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Updated: May 9, 2026
Identification of Rare Bacterial Pathogens by 16S rRNA Gene Sequencing and MALDI-TOF MS
Published on: July 11, 2016
Identification of non-tuberculous mycobacteria in slaughtered cattle from Chennai, India
Harini Ramanujam1, Manohar Nesakumar2, Kannan Thiruvengadam3
1Department of Immunology, ICMR-National Institute for Research in Tuberculosis, Chetpet, Chennai, India.
Abstract:
Non-tuberculous mycobacteria (NTM) are emerging pathogens in human and veterinary medicine, with a globally increasing incidence. In India, sporadic studies have identified an upward trend in NTM infections, but accurate prevalence estimates are lacking due to the absence of nationwide surveillance. Non-tuberculous mycobacteria have been reported in clinically healthy cattle and wildlife globally, complicating tuberculosis (TB) diagnostics and surveillance. This study aimed to characterize NTM species isolated from tissue samples of slaughtered cattle in Chennai using culture and targeted hsp65 gene sequencing. A total of 118 presumed NTM samples from 115 animals were processed, and 49 isolates were confirmed as NTMs by PCR. Sequencing identified 18 different species, with Mycobacterium intracellulare (9/49) being the most frequent, followed by Mycobacterium sp. strain 79_MI18_10584 (6/49) and Mycobacterium elephantis (6/49). Several identified species, including M. intracellulare, M. fortuitum (5/49), M. kansasii (4/49), and M. avium, have caused infections in humans as well. NTMs in cattle lymph nodes without visible lesions suggest their asymptomatic persistence, albeit there being a possibility of transient colonization. Non-tuberculous mycobacteria complicate bovine tuberculosis (bTB) diagnostics by inducing cross-reactive immune responses and forming granulomatous lesions resembling those caused by Mycobacterium tuberculosis complex (MTBC). This study highlights the presence and diversity of NTMs in Indian cattle and emphasizes the need for better surveillance, improved molecular characterization, and better understanding of their epidemiological and immunological roles in both veterinary and public health contexts.
Insights
Non-tuberculous mycobacteria (NTM) are increasingly found in Indian cattle, complicating tuberculosis diagnostics. This study identified 18 NTM species, highlighting the need for better surveillance and understanding of their public health impact.
Area of Science:
- Veterinary Microbiology
- Public Health
- Molecular Diagnostics
Background:
- Non-tuberculous mycobacteria (NTM) are emerging pathogens with rising global incidence in human and animal health.
- Accurate prevalence data for NTM infections in India is scarce, hindering effective surveillance.
- NTM in cattle can interfere with bovine tuberculosis (bTB) diagnostics and surveillance.
Purpose of the Study:
- To characterize NTM species in cattle tissue samples from Chennai, India.
- To assess the diversity and prevalence of NTM in slaughtered cattle.
- To understand the implications of NTM in cattle for veterinary and public health.
Main Methods:
- Culture and targeted hsp65 gene sequencing of NTM isolates from cattle lymph node tissue.
- Polymerase Chain Reaction (PCR) for NTM confirmation.
- Molecular identification of NTM species.
Main Results:
- 49 out of 118 samples were confirmed as NTM, representing 18 different species.
- Mycobacterium intracellulare was the most frequent species (9/49), followed by Mycobacterium sp. strain 79_MI18_10584 and Mycobacterium elephantis (6/49 each).
- Identified NTM species, including M. intracellulare and M. fortuitum, are known human pathogens.
Conclusions:
- NTMs are present and diverse in Indian cattle, including in animals without visible lesions, suggesting asymptomatic persistence.
- The presence of NTMs complicates bTB diagnostics due to cross-reactive immune responses.
- Enhanced NTM surveillance, molecular characterization, and research into their epidemiological role are crucial for veterinary and public health in India.
