Non-Tuberculosis mycobacterium speciation using HPLC under Revised National TB Control Programme (RNTCP) in India

Global Epidemiology of Nontuberculous Mycobacterial Pulmonary Disease: A Review

Nontuberculous mycobacterial (NTM) isolation and pulmonary disease (NTM-PD) have continued to increase in most regions of the world, driven mainly by Mycobacterium avium. Single-center studies also support increasing trends as well as a persistent burden of undiagnosed NTM among persons suspected of having tuberculosis (TB), in countries with moderate-to-high TB prevalence. Cumulative exposure to water and soil presents an increased risk to susceptible hosts, and trace metals in water supply are recently recognized risk factors. Establishing standard case definitions for subnational and national surveillance systems with mandatory notification of NTM-PD are needed to allow comparisons within and across countries and regions.

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 Mycobacterium kansasii using a combination of loop-mediated isothermal amplification (LAMP) and lateral flow biosensors

Mycobacterium kansasii is an opportunistic pathogen that causes both intrapulmonary and extrapulmonary infections. The symptoms of the pulmonary diseases caused by M. kansasii closely resemble Mycobacterium tuberculosis. Rapid and accurate differentiation of M. kansasii from M. tuberculosis, as well as other mycobacteria, is crucial for developing effective therapeutics and disease treatment. In this study, we combined loop-mediated isothermal amplification (LAMP) with lateral flow biosensors (LFB) to detect M. kansasii, by targeting the species-specific sequence of rpoB, a gene which encodes the β subunit of bacterial RNA polymerase. The assay was validated to ensure that it was highly selective by testing M. kansasii, M. tuberculosis, other species of respiratory bacteria, and other nontuberculous mycobacteria. The detection limit of the assay was 1 fg/μL of DNA and 50 CFU of bacilli in sputum. The M. kansasii-LAMP-LFB assay is a fast, cheap, and accurate method for detecting M. kansasii by constant temperature amplification and simple interpretation.

Diagnostic performance of real time PCR and MALDI-TOF in the detection of nontuberculous mycobacteria from clinical isolates

This study aimed to evaluate the performance of real-time PCR (qPCR) and MALDI-TOF for accurate and timely detection of nontuberculous mycobacterium (NTM) from clinical isolates. We collected fifty NTM suspected Mycobacteria Growth Indicator Tube (MGIT) cultures and analysed the diagnostic performance of qPCR and VITEK MS using Line Probe Assay (LPA) GenoType CM (Common Mycobacteria) as gold standard. The qPCR assays targeting 16S rRNA, ITS and IS6110 genes were developed for the identification of NTM and Mycobacterium tuberculosis complex (MTBC). LPA GenoType CM, a PCR technique targeting 23S rRNA gene, followed by reverse hybridization and line probe technology identified 90% of Mycobacterium species including M. fortuitum (16%,n = 8), M. intracellulare (10%,n = 5), M. gordonae (10%,n = 5), M. xenopi (4%,n = 2), M. scrofulaceum (4%,n = 2), Mycobacterium additional species (AS) (32%,n = 16) and MTBC (14%,n = 7), qPCR detected 80% of Mycobacterium species (NTM, 66% (n = 33) and MTBC, 14% (n = 7)) and MALDI-TOF, 52% (M. fortuitum (12%,n = 6), M. intracellulare (10%, n = 5), M. simiae (8%,n = 4), M. gordonae (8%,n = 4), and MTBC (14%,n = 7)). Sensitivity of qPCR and MALDI-TOF was 88.9% and 57.8%, respectively with 100% specificity. The combination of qPCR and MALDI-TOF remains an appropriate test for timely diagnosis of Mycobacterium species. This may eventually assist to detect the cases that may have been missed by phenotypic tests and enhance the NTM diagnosis capability to improve effective patient management.

Of tuberculosis and non-tuberculous mycobacterial infections - a comparative analysis of epidemiology, diagnosis and treatment

Pulmonary diseases due to mycobacteria cause significant morbidity and mortality to human health. In addition to tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), recent epidemiological studies have shown the emergence of non-tuberculous mycobacteria (NTM) species in causing lung diseases in humans. Although more than 170 NTM species are present in various environmental niches, only a handful, primarily Mycobacterium avium complex and M. abscessus, have been implicated in pulmonary disease. While TB is transmitted through inhalation of aerosol droplets containing Mtb, generated by patients with symptomatic disease, NTM disease is mostly disseminated through aerosols originated from the environment. However, following inhalation, both Mtb and NTM are phagocytosed by alveolar macrophages in the lungs. Subsequently, various immune cells are recruited from the circulation to the site of infection, which leads to granuloma formation. Although the pathophysiology of TB and NTM diseases share several fundamental cellular and molecular events, the host-susceptibility to Mtb and NTM infections are different. Striking differences also exist in the disease presentation between TB and NTM cases. While NTM disease is primarily associated with bronchiectasis, this condition is rarely a predisposing factor for TB. Similarly, in Human Immunodeficiency Virus (HIV)-infected individuals, NTM disease presents as disseminated, extrapulmonary form rather than as a miliary, pulmonary disease, which is seen in Mtb infection. The diagnostic modalities for TB, including molecular diagnosis and drug-susceptibility testing (DST), are more advanced and possess a higher rate of sensitivity and specificity, compared to the tools available for NTM infections. In general, drug-sensitive TB is effectively treated with a standard multi-drug regimen containing well-defined first- and second-line antibiotics. However, the treatment of drug-resistant TB requires the additional, newer class of antibiotics in combination with or without the first and second-line drugs. In contrast, the NTM species display significant heterogeneity in their susceptibility to standard anti-TB drugs. Thus, the treatment for NTM diseases usually involves the use of macrolides and injectable aminoglycosides. Although well-established international guidelines are available, treatment of NTM disease is mostly empirical and not entirely successful. In general, the treatment duration is much longer for NTM diseases, compared to TB, and resection surgery of affected organ(s) is part of treatment for patients with NTM diseases that do not respond to the antibiotics treatment. Here, we discuss the epidemiology, diagnosis, and treatment modalities available for TB and NTM diseases of humans.

A prospective study of non-tuberculous mycobacterial disease among tuberculosis suspects at a tertiary care centre in north India

Background & objectives

The burden of non-tuberculous mycobacterial (NTM) disease is increasing worldwide. The disease shares clinicoradiological features with tuberculosis (TB), Nocardia and several fungal diseases, and its diagnosis is frequently delayed. The present study was performed to determine the frequency of NTM disease among TB suspects in a tertiary care centre in north India.

Methods

In this prospective study, mycobacterial culture isolates from pulmonary and extrapulmonary specimens among TB suspects were tested with immunochromatographic assay (ICA). All ICA-negative isolates were considered as NTM suspects and further subjected to 16S-23S rRNA internal transcribed spacer gene sequencing for confirmation and species identification. Patients with active disease were treated with drug regimen as per the identified NTM species. Follow up of patients was done to determine clinical, radiological and microbiological outcomes.

Results

Of the 5409 TB suspects, 42 (0.77%) were diagnosed with NTM disease. Patients with active disease consenting for treatment were treated and followed up. Thirty four patients had NTM pulmonary disease (NTM-PD) and the remaining eight had extrapulmonary NTM (EP-NTM) disease. Mycobacterium intracellulare and M. abscessus, respectively, were most frequently isolated from NTM-PD and EP-NTM patients. Fifteen NTM-PD and seven EP-NTM patients successfully completed the treatment. Ten patients died due to unrelated causes, five were lost to follow up and another four declined the treatment.

Interpretation & conclusions

Our study showed that the frequency of NTM disease was low among TB suspects at a large tertiary care centre in north India and this finding was similar to other Indian studies. More studies need to be done in other parts of the country to know the geographical variation in NTM disease, if any.