Epidemiology and infectious diseases

Tuberculosis

I . Introduction

Tuberculosis is or TB is an infectious disease that usually affects the lungs . The most common form is caused by Mycobacterium tuberculosis , a slender , rod-like bacterium commonly called the tubercle bacillus . The tubercle bacillus is very hardy , surviving when many other bacteria cannot . In addition to affecting the lungs , tuberculosis can affect almost all other organs of the body

Tuberculosis , which in the past called phthisis and consumption , has afflicted man for thousands of years . Evidence of the disease has been found in Egyptian mummies . Tuberculosis was

once a leading cause of death in all age groups , but its severity has decreased with improved medical care and better living standards

Most persons have a natural resistance to the tubercle bacillus . Even though large numbers of persons , especially in cities , become infected by the bacillus early in life , only a small percentage actually develops the disease

This intent to (1 ) know the occurrence of tuberculosis and how it is being spread (2 ) be aware of its symptoms and detection and (3 figure out its treatment and control

II . Background

Tuberculosis is an infectious disease caused by the bacterium Mycobacterium tuberculosis , a slender rod and an obligate aerobe . The rods grow slowly (20-hour generation time , sometimes form filaments and tend to grow in clumps . On the surface liquid media , their growth appears moldlike , which suggested the genus name Mycobacterium , from the Greek mykes , meaning fungus

These bacteria are relatively resistant to normal staining procedures When stained by the ZiehlNeelson or Kinyoun technique that stains the cell with carbolfuchsin dye , they cannot be decolorized with a mixture of acid and alcohol and are therefore classified as acid-fast . This characteristic reflects the unusual composition of the cell wall , which contains large amounts of lipid materials (American Thoracic Society 2000 . These lipids might also be responsible for the resistance of mycobacteria to environmental stresses , such as drying . In fact , these bacteria can survive for weeks in dried sputum and are very resistant to chemical antimicrobials used as antiseptics and disinfectants

Tuberculosis is a good example of the importance of the ecological balance between host and parasite in infectious disease . Hosts are not usually aware of pathogens that invade the body and are defeated . If defenses fail , however , hosts become very much aware of the resulting disease . Several factors may affect host resistance levels - the presence of other illness and physiological and environmental factors such as malnutrition , overcrowding , and stress

Tuberculosis is most commonly acquired by inhaling the tubercle bacilli reach the lungs , where they are usually phagocytized by a macrophage in the alveoli . The macrophages of a healthy individual usually destroy the bacilli . If they do not , the macrophages actually protect the microbe from the chemical and immunological defenses of the body , and many of the bacilli survive and multiply within the macrophage (American Thoracic Society , 2000

These macrophages eventually lyse , releasing an increased number of pathogens . The tubercle bacilli released from dying macrophages form a lesion . A hypersensitivity reaction against...