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Tuberculosis essay

Categories: BiologyTuberculosis

First, I would like to thank God for giving me enough knowledge, strength, and guidance to be able to finish this term paper. And also I would like to thank my cousins for helping and giving me some information about this. To my family for being my inspiration.

To my uncle/auntie for giving financial support.
To the authors of Wikipedia or Google and reference book that contribute a lot for making this term paper. And lastly to my Instructor Mr.

Lacdao for checking my typographical error. Dedication I dedicate this research work to my subject teacher who never failed to teach and guide me, to my family who supports me in everything, to my friends who helped me finished this project, and most of all to the Almighty God who gives me strength and good health while doing this.

“We have a unique historic opportunity to stop Tuberculosis, but we must act now. The challenge now is for people to work together in putting the plan into action, in order to stop one of the oldest and most lethal diseases known to humanity.

This plan tells the world exactly what we need to do in order to defeat this global killer.” (Dr. Marcos Espinal)


Tuberculosis has been present in humans since antiquity. The earliest unambiguous detection of “mycobacterium tuberculosis” is in the remains of bison dated 18,000 years before the present. Whether tuberculosis originated in cattle and then transferred to humans, or diverged from a common ancestor infecting a different species, is currently unclear.

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However, it is clear that “M.Tuberculosis” is not directly descended from “M.bovis”, which seems to have evolved relatively recently. Skeletal remains from a Neolithic Settlement in the Eastern Mediterranean show prehistoric humans (7000BC) had TB, and tubercular decay has been found in the spines of mummies from 3000-2400BC. Phthisis is a geek terms for tuberculosis; around 460 BC, Hippocrates identified phthisis as the most widespread disease of the times involving coughing up blood and fever, which was almost fatal. In South America, the earliest evidence of tuberculosis is associated with Paracas-Caverna culture (circa 750 BC to circa 180 AD). In the past, tuberculosis has been called consumption, because it seen to consume people from within, with a bloody cough, fever, pallor, and all relentless wasting.

Other names included “Phthisis” (Greek from consumption) and “Phthisis pulmonalis”, scrofula (in adults), afeecting the lymphatic system and resulting in swollen neck glands; “Tabes mesenterica”, TB of the abdomen and “lupus vulgaris”, TB of the skin: wasting disease; white plague, because sufferers appear markedly pale; king’s evil, because it was believe that the king’s touch would heal scrofula; and Pot’s disease, or gibbous of the spine and joints. Tuberculosis is said to be one of the world’s most infectious disease that can affect our lives. And Dr. Marcos Espinal is right, we need to work together to prevent the spread disease which is according to him is a global killer. This term paper can help us to become knowledgeable about this particular disease. We will be able to determine how infectious and dangerous the tuberculosis is. We will become well informed for this global killer. __________

What is tuberculosis?

Tuberculosis, MTB, TB (short for tubercle bacillus) is a common, and in many cases lethal, infectious disease caused by various strains of mycobacteria, usually Mycobacteria tuberculosis. One of the most important infectious diseases of the world, and one that has made its impact felt down through the ages. It is spread through the air when people who have an active MTB infection cough sneeze, or otherwise transmit their saliva through the air.

What are the signs and symptoms of tuberculosis?
Most people who become infected with the bacteria that cause tuberculosis actually do not present symptoms if the disease. However, when symptoms are present they include: Unexplained weight loss
Shortness of breath
Loss of appetite
Symptoms specific to the lungs include:
Coughing that last for 3 or more weeks
Coughing up blood
Chest pain with breathing or coughing
Classic symptoms
Night sweats
Only 5 – 10% of those infected with tuberculosis, without HIV develop active disease. In contrast 30% of those co-infected with HIV develop active disease. Extra pulmonary TB may co-exist with pulmonary TB. _________

Encyclopedia Britannica, Volume 27

What are the causes of tuberculosis?
The main cause of TB is Mycobacterium tuberculosis, a small aerobic non-motile bacillus or less commonly the closely related Mycobacterium bovis. The high lipid content of this pathogen accounts for many of its unique clinical characteristics every 16 to 20 hours, an extremely slow rate compared with other bacteria, which usually divide in less than an hour. Since MTB has a cell wall but lacks a phospholipids outer membrane, it is classified as a Gram positive bacterium.

However, if a Gram stain is performed, MTB either stains very weakly Gram positive or does not retain dye as a result of the high lipid and mycolic acid content of its cell wall. MTB can withstand weak disinfectants and survive in a dry state for weeks. In nature, the bacterium can grow only within the cells of a host organism, but M.Tuberculosis can be cultured in the laboratory. The M.Tuberculosis is complex includes four other TB – causing mycobacteria:

M.africanum is not widespread, but in parts of Africa it is a significant cause of tuberculosis. M.bovis was once a common cause of tuberculosis, but the introduction of pasteurized milk has largely eliminated this as a public health problem in developed countries. M.Canetti is rare and seems to be limited to Africa, although a few cases have been seen in African emigrants. M.Microti is mostly seen in immunodeficient people, although it is possible that the prevalence of this pathogen has been underestimated.

Other known pathogenic mycobacterium includes Mycobacterium leprae, Mycobacterium avium, and Mycobacterium kansasii. The latter two are part of the nontuberculous mycobacteria. (NTM) group. Nontuberculous mycobacteria cause neither TB nor leprosy, but they do cause pulmonary diseases resembling TB.

________ Effects of tuberculosis on lung tissue
Tuberculosis, an airborne disease caused by Mycobacterium tuberculosis, primarily affects the lungs though it can spread to other organs. More than 13,000 new cases of tuberculosis were reported in the United States in 2007, according to Merck Manuals Online Medical Library. Tuberculosis affects the lungs tissues in many ways, depending on the severity of the disease. Scarring

In latent TB, a dormant from of tuberculosis, bacteria breathed into the lungs are surrounded by white blood cells. If the white blood cells, called macrophages, contain the infection, bacteria remain walled off in the areas called granulomas and active infection doesn’t develop. Small scars appear in the lungs where the bacteria are walled off. Immune substances released from the soft, crumbly center kill off most of the bacteria, although some may remain.

Tuberculosis Pleurisy
If the granuloma ruptures and leaks fluid into the space between the lung and the chest wall, called the pleural cavity, tuberculosis pleurisy can develop. Fluid within the space increases, causing shortness of breath and chest pain that worsens when the person breathes in. Most cases resolve spontaneously but about two-thirds will develop active tuberculosis pleurisy within five years, reports.

Cavity Formation
The bacteria in the lungs may re-activate if the immunes system is damaged by disease such as alcoholism or malnutrition, by treatments such as chemotherapy or by prolonged use of medications such as corticosteroids that cause immune suppression. Advanced age can also impair the immune system and cause re-activation of latent TB. When this happens, granuloma starts to break down and liquefied material escapes in the airway.

A cavity forms in the lung, which allows oxygen and carbon dioxide to enter. Since these provide an excellent medium for bacterial growth, the TB bacteria reproduce rapidly. Cavity formation causes destruction of lung tissue, with coughing, spitting up blood, fever, night sweats and weight loss. People with cavity TB are very contagious, a Health community warns.

Nodule Formation
In military TB, small nodules that look like millet seeds from throughout the lung shortly after the initial infection. The chest X-ray may initially appear normal, making diagnosis difficult. Military TB is a serious form of TB that can result in death.



When people with active pulmonary TB cough, sneeze, speak, sing, or spit, they expel infectious aerosol droplets 0.5 to 5 µm in diameter. A single sneeze can release up to 40,000 droplets. Each one of these droplets may transmit the disease, since the infectious dose of tuberculosis is very low
and inhaling fewer that ten bacteria may cause an infection.

People with prolonged, frequent, or intense contact are particularly high risk of becoming infected, with an estimated 22% infection rate. A person with active but untreated tuberculosis can infect 10-15 other people per year. Others at risk include people in areas where TB is common, people who inject illicit drugs, residents and employees of high-risk congregate settings, medically under-served and low-income populations, high-risk racial or ethnic minority populations, children exposed to adults in in high-risk categories, those who are immunocompromised by conditions such as HIV/AIDS, people who take immunosuppressant drugs, and health care workers serving these high-risk clients.

Transmission can only occur from people with active –not latent—TB. The probability of transmission from one person to another depends upon the number of infectious droplets expelled by carrier, the effectiveness if ventilation, the duration of exposure, and the virulence of the Mycobacteria tuberculosis strain. The chain of transmission can be broken by isolating people with active disease and starting effective anti-tuberculosis therapy. After two weeks of such treatment, people with non-resistant active TB generally cause to be contagious. If someone does become infected, then it will take three to four weeks before the newly infected person can transmit the disease to others.

About 90% of those infected with mycobacterium tuberculosis have symptomatic, latent TB infection (sometimes called LTBI), with only a 10% lifetime chance that a latent infection will progress to TB disease. However, if untreated, the death rate for this active TB cases is more than 50%. TB infection begins when the mycobacteria reach the pulmonary alveoli, where they invade and replicate within the endosomes of alveolar macrophages. The primary site of infection in the lungs in the lungs is called the Ghon focus, and is generally located in either the upper part of the lower lobe, or the lower part of the upper lobe. Simon foci may also be present.

Bacteria are picked up by dendritic cells, which do not allow replication, although these cells can transport the bacilli to local (mediastina) lymph nodes. Further spread is through the bloodstream to other tissues and organs where secondary TB lesions can develop in other parts of the lung (particularly the apex of the upper lobes), peripheral lymph nodes, kidneys, brain and bone. All parts of the body can be affected by the disease, though it rarely affects the heart, skeletal muscles, pancreas and thyroid.

Tuberculosis is classified as one of the granulomatous inflammatory conditions. Macrophages, T lymphocytes, B lymphocytes, and fibroblasts are among the cells that aggregate to form granulomas, with lymphocytes surrounding the infected macrophages. The granuloma prevents dissemination of the mycobacteria and provides a local environment for interaction of cells of the immune system. Bacteria inside the granuloma can be dormant, resulting in a latent infection. Another feature of the granulomas of human tuberculosis is the development of abnormal cell death (necrosis) in the center of the tubercles. To the naked eye this has the texture of soft white cheese and is termed caseous necrosis.

Tuberculosis is diagnosed definitely by identifying the causative organism (mycobacterium tuberculosis) in a clinical sample (sputum or pus). Diagnosis may be made using imaging. (X-rays or scans) o tuberculin skin test. (manteaux test) or a interfen Gamma Release Assay (IGRA) A complete medical evaluation for TB must include:

Medical history
Physical examination
Chest X-ray
Microbiological smears
It may also include a tuberculin skin test, a serological test. The interpretation of the tuberculin skin test depends upon the person’s risk factors for infection and progression to TB disease, such as exposure to
other cases of TB or immunosuppression. New TB tests have been developed that are fast and accurate. These include polymerase chain reaction assays for the detection of bacterial DNA. One such molecular diagnostics test gives result in 100 minutes and is currently being offered to 116 low-and-middle-income countries at a discount with support from WHO and the Bill and Melinda Gates Foundation. Another such test, which was approved by the FDA in 1996, is the amplified mycobacterium tuberculosis direct test (MTD, Gen-Probe). This test yields results in 2.5 to 3.5 hours, and it is highly sensitive and specific when used to test smears positive for acid-fast bacilli (AFB). Screening

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 Mycobacterium tuberculosis. _______
Treatment for TB depends on the whether the disease is active of latent. If TB is in an active state, an antibiotic called isoniazid, (INH) is prescribed for six to twelve months. INH is not prescribed to pregnant women, and it can cause side effects such as liver damage and peripheral neuropathy. Active TB is treated with INH as well as drugs such as rifampin, ethambutol, and pyrazinamide. It is also not uncommon for TB patients to receive streptomycin if the disease is extensive. Drugs therapies for TB may last many months or even years.

If a patient has a drug-resistant strain of TB, several drugs in addition to the main four are usually required. In addition, treatment is generally much longer and can require surgery to remove damage lung tissue. The largest barrier to successful treatment is the patients tend to stop taking their medicines because they begin to feel better. It is important to finish medications in order to completely eradicate the TB bacteria from the body. Risk Factors

There are number factors that make people more susceptible to TB infections.

Worldwide the most important of these is HIV with co-infection present in about 13% of cases. This is a particular problem in Sub-Saharan Africa where rates of HIV are high. Tuberculosis is closely linked to both overcrowding and malnutrition making it one of the principal diseases of poverty. Chronic lung disease is a risk by two to four times and silicosis increasing the risk about 30 fold. Other disease states that increase the risk of developing tuberculosis include alcoholism and diabetes mellitus (threefold increase).

Certain medications such as corticosteroids and infliximab (an anti-a TNF monoclonal antibody) are becoming increasingly important risk factors, especially in the developed world. There is also a genetic susceptibility for which overall importance is still undefined. Tuberculosis is spread from person to person through tiny droplets of infected sputum that travel through the air. If an infected person coughs, sneezes, shouts, or spits, bacteria can enter the air and come into contact with uninfected people who breathe the bacteria into their lungs.

Although anyone can become infected with TB, some people are at a higher risk, such as: Those who live with others who have active TB infections
Poor or homeless people
Foreign-born people who come from countries with endemic TB
Older people, nursing home residents, and prison inmates
Alcoholics and intravenous drug users
Those who suffer from malnutrition
Diabetics, cancer patients and those with HIV/AIDS or other immune systems problems Health-care workers
Workers in refugee camps or shelter
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. Vaccine

There is a vaccine available for tuberculosis called BCG vaccine that is used in several parts of the world where TB is common. This vaccine usually protects children and infants from the disease, but adults can still get TB after being vaccinated as children. 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% children vaccinated. However the immunity that it induces decreases after about ten years. The protective efficiency of BCG for preventing serious form of TB (ex. Meningitis) in children is greater than 80%. Its protective efficiency for preventing pulmonary TB adolescents and adults varies by country for as low 0% in South India. In the United Kingdom, its effectiveness exceeds 75%.

Better methods of preventing tuberculosis or TB relapses include eating a healthful diet that takes care of your immune system, getting a TB test regularly if you work or live in a high risk environment, and fishing TB medications. To prevent transmitting the disease to others if you are infected, stay home, cover your mouth, and ensure proper ventilation. Prognosis

Progression from TB infection to TB disease occurs when the TB bacilli overcome the immune system defenses and begin to multiply. In primary TB disease 1-5 of cases this occurs soon after infection. However, in the majority of cases, a latent infection occurs that has no obvious symptoms. These dormant bacilli can produce tuberculosis in 2-23% of these latent cases, often many years after infection. The risk of reactivation increases with immunosuppression, such as that caused by infection with HIV. In people co-infected with mycobacteria tuberculosis and HIV, the risk of reactivation increases to 10% per year. Studies utilizing DNA fingerprinting of mycobacteria tuberculosis strains have shown that reinfection contributes more substantially to recurrent TB than previously thought, with estimates that it might account for more than 50% in areas where TB is common. The chance of death from a case of tuberculosis is about 4%.


Roughly a third of the world’s population has been infected with M.tuberculosis, and new infections occur at a rate of one per second. However, not all infections with M.tuberculosis cause TB disease and many infections are asymptomatic. In 2007 there were an estimated 13.7 million chronic active cases, and in 2010, 8.8 million new cases, and 1.45 million deaths, mostly in developing countries. The absolute number of tuberculosis cases has been decreasing since 2005 and new cases since 2002. Tuberculosis is the world’s greatest infections killer of women of reproductive age and the leading cause of death among people with HIV/AIDS. This is due to the fact that worldwide, women have a larger burden from poverty, ill-health, malnutrition and disease than men.

Tuberculosis results in more deaths among women than all causes of maternal mortality combined, and more than 900 million women are infected with TB worldwide. It also kills more young people and adults than any other known infectious disease. The rise in HIV infections and the neglect of TB control programs have enabled a resurgence of tuberculosis. The emergence of drug-resistant strains has also contributed to this new epidemic with, from 2000 to 2004, 20% of TB cases being resistant to standard treatments and 2% resistant to second-line drugs. The rate at which new TB cases occur varies widely, even in neighboring countries, apparently because of differences in health care systems.


I would like to recommend this term paper to be read by everyone who doesn’t have enough knowledge about tuberculosis. To all my classmates for them to realize the importance of being educated about a certain disease like this. Conclusion

I therefore that tuberculosis is truly one of the global killer and the same time global problem that exist since antiquity. It can cause destitution to every one of us since the spread of this disease occurs when an infected person coughs, sneezes, shouts, sing or speak; obviously this disease can transmit to one another easily. It is quite obvious that the person who lives in poverty, health workers, workers in refugee camps, prison inmates, and those who suffer from malnutrition are those people who get tuberculosis easily. This disease kills more than any other known infectious disease in this world.

Encyclopedia Britannica, Volume 27

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