Laboratory diagnosis of pulmonary tuberculosis

Laboratory diagnosis of pulmonary tuberculosis

Steps:

1. Special collection:
   
   -          3 Sputum samples (on 3 consecutive mornings)-          Blood-          Swab-          Bronchial aspirates.

2. Microscopic examination:

1. Ziehl-Neelsen staining

Finding : M.tuberculosis appears as straight or slight curved rods.

2. Dark ground illumination (DGI)

Finding: Yellow –orange bacilli.

3. Fluorescence microscopy .

Aura mine / Rhoda mine stain (for rapid screening purpose)

3. Isolation & identification from culture:

1. Lowenstein –Jensen medium:

Incubate at 37°C for 4-6 weeks aerobically.

Findings:

-Colonies are dry, wrinkled &tenacious.

- At first white and later on Buffy colored.

1. BACTEC broth medium.

2. Dubo’s medium : Time taken for growth is about 10-17 days.

3. Tissue culture medium.

- Tubercle bacilli grow around nuclei in the form of cords after about 5 days.

4. Middle brook media.Immunological tests:

-Tuberculin test (Monteux  test).

- ICT (Immunochromatography test)for antibody.

-ELISA for antibody and antigen.

5. Nucleic acid based technique :

Polymerase chain reaction (PCR).