Wednesday, March 02, 2011

tb paper

            Consumption, or what is more commonly known as Tuberculosis, first showed itself in humans about eight thousand- ten thousand years ago. Some theorist believed that Tuberculosis did not originate in humans, but animals were the primary carry before it spread. The initial spread of Tuberculosis (TB) came from cows, and the fact that early settlers used to live in close quarters with their animals made the transmission of this disease easy between both species (Reichman). New research however suggests that TB first came from humans( Furlow). In the early times of TB when not much was known about the disease, there was very little hope for surviving it once infected.
            During the eighteenth century, TB was responsible for one-fifth of deaths in the US as well as one-third of deaths in Europe. This was a disease the world soon realized that did not distinguish between social class or age. TB was considered an epidemic, sweeping across the United States killing over 2 million people a year. Sometime between the late 1950's and the early 1980s the growing number of TB cases started to go down. Between the mid 1980's and the early 1990s the epidemic rose again, the cause of this is contributed to the AIDS virus, and the immune deficiency problems that coincided with it (Daniel). Today, there are one hundred sixty million new infections of TB every year, but thanks to advance medical technology not everyone who has the disease will die from it (Reichman).
            A person who has been infected with TB will exhibit coughing; sometimes coughing up blood or septum, fevers, nights sweats, and severe weight loss. Since this is a disease that primarily associates itself in the lungs, the person will also experience horrible chest pain (Furlow). These symptoms are so non-specific it is often hard to be certain whether or not a patient has Tuberculosis without doing further testing. If the infection is outside the lungs, (extra pulmonary), other symptoms will occur, such as meningitis if it's in the nervous system. TB can also spread to the blood stream, bones, and lymphatic's (Knechel, 34).
            Tuberculosis comes from the aerobic bacterium Mycobacterium tuberculosis, which is a non-spore forming acid-fast bacilli. Once inside the body this bacterium has quite the defense against the body's immune system. The cell wall of these bacilli contain an antigen that is immunogenic, which helps fight off macrophages that are released through the body's immune system to kill these foreign invaders. The cell wall also contains an extremely resistant lipid barrier which does not allow some antibiotics to penetrate it. This cell wall is one of the things that make TB so successful at infecting people (Knechel).
            The primary source that TB will infect will be the lungs. Generally, TB will get inhaled through the nose or mouth, once inside the body it will either be expelled via nose hairs, or by mucus secreted by goblet cells. If the bacteria make it past these defenses, then it will settle down into the deepest part of the lungs, called the alveoli. It is here that it will begin to fight off the macrophages and the bacteria will begin to multiply into a full on infection. If the body's immune system is able to keep the infection in check, which essentially keeps the infection from spreading, then the patient will have what is called latent Tuberculosis (Furlow).
            Tuberculosis spreads through the air. Any infected person who coughs, laughs, sneezes, talks, will expel tiny droplets that contain nuclei. These nuclei can remain in the air of any area that does not have proper ventilation or UV light. These nuclei cannot survive exposure to UV lights, and the ventilation will cause them to be swept away. Any person who is infected with TB has the potential to infect another person. This risk for infection becomes higher if the person is in a small space with a lot of other people, and if this person is exposed to the same people over long periods of time. It was not always known that this disease was a infectious one, which is why so many people died in the eighteenth and nineteenth centuries (Reichman).
Isolation, Diagnostic Testing, Identification
            In 1865 a French military physician, Jean-Antoine Villemin succeeded in transmitting Tuberculosis to rabbits.  Villemin recovered pus from the lung cavity of a tuberculosis patient that had died thirty-three hours earlier and injected it under the skin of two healthy rabbits.  Villemins severest critic, Hermann Pidoux, said consumption in the poor was due to conditions of poverty including overwork, malnutrition, unsanitary housing, and other deprivation. When consumption developed among the rich, Pidoux claimed it was brought about by their overindulgence in their wealth, laziness, flabbiness, overeating, excessive ambition, and habits of luxury. Such blind rejection of the infectious nature of TB remained until 1882, when German physician Robert Koch made a presentation before the Berlin Physiological Society. Koch announced that he had discovered the microbe of TB. Koch was also able to show, as Villemin had, that bovine TB could be infectious to humans, principally via the milk (Sherman).
Koch thought he had developed a protective substance made from an extract of the bacillus called tuberculin, known today as purified protein derivative or PPD. Instead of being curative, tuberculin turned out to be dangerous, because it sensitized the body to tuberculin which was able to kill via a delayed hypersensitivity reaction. It did serve a practical purpose as a diagnostic test and remains one of the most useful methods of determining previous exposure to TB.  A  positive tuberculin skin test does not indicate whether the disease is active however, and only ten percent of people exposed to M. tuberculosis develop an active disease (Sherman).
            In order to identify and diagnose tuberculosis several tests have to be done.  First, there will be a chest radiograph to see if there is anything abnormal about the lungs. If the findings are abnormal then the next step would be to make a smear of the patients sputum, this sample should be collected every day for three days. This test does not give the definitive answer of TB, but it does test to see if acid-fast bacilli are present. A sample of this can be taken, placed on a slide, and stained for acid fast positive or negative. If the staining indicates positive acid-fast, more than likely this is tuberculosis. Acid fast stains are positive if after the staining procedure the bacilli are left a red color, which would be a different color than the rest of the media on the slide.  A culture of the septum will also need to be made and tested; this process can take about eight weeks. This culture is the test that will give the definitive answer of yes or no to whether a person is infected with TB (Knechel).
            Since TB takes such a long time to isolate and culture, there have been new tests made that guarantee faster results, not only are these results faster but they are just as accurate. This test, called Polymerase chain reaction, will detect for bacterial DNA. The results of this test take much less time and can be available in just a little over two hours. Some other tests that can be done to detect TB include skin tests as well as blood tests, however unlike the previous two test stated above the skin and blood tests cannot give a definitive answer as to whether or not a person is infected, more so these test work better at detecting latent tuberculosis (Knechel).
As long as Tuberculosis was diagnosed only in its late phase, the relief of distressing symptoms occupied the most important place in treatment. Many ancient procedures which have little or no effect on the course of the disease such as: inhalation of vapors, sucking of cracked ice, and the use of opiates for quieting the cough and pains of intestinal tuberculosis maintained a lasting popularity. The belief in the value of mild southern climates for the treatment of tuberculosis persisted throughout the 19th century, gaining support from the observation that people moving from southern to more northern regions were likely to contract fatal Tuberculosis.  It was clinical experience that revealed the therapeutic effects of healthy living, good food, and rest in tuberculosis.  But it took the resources of physiological, pathological, bacteriological, and chemical sciences to bring about the more active forms of treatment such as pulmonary collapse, surgery, and the use of antimicrobial drugs (Dubos).
            The BCG vaccine is an attenuated, weakened strain of Mycobacterium bovis.  In 1908, two French scientists from the Louis Pasteur Institute, Calmette and Guerin, cultured a virulent tubercle bacillus from the udder of a tuberculent cow.  In 1921, they first used the vaccine they'd created on infants in Paris. The first use of the vaccine was an oral dose mixed with milk; it remained avirulent. In 1929, doctors in Lubeck, Germany, gave the oral BCG vaccine to two hundred and fifty -one infants. This batch of vaccine was contaminated with a virulent strain of Mycobacterium tuberculosis, and seventy-three infants died. Later, the vaccine was given subcutaneously, but this caused abscesses. The vaccine was widely used in France but was not readily accepted for use in Great Britain or the United States (Hadden). Even when practiced under ideal conditions, vaccination never succeeds in completely preventing tuberculosis in the vaccinated group (Dubos).
            The United States declared a, "War on Consumption" beginning in the early 1900s. This consisted of vigorous anti-TB campaigns, the most famous being Christmas Seals of the National Tuberculosis Foundation, which later became the American Lung Association. The greatest benefits of this was education, loss of stigma, abandonment of TB as a spiritualizing and romantic force, a greater understanding of contagion, the initiation of attempts to clean up tenements, and improvements in medical diagnosis and care (Sherman).
            In 1940 Selman Waksman developed methods for growing soil microbes and screening them for their antibiotic properties. Walksman's graduate student, Albert Schatz discovered that a mold, Streptomyces griseus, was an antagonist and limited the survival of the TB bacteria in both soil and in sewage. In 1943 the inhibitory substance streptomycin was isolated from the cultures.   Streptomycin inhibited the growth of tubercle bacilli in both the body and in test tubes. By 1945, it was in clinical use for treatment of TB (Sherman).
In 1949 streptomycin resistant TB bacilli were treated with para-amino salicylic acid (PAS), and in 1952 isoniazid, a drug first synthesized from coal tar in 1912, became the mainstay in the treatment of drug resistant TB. Isoniazid also blocks the synthesis of mycoliac acids, which are the main constituent of the waxy wall of M. tuberculosis. Streptomycin and other drugs did not eradicate TB; they did effectively eliminate sanitaria however (Sherman).
In 1963, rifampin was introduced as a treatment. To minimize the emergence of drug resistance, patients are treated with a drug cocktail, called MDT (multiple-drug therapy).  Currently the most commonly used treatment regimen is isoniazid, rifampin, and pyrazinamide.  More than eighty-five percent of patients who receive both isoniazid and rifampin have negative sputum cultures within two months after the intitiation of treatment (Sherman).
            More than fifty years after the first effective use of chemotherapy for TB, the disease remains unconquered.  The emergence of multidrug-resistant strains of M. tuberculosis are often due to the initiation of treatment followed by a lapse after a few weeks, allowing larger numbers of mutant bacteria to survive; these mutants overcome and resist the drugs.  In the late 1980's, it became clear that a substantial number of patients weren't completing treatment.  To address this, the Center for Disease Control and Prevention recommended that direct observational therapy (DOT) by a trained health care worker be considered for all patients (Sherman).
            There is evidence from twin studies that susceptibility to TB has a genetic basis, but no major TB susceptibility gene has ever been identified. Susceptibility to TB is dramatically enhanced in HIV-infected persons, and the spread of AIDS has been paralleled by resurgence in TB cases (Sherman).
Tuberculosis is the leading cause of death from a curable infectious disease. In many resource-poor countries, especially those blighted with HIV, TB is on the rise, with one person infected every second (Sherman). However, TB is a largely forgotten disease in the United States, having been replaced by cancer, AIDS, and cardiovascular diseases in the public awareness (Sherman). Public opinion research shows that perception of Tuberculosis is not a problem in the United States. This is due in part to the demographic of the disease, the majority of those affected with Tuberculosis are at the margins of society, and to the fact that the disease is once again in decline. Although multidrug resistant Tuberculosis is a very serious problem, with a potential to worsen in the future, it represents a small and decreasing number of cases in the United States (Geiter).

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