AN OVERVIEW ON TUBERCULOSIS

Abstract:

Tuberculosis is a leading killer of young adults worldwide and the global scourge of multi-drug resistant tuberculosis is reaching epidemic proportions. It is endemic in most developing countries and resurgent in developed and developing countries with high rates of human immunodeficiency virus infection. This article reviews the current situation in terms of drug delivery approaches for tuberculosis chemotherapy. A number of novel implant-, microparticulate-, and various other carrier-based drug delivery systems incorporating the principal anti-tuberculosis agents have been fabricated that either target the site of tuberculosis infection or reduce the dosing frequency with the aim of improving patient outcomes. These developments in drug delivery represent attractive options with significant merit, however, there is a requisite to manufacture an oral system, which directly addresses issues of unacceptable rifampicin bioavailability in fixed-dose combinations. This is fostered by the need to deliver medications to patients more efficiently and with fewer side effects, especially in developing countries. The fabrication of a polymeric once-daily oral multiparticulate fixed-dose combination of the principal anti-tuberculosis drugs, which attains segregated delivery of rifampicin and isoniazid for improved rifampicin bioavailability, could be a step in the right direction in addressing issues of treatment failure due to patient non-compliance.

Introduction :

Tuberculosis (TB) is an infectious disease caused by bacteria whose scientific name is Mycobacterium tuberculosis. It was first isolated in 1882 by a German physician named Robert Koch who received the Nobel Prize for this discovery. TB most commonly affects the lungs but also can involve almost any organ of the body. Many years ago, this disease was referred to as "consumption" because without effective treatment, these patients often would waste away. Today, of course, tuberculosis usually can be treated successfully with antibiotics.

There is also a group of organisms referred to as atypical tuberculosis. These involve other types of bacteria that are in the Mycobacterium family. Often, these organisms do not cause disease and are referred to as "colonizers" because they simply live alongside other bacteria in our bodies without causing damage. At times, these bacteria can cause an infection that is sometimes clinically like typical tuberculosis. When these atypical mycobacteria cause infection, they are often very difficult to cure. Often, drug therapy for these organisms must be administered for one and a half to two years and requires multiple medications.One third of the world's population is thought to have been infected with  M.tuberculosis, and new infections occur at a rate of about one per second. In 2007 there were an estimated 13.7 million chronic active cases, and in 2010 there were 8.8 million new cases, and 1.5 million deaths, mostly in developing countries. The absolute number of tuberculosis cases has been decreasing since 2006 and new cases since 2002. In addition, more people in the developing world contract tuberculosis because their immune systems are more likely to be compromised due to higher rates of AIDS. The distribution of tuberculosis is not uniform across the globe; about 80% of the population in many Asian and African countries test positive in tuberculin tests, while only 5–10% of the U.S. population test positive.

Signs and Symptoms:

Main symptoms of variants and stages of tuberculosis with  many symptoms overlapping with other variants, while others are more (but not entirely) specific for certain variants. Multiple variants may be present simultaneously.Only about 5-10% of those without HIV, infected with tuberculosis develop active disease during their lifetime. In contrast 30% of those co-infected with HIV develop active disease. Tuberculosis may infect any part of the body but most commonly occurs in the lungs (known as pulmonary tuberculosis). Extra pulmonary TB is when tuberculosis occurs outside of the lungs and may co-exist with pulmonary TB. General symptoms such as: fever, chills, night sweats, appetite loss, weight loss, fatigue, and finger clubbing may also occur.

Diagnosis :

Mycobacterium tuberculosis(stained red) in sputum
Diagnosing tuberculosis based on signs and symptoms is difficult. A definitive diagnosis is made by identifying the causative organism (Mycobacterium tuberculosis) in a clinical sample (for example, sputum or pus). When this is not possible, a probable—although sometimes inconclusive—diagnosis may be made using imaging (X-rays or scans), a tuberculin skin test (Mantoux test), or a, Interferon Gamma Release Assay (IGRA).

 Mantoux tuberculin skin test

Mantoux tuberculin skin tests are often used for routine screening of high risk individuals. Currently, latent infection is diagnosed in a non-immunized person by a tuberculin skin test, which yields a delayed hypersensitivity type response to an extract made from M. tuberculosis Those immunized for TB or with past-cleared infection will respond with delayed hypersensitivity parallel to those currently in a state of infection, so the test must be used with caution, particularly with regard to persons from countries where TB immunization is common.

Prevention
Tuberculosis prevention and control efforts primarily rely on the vaccination of infants and the detection and appropriate treatment of active cases. The World Health Organization has achieved some success with improved treatment success and a small decrease in case numbers.

Vaccines
The only currently available vaccine as of 2011 is Bacillus Calmette-Guérin (BCG) which while effective against disseminated disease in childhood, confers inconsistent protection against pulmonary disease. It is the most widely used vaccine worldwide with more than 90% of children vaccinated However the immunity that it induces, decreases after about ten years.

Public Health

The World Health Organization (WHO) declared TB a global health emergency in 1993  and in 2006 the Stop TB Partnership developed a Global Plan to Stop Tuberculosis that aims to save 14 million lives between its launch and 2015. A number of targets that they have set are not likely to be achieved by 2015 due to the increase in HIV associated tuberculosis and multi-drug resistant tuberculosis.