Species Identification of Non-tuberculous Mycobacteria (NTM) from Sputum Samples of TB Suspects in a Tertiary Care Centre from North India
Rohini Sharma1, Binit Kumar Singh1, Pankaj Jorwal1*, Indra Mani1, Vishwanath Upadhyay1, Manish Soneja1, George Sebastian3, Ranjani Ramachandran2, Prahlad Kumar3 and Naveet Wig1
1Department of Medicine, All India Institute of Medical Sciences, New Delhi, India
2TB Lab Focal Point, World Health Organization New Delhi, India
3National Tuberculosis Institute, Bangalore, India
*Corresponding Author: Pankaj Jorwal, Department of Medicine, All India Institute of Medical Sciences, New Delhi, India.
July 27, 2021; Published: August 21, 2021
Purpose: Non-tuberculous Mycobacteria (NTM) infections are often misdiagnosed as tuberculosis due to the similar clinical and radiological presentations. NTM infections can be differentiated from tuberculosis only through species identification. Here we performed a species-level identification of NTM from sputum samples using ITS sequencing of the 16S-23S rRNA gene.
Materials and Methods: Twenty-one immunochromatographic assay negative isolates from smear-positive patients were collected and evaluated. The isolates were then subjected to mycolic acid extraction for HPLC, DNA isolation for line probe assay (LPA), hsp65 and 16S-23S rRNA gene ITS sequencing.
Results: After evaluating all the diagnostic modalities for NTM, it was observed that the Mycobacterium intracellulare was the predominant slow-growing NTM (9/20, 45%), while Mycobacterium abscessus (subsp. bolletii) was the dominant rapid grower (5/20, 25%). One isolate, which could not be identified either by LPA or by HPLC, was detected as Nocardia cyriacigeorgica, by sequencing a non mycobacterial species predominantly found in pulmonary infection. The results of HPLC and LPA were 100% concordant. One isolate was identified as M. abscessus by sequencing, but HPLC and LPA detected it as Mycobacterium chelonae.
Conclusion: NTM should be considered as the key pathogen in immunocompromised patients and in patients with manifestations similar to tuberculosis. In such cases, species identification is critical for initiation of appropriate therapy. The 16S-23S rRNA gene ITS sequencing method is a rapid and accurate technique for NTM species identification up to subspecies.
Keywords: tuberculous Mycobacteria; Internal Transcribed Spacer Sequencing; Line Probe Assay; HPLC
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