Species Typing of Nontuberculous Mycobacteria by Use of Deoxyribozyme Sensors.

BACKGROUND: Nontuberculous mycobacteria (NTM) species are a rising threat, especially to patients living with pulmonary comorbidities. Current point-of-care diagnostics fail to adequately identify and differentiate NTM species from Mycobacterium tuberculosis (Mtb). Definitive culture- and molecular-based testing can take weeks to months and requires sending samples out to specialized diagnostic laboratories. METHODS: In this proof-of-concept study, we developed an assay based on PCR amplification of 16S ribosomal RNA (rRNA) rrs genes by using universal mycobacterial primers and interrogation of the amplified fragments with a panel of binary deoxyribozyme (BiDz) sensors to enable species-level identification of NTM (BiDz-NTMST). Each BiDz sensor consists of 2 subunits of an RNA-cleaving deoxyribozyme, which form an active deoxyribozyme catalytic core only in the presence of the complimentary target sequence. The target-activated BiDz catalyzes cleavage of a reporter substrate, thus triggering either fluorescent or colorimetric (visually observed) signal depending on the substrate used. The panel included BiDz sensors for differentiation of 6 clinically relevant NTM species (Mycobacterium abscessus, Mycobacterium avium, Mycobacterium intracellulare, Mycobacterium fortuitum, Mycobacterium kansasii, and Mycobacterium gordonae) and Mtb. RESULTS: Using the fluorescent BiDz-NTMST assay, we successfully identified the species of 38 clinical isolates. In addition, a subset of strains was tested with visual BiDz sensors, providing proof-of-concept for species typing of NTM by the naked eye. CONCLUSIONS: The BiDz-NTMST assay is a novel platform for rapid identification of NTM species. This method is highly specific and significantly faster than current tools and is easily adaptable for onsite diagnostic laboratories in hospitals or clinical laboratories. (C) 2018 American Association for Clinical Chemistry