The high complexity and cost of polymerase chain reaction-based molecular diagnostics sometimes limits their use in the clinical diagnostics setting. A new helicase-based isothermal amplification method offers an alternative to standard polymerase chain reaction, allowing amplification and detection of specific DNA sequences at a constant reaction temperature without thermocycling equipment. Herein, we describe the development of a novel one-tube isothermal reverse transcription-thermophilic helicase-dependent amplification (RT-tHDA) platform for RNA target detection based on the already established tHDA system. The RT-tHDA platform is highly sensitive and specific for a variety of RNA targets tested, including purified RNA molecules, armored RNA particles, and RNA virus. Moreover, rapid one-step RT-tHDA can be achieved by inclusion of an extreme thermostable single-stranded DNA binding protein in the reaction, resulting in one millionfold amplification of Ebola virus-armored RNA in less than 10 minutes. This RT-tHDA method expands on the known methods to amplify specific RNA targets and results in an easily prepared and contained platform.
A simple, rapid, and user-friendly procedure has been developed to identify Staphylococcus aureus and determine its methicillin resistance directly from gram-positive cocci in cluster-containing blood culture medium. The specimens were diluted and heated prior to amplification of the nuc and mecA genes with isothermal helicase-dependent amplification. Amplicons were detected using a disposable detection device. The analytical sensitivity of the assays was 50 CFU per reaction, and the clinical sensitivity and specificity were both 100% for S. aureus detection and 100% and 98% for methicillin resistance determination, respectively.
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