Discovery of the New Target for Identification of <i>Mycobacterium tuberculosis</i>

Masoud Keikha

doi:10.5812/ajcmi.14911

Discovery of the New Target for Identification of Mycobacterium tuberculosis

Masoud Keikha ^{1 , *}

Author Information

¹ Department of Microbiology, School of Medicine, Isfahan University of Medical Sciences, Isfahan, IR Iran

Article Notes and Dates

Avicenna Journal of Clinical Microbiology and Infection: November 2017, 4 (4); e14911.Published Online: November 29, 2017

Article Type: Letter; Received : June 9, 2017; Revised : October 23, 2017; Accepted : October 25, 2017
DOI: http://dx.doi.org/10.5812/ajcmi.14911

To Cite : Keikha M. Discovery of the New Target for Identification of Mycobacterium tuberculosis, Avicenna J Clin Microb Infec. 2017 ;4(4):e14911. doi: 10.5812/ajcmi.14911.

Copyright: Copyright © 2017, Avicenna Journal of Clinical Microbiology and Infection. This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International License (http://creativecommons.org/licenses/by-nc/4.0/) which permits copy and redistribute the material just in noncommercial usages, provided the original work is properly cited.

Dear Editor,

Tuberculosis has been one of the most important infectious diseases in human history, which causes deaths of 2 million people around the world annually (1). Inhalation of 1 - 3 bacillus Mycobacterium tuberculosis is sufficient for infection with this bacterium. According to the existing reports, almost one-third of the world's population is infected with M. tuberculosis, although they may not show any symptoms of this disease (2, 3). Due to the spread of HIV epidemics in the world, and emergence of the drug-resistant strains of Mycobacterium tuberculosis (DR-TB), eradication of tuberculosis is impossible (1).

One of the most important strategies of TB control is to identify those patients with active TB and to prevent transmission of infection from these patients to healthy people. In addition, patients with latent tuberculosis, who are infected with HIV are in fact the source of infection and should be identified and treated quickly (4, 5). Conventional methods for diagnosis of tuberculosis such as acid-fast staining, biochemical tests, and drug susceptibility testing are time-consuming, confusing, and require trained technicians. In addition, these methods are of poor accuracy and specificity in cases of extra-pulmonary tuberculosis (6, 7). Molecular methods, including hybridization techniques, DNA probes, and sequencing are more rapid and cheaper in comparison to culture and phenotypic tests. In addition, they can determine the antimicrobial susceptibility results before culture and traditional tests (6, 7). However, molecular tests on samples with low numbers of TB bacilli are usually false negative; this method could not distinguish between live microorganisms and dead bacteria. Consequently, these tests could not be used to evaluate the response to treatment. Moreover, in many of the developing countries, molecular techniques are not utilized due to high costs and the need for equipment. Therefore, the conventional method is known as the gold standard and the molecular techniques could be applied as complementary methods (8).

For molecular identification of Mycobacterium tuberculosis complex, some genes including IS6110, IS986, IS990, IS1081, mtb-40,dnaJ, groEl, and also those genes that code 32 KDa, 38 Kda, and 65 KDa proteins, devR response regulator gene, hupB, pncA, CYP141, and oxyR could be used (9, 10). IS elements such as IS6110 are the most important ones for detection of Mycobacterium tuberculosis strains, however, today it has become clear that IS6110 in Beijing strains (one of the most common strains of Mycobacterium tuberculosis in the world) lacks this gene. Mycobacterium bovis strains contain few copies of this gene that leads to limitations for detection of these strains. Additionally, the methods based on this IS element require a large amount of pure DNA and analysis of the results of these methods is time-consuming and requires trained personnel (10, 11). The mtp-40 and CYP 141 genes are not present in all members of the Mycobacterium tuberculosis strains and, therefore, are not useful for differentiating Mycobacterium tuberculosis from Mycobacterium bovis (10, 11). The gene for histone-like protein hupB of Mycobacterium tuberculosis has been identified as a target for differentiation of MTB complex and also polymorphisms in pncA and oxyR are good options for rapidly differentiate M. bovis from M. tuberculosis; thus, for rapid and reliable detection of Mycobacterium tuberculosis complex from clinical specimens, it is needed to study genes that are simply analyzed and are conserved (9-12).

In summary, in order to control tuberculosis, we require the rapid diagnosis of TB patients, who act as the source of disease. If remain untreated, these patients can spread the disease throughout the population. Therefore, we need to introduce and discover the new targets for quick and accurate identification of Mycobacterium tuberculosis strains, while it seems IS6110-RFLP and MIRU-VNTR typing are best methods for accurate identification, epidemiological study and genetic relationships between strains of Mycobacterium tuberculosis complex.

Footnotes

References

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Avicenna Journal of Clinical Microbiology and Infection

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Discovery of the New Target for Identification of Mycobacterium tuberculosis

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