Health Information

The use of DNA analysis is a novel and revolutionary approach for specifically identifying the disease-causing pathogenic organisms. This is in contrast to the traditional methods of disease diagnosis by detection of enzymes, antibodies etc., besides the microscopic examination of pathogens. Although at present not in widespread use, DNA analysis may soon take over the traditional diagnostic tests in the years to come. Diagnosis of selected diseases by genetically engineered techniques or DNA probes or direct DNA analysis is briefly described.

Tuberculosis

Tuberculosis is caused by the bacterium mycobacterium tuberculosis. The commonly used diagnostic tests for this disease are slow and sometimes may take several weeks. This is because M. tuberculosis very slowly.

A novel diagnostic test for tuberculosis was developed by genetic engineering. A gene from firefly, encoding the enzyme luciferase is introduced into the bacteriophage specific for M. tuberculosis. The bacteriophage is a bacterial virus, frequently referred to as luciferase reporter phage or mycophage. The genetically engineered phage is added to the culture of M. tuberculosis. This phage attaches to the bacterial cell wall, penetrates inside, and inserts its gene into the M. tuberculosis chromosome. The enzyme luciferase is produced by the bacterium. When luciferin and ATP are added to the culture medium, luciferase cleaves luciferin. This reaction is accompanied by a flash of light which can be detected by a luminometer. This diagnostic test is quite sensitive for the confirmation of tuberculosis.

The flash of light is specific for the identification of M. tuberculosis in the culture. For other bacteria, the genetically engineered phage cannot attach and enter in; hence no flash of light would be detected.