Development of multiplex PCR assays based on the 16S-23S rRNA internal transcribed spacer for the detection of clinically relevant nontuberculous mycobacteria

Abstract

To accelerate the identification and differentiation of clinically relevant nontuberculous mycobacteria (NTM) with two sets of multiplex PCR (mPCR) targeting the 16S-23S rRNA internal transcribed spacer (ITS) region for timely patient management. Two mPCR assays were developed: Slow-Growers (SG) mPCR was used for the detection of slow-growing mycobacteria, which included Mycobacterium avium complex, Mycobacterium kansasii, Mycobacterium gordonae and Mycobacterium xenopi whilst the other mPCR assay labelled as Fast-Growers (FG) mPCR was used for the detection of Mycobacterium fortuitum complex, Mycobacterium abscessus and Mycobacterium chelonae. In these assays, a common forward primer based on a conserved section of the 16S rRNA region was used in conjunction with species-specific reverse primers. The mPCRs were tested against 247 clinical mycobacterial isolates and demonstrated 100% specificity and sensitivity. Identification of the mycobacterial species was also validated by DNA sequencing of the 16S-23S ITS region and when further confirmation was needed, hsp65 sequencing was performed. The mPCR assays could be a potentially useful diagnostic tool for the rapid and accurate identification of clinically relevant NTM. In this study, we looked at the frequency of hospital isolated NTM over the last 5 years (2005-2010), and an mPCR targeting the ITS region was developed for NTM species that appeared to be more prevalent in the context of Singapore.