectiveness, has evolved as one of the most sensitive and specific methods for the detection of a broad range of pathogenic microorganisms including African trypanosomes. While many LAMP-based assays are sufficiently sensitive to detect DNA well below the amount present in a single parasite, the detection limit of the assay is restricted by the number of parasites present in the volume of sample assayed; i.e. 1 per µL or 103 per mL. We hypothesized that clinical sensitivities that mimic analytical limits based on parasite DNA could be approached or even obtained by simply adding detergent to the samples prior to LAMP assay. Methodology/Principal Findings: For proof of principle we used two different LAMP assays capable of detecting 0.1 fg genomic DNA (0.001 parasite). The assay was tested on dilution series of intact bloodstream form Trypanosoma brucei rhodesiense in human cerebrospinal fluid (CSF) or blood with or without the addition of the detergent Triton X-100 and 60 min incubation at ambient temperature. With human CSF and in the absence of detergent, the LAMP detection limit for live intact parasites using 1 µL of CSF as the source of template was at best 103 parasites/mL. Remarkably, detergent enhanced LAMP assay reaches sensitivity about 100 to 1000-fold lower; i.e. 10 to 1 parasite/mL. Similar detergent-mediated increases in LAMP assay analytical sensitivity were also found using DNA extracted from filter paper cards containing blood pretreated with detergent before card spotting or blood samples spotted on detergent pretreated cards. Conclusions/Significance: This simple procedure for the enhanced detection of live African trypanosomes in biological fluids by LAMP paves the way for the adaptation of LAMP for the economical and sensitive diagnosis of other protozoan parasites and microorganisms that cause diseases that plague the developing world. Author Summary: Human African trypanosomiasis or sleeping sickness is a fatal disease (if untreated) spread by bloodsucking tsetse flies. Trypanosome parasites first enter the blood and lymph and eventually invade the brain. In rural clinical settings, diagnosis still relies on the detection of these microbes in blood and cerebrospinal fluid (CSF) by microscopy. LAMP, or loop-mediated isothermal amplification of DNA, is a technique that can specifically detect very small amounts of DNA from an organism. It is similar to PCR, the polymerase chain reaction, another DNA amplification technique widely used for diagnosis of infectious diseases. LAMP's advantages are that the reaction works at one temperature, whereas PCR needs a thermocycler, and LAMP is not affected by blood components that inhibit PCR. We show that by simply adding detergent during sample preparation, the analytical sensitivity of LAMP targeting many gene copies is greatly improved, presumably because DNA is released from the pathogen cells and dispersed through the sample. To demonstrate proof of principle, we used pathogenic trypanosomes in different human body fluids (CSF or blood), but this simple modification should be applicable for diagnosis of other microbial infections where cells are sensitive to detergent lysis.
- Subjects
AFRICAN trypanosomiasis; NUCLEIC acid amplification techniques; DEVELOPING countries; TSETSE-flies; LAMPS; AFRICAN swine fever; NEUROCYSTICERCOSIS
- Publication
PLoS Neglected Tropical Diseases, 2011, Vol 5, Issue 8, p1
- ISSN
1935-2727
- Publication type
Article
- DOI
10.1371/journal.pntd.0001249