Origin And Effects Of Tuberculosis Biology Essay

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The main mycobacterial infections in humans are tuberculosis and leprosy both typically chronic infections; caused respectively by Mycobacterium tuberculosis and Mycobacterium leprae. Tuberculosis was for centuries a major killer disease, less then 40 years ago, new drugs were developed and put to use and tuberculosis came to be seen as an easily curable infection. It is characterized as a chronic bacterial infect ion caused by Mycobacterium tuberculosis, Tuberculosis is a major threat; killing about 2 million people each year. The World Health Organization estimates that 1 billion people will be newly infected in the period 2000-2020, resulting in 35 million more deaths. TB is currently the leading killer of youths, women, and AIDS patients in the world41 . The bacillus causing tuberculosis, Mycobacterium tuberculosis, was identified and described on March 24, 1882 by Robert Koch.Mycobacterium tuberculosi s is transmi t ted primari ly via the respi ratory route . M. tuberculosis var hominis is an aerobic organism, a non-motile bacillus 1-2 µm long and 0.3 - 0.6µ m wide.

The organism appears in water droplets expel led during coughing, sneezing, or talking. Either in the droplet form or as the desiccated ai rborne bacil l i, the organism enters the respi ratory tract . The infectiousness of an individual will depend on the extent of the disease, the number of organisms in the sputum, and the amount of coughing. TB is a disease that mainly af fects the lungs (80-85% of the cases).

Because of the effect of the AIDS virus on the immune system, all HIV-infected individuals should be screened for TB, and if infected, the patient should be treated for TB before an active

infections develops. Patients with HIV infection and TB are 100-fold more likely of developing an active infect ion than noninfected patients. Individuals diagnosed with active TB should be counseled and tested for HIV, because the TB may have developed in conjunct ion with the weakened immune system seen in the patient with HIV infection.

The situation has become more critical because of the presence of some complicating factors like, emergence of multi-drug resistant tuberculosis8, HIV co- infection6, lack of patient compliance with chemotherapy, and variable efficacy of Bacilli- Calmette Guerin (BCG) vaccine. Multi drug resistant tuberculosis is defined as disease due to M. tuberculosis that is resistant to Isoniazide and Rifampicin with or without resistance to other drugs. In the years to come tuberculosis is bound to be an important health problem, particularly in immuno-compromised host.

Mycobacterium Avium-Intra cellulare Complex (MAC)

Mycobacterium avium and Mycobacterium intracel lulare are atypical acid-fast bacilli that are ubliquitous in the environment and usually considered to be nonpathogenic in healthy individuals.

Unfottunately, in immune-compromised individuals, these and possibly other, unidentified

mycobacteria cause severe, l fe-threatening infect ions. Disseminated Mycobacterium avium-

intracel lulare complex (MAC) is the most common bacterial opportunisic infection seen in

patients with AIDS and the third most common opportunistic infect ion behind candidal esophagitis and primary Pneumocystis carinii pneumonia reported in pat ients with AIDS.

Today, approximately half of al patients with AIDS develop an infect ion caused by MAC. The lungs are the organs most commonly involved in patients without AIDS, but the infection may involve bone marrow, lymph nodes, liver, and blood in patients wth AIDS. The

CD4 T-lymphocyte count is used as a predictor for risk of disseminated MAC; a count of less than 50 cells/mm3 in an HIV-infected person (adult or adolescent) is an indication of a potential infection and a recommendation for chemoprophylaxis. The MAC organisms grow within macrophages; therefore, the drug must be capable of penetration of the macrophage. Treatment of MAC, both prophylactical ly and for diagnosed infect ions, requires the use of multidrug.

Current Tuberculosis Drug Therapy

Treatment of tuberculosis is classified into two major categories:

"First line" agents combine the greatest level of efficacy with an acceptable degree of toxicity; these include Isoniazid (INH), Rifampin (RIF), Ethambutol (EMB), Streptomycin (STM) and Pyrazinamide (PZA). The large majority of patients with tuberculosis can be treated successfully with these drugs.

Occasionally however, because of microbial resistance or patient related factors, it may be necessary to resort to a "Second line" of drugs; This category of agents includes. p-amino salicylic acid (PAS), Kanamycin, Cycloserine (CS), Ethionamide (ETA), Amikacin, Capreomycin, Thiacetazone, Fluoroquinolones, etc.

A major advances in treatment of tuberculosis was signaled by introduction of antibiotic rifampicin in to therapy.Clinical studies indicated that when rifampicin included in regimen particularly with isoniazide and ethambutol (or pyrazinamide) the period requird for successful therapy is shortened significantly….

Current tuberculosis therapy known as DOTs (directly observed treatment, short course) consist of an initial phase of treatment with 4 drugs, INH, RIF, PZA and EMB, for 2 months daily, followed by treatment with INH and RIF for another 4 months, three times a week.

Antituberculosis a ctivity

Composition Nutrient Broth

Ingredients Gms / Litre

Peptic digest of animal tissue 5g

Sodium chloride 5g

Beef extract 1.5g

Yeast extract 1.5g

Final pH ( at 25°C) 7.4±0.2

Composition of Muller hinton agar

Ingredients Gms / Litre

Beef Extract...............................................................................2 g

Acid Hydrolysate of Casein......................................................17.5 g

Starch..................................................................................... 1.5 g

Agar.........................................................................................17 g

Final pH 7.3 ± 0.1 at 25°C

Methods for antibacterial stability test

The standard Kirby-Bauer disk diffusion method was used to determine the antimicrobial chemicals. The M.tuberculosis strain were inoculated in nutrient broth and incubated at 37° C for overnight. After overnight incubation, the bacterial culture was swapped in solidified Muller hinton agar plate and made wells of 6mm diameter were punched in the plate. Then add different concentration of chemicals was dispensed in separate wells such as 2.5mg, 5mg, 7.5 and 10mg and add 100 µl of DMSO to

centre well as control. The plates were incubated at 37° C for 24 hour. After incubation, the diameter of zone of inhibition around the wells were measured and recorded.




Con. Of chemicals (Inhibition Zone in mm)

2.5 mg












2 .




























All chemicals dissolved in DMSO (100mg/1ml) and add different dilutions of chemicals in each well (2.5mg, 5mg, 7.5mg and 10 mg)

Control - DMSO as a control

-- indicate as negative (None zone)