Molecular Test Detection

Test : Mycobacteria - DNA probe


Indications : The test is ordered to obtain rapid detection of M. tuberculosis in clinical specimens. Sputum is the most common sample used for the test.

The sputum sample is decontaminated and concentrated in a pellet by centrifugation. DNA is separated from a sample of this concentrate using standardized procedures. The DNA sample is then subjected to the PCR method to amplify the target sequences in the DNA .The target sequence in this case is the DNA of the Mycobacteria which is integrated to the DNA of the patient.

The amplified product is then fragmented and made to run on an agrose gel after which it is transferred to a nylon membrane to carry out the southern blotting method. Probes are added to this membrane and incubated to enable them to hybridize with the target sequence. This hybridization is detected through chemiluminescence.

Physiology : Mycobacteria are a group of non- motile, gram- positive , pathogenic bacteria that are capable of causing serious illnesses in humans, the most common being tuberculosis (brought about by M.tuberculosis) and leprosy (brought about by M.leprae).They also cause many other illnesses , especially in those with low immunity.

Despite therapeutic efforts increasing in leaps and bounds over the years, mycobacterium tuberculosis infections have increased dramatically in the last few years making it necessary to diagnose them quickly and efficiently.

Normal Range : This tests improve the detection of mycobacteria, and the test as increased sensitivity and specificity.

Interpretation : If addition of probes does not reveal the presence of bacterial DNA then the sample does not have the presence of Mycobacterium tuberculosis.

Sample : No mycobacteria DNA detected.

Test Method : DNA hybridization

Related Tests : Whole blood, sputum, pleural fluid, cerebrospinal fluid, bronchial aspirates, urine and tissue biopsy.

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