Non-tuberculous mycobacteria: a disease beyond TB and preparedness in India

BACKGROUND AND METHODS

Fifty-six Indian studies on NTM diseases were selected between 1981 and 2020 from various electronic databases (PubMed, EMBASE, Medline, BIOSIS preview, and Scopus) for systematic review.

RESULTS

NTM isolation rates increased from 0.9% between 2001 and 2010 to 1.6% between 2011 and 2020. Prevalence of NTM-pulmonary disease (NTM-PD) among presumptive-TB patients in India was 1.1% (395/34,829). M. avium complex (MAC) (19%) was most commonly isolated from pulmonary specimens followed by M. chelonae (10%), M. fortuitum (9.8%), and M. abscessus (8.8%). M. fortuitum (35.5%), M. chelonae (23.6%) and M. abscessus (15%) were frequently reported from extra-pulmonary specimens. Patients with NTM-PD were mostly treated with a macrolide-based three-drug regimen. Clarithromycin-based-drug regimen in combination with amikacin, ciprofloxacin and several other drugs (rifampicin, imipenem, ofloxacin, linezolid, azithromycin) was used for treatment of EP-NTM. Median duration of the treatment in NTM-PD was 12 months, (6-18 months) whereas it was 6 months (3.1-8.7 months) in EP-NTM. Treatment was successful in 45% (19/42) of NTM-PD patients and 75% (93/124) of EP-NTM patients.

CONCLUSION

It is concluded from this review that most Indian studies have published laboratory data on NTM isolation and speciation and lacked information on clinical, microbiological and radiological correlation and treatment outcome details. Future studies should address these issues while publishing on NTM diseases.

Detection of clinically important non tuberculous mycobacteria (NTM) from pulmonary samples through one-step multiplex PCR assay

Background

The burden of non-tuberculous mycobacterial (NTM) disease is increasing worldwide but still its diagnosis is delayed and it is mistaken as multidrug-resistant tuberculosis (MDR-TB).The present study was performed to develop a multiplex PCR assay for detection and identification of clinically most common NTM to the species level from pulmonary samples.

Results

Out of 50 isolates, 26 were identified as Mycobacterium kansasii (MK), 20 were identified as Mycobacterium abscessus (MA) and 4 were identified as Mycobacterium avium complex (MAC) through multiplex PCR and further confirmed by sequencing.

Conclusion

Our study showed that multiplex PCR assay is a simple, convenient, and reliable technique for detection and differential identification of major NTM species.

Comparison of polymerase chain reaction-restriction enzyme analysis method and DNA sequence analysis results in the identification of non-tuberculous mycobacteria

The typing of non-tuberculous mycobacteria (NTM) is important from a clinical and epidemiological perspective. The polymerase chain reaction-restriction enzyme analysis (PRA) method and DNA sequence analysis method were utilized to target a gene region that codes the 65-kDa heat-shock protein for typing 150 suspected NTM samples isolated from the respiratory tract. Mycobacterium abscessus, Mycobacterium xenopi, Mycobacterium fortuitum, and Mycobacterium peregrinum were most frequently found by both methods. Six isolates that could not be defined by the PRA method were defined as Nocardia cyriacigeorgica, Nocardia abscessus, and Mycobacterium intracellulare by DNA sequence analysis. Discordance between the results of the two methods was observed for only one isolate. The isolate that was defined as Mycobacterium gordonae type 6 by the PRA method was defined as Mycobacterium senegalense by sequence analysis. The PRA method is simple and gives rapid results. Compared with DNA sequence analysis, it gives consistent and reliable results up to a ratio of 90%. DNA sequence analysis is the gold standard method in which all strains can be defined. However, given our laboratory conditions, its disadvantage is that it takes longer to reach a diagnosis than through the PRA method.