Tuberculosis and Typhoid Fever
Tuberculosis (TB) is caused by repeated exposure to airborne droplets contaminated with a rod-shape bacterium, Mycobacterium tuberculosis. The TB bacterium is also known as the tubercle bacillus. A person with active pulmonary tuberculosis can spread the disease by coughing and sneezing. Once the person is infected with Mycobacterium tuberculosis, the infection will slowly progress to disease.
More than 8 million new cases of Tuberculosis (TB) have been diagnosed each year and are responsible for more than three million deaths per year. Almost two and three quarter billion people (2.75 billion) or 33% of population are latently infected with TB.
Among screening infectious diseases, a rapid and accurate diagnostic method of tuberculosis is very important for human health maintain and the disease control. At present, the clinical check (X-ray) coupling with the microscope examination and specimen bacterial culture is the major diagnostic method for the tuberculosis. However, this often takes 4-6 weeks, and the results sometime inaccurate.
In the early days, the antibody detection in the blood test was regarded as a convenient method. However, its sensitivity and specificity appeared very poor. For the last 50 years, the successful program for screening tuberculosis is based on the tuberculin skin test (TST) by using the purified protein derivates (PPD) to stimulate the T cells. However, the major drawback of TST with PPD is its cross-reaction with BCG immunized persons.