ABSTRACT
A combined loop-mediated isothermal amplification lateral flow dipstick (LAMP-LFD) format was evaluated in the detection of human infective trypanosome DNA from clinical samples. The LAMP-LFD showed analytical sensitivity equivalent to 0.01 tryps/mL, levels that were identical to using gel electrophoresis and SYBR Green I dye. The LAMP-LFD showed superior specificity to SYBR Green I when supernatant prepared from boiled human biological samples was used as template. These results indicate that the use of nonspecific DNA intercalators may produce false positives when partially processed templates are used. The LAMP-LFD format presented here is simple, rapid, and has future potential use in diagnosis of sleeping sickness.
Subject(s)
Nucleic Acid Amplification Techniques , Trypanosoma brucei gambiense/genetics , Trypanosomiasis, African/diagnosis , Base Sequence , Genes, Protozoan/genetics , Humans , Interspersed Repetitive Sequences/genetics , Molecular Sequence Data , Sensitivity and SpecificityABSTRACT
Loop-mediated isothermal amplification (LAMP) of DNA is a novel technique that rapidly amplifies target DNA under isothermal conditions. In the present study, a LAMP test was designed from the serum resistance-associated (SRA) gene of Trypanosoma brucei rhodesiense, the cause of the acute form of African sleeping sickness, and used to detect parasite DNA from processed and heat-treated infected blood samples. The SRA gene is specific to T. b. rhodesiense and has been shown to confer resistance to lysis by normal human serum. The assay was performed at 62 degrees C for 1 h, using six primers that recognised eight targets. The template was varying concentrations of trypanosome DNA and supernatant from heat-treated infected blood samples. The resulting amplicons were detected using SYTO-9 fluorescence dye in a real-time thermocycler, visual observation after the addition of SYBR Green I, and gel electrophoresis. DNA amplification was detected within 35 min. The SRA LAMP test had an unequivocal detection limit of one pg of purified DNA (equivalent to 10 trypanosomes/ml) and 0.1 pg (1 trypanosome/ml) using heat-treated buffy coat, while the detection limit for conventional SRA PCR was approximately 1,000 trypanosomes/ml. The expected LAMP amplicon was confirmed through restriction enzyme RsaI digestion, identical melt curves, and sequence analysis. The reproducibility of the SRA LAMP assay using water bath and heat-processed template, and the ease in results readout show great potential for the diagnosis of T. b. rhodesiense in endemic regions.
