**16. Recent developments in diagnostic approaches for tuberculosis**

It is not easy to conduct a clinal diagnosis of tuberculosis very frequently as confirmed diagnosis requires culturing the bacteria *M. tuberculosis* in a sample from the patient [5] and which is very slow-growing. For lung diseases, we take morning sputum for culture purpose and microscopic studies. We also have to do Biopsies of the affected tissues, because that will provide us with a sample for culture and also for looking histologically for the characteristic presence of granulomas [53]. Mycobacterial culture confirms the presence of mycobacterium in given samples by microscopy analysis, and we may also draw the resistance profile i.e., whether the present strain belongs to the sensitive *M. tuberculosis* group or has resistance to some drugs that can be used to treat it. The major obstacles in culture MTB are that it is slow-growing bacteria and may take 3–4 weeks in liquid culture media [51]. The acid-fast bacilli of mycobacterial infection are detected by the microscopy analysis whereas latent tuberculosis disease is identified by immunological responses to tuberculosis antigens, i.e., i) Heaf test / Montoux: cofounded by BCG ii) Interferon Gamma Release Assays (IGRA) [48, 49]. There are some tools developed recently for the detection of drug-resistant MTB that facilitates early detection too, such GeneXpert, line prob. assay, LAMP assay etc.

#### **16.1 GeneXpert**

GeneXpert can detect mutations that cause resistance against Rifampicin. The test is a molecular TB test that detects the DNA of *Mycobacterium tuberculosis*. It uses a sputum sample and thus provides result in less than 2 hours. It can also detect the genetic mutations which are associated with drug Rifampicin resistance [65]. WHO recommended that this test should be used as the primitive diagnosis test in individuals suspected of having Multi-drug resistant TB, or HIV associated TB.

#### **16.2 Line probe assay (LPA)**

This technique also helps to detects mutations causing resistance against Rifampicin. Moreover, this assay can also detect mutations related to drug isoniazid [66]. The line probe assay (LPA), is typically based on strip technology and thus is used in the diagnosis of TB. It also detects RIF as well as Isoniazid (INH) resistance caused due to mutations in *rpo*β, and both *inhA* and *katG* genes.

#### **16.3 Loop-mediated isothermal amplification (LAMP) assay**

WHO has recommended the TB-LAMP (loop-mediated isothermal amplification) test that requires minimal laboratory infrastructure and has been evaluated as an alternative to sputum smear microscopy, which remains the most widespread test used in resource-limited environments. TB-LAMP is a unique temperatureindependent way to amplify the DNA of tuberculosis patients. It is a manual test that takes less than one hour and results can be visualized with the naked eye under UV light. The potent TB-LAMP instrument can be used at the level of the peripheral health center where microscopy is often performed. (https://www.who.int/tb/ features\_archive/TB\_LAMP/en/).

**23**

*Challenges in Drug Discovery against Tuberculosis DOI: http://dx.doi.org/10.5772/intechopen.97857*

At present treatment of tuberculosis requires more than one antibiotic with prolonged combination therapies to eradicate the infection and prevent resistance [58] and the standard therapy may include 4 antibiotics i.e., Isoniazid & Rifampicin (most effective drugs and these are given for six months and thus these two helps in killing the bacteria), Pyrazinamide & Ethambutol (given for first two months only) [67, 68]. During treatment antibiotics are required for a long period, the minimum treatment period is six months and if the patient is having CNS or bone disease it often goes on for at least 12 months [69]. The patient is asked to take four drugs for two months and then followed by two drugs for four months, and the actual dose given to the patient is decided by their body weight such as if a patient is lower than 50 kg, they get a lower

Corticosteroids are given to patients with CNS or pericardial disease because this reduces the further chances of having long term brain damage. All the cases need to be monitored and notified so that there can be a screening process of the patient's

*M. tuberculosis* is a difficult pathogen to combat and the frontline drugs currently in use are between 40 and 60 years of age. There is an urgent need of novel tuberculosis drugs, but the time to identify, develop and ultimately advance new drug regimens on the market has been extremely slow in the past decade. Organic biochemistry remains to be performed to know the mechanism of activity, to

empower lead advancement, and to ensure in vivo effectiveness [20]. Current efforts to develop drugs against tuberculosis are not enough to end the global tuberculosis epidemic. Due to the diversification and complexity of the infection for *M tuberculosis*, no model can completely define the in-vivo conditions in which mycobacteria are found in Tuberculosis patients and there is no sole standard detection condition for generating successful compounds for tuberculosis drug development*.* Recent efforts have focused on the development of whole-cell screening trials because objectivebased biochemical screens of inhibitors over the past two decades have not provided new tuberculosis drugs [68]. There are significant challenges in the discovery of antituberculosis drugs due to the nature of the causative bacteria. The lack of predictive models for the entry of compounds into mycobacteria is also a limiting factor. Several additional barriers in the development of tuberculosis drugs include: there are no well-established (PK)– (PD) paradigms, lack of validation and human-like pathology of animal models currently available for drug discovery, lack of clinical laboratories suitable for clinical trials, and the lack of adequate research funds. The biggest challenge in the development of anti-tuberculosis drugs is to reduce the duration of treatment for patients with drug-sensitive tuberculosis [18]. Noval drugs are needed to achieve this and overcome drug resistance. In addition, it should be possible to use new drugs for patients with HIV/AIDS co-infection. The present condition of tuberculosis drug development is far better than what was seen past 10–15 years ago. Howsoever, the development is still lacking behind because of the significant challenges in the drug discovery against drug-resistant tuberculosis and the shorter duration of the treatment required for tuberculosis prevention [12, 13]. We need to identify essential Tuberculosis targets based on better knowledge of the disease pathogen and physiology, develop sharp screening trials, and prepare compounds specifically designed to provide better clues for antibacterial activities [11].

dose while if the patient is above 50 kg, they get a higher dose [13].

**17. Available treatment**

close contacts as well [14, 17].

**18. Conclusion**
