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Mycobacterium Tuberculosis Essay

explanatory Essay
3160 words
3160 words
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Introduction
Over 130 years ago in 1882, during a milestone lecture, physician Robert Koch introduced and described the infectious agent causing tuberculosis (TB), previously thought to be an inherited condition, as Mycobacterium tuberculosis (M. Tuberculosis).1 He said that if the significance of an infectious disease was defined by it’s fatalities, TB would stand above those most feared. The agent was a small, rod-shaped, slow-growing, non-motile bacterium incapable of spore formation.1,2 Appearances can deceive, and Koch’s remarks of the effects of this microscopic being were not dramatization – TB caused approximately one billion deaths in the two hundred years leading up to 1900 and was dubbed “consumption” because of the severe internal damage it caused.3 Koch’s work made him a Nobel laureate in 1905.3 Later, eight distinct species of Mycobacterium, all TB-causing agents in humans and other mammals, came to form the Mycobacterium TB complex.4
With discovery of the cause of TB, focus turned to treatment and prevention. A breakthrough came in 1944, when the disease became curable with streptomycin, an antibiotic discovery attributed to American Selman Waksman and his fellow researchers.3 Antibiotic discoveries pertaining to TB were regular for the 20 years following.4
That would have been the end of the story, TB eradicated, but bacteria, as all living things, are not impartial to the process of natural selection, and M. tuberculosis soon evolved resistance. Furthermore, an appearance on a new epidemic brought TB back into the limelight. Today, a number of antimicrobials are in use to treat persons with TB and prevention programs, including use of a vaccine, are in place to some degree worldwide.5
Despite the advances, the ...

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...nuated and therefore does not cause infection, simply priming the immune system. In countries where TB prevalence is high, the vaccination is given at birth and the success rate of fending off TB infection is estimates to be 50%. The BCG vaccine is not administered to persons with compromised immune systems because the weakened bacterium may be sufficient to cause active infection. Moreover, the efficiency of the vaccine as a means of TB prevention in adults has been challenged with reports of its failure.
The most notable ongoing global campaign for TB eradication was established by WHO, with goals for a 50% TB rate drop set for the year 2015 as well as a STOP TB Strategy, with guidelines endorsed for implementation globally to manage the infectious disease. With a 45% decrease in rates of TB since 1990, the world is on track to fulfill the set goals.
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In this essay, the author

  • Analyzes how physician robert koch introduced and described the infectious agent causing tuberculosis (tb), previously thought to be an inherited condition.
  • Explains that tb became curable with streptomycin, an antibiotic discovery attributed to american selman waksman and his fellow researchers. antibiotic discoveries were regular for the 20 years following.
  • Explains that bacteria are not impartial to the process of natural selection, and m. tuberculosis evolved resistance. an appearance on a new epidemic brought tb back into the limelight.
  • Opines that despite advances, the disease persists, concentrated in poor and developing regions, and evolution of a form of m. tuberculosis resilient to all currently used medicines threatens the efforts for eradication.
  • Explains that m. tuberculosis is a pulmonary infection that is transmitted via sneezing or spitting. it is airborne, but is also possible via sexual intercourse or skin lesions.
  • Explains that tb is interesting, although disturbing, because one can breathe in the particles from the environment, become infected, but be unaware of the infection.
  • Explains that mycobacterium tuberculosis must make its way into a host organism in order to survive, and cause illness in the host. it thrives in oxygen rich environments, hence the common localization of infection to the lungs.
  • Explains that m. tuberculosis bacteria can survive outside of the host for long-term survival. the duration of survival on dry nonliving surfaces ranges from one day to four months.
  • Explains that environmental factors, the infected, and the person exposed determine the outcome with respect to tb infection.
  • Explains that tuberculosis is second only to hiv/aids as a leading cause of death globally, but distribution is disproportionate throughout the world, with the highest rates of the disease belonging to the eastern hemisphere's poorer regions.
  • Analyzes how koch's discovery of m. tuberculosis in 1882 led to a decline in tb-related deaths. the hiv/aids epidemic and drug resistant strain of the bacterium made the disease an easy catch.
  • Explains that treatment and control strategies created by organizations such as who and implemented globally have led to a fatality rate decline of 45% between 1990 and 2012.
  • Explains that active tb is present in a third of the world's people. there are variable reports with respect to the risk of becoming ill with the latent infection.
  • Explains that a person afflicted with active tb coughs, sending infectious particles into the surrounding air. these particles are droplet nuclei that carry the bacteria m. tuberculosis.
  • Explains that tb is a global health issue, and the pathogen evades the immune defenses.
  • Explains the role of macrophages in the innate immune response.
  • Explains that the prr tlr2 of the alveolar macrophage cell membrane recognizes the cell wall glycolipoprotein on m. tuberculosis.
  • Explains that the prr tlr9 molecule recognizes a pathogen by specific sequences in the pathogenic dna, the mamp. its interaction produces cytokines and chemokines in an inflammatory immune response.
  • Explains that the immune response generated by macrophages and subsequent action by t cells, specifically cd4+ and cd8+ types, can keep the infection under control, but does not rid the body of the pathogen entirely.
  • Explains that the two cell death mechanisms have opposing functions. apoptosis kills the invading pathogen, while necrosis is oppositional.
  • Explains that the prr cd209 is found on the cell membrane of dendritic cells and recognizes bacterial cell wall products. interleukin 10 is anti-inflammatory because it inhibits macrophages.
  • Explains that in active tb, anti-inflammatory mediators act in opposition to the action of proinflammatory cytokines in the immune response.
  • Explains that numerous studies have been carried out using mice as animal models of the human tb disease.
  • Explains that latent tb is asymptomatic and not infectious, but requires management due to the capacity of the bacteria to transform to active form. the duration of treatment ranges from three months to nine months.
  • Explains that treatment of tb disease, that is, the active bacteria, currently consists of administration of drug isoniazid, rifampin, and ethambutol or pyrazinamide.
  • Explains that the multi-drug-resistant strain of m. tuberculosis is unaffected by isoniazid and rifampin and requires treatment with a combination of less commonly used drugs.
  • Explains that a vaccine for tb called bacilli calmetter-guerin uses mycobacterium bovis, which is attenuated and does not cause infection, simply priming the immune system.
  • Opines that the world is on track to fulfill the set goals for tb eradication, with a 45% decrease in rates since 1990.
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