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American Journal of www.biomedgrid.com Biomedical Science & Research ISSN: 2642-1747 --------------------------------------------------------------------------------------------------------------------------------- Review Article Copy Right@ Ayanwale O Abraham Mechanism of Drug Resistance in Mycobacterium Tuberculosis Ayanwale O Abraham*1, Adabara U Nasiru1, Adeniyi K Abdulazeez2, Oyewole O Seun3 and David W Ogonna4 1Department of Microbiology, Federal University of Technology, Nigeria 2Department of Animal Biology, Federal University of Technology, Nigeria 3Department of Microbiology, Obafemi Awolowo University, Nigeria 4Department of Biochemistry and molecular biology, Obafemi Awolowo University, Nigeria *Corresponding author: Ayanwale O Abraham, Department of Microbiology, Federal University of Technology, Nigeria. To Cite This Article: Ayanwale O Abraham, Mechanism of Drug Resistance in Mycobacterium Tuberculosis. 2020 - 7(5). AJBSR.MS.ID.001181. DOI: 10.34297/AJBSR.2020.07.001181. Received: February 05, 2020; Published: February 26, 2020 Summary Mycobacterium tuberculosis the causative agent of tuberculosis has many intrinsic features which enable it to evade the activity of antibiotics. Many studies have been carried out to understand the mechanisms of drug resistance by this organism. An attempt was made in this write up to Drug resistance in Mycobacterium tuberculosis is not a product of a single homogeneous genetic unit. Rather it is as a result of frequent mutation in variouselucidate genes the variouswhich encode mechanism for resistance of drug resistanceto antibiotics. in M. Also, tuberculosis, the slow metabolism including its during innate a prolongedimpermeable dormant cell wall stage and greatly mutation enhances of specific it resistance genes. Having an adequate knowledge on the molecular mechanisms of drug resistance in M. tuberculosis may be helpful in exploring new targets for drug development.to drug, the waxy impermeable cell wall with the presence of numerous efflux pump are essential for withstanding the potency of antibiotics. Keywords: Tuberculosis, Drug resistance, Antibiotic, Mycobacterium, Mechanism Introduction resistance, while a situation in which resistance developed due to Tuberculosis (TB) is an infectious disease caused by inadequacy of treatment is referred to as acquired resistance [2,3]. Mycobacterium tuberculosis. Streptomycin, with high bactericidal activity was the earliest curative agent used in its treatment. The complexity of the mechanisms used by M. tuberculosis in However, drug-resistant strains began to emerge few years later. drug resistance has led scientists to studying M. tuberculosis at Initially, this was thought to result mainly from using only single the molecular level. Various researchers have been able to identify drug, streptomycin, to treat the infection, prompting the use of some molecular features which have been attributed to drug multi-drug therapy for controlling the infection, but in recent resistance in the organism. When considering the mechanisms of decades multi-drug resistant (MDR) has emerged [1]. Furthermore, drug resistance in M. tuberculosis, it is imperative to understand the reports gave by World Health Organization in 2010 reveal two the interplay between the molecular mechanisms, adaptive features other more classes which are, extensively- drug resistant (XDR), and the innate attribute which play crucial role in resistant-MTB which is resistant to at least 4 of the core anti-TB drugs and totally- strain. Both [4] and Blair (2015), accentuated that drug resistance drug resistant (TDR) strains of TB. A type of TB resistance in people in Mycobacterium tuberculosis is not a single homogeneous who are originally infected by the antibiotics resistant strain but biological unit, thus suggesting that the complexity and severity of have not used any anti-TB chemotherapy is regarded as the primary resistance in the pathogen is due to some other intrinsic factors. This work is licensed under Creative Commons Attribution 4.0 License AJBSR.MS.ID.001181. 378 Am J Biomed Sci & Res Copy@ Ayanwale O Abraham cycle, a fundamental metabolic pathway [12]. This triacylglycerol resistance in M. tuberculosis, presenting a comparative review of is extensively produced by Mycobacterium tuberculosis when This study aims to present findings on the mechanism of drug the molecular mechanism, the adaptive features and the innate responding to diverse stress conditions such as oxygen deprivation, mechanisms through which the organism develop resistance to antitubacular drugs. the organism to grow under acidic condition is aided genetically acidic pH, and iron deficiency [13,14], observed that the ability of and not only limited to physiological adaptations. Mechanistic Innate Features of Drug Resistance Also, evaluating the metabolic status of the organism at each Impermeable Cell Wall stage of its pathogenesis is challenging since the organism can The fundamental characteristics of passive resistance to adapt to various microenvironment within the host. Furthermore, antibiotics in M. tuberculosis are due to its impermeable cell the extent of heterogeneity of infecting population in various wall [5]. M. tuberculosis has a cell wall that is composed of three cellular compartment within the same host adds to the challenges main components, these are: mycolic acids, Wax-D and the cord of targeting the metabolism processes [15] for therapeutic purpose. factors [6]. The hydrophilic arabinogalactan layer ensures the impermeability of the cell wall to hydrophobic chemicals. This Possession of Numerous Efflux Pumps layer is further contained in hydrophobic mycolic acids which This protein channels play crucial role in the normal metabolism extremely impede the entrance of hydrophilic molecules [7]. This and physiology of the organism such as signaling molecules across impermeability result in accumulation of antibiotics slowly around the cell wall, and toxins, waste, and nutrient transportation [16]. the cell, the accumulated drugs around the cell wall are slowly detoxify by different cellular component or by release of enzyme. Efflux pumps have also been shown to be adapted to drug resistance and outer membranes and serve as an outlet for antibiotics from in M. tuberculosis. Multidrug efflux pumps pass through the inner of peptidoglycan (rigidity structure) into the cell wall, are degraded [8], showed that β-lactams, which are inhibitive to the incorporation the cell [17]. Drug efflux pumps in M. tuberculosis have been found expression and thus specializing them for drug resistance roles by M. tuberculosis because it possesses β-lactamases, an enzyme to possess regulatory protein systems; which controls efflux pump [16]. thatDanilchanka effectively degrade O et al. β-lactam [7], reported antibiotics. the presence of an outer membrane channel protein CpnT in both M. tuberculosis and M. Molecular Mechanisms bovis, which performs a dual role of nutrient uptake and selective Acquisition of antibiotics resistance in M. tuberculosis has been susceptibility to antibacterial agents. The report showed that the shown to result from spontaneous mutation in several chromosomal CpnT mutant of M. bovis is more resistant to most antitubercular genes, this frequent mutation has been found to confer alteration to drugs, including the bactericidal nitric oxide, which is utilized in the required interaction between each anti-tuberculosis drug and controlling M. tuberculosis infection in mice. Slow Metabolism Mechanism Rifampicintheir specified target. Bacteria with slow metabolic processes and long generation This is a fundamental lipophilic annamycin chemotherapeutic agent initiated into the multi-drug treatment scheme of tuberculosis metabolically active and replicate quickly are good target for time are difficult target for most antibiotics i.e., bacteria that are antibiotics [9]. However, in M. tuberculosis, it is not still clear if the chemotherapy in the treatment of tuberculosis [18]. Rifampicin long generation time corroborate its drug resistance. According to in the 1970s. It is usually combined with isoniazid as the first line is known to have an inhibitory effect against slow and actively [10], the long generation time in M. tuberculosis does not impact growing tuberculosis [19]. Rifampicin mode of action is by binding drug resistance ability on the organism. [11]. Also reported a negative association between drug resistance and generation time of messenger RNA [20]. Rifampicin resistant strain of Mtb, usually in the organism. However, the slow growth rate of M. tuberculosis to the β-subunit of the RNA polymerase, inhibiting the elongation serve as an indicator for multi-drug resistant tuberculosis, because has been reported to play a key role in its drug resistance, for these strains are not sensitive to all other tubercular drugs Comas example, unstable antibiotics such as carbapenems loses their et al., (2011) [21]. activity at a faster rate than the mycobacterial growth rate [12], Resistance to rifampicin in M. tuberculosis have been found to grow in oxygen-deprived (stress) conditions, most of which are identified some specific genes which allow M. tuberculosis to directly involved in triacylglycerol production. Triacylglycerol be due to mutation in rpoB of RNA polymerase retarding affinity causes slowdown in the metabolic processes of Mycobacterium codon which can causes rifampicin resistance when mutation occur for rifampicin [20]. Some studies have been able to identify specific
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